Northeast Fisheries Science Center Reference Document 07-15
Characterization of the Northeast and Mid-Atlantic Bottom and Mid-water Trawl Fisheries Based on Vessel Trip Report (VTR) Data
by Christopher D. Orphanides and Gisele M. Magnusson
National Marine Fisheries Serv, Woods Hole Lab, 166 Water St, Woods Hole MA 02543-1026
Print
publication date September 2007;
web version posted September 20, 2007
Citation: Orphanides CD, Magnusson GM. 2007. Characterization of the Northeast
and
Mid-Atlantic Bottom and Mid-water
Trawl Fisheries Based on Vessel Trip Report (VTR) Data. U.S. Dep. Commer., Northeast Fish.
Sci. Cent. Ref. Doc. 07-15; 127 p.
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ABSTRACT:
An overview of the United States Northeast and Mid-Atlantic trawl
fisheries was created to support the development of a Take Reduction Plan (TRP) by
the Atlantic Trawl Gear Take Reduction Team (ATGTRT). The analysis focused on
aspects of the fisheries that correlated with marine mammal bycatch and
characterized the trawl fisheries from Maine to North Carolina
for the period 1996 to 2004 by temporal and spatial effort distributions,
harvest patterns, vessel characteristics, gear configurations, and
environmental relationships. The primary data used were vessel trip reports
(VTRs); additional data sources included remotely sensed data for environmental
variables, federal commercial dealer records, and vessel permit data.
The number of vessels in the bottom trawl fishery declined by 28%
between 1996 and 2004. Over the same period total trips declined by 15%, days
absent declined by 26%, and days fished declined by 40%. Total landings varied from
a low of 92,159 metric tons (live) in 2002 to a high of 116,911 metric tons in
2004. Based on a 9-year average of landings, the top 5 species were Loligo squid, silver hake, Illex squid, skates, and monkfish.
Inflation adjusted value declined for the fishery, reaching a low in 2003 but
increasing in 2004. Based on a 9-year average of adjusted values, the top 5 species
were Loligo squid, fluke, monkfish, cod, and winter flounder. Over all years, the majority of bottom trawl effort
occurred north and east of the Hudson Canyon, although some significant effort occurred
along the shelf break south of Hudson Canyon. Effort shifted tothe south during the winter. Southern regions tended to use nets with a smaller
mesh than northern areas, while gear size, measured as foot rope length, was
closely linked to vessel size.
The number of vessels in the mid-water trawl fishery declined by
18% between 1996 and 2004. Effort measured in trips declined by 1%, days absent
declined by 5% and days fished declined by 38%. There were clear differences in
data on the fishery after the implementation of the Atlantic Herring Fishery
Management Plan in 2001. The 9-year average landings were composed of 80%
herring and 18% mackerel, while herring accounted for 65% and mackerel 27% of
the average inflation adjusted value. Total landings grew steadily and peaked
in 2004; the inflation adjusted value doubled over the 9 years. The mackerel
and herring fisheries had a small overlap in effort south of Rhode Island. Herring was harvested year
round, with effort focused in the Gulf
of Maine (GOM), the northern edge of Georges Bank (GB), and south of Rhode Island. Mackerel
were fished from south of New England down
through the mid-Atlantic from November through May with larger gear (foot rope
length) and larger mesh size than herring.
Both fisheries landed the majority of their catch in Massachusetts; other important states included Rhode Island, Maine, New
York, and New Jersey. Effort in both fisheries was concentrated in waters where
the sea surface temperature (SST) was less than 10 °C, depth was less than 100
meters and bottom slope was less than 0.5°.
VTRs are compulsory for nearly all vessels participating in the
U.S. Northeast and Mid-Atlantic bottom and mid-water trawl fisheries; thus, the
records should nearly provide a census of fishing effort for the fisheries. Data
accuracy, in particular with measures of effort, was examined; over 90% of the
records fell within the norms for the variables. It appears that the VTR data
provides a reasonably accurate overall picture of the trawl fishery.
Introduction
Bottom and mid-water trawl fisheries are a major component of the
United States Northeast and Mid-Atlantic fisheries. In September 2006, the National
Oceanic and Atmospheric Administration’s (NOAA) National Marine Fisheries Service
(NMFS) convened the Atlantic Trawl Gear Take Reduction Team (ATGTRT) to address
incidental takes of pilot whales (Globicephala
spp.), common dolphins (Delphinus
delphis), and white-sided dolphins (Lagenorhynchus
acutus) in U.S. Atlantic trawl fisheries. The goal of the ATGTRT is to
develop a Take Reduction Plan to limit the serious injury and mortality of
these marine mammals due to accidental entanglement in commercial fishing gear.
This paper characterizes a subset of the U.S. Northeast and Mid-Atlantic trawl
fisheries to aid in the development of a take reduction plan. Specifically this
paper aims to assess characteristics of the fishery that were identified as
correlated to marine mammal bycatch. However, it is also expected that this
characterization will be comprehensive enough to serve as a reference for other
research on these fisheries.
The trawl fisheries havebeen the subject of much analysis; however, most studies have focused on
subsets of the fisheries. As such, the recent literature lacks an overall
characterization or description of the U.S. Northeast and Mid-Atlantic trawl
fisheries for use by the ATGTRT. Studies within the peer-reviewed literature
tend to focus on small subsets of the fisheries and issues may not be relevant
for management considerations under a take reduction team process. A
significant amount of information on the fisheries is contained in various
fishery management plans (FMPs)[1], in particular the
Northeast Multispecies FMP documents. However, trawl gear is one of several
gear types examined and vessels identified for inclusion in the analysis may be
limited to those that hold permits for the species of interest. Rountree
(1997) summarized the spatial and temporal patterns for otter trawl vessels for
1982 to 1992. The age of the analysis limits comparisons with this study[2]. A study by Stevenson et al. (2004) focused on
gear impacts on fish habitat, and mapped effort in days absent for bottom trawl
vessels. The maps allow for partial validation of the results of this study;
however, characteristics important to bycatch reduction are not examined[3].
Historically, reductions in bycatch have been achieved through
methods such as gear modifications and time and/or area closures, which require
knowledge of the relationship between bycatch, the fleet, and fishing
characteristics. Recent research suggests that trawl bycatch of pilot whales,
common dolphins, and white-sided dolphins are primarily a function of the
spatial and temporal aspects of fishing effort (Rossman [in prep]; Palka [in
prep]). However, numerous other fishing characteristics such as gear fished,
vessel characteristics, and species targeted have been shown to be correlated
with bycatch and could play a role in mitigation measures. As such, this paper covers
a broad range of characteristics including the spatial and temporal aspects of
fishing effort, the gear fished, the species harvested, and the vessels
involved. In addition, this paper summarizes fishing effort and revenues to
provide information that could help assess the impacts of proposed mitigation
measures.
The organization of the paper is as follows. First, to provide
context for the variables examined and the changes identified, information is
provided on trawl bycatch calculations and relevant changes in management
regimes. Second, fishing effort and variables correlated with bycatch are summarized
for 1996 to 2004 and presented separately for bottom and mid-water trawl
fisheries. Third, the discussion identifies data concerns and areas for future
study.
Background
I. Variables important to assessing marine mammal
bycatch in trawl fisheries
Studies on bycatch of
marine mammals in the U.S. Northeast and Mid-Atlantic bottom and mid-water
trawl fisheries were used to select the fishing characteristics summarized in
this paper. The primary predictor variables identified varied by bycatch
species and fishery. In the bottom trawl fishery the predictor variables were
target species[4], vessel horsepower, and
bottom slope for pilot whale bycatch, SST, and bottom depth for white-sided
dolphin bycatch, and statistical area for common dolphin bycatch (Rossman [in
prep]). In the mid-water trawl fishery bottom depth and latitude were the most
important factors in estimating white-sided dolphin and pilot whale bycatch
(Palka [in prep]). The primary predictor variables were used to estimate
bycatch rates that were expanded to estimate total bycatch using stratified
effort measured in days fished.
In addition to the predictor variables, there were other variables that had significant
correlations to bycatch rates but were not used as predictor variables. The
correlations do not necessarily indicate a cause and effect relationship, but
do point to possible research areas that could lead to effective ways to limit
bycatch. The bycatch models use data from the NMFS observer database. The
Observer records include many variables that are not included in the vessel trip
reports (VTRs) or permit databases nor can they be derived from VTR data. For the
bottom trawl fishery[5], significant correlated
variables in addition to the predictor variables mentioned above were:
- Latitude*[6]
- Longitude*
- Month*
- Foot
rope length*
- Tow
duration*
- Gross
vessel tons*
- Vessel
length*
For the mid-water trawl fishery, additional significant
correlated variables included:
- Bottom
slope*
- SST*
- Region
(Northeast vs. Mid-Atlantic)*
- Longitude*
- Date*,
month*, and season*
- Target
species
- Time
of day
II. Relevant
fisheries management actions, 1996–2004
Management actions have
the potential to affect a number of variables examined in this report[7]. The diversity of
harvest by the U.S. Northeast and Mid-Atlantic trawl fishery puts it in contact
with a large body of management measures. Management authority for the
species caught by the trawl fisheries resides with the New England Fishery
Management Council (NEFMC), Mid-Atlantic Fishery Management Council (MAFMC),
and the Atlantic States Marine Fisheries Council (ASMFC). There are 37 FMPs between
the 3 organizations, covering about 60 species (Appendix A). As well, the national
Highly Migratory Species Plan covers sharks, swordfish, tuna, and billfish. Despite
this range of regulations, the principal species harvested suggests a smaller
number of FMPs are of major importance to the U.S. Northeast and Mid-Atlantic
trawl fishery; in particular, the FMPs for groundfish (multispecies), Atlantic
herring, monkfish, mackerel/squid/butterfish, and summer flounder/scup/black
sea bass. Aspects of these FMPs relevant to this report are described below.
i. Northeast Multispecies (Groundfish) FMP
By 1996, some management measures were already in place under the
Northeast Multispecies FMP. These measures included a minimum mesh size (5.5”), a ban on the
use of paired trawls, seasonal closures in the Gulf of Maine (GOM), Georges
Bank (GB), and Southern New England (SNE), and year-round closures in Closed
Area (CA) I, CA II, and the Nantucket Lightship CA. Amendment 5 (1996) placed a
moratorium on new entrants to the fishery and developed a plan to reduce effort
by decreasing historical days-at-sea (DAS) by 50%. Mandatory VTR and observer
program requirements increased the information available on the fishery. Minimum
mesh size for the GOM/GB Regulated Mesh Area (RMA) (Figure
1) was increased to
6.0”.
Closed areas have been expanding in size and duration since 1996,
although the general locations were consistent; Figure
2 (seasonal) and Figure
3 (year-round)
represent groundfish closed areas as of 2007. Under Amendment 7 (1996), the GOM
seasonal closures were expanded to cover all gear types, including trawl gear. The
Cashes Ledge CA was implemented as a seasonal closure in 1998, but became
year-round in 2002. The Western GOM year-round closure was implemented as a
temporary measure in 1998, but remained beyond 2004. In 2004, Amendment 13 created
7 essential fish habitat (EFH) closure areas, which prohibited bottom trawl
gear year-round.
Numerous amendments and framework adjustments continued to cap
and reduce DAS for vessels. Amendment 13 (2004) resulted in significant changes
to DAS, setting unrestricted DAS at 60% of the vessel’s baseline DAS.
Regulated changes in mesh size have been limited. In 1999, the
minimum mesh size was increased to 6.5” square for the GOM, GB, and SNE RMAs.
This has remained unchanged except for SNE where the minimum was increased to
7.0” square or 6.5” diamond in 2002. Amendment 13 (2004) clarified the mesh
size requirements, indicating that vessels with large mesh permits were to have
minimum mesh size of 8.5” diamond or square throughout the net in GOM, GB, and SNE
RMA, and 7.5” in Mid-Atlantic RMA.
ii. Atlantic Herring FMP
When the Atlantic Herring FMP was developed, the resource was
considered under-exploited (New England Fisheries
Management Council 1999).
The ASMFC Herring FMP was implemented in 2000, while the NEFMC Herring FMP was
effective for the 2001 fishing year. Thus, prior to 2001, herring records are
considered incomplete (New England Fisheries
Management Council 2006),
as not all herring vessels were engaged in other fisheries that had VTR
requirements.
The FMP limited herring permitted vessels to less than 165 feet
in length overall, less than 750 Gross Registered Tons (GRT) or with propulsion
less than 3,000 shaft horsepower. The fishery was divided into 4 fishery management
areas (FMAs; Figure
4). Each year a target total allowable catch (TAC) was
determined for each management area. When catch reached 95% of the FMA’s TAC,
targeted harvesting would be halted. Closures, in particular for FMA 1A, were
common. In 2002, Framework Adjustment 1 created two quota periods in FMA 1A,
winter/spring (January–May) and summer/fall (June–December), in an effort to
increase the amount of quota available during the summer/fall peak demand
period.
iii. Monkfish FMP
The monkfish fishery is jointly
managed by the NEFMC and the MAFMC. The monkfish FMP came into effect November
1999 and thus data may be incomplete for earlier years. Limited access permits
differentiated between those in the directed fishery and those for which
monkfish was primarily a bycatch (holders of multispecies and scallop DAS). Permit
holders were each allocated 40 Monkfish DAS. The TAC was to be achieved through
a combination of limited access and trip limits. The fishery was divided into
the Northern FMA and the Southern FMA; the dividing line runs from the intersection of 70° W. longitude and the south-facing
shoreline of Cape Cod, MA southward along longitude 70°W to latitude
41°N, then eastward to the U.S.-Canada maritime boundary. Trip limits
have been more restrictive in the Southern FMA.
When using only a monkfish DAS (i.e., directed fishing), the minimum mesh size
for trawls was set at 10” square or 12” diamond[8].
In May 2003, Framework Adjustment 2 increased trip limits for the
Southern FMA for monkfish-only vessels, while there remained no trip limit for
the Northern FMA. The 2004 rule restricted use
of a vessel’s DAS in the Southern FMA to a
maximum of 28 DAS and reduced trip limits for the area.
iv. Atlantic Mackerel, Squid, and Butterfish FMP
The MAFMC plan covers all Atlantic mackerel, butterfish, Loligo pealei (long-finned squid), and Illex illecebrosus (short-finned squid)
under U.S. jurisdiction. In May 1996, Amendment 5 included a joint moratorium permit for Loligo squid and butterfish, a minimum
mesh size of 1 7/8” diamond for Loligo vessels, and seasonal quotas for Loligo. Vessels
fishing for Illex squid during June–September
seaward of a line roughly matching the 50-fathom line were exempt from the
minimum mesh size requirements; at that time the Illex squid fishery was considered underutilized. Closures for the
directed fisheries in Loligo, Illex, butterfish, and mackerel are
based on a percentage of the Domestic Annual Harvest level; the trigger is 80%
for mackerel and 95% for all others. Over the years both Loligo and Illex squid
fisheries have been closed as the triggers were reached.
In the late 1990s, mackerel was considered underutilized, and a
declining annual allocation to joint venture processing sector was provided. Amendment
8 (1999) placed a size restriction on vessels that could fish in the Atlantic
mackerel fishery to less than or equal to 165 feet in length and 750 GRT or
less than or equal to 3,000 shaft horsepower.
v. Summer Flounder, Scup, and Black Sea Bass FMP
The MAFMC was responsible for the summer flounder (fluke) FMP; in
1996, scup and black sea bass were added to the FMP. Beginning in 1997, vessels
issued permits for these species were required to submit VTRs.
All 3 species have been managed with commercial landings quotas
that have resulted in closures of the fishery. Fluke used state level quotas,
and state level closures have been frequent. Black sea
bass initially operated under a coast-wide quarterly quota, but that was
converted to a state level quota in 2003. Scup has operated under a coast-wide
trimester quota.
Minimum mesh size requirements for trawl vessels differed by
species. In 1997, trawls holding a scup moratorium permit were required to use
nets with 4” or more diamond mesh. Black sea bass moratorium permit holders
were required to use nets with a minimum of 4” diamond or 3.5” square mesh. For
fluke, mesh had to be 5.5” diamond or 6.0” square mesh. In 1998, the scup minimum
mesh size requirement was set at 4.5” diamond. In 2001, mesh size for black sea
bass was increased to 4.5” diamond.
Data
The primary source of data for this analysis was the fishing VTR
database. Additional data sources included the Commercial Fisheries Dealer
Database (CFDBS), often termed “dealer data,” and the NMFS Northeast Regional
Office’s (NERO) permit database.
The VTR is logbook information provided by fishermen, after completing a fishing trip. The number
of vessels required to submit reports have grown over the years, and most
federally managed fisheries in the Northeast required VTRs by 2004[9]. Owners or operators of federally
permitted vessels are required to provide reports for all trips, including trips
targeting species without VTR requirements and trips with no catch. A separate
report is required for each portion of a trip when changes occur in gear (mesh or
gear size) or location (based on chart or statistical area). Thus, a single
trip may have multiple reports, or sub-trips. Each report (Figure
5) includes: (i)
vessel and operator identification; (ii) dates of sailing and landing and port
landed; (iii) type of trip; (iv) gear characteristics; (v) location fished; (vi)
descriptors of effort; (vii) details on species caught, including kept and
discarded, and (viii) to whom sold.
VTR data from 1996 through 2004 was retrieved for otter trawl fish
(OTF), otter trawl other (OTO), otter trawl mid-water (OTM), and paired mid-water
trawl (PTM) gear types. These fisheries had documented marine mammal bycatch and
were part of the ATGTRT.
Key variables, including gear size, mesh size, tow time, and
number of hauls, were checked for errors, and unreasonable outliers were replaced
with median values. Most outliers were determined using a table of reasonable
expected values developed for data quality checks. The table of reasonable
expected values was developed by examining both observer and VTR data to
determine the real world maximum and minimum values for particular variables in
each fishery. However, some variables, such as the number of hauls per trip,
were not included in this table. In this case, the number of hauls per trip was
examined through calculation of the number hauls per day, since the length of
trips vary. After examining the distribution of both VTR and observer data, 10 was
set as the maximum number of hauls per day. Tow hours and number of hauls were
also compared to the amount of fish kept as a means of checking for invalid
zero values. For example, if a trip had positive pounds kept but no hauls, then
the number of hauls was replaced with a median value. Tow hours were dealt with
in a similar manner; for instance, positive tow hours with no hauls were not
considered valid.
To calculate median
values, trips were stratified by hull number, gear type, FMP group[10], year, and state; each
unique combination of these variables had a matching median. Outliers were
substituted with the stratified median values; each replaced value was
representative of similar trips by the same vessel. In cases where an outlier
needed to be replaced and no median was available based on the stratification,
the hull number was dropped from the stratification criteria and a median was created
based on the remaining variables. About 2% of the data for these variables were
replaced with median values, although roughly 6% of the gear size observations
were replaced (Table
1).
Two additional variables
were created from existing VTR variables: “days fished” and “main species.” A
“days fished” effort variable was created using tow hours, tow minutes, and
number of hauls recorded. The average tow time per haul for a trip was
converted to decimal days and multiplied by the number of hauls for that trip. A
variable describing the “main species” landed on a trip was based on the
species with the largest percentage of the trip’s live weight[11]. For example, if a trip
caught more pounds of fluke than any other individual species, the
characteristics of that trip were fully attributed to fluke. The implicit
assumption was that vessel captains were targeting the species of which they
caught the most, having modified gear, season, and location accordingly. The
main species categorization was used to examine gear characteristics and effort
measures. For some species (e.g., mackerel) more than 80% of the live weight
reported in the VTR was harvested by trips where that species (e.g., mackerel)
was identified as the main species (Table
2). However, for some species (e.g.,
cod, plaice, and witch flounder) less than 50% of the total reported live
weight landed was harvested on trips where that species (i.e., cod, plaice or
witch flounder) was identified as the main species. The impact of this
difference on the summary statistics is unclear.
Environmental variables, including SST, bottom
depth, and bottom slope, were created based on location information recorded in
the VTR dataset. SST data for each trip was obtained from 5-day SST composites
derived from several satellite imagery sources, or 5-day climatology images obtained
from NASA’s Jet Propulsion Laboratory[12]. Satellite SST imagery sources
included AVHRR Pathfinder Version 5, Modis Aqua, Modis Terra, and GOES
satellites[13]. These sources were combined when
available to create one 5-day median composite image for each day. A Visual
Basic for Applications routine in ArcGIS 9.1 extracted SST values at point
locations, and using a 3x3 cell window, for both the 5-day median composites
and the climatology. The VTR data location variable is reported as the center
point of a trip that occurs in one area and in which a consistent gear type and
size was used. When choosing which SST to use in the analysis, the 5-day
medians were preferred over the climatology, and point locations were preferred
over the 3x3 cell medians. Lastly, the resulting SST value was compared to the
climatology data to screen for incorrect temperature values.
Depth data for each sub-trip was obtained using
bathymetry data acquired from the National
Geophysical Data
Center[14]. Like SST, bottom depth (Figure
6A)
was sampled with ArcGIS at each fishing location recorded by the vessel log. This
depth data was preferred over that reported in the VTR for its consistency both
in location and in its source[15]. Bottom slope in degrees was
calculated using the ArcGIS slope function after projecting the bathymetry data
to a Lambert Conformal map projection customized for the area off the Northeast U.S. coast (Figure
6B). Bottom depth and
bottom slope are closely correlated.
To estimate revenue, a
price series was created from the CFDBS database. For each species, an average
weighted price per live pound landed was calculated by year and month. The
weighted price took into account the allocation of the species between
different grades (e.g., round, dressed) and between ports of landing. For
species where the majority of the landings were “unclassified” for a species
group (e.g., skates) in the CFDBS, the VTR records were grouped similarly. The
price is an average by month over all grade types and ports from Maine to North
Carolina, so it does not reflect spatial price
differences but does reflect seasonal differences. The value is referred to as
the “calculated value” to indicate that it was calculated using the VTR data,
rather than taken directly from the CFDBS which is considered a more accurate
determination of trip value. Unless indicated, calculated values are in nominal
dollars (i.e., not adjusted for inflation), meaning that averages across years
are not appropriate. However, where indicated adjusted calculated values were
adjusted for inflation using the annual GDP implicit price deflator[16] with a base year of 2000
(i.e., 2000=100).
The NERO permit database was the source of information on vessel
characteristics such as GRT, vessel horsepower (VHP), and vessel length. While
the majority of vessels within the VTR dataset have associated records in the
permit dataset, occasionally a match will not be found. Rather than exclude
these vessels from the results, these records are identified separately.
To organize the data spatially, 5 fishing regions were defined by
grouping statistical areas (Figure
7A). The regions are based on the fishing
areas used by NERO and the NEFMC. The NEFMC regions are not exactly aligned
with the statistical area boundaries, so adjustments were made. These
adjustments were, in part, guided by the ecosystem regions (Figure
7B)
identified based on fish communities (Gabriel 1992). The goal was to define
regions that were meaningful from both management and ecosystems perspectives.
The fishing regions include: GOM, GB, North Southern New England (NSNE), South
Southern New England (SSNE), and Mid-Atlantic (MA). Records that lack location
information are included in the “unknown” category rather than excluded. The
fishing regions are very different in size, and are subject to different
management regulations, so comparisons based on total values should be done
with caution.
Results
The results are reported separately for the bottom trawl and
mid-water trawl fisheries; however, each section follows a similar format. Each
fishery is examined in terms of characteristics of effort, harvest, vessels,
gear, and environmental variables.
I. Bottom Trawl Fishery (OTF and OTO)
Only vessels reporting the use of OTF and OTO gear on the VTRs
are considered in this analysis. While most of these vessels indicate otter
trawl gear on all their VTR records, vessels that occasionally report use of
otter trawl gear are also included. The number of vessels using bottom (otter)
trawl gear decreased between 1996 and 2004 from 944 to 732 (Table
3), a 23% decline.
Despite an increase in the number of fisheries covered by VTR requirements
during this period, the number of reported trips decreased from 38,748 in 1996
to 33,089 in 2004, a decline of 15%.
i. Effort characteristics
Bycatch rates are multiplied by stratified effort to calculate
total bycatch; thus, it is important to understand the distribution of effort
relative to factors correlated with bycatch rates. For the Atlantic trawl
bycatch estimates, bycatch rates are expanded by days fished. “Days fished” is
an encompassing measure of effort that accounts for tow time and hauls and, to
some degree, days absent. The focus of this section is the general spatial and
temporal distribution of effort, in terms of days fished and its components. Effort
is also considered later when fishing and vessel characteristics are examined
in other sections, to provide additional information that could be helpful in
the assessment of impacts of proposed TRP mitigation measures.
a. Days fished
Over the entire 9-year period, 1996 to
2004, effort in the bottom trawl fishery was focused from the Hudson Canyon
north, with areas of high density along the axis of the Hudson Canyon, along
the shelf edge, on GB, and in the GOM, particularly off the Massachusetts coast
in the transition zone between the GOM, and GB (Figure
8). Some effort extended
south of the Hudson Canyon
along the shelf break, and along the mid-coast
of Virginia and North Carolina. This overall distribution
illustrates some of the key fishing grounds for the bottom trawl fishery;
however, some of the discontinuities in the distribution of effort closely
match closures for management purposes, discussed and illustrated above. The
overall distribution of effort also masks changes over the 9 years in terms of
the relative importance of areas.
Between 1996 and 2004, the total days fished by the bottom trawl
fishery decreased from 37,381 to 22,324 (Table
4), a 40% decline. Days fished
declined in all fishing regions, although the declines were not evenly
distributed. The greatest impact was in the GOM, where days fished declined in
all years except 2001; the total days fished decreased from 15,806 in 1996 to
8,262 in 2004, representing a 48% decline. This was followed closely by NSNE,
where there was a decline in every year except 1998; the total days fished fell
from 12,896 in 1996 to 6,926 in 2004, a decrease of 46%. The MA had moderate
increases in days fished in 1998 and 2002, but still had an overall decrease
from 2,328 to 1,522, for a total decline of 35% over the 9 years. The least
affected region was GB, where there were slight increases in days fished in 6 of
the 9 years; however, the total decreased between 1996 and 2004 from 5,871 to
5,565, a 5% decline.
As a result of the differences in the decline of days fished by
fishing region, the relative importance of the regions in terms of effort has
shifted (Table
4). In 1996, The GOM accounted for 42% of total bottom trawl
effort (=15,806/37,381), NSNE for 34% (=12,896/37,381), and GB accounted for 16%
(=5,871/37,381). By 2004, days fished in the GOM were 37% of the total
(=8,262/22,324), NSNE accounted for 31% (=6,926/22,324), and GB accounted for
25% (=5,565/22,324).
The average amount of time spent fishing per trip, as measured by
days fished per trip, declined by about 30% between 1996 and 2004 (Figure
9). This
decline extended to all fishing regions (Table
5). The relative decline was
greater in NSNE where mean days fished per trip decreased from 0.65 in 1996 to
0.36 in 2004, a 45% decline. The smallest decline was in GB, where mean days
fished per trip decreased from 3.55 to 3.05, a 14% decline. On average, trips
to GB fished the most, while vessels on trips in the NSNE fished the least
amount of time per trip.
The amount of effort used in the pursuit of different species has
declined overall (Table
6), with a few notable exceptions. Main species trips
for haddock increased from 30 days fished in 1996 to 1,594 in 2004, a 52-fold
increase, while days fished on Atlantic croaker main species trips doubled from
42 in 1996 to 86 in 2004. There were also small increases in the total days
fished for yellowtail flounder and Loligo squid trips. The most significant declines in days fished were for American
plaice trips, which declined by 90% from 4,517 days to 424 days between 1996
and 2004, and cod, which declined from 4,863 to 1,484 days, a 70% decline.
Silver hake, winter flounder, and monkfish trips also exhibited declines in
days fished between 1996 and 2004. These changes resulted in some shifts in the
relative fishing effort between species (Table
7). In 1996 cod and monkfish
main species trips both accounted for approximately 13% of effort in days
fished, while American plaice was second at 12% and fluke third at 10% of days
fished (Table
7). In 2004, monkfish accounted for 14% of the days fished, fluke
accounted for 13%, and Loligo squid
for 11%; cod had fallen to 7% and plaice to 2%.
Seasonality for the bottom trawl fishery is evident in the average
days fished per trip by month (Figure
10). The highest means occurred in the
first quarter, fell to fell until July then increased through December; the
average for February was almost twice that for July. This seasonality could be
in part due to seasonal differences in the species targeted.
Disaggregating average days fished per trip by main species
illustrates the high degree of variability within the broadly defined bottom
trawl fishery (Figure
11). Differences exist between species, and within a
species between months. Among the Northeast multispecies, witch flounder, silver
hake (Figure
11A), and other groundfish (Figure
11D) exhibited the same
seasonal pattern as the overall fishery, while winter flounder (Figure
11A) had
an opposite pattern. Haddock (Figure
11A) and monkfish (Figure
11C) had the
highest days fished per trip, but with opposite seasonal patterns; thus, haddock
was highest in the third and fourth quarters while monkfish was highest in the
first 2 quarters.
The spatial distribution
of days fished by main species (Figure
12) closely matches the distribution of
the species[17]. An examination of the
maps of effort indicates that the species harvested break into 5 groups
spatially:
- croaker (Figure
12C) and Illex squid (Figure 12H) have a southern distribution;
- butterfish (Figure
12A), scup (Figure
12M),
fluke (Figure
12E), Loligo squid
(Figure
12I), and mackerel (Figure
12J) have a distribution from Rhode Island
and southern GB and south;
- monkfish (Figure
12K), silver hake (Figure
12N),
skate (Figure
12O), winter flounder (Figure
12P), and yellowtail flounder (Figure
12R) span between Rhode Island and GB up into the GOM;
- cod (Figure
12B), haddock (Figure
12F), American
plaice (Figure
12L), and witch flounder (Figure
12Q) are primarily on the
northern flank of GB and north into the GOM;
- dogfish (Figure
12D) and Atlantic herring (Figure
12G) are caught throughout the study region.
b. Tow time and number of hauls
The examination of the haul and tow time variables was limited as
they were used to calculate the days fished variable, which was examined in
detail above. The total number of hauls decreased from 301,241 to 191,032
between 1996 and 2004 (Table
8), a 37% decline. The number of hauls decreased
for all main species, except for Atlantic croaker, witch flounder, yellowtail
flounder, haddock, and scup. The allocation of hauls between species (Table
9)
is similar to that for days fished by species. However, fluke trips generally
have a higher percentage of hauls than days fished, while monkfish is the
opposite (Table
9 and Table
7). This suggests that fluke tow times are shorter
than average, and monkfish tow times are longer than average.
The mean number of hauls per trip declined by about 30% over the 9
years (Figure
13), while mean average tow time per haul both declined by about
10% (Figure
14). Both variables exhibited seasonality, although there were some
differences. The mean number of hauls per trip peaked in February and was at
its lowest level in July (Figure
15), with about a 40% difference between the
two. Mean average tow time per haul was highest in March and lowest in July–September
(Figure
16), with about a 30% difference.
c. Days absent
“Days absent” is calculated from the VTR as the number of days
between departure and landing, rounded up to the nearest whole day. Days absent
is a combination of steam time and fishing time. In the bottom trawl fishery,
days absent declined from 101,790 in 1996 to 74,852 in 2004 (Table
10), a 26%
decline. This is less than the decline in days fished discussed above. Days
absent could increase relative to days fished if vessels must travel further to
fish.
The fishing regions had different patterns in terms of reported
days absent (Table
10). The changes in days absent were not consistent between
years or in direction; however, the overall trend was downward. The GOM exhibited
the largest overall decline in days absent, from 35,635 in 1996 to 20,861 in
2004 (a 42% decline). In the NSNE region, days absent declined from 44,805 to
33,074 (26% decrease). The GB and MA regions both experienced small increases
in days absent over the 9 years. The GB region’s days absent increased from
12,839 to 13,085, a 2% increase, while the MA went from 7,294 to 7,600, a 4%
increase.
Seasonal variation in length of trips, measured by days absent, is
evident (Table
11), however, high coefficient of variation (CV) values mean the
differences are not statistically significant. Trips in the first quarter (January–March)
were slightly longer, while trips in the second and third quarters were shorter.
There appears to a less variation in the mean value, as measured by the CV, in
January and February, when trip length is near its maximum mean value.
ii. Harvest characteristics
Landings and value for the fishery are important from the
perspective of potential impacts from proposed TRP actions. The spatial and
temporal patterns of harvest help identify groups of fishermen and regions that
may be affected by TRP mitigation actions, while value provides an indication
of the level of economic impacts.
a. Species
Over the 9-year period 1996 to 2004, the main species algorithm
classified the majority of the trips as fluke trips, followed by Loligo squid, cod, winter flounder, and silver
hake trips (Table
12). The species making up the majority of the trip’s catch
by live weight was considered the “main species.” These rankings differed from
those based on total value and total kept weight, though the top species are
similar. In terms of total kept weight (live) the top 5 species based on a 9-year
average were Loligo squid, silver
hake, Illex squid, skates, and monkfish
(Table
13). The difference in ranking suggests that fluke, cod, and winter
flounder trips may be frequent with a small harvest, and indeed there were small
trips limits for each species over much of the time examined.
The importance of species by value is expected to differ from
measures based on weight as many high volume species (e.g., herring, mackerel,
skates, and Illex squid) have relatively
lower prices per pound, either nominal (Table
14) or adjusted for inflation
(Table
15). Nominal calculated value illustrates within-year differences in
value (Table
16); however, to compare values between years the adjusted value
must be used (Table
17). The top 5 species based on an average of adjusted
values are Loligo squid, fluke,
monkfish, cod, and winter flounder, respectively. Most species have lost real
value over the years, although haddock and Illex squid posted gains.
b. Fishing regions
The NSNE region, which encompasses the northern Mid-Atlantic
Bight, has consistently harvested the most fish by weight (Table
18). The
second most productive region for the bottom trawl fishery was more variable,
shifting between GB and the GOM. In terms of calculated value (Table
18), the
ranking was consistent from 1996–2000, with NSNE first, followed by the GOM, GB,
and the MA. Since 2001, the calculated values for the GOM, GB, and NSNE have
been similar with each taking a turn at the top valued region.
As the fishing regions are based on ecosystem regions, one would
expect differences in the species harvested by fishing region. All the top
species were harvested in all fishing regions (Table
19) except for SSNE;
however, the importance of individual species to the regional total harvests differed.
For the GOM the top 5 species harvested were other groundfish, cod, plaice,
monkfish, and winter flounder (Table
19). For GB the top 5 were silver hake, yellowtail flounder, cod, monkfish, and haddock (Table
19). For NSNE the
top 5 were Loligo squid, Illex squid, skates, silver hake, and mackerel, and for the MA the top 5 were croaker, Illex squid, fluke, mackerel, and Loligo squid (Table
19). The overlap in the top 5 between adjacent regions may be
partly explained by statistical areas that include more than one eco-region,
but there are is also seasonal movement by species. This becomes more apparent
when landings by species are examined by region and month (Appendix B).
Examination at the month-region-species level illustrates shifts between
species that allow harvest levels to be maintained throughout the year.
c. Port of landing
The top states in terms of landings are those closest to the GOM
and the NSNE fishing regions (Table
20), where effort is concentrated. Massachusetts was
usually the top state for bottom trawl landings, with the exception of 1998 and
2004. In terms of inflation adjusted calculated value, Massachusetts was consistently the top state
by a significant margin (Table
20). Over the 9-year period, the average
adjusted value indicates Massachusetts was the
top state, with almost twice the value of second place Rhode
Island, followed by Maine as
third, and New York and New Jersey nearly tied as fourth.
iii. Vessel characteristics
Most bottom trawl vessels only report using OTF gear, and
dependence on this single gear increased between 1996 and 2004 (Appendix C). In
1996, of the 944 vessels reporting use OTF gear, 623 (66%) used only that gear
type. By 2004, 588 of the 732 vessels (80%) reporting use of OTF used only that
gear type. Only OTF and OTO VTR records are used in the calculation of the
information in this report.
a. Fleet
Most average measures of effort and landings per vessel have
remained steady across the 9 years, with small differences rendered
insignificant by large CVs. While the number of vessels has steadily declined,
the average number of trips increased from 42 per vessel per year to 45 (Table
21); however, the CV remained around 100% throughout the period. While the CVs
for average days absent per year and days fished were below 100%, the small
declines are insignificant (Table
21). All weight-based measures – including
average landings per year (live weight), landings per day absent, and landings
per day fished – increased (Table
21), although much of the gain occurred in
the last year. Both nominal and inflation adjusted values increased over the
years, despite drops in 2002–03 (Table
21). The real value per vessel (revenue,
base year 2000) increased from $184,728 in 1996 to $222,160 in 2004 (Table
21),
a 20% increase.
b. Ton class
A possible reason for the large CVs for the averages per vessel,
discussed above, is a high degree of heterogeneity within the bottom trawl
fishery. To address this heterogeneity, vessels may be categorized by a number
of categories including size characteristics, depending on the type of
analysis. The only “standard” set of categories is that for GRT; the ton class
(TC) categories for vessels are: TC1 (1–4 GRT); TC2 (5–50 GRT); TC3 (51–150);
TC4 (151–500 GRT); and TC5 (>500 GRT). The majority of bottom trawl vessels
were of TC2 and TC3 (Table
22), with small numbers in TC4 and very few in TC1. The
number of vessels within each class declined over the 9 years, although not
equally.
Within TC categories, vessel size measures exhibited a high
degree of homogeneity (Table
23). The average VHP had the highest overall level
of variation within a TC; however the means were relatively stable over the
years. Average vessel length was very stable within a TC, and had CVs below 20%
for all groups except TC1, which had a slightly more erratic pattern. As with
length, the average GRT within each class was very stable, both in terms of the
mean and CV; the CV was larger for TC2 than TC3, which had more vessels.
Despite the number of vessels in TC2 being slightly smaller than
TC3, the TC2 group has consistently taken more total trips than TC3 vessels
(Table
24). The trips by TC2 vessels are substantially shorter than TC3 trips
as the total number of days absent by TC3 vessels is nearly double that of the
TC2 group. Additionally, the total days fished by the TC3 group are almost 3
times greater than that for the TC2 group. The small TC4 group has a higher
number of total days absent and total days fished relative to the number of
trips than any of the other size groups. The percentage of time spent fishing
is greater for the larger TC groups. For example, in 2004 TC2 vessels spent 23%
of days absent fishing (=4,950 days fished/21,054 days absent) while TC4
vessels spent 39% of the time fishing (4,546 days fished/11,748 days absent).
Differences in the proportion of time spent fishing may, in part,
explain some of the differences in the distribution of harvest and revenues
between the ton classes (Table
25). Vessels in TC3 landed 4–6 times the weight
of fish as did the similar number of vessels in TC2, while the smaller group of
vessels in TC4 vessels landed 3–5 times as much fish as the TC2 vessels. The
pattern for nominal and inflation adjusted value (i.e., revenue) is similar
(Table
25).
Differences in the species composition of landings by vessels in
the TC categories (Table
26) may partly explain differences in both effort and
landings. The TC4 vessels had higher average annual landings of squid (Illex and Loligo), silver hake, and mackerel, relative to other species, than
did other TC groups. For TC4 vessels the 4 species accounted for 57% (=7,504 + 6,682
+ 4,606 + 3,759/39,778) of average kept live weight landings. For TC3 vessels, Loligo squid and silver hake are also
important, but other top species include skates, other groundfish, monkfish, fluke, and yellowtail
flounder, while the top species for TC2 vessels include skates, cod, plaice,
fluke, monkfish, Loligo squid, and winter
flounder. The smallest vessels, TC1, are almost fully dependent on groundfish,
including cod, witch flounder, plaice, yellowtail flounder, monkfish, and other
groundfish.
iv. Gear characteristics
Two gear characteristics are available in the VTR records: codend
mesh size, and gear size as measured by footrope length. Mesh size is
determined by target species and fishing method, which in turn are limited by
regulations. Minimum mesh size restrictions have been in place for most species
fished by the bottom trawl fishery for the entire 9-year period. While numerous
exemptions exist for specific times, areas, and target species, one would
anticipate that the self-reported data (i.e., VTRs) would closely follow the
regulated sizes for the associated main species. In contrast, gear size in
terms of footrope length for trawl nets for the most part is not regulated but
is limited by fishing conditions and vessel characteristics.
a. Mesh size (codend)
The mean codend mesh (inches) increased over the years (Figure
17A); however, the total increase has been a little over 1/2 inch since the
smallest average in 1998. There is a greater difference between months in
average mesh size (Figure
17B), perhaps illustrating shifts in targeted
species. There are two peaks in mesh size; generally mesh size was large in the
winter and early spring, and decreased in size from June through October
(Figure
17B).
There is almost no seasonality present in codend mesh size for a
given species (Figure
18), though differences are evident between species. Many
of the northeast demersal species have mesh sizes of about 6 inches including haddock,
yellowtail flounder, American plaice, winter flounder, witch flounder, cod
(Figure
18A), monkfish, and skate (Figure
18B). Scup and fluke, which have
distributions from Rhode Island
and south, have average mesh sizes of roughly 4.5 and 5.5, respectively (Figure
18B). Spiny dogfish, whose distribution spans the Northeast and MA had a mesh
size between 4–5 inches. Squid, herring, mackerel, and butterfish, which are
more pelagic and are often caught together, had mesh sizes between 2–3 inches. Silver
hake, which often feed on herring and young mackerel (Bigelow and Schroeder
1953), also had an average mesh size of about 3 inches.
When examined by fishing region, the GOM and GB used larger size
mesh than NSNE and MA (Table
27). The SSNE region, which is primarily offshore,
generally had the smallest mesh size. The general pattern is a decrease in size
from north to south, which generally corresponds to the spatial pattern seen by
species. All fishing regions except SSNE exhibited an increase in mesh size
over the 9 years.
While mean mesh size appears to get smaller as the vessel size
increases (Table
28), the differences are small and the CV is large enough to
render the sizes indistinguishable. The relatively smaller CV in the TC1 group
may suggest a more uniform targeting of species than in the TC4 group, which
has a much larger CV.
b. Gear size (footrope length [18])
The average footrope length for the bottom trawl fleet was about
84 feet from 1996– 1999; in 2000 there was a sharp increase to almost 88 feet
followed by a steady decline to 85 feet in 2004 (Figure
19A). Seasonality was
evident (Figure
19B), with larger footrope lengths in the first quarter, which
drop sharply from March to the low in May, and followed by a steady increase in
size until December. There are some differences in mean gear size between
species (Figure
20). Compared to other species, gear size was smaller for trips
that caught winter flounder, cod, yellowtail flounder (Figure
20A), fluke
(Figure
20B), skate, dogfish, and Atlantic herring (Figure
20C). Trips that
caught haddock (Figure
20A), Illex squid (Figure
20B), and monkfish (Figure
20C) tended to have larger gear. For
most species, seasonal variation was limited (Figure
20). Seasonality was evident
for witch flounder, American plaice (Figure
20A), scup, butterfish, both squid
species (Figure
20B), and monkfish (Figure
20C).
Gear size varied by fishing region, with the largest gear used in
GB, followed by GOM, NSNE, and MA (Table
29). Within each region the CV
remained around 30% over the years. The GOM and GB both exhibited a steady
increase in the gear size over the 9 years except for 2004, when the average
size used decreased in GB region. The NSNE and MA regions had declines in gear
size over the years, with the difference larger for the MA. The SSNE region
exhibited no clear pattern for gear size, although this may be influenced by
the limited number of trips in the fishing region.
The average size of gear (in feet of footrope) was larger for
larger vessels (Table
30), and appears to have increased over the 9-year period
for all categories.
v. Environmental and Habitat Characteristics
Fish and marine mammals have particular habitat requirements
which may depend in part on environmental variables such as SST, water/bottom
depth and bottom slope.
a. Sea Surface Temperature
The annual mean SST for bottom trawl trips varied considerably
over the 9-year period from a low of about 13°C in 1996, 1997, and
1998, to a peak of 14°C in 2000 (Figure
21A). This could be the
result of inter-annual variability, but may also reflect changes in the
location of effort over time, which in turn is related to the species harvested.
As one would anticipate, seasonal differences in water temperature were evident
(Figure
21B); the monthly mean SST for trips was lowest in the first quarter,
increased steadily until August, and then declined to the end of the year. This
shift in SST occurred despite shifts in effort between the seasons (Figure
22).
There was a greater concentration of effort in the south during the winter
(Figure
22A), while during the spring (Figure
22B) and summer (Figure
22C)
effort shifted north, and then began to shift back to the south in the fall
(Figure
22D).
The mean monthly SST did not differ greatly between species
(Figure
23), with patterns that closely reflect the overall seasonal pattern. During
the winter and spring, trips that caught predominantly silver hake had a warmer
temperature profile than the rest of the Northeast multispecies group (Figure
23A).
The mean temperature signature for Illex squid (Figure
23B) and Atlantic croaker (Figure
23C) was warmer than almost all
other species throughout the year; however, the series for croaker was
discontinuous due to the limited number of main species trips. The Mid-Atlantic
FMP species (Figure
23B) had warmer temperatures than most of the Northeast multispecies
group (Figure
23A). Dogfish, herring, and monkfish (Figure
23C) all had similar
temperature distributions, though dogfish had a slightly warmer signature than
the other two species during the winter and spring. The temperature
distribution for the “other finfish” category (Figure
23D) was warmer in the
spring due to several species captured at the southern edge of the MA.
The effort within different SST groups has shifted over the years
(Table
31), which in part explains the annual changes noted above. Between 1996
and 2004, the days fished in waters with a SST between 0–5°C declined from 9,010
to 3,984, a 56% decline. As effort overall was declining, other SST groups also
saw declines in days fished; however, they were not as great as that for the 0–5°C group. The result was a shift in the distribution of effort to warmer waters
(Table
31), which was more apparent in 2001 and 2002.
The number of hauls within each SST groups also declined and
shifted (Table
32), with the 0–5°C group shifting from 24% of the total in
1996 to 14% in 2004. The shift from the lowest SST group to higher temperature
groups is more pronounced when measured by hauls than by days fished,
suggesting that tow time may have increased in the 0–5°C group, shortened in
other SST groups, or both.
b. Bottom Depth
The distribution of effort in days fished relative to bottom
depth indicates that the majority of effort is between 0 and 100 meters, but
there was a shift over the 9-year period (Table
33). In 1996 42% of the days
fished were in the 0–50 meter depth category, but by 2004 this had dropped to 33%.
The majority of the effort shifted to the 50–100 meter category, which
increased from 21% to 29% of effort; there was also a small increase in effort
in the 200–2000 meter category.
The pattern of change was very similar for effort measured by
number of hauls (Table
34), although hauls were more heavily concentrated in
the 0–50 meter depth category than were days fished. In 1996, 51% of the hauls
were in waters 0–50 meter deep. By 2004, the share had declined to 43%; the
decline was matched by an increase in the 50–100 meter depth category. When
considered by bottom depth categories, shallow waters (100 meters or less) had
a higher percentage of hauls than days fished, suggesting that tow times were
longer for trips in deeper waters.
c. Bottom Slope
The sea floor has relatively little bottom slope over the
continental shelf and significantly more slope along the shelf break. The slope
decreases again on the continental slope, though it generally is not as flat as
on the continental shelf. Effort, in days fished, for the bottom trawl fishery
overall and by species is concentrated on the continental shelf where bottom
slope is slight. Almost 90% of days fished have been concentrated in the 0–0.5°
slope category for the 9-year period (Table
35), and the pattern is similar for
effort measured by hauls (Table
36).
II. Mid-water Trawl Fishery (OTM and PTM)
The mid-water trawl fishery consists of both single and pair
mid-water trawl vessels. The fishery is smaller and its harvest less diverse
than the bottom trawl fishery. All trip reports where the gear was listed as
OTM or PTM were included in the analysis. This included vessels that also
fished in other fisheries, including the bottom trawl; however, only the
records relating to mid-water trawl activity are included.
The number of vessels participating in the mid-water trawl
fishery declined from 40 in 1996 to 33 in 2004 (Table
37), an 18% decline. The
decline in the number of trips was small, from 1,247 to 1,231 (Table
37), a 1%
decline.
i. Effort characteristics
Bycatch rates are multiplied by effort to
calculate total bycatch; thus, it is important to understand the distribution
of effort relative factors correlated with bycatch rates. For the Atlantic
trawl bycatch estimates, bycatch rates are expanded by days fished. “Days
fished” is an encompassing measure of effort that accounts for tow time and hauls
and, to some degree, days absent. The focus of this section is the general
spatial and temporal distribution of effort, in terms of days fished and its
components. Effort is also considered later when fishing and vessel
characteristics are examined in other sections, to provide additional information
that could be helpful in the assessment of impacts of proposed TRP mitigation
measures.
a. Days fished
Over the entire 9-year period
of 1996–2004, effort in terms of days fished for the mid-water trawl fishery was
focused on the shelf south of New England, on the northeastern edge of GB, and
in the western GOM (Figure
24). The total number of days fished by the
mid-water trawl fishery declined from 484 in 1996 to 302 in 2004 (Table
38), a
38% decline. The decline has not been equal across fishing regions; in fact GB
had an increase in days fished from 27 to 40 (Table
38), a 48% increase.
However, GB remains a distant third in terms of days fished for the mid-water
fishery. In 2001, the GOM became the most important region in terms of days
fished, replacing the NSNE. The MA region, which accounted for about 20% of
effort in 1996 (=94/484), declined to the point where by 2004 only 7% (=21/302)
of days fished were in the region.
The mean days fished per trip for the fishery decreased after the
late 1990s (Figure
25), although the true difference was only a little over 0.1
day fished or a little over 2 hours. This decline extended to all fishing
regions (Table
39). Overall declines from 1996 to 2004 mask fairly steady days
fished per trip for the top 3 regions, GOM, GB, and NSNE, since 2001. In 2004,
trips to GB spent the most time fishing at 0.51 days per trip, while those in
the GOM spent the least time fishing at 0.19 days per trip.
The amount of effort in days fished declined for all main species
trips, except for mackerel, which increased from 35 to 71 from 1996 to 2004
(Table
40), a 106% increase. The mid-water fishery was a more diverse fishery
in the 1990s when several different main species were evident. However, by 2004
herring and mackerel trips accounted for 93% (=70%+23%) of all days fished in
the fishery (Table
41).
The mean number of days fished per trip varied with month (Figure
26). Fishing effort per trip peaked in March–April and September–October, and reaching
lows during January and June. When considered by main species and month (Figure
27), the mean days fished per trip are fairly constant through out the year for
Atlantic herring. Atlantic mackerel, however, shows a discontinuous series with
a sharp increase in May.
The spatial distribution of effort, in days fished, for mid-water herring
and mackerel are distinct, except for a small overlap south of Rhode Island (Figure
28).
Herring was fished in the GOM, northern edge of GB and south of Rhode Island (Figure
28A), while mackerel was fished from
south of New England down through the
mid-Atlantic (Figure
28B).
b. Tow time and number of hauls
The examination of the haul and tow time variables was limited as
they were used to calculate the days-fished variable, which was examined in
detail above. The total number of hauls in the mid-water fishery decreased from
4,162 in 1996 to 2,632 in 2004 (Table
42), a 37% decline, which closely mirrors
the decline in days fished. The distribution of hauls between main species
trips (Table
43) shows increased concentration in the herring and mackerel
fisheries. The distribution of hauls between fisheries is almost identical to
that of days fished, suggesting tow times may not differ between herring or
mackerel trips.
c. Days absent
Days absent is calculated from the VTR as the number of days
between departure and landing, rounded up to the nearest whole day. In the mid-water
trawl fishery, the total number of days absent declined from 3,534 in 1996 to
3,350 in 2004 (Table
44), a 5% decline. The decline in days absent was
substantially less than that for days fished, suggesting less time was spent
fishing in 2004 than in 1996. All fishing regions experienced declines in days
absent except the GB region, which showed an increase (Table
44); however, in
2004 the GB region remained a region with limited use by mid-water trawls, with
only 328 days absent of the total 3,350 or about 10% of the total.
There appear to be seasonal differences in the length of mid-water
trawl trips, with shorter trips in the summer and early fall (Table
45);
however, the high CV makes it unlikely that these differences are statistically
significant. There appears to less variation in the mean value in August–September
and November–December, when trip length is near the lower end of its range.
ii. Harvest characteristics
a. Species
Between 1996 and 2004, nearly 83% of mid-water trawl trips were
classified as Atlantic herring main species trips (Table
46). The species making
up the majority of the trip’s catch by live weight was considered the “main
species.” Atlantic mackerel is the main species on almost 10% of the trips. Other
species that are occasionally determined to be the main species on a trip
include Atlantic croaker, bluefish, Illex squid, Loligo squid, and scup,
although this is largely an artifact of data from 1996–2000. Landings have been
quite volatile but have grown over the 9 years (Table
47), and herring has
accounted from the majority of landings for the entire period. However, the
dominance of herring began to erode in 2002, and by 2004 herring accounted for
only 71,446 of the 124,493 metric tons (live weight) landed by the fleet, or
57% of the total. Mackerel landings accounted for an increasing share of the growing
landings for the mid-water trawl fishery.
The price for mackerel was higher than that for herring
throughout the 9-year period both in nominal (Table
48) and inflation-adjusted
prices (Table
49), although the difference narrowed from 2001 onward. The nominal
value of the mid-water trawl fishery showed a steady increase from almost $11
million in 1996 to almost $25 million in 2004 (Table
50), a 133% increase. In
inflation-adjusted terms (2000=100), the value of the fishery doubled from a
little over $11 million to a little over $22 million (Table
51). During this
time the value of other species dropped to under $200,000, while the value of
mackerel increased to nearly equal that of herring.
b. Fishing regions
In terms of fishing regions, the share of landings from GB and MA
has grown (Table
52); however, the GOM and NSNE continue to be the major source
of landings. Despite having similar landings in the last few years of the time
series, the NSNE region provided a slightly higher share of calculated value than
the GOM (Table
52). In nominal and real terms, the combined value of landings
from GB and the MA have accounted for approximately one-third of value
throughout the time series, with the GOM and NSNE accounting for approximately
one-third each.
The species composition of landings by fishing region (Table
53) illustrates
a north–south pattern. In the GOM and GB herring dominate. In the NSNE region,
landings of herring and mackerel were similar. In the MA, mackerel is the dominant
species harvested. Most of the Illex and Loligo squid was landed in NSNE,
while the croaker was predominately landed in the MA. As well as spatial
differences, there are seasonal differences in landings when examined by
fishing region and month (Appendix
D).
c. Port of landing
The port location where mid-water trawl vessels landed their
harvest was closely linked to the location of the harvest, with the top states
being those closest to the GOM and NSNE fishing regions, which includes Maine,
Massachusetts, and Rhode Island (Table
54). On average over the 9-year period, Massachusetts was the
top state in terms of landings and value for the mid-water trawl fishery (Table
54); however, the top state within a give year was variable.
iii. Vessel characteristics
The majority of mid-water trawl vessels participate in other
trawl fisheries, in particular the bottom trawl fishery (Appendix
C); however,
by 2004 the majority of pair-trawl vessels used only that gear type. The number
and share of vessels dependent only on mid-water trawl has increased, even
while the total number of vessels in the mid-water trawl fishery declined from
40 to 33 from 1996 to 2004 (Table
55), a 18% decline.
a. Fleet
Most average measures of effort and landings per vessel show a
clear difference between the periods from 1996–2000 and from 2001–2004 (Table
55). In 2001 the average number of trips per year taken by a mid-water trawl
vessel increased from 29 to 36, while days absent increased from 65 to 94
(Table
55). Landings per vessel, per day absent, and per days fished all
increased sharply, as did nominal and inflation-adjusted value per vessel. This
suggests a sharp change in the fishery, and in 2001 the Atlantic Herring FMP
came into effect, requiring VTRs from all vessels permitted for herring. The
only measure that did not appear to change was the total days fished per year
per vessel, which remained around 9–10 days from all periods after 1996 (Table
55).
b. Ton class
Large CVs for these values may make the measures more apparent
than significant. High CVs can be a sign of a heterogeneous fleet. Categorizing
vessels may provide for more uniform strata with smaller CV values. One
standard set of categories is for GRT (see “Ton Class” under the “Bottom Trawl
Fishery” section, above). The distribution of vessels between the size
categories has changed between 1996 and 2004 (Table
56). There were no vessels
in TC1 or TC5. The number of vessels in TC2 remained relatively constant, while
those in TC3 declined and those in TC4 increased (Table
56). By 2004, 20 of the
33 vessels were in TC4, which accounted for over 60% of the mid-water fleet.
Vessel size measures have relatively low CV values within a TC
(Table
57). While there is some variation between years, average VHP has
increased for all 3 TCs represented. Average vessel length and average GRT have
remained steady over the years within TC2 and TC3 (Table
57); however, both
measures have increased for TC4. The CV for average length and GRT have been
small and steady within TC2 and TC3, but growing in TC4.
Looking at total effort measures by ton class shows strong
differences between the different groups of vessels (Table
58). Since 2001,
vessels in TC2 have operated as day boats where the number of trips is equal to
the number of days absent. There has also been a sharp contraction for TC3
vessels in the number of trips and days absent, which in part reflects a
decrease in the number of vessels. Vessels in TC4 showed a decline in trips and
days absent in the 1997–2000 period, but both measures increased since 2001. In
terms of actual fishing effort, TC4 vessels dominate the fishery. As mentioned
above, in 2004 vessels in TC4 made up 61% of the mid-water vessels; however, in
2004 they accounted for 1,089 of the 1,231 trips (88%), 3,078 of 3,332 days
absent (92%), and 278 of 302 days fished (92%).
A similar pattern emerges when total landings and value are
examined by ton class (Table
59); the TC4 vessels contributing the majority of
landings and calculated value. Average landings by ton class illustrate those
vessels in the largest class, TC4, predominately target herring while those in
TC3 land a mix of herring and mackerel (Table
60).
iv. Gear characteristics
There are two gear characteristics available in the VTR records,
codend mesh size, and gear size measured by footrope length.
a. Mesh size (codend)
The mean codend mesh decreased by approximately 0.5 inches from a
peak in 1998 (Figure
29A), although size was steady around 1.5 inches since
2001. Monthly mean mesh size was highest during the January–April period, was
steady around 1.5 inches from May–October, then increased through November and
December (Figure
29B). The reason for this seasonal pattern is evident when
mesh size was examined by species (Figure
30). Atlantic mackerel was fished
with larger mesh, and only occurred in the first 5 months of the year. Herring
is fished throughout the year and uses a smaller mesh size.
Average mesh size by fishing region shows differences that are
the result of species targeted (Table
61). In the GOM and GB, where herring is
the principal species, mesh size is the smallest and has been steady over the
years. In NSNE, where both herring and mackerel are landed the average mesh
size is slightly larger and more variable, illustrating the different mix of
landings over the years. In the MA, where mackerel is the principal species
landed, average mesh size is considerably larger than in the other fishing
regions.
Mean codend mesh size by TC illustrates the focus of the
different groups of vessels between herring and mackerel (Table
62). Vessels in
TC4 have the smallest average mesh size, and it was shown earlier that landings
by these vessels are dominated by herring. The average mesh size for vessels in
TC3 is larger than that for TC4 vessels, reflecting the greater role of
mackerel in the landings for these vessels.
b. Gear size (footrope length)
Gear size, measured as footrope length in feet, shows a sharp increase
in 2000 (Figure
31A), after which it has been relatively stable around 200
feet. Footrope length showed a seasonal pattern (Figure
31B), with the shortest
lengths in August, slowing increasing to January, sharply decreasing in
February, and then slowly increasing to June. Atlantic mackerel trips were
distinguished from Atlantic herring trips by their larger footrope length and
their limited fishing season from January–May (Figure
32).
There have been changes in average gear size used in the fishing
regions (Table
63), and much variation between years. In 1996, the shortest
footrope was used in the MA and the longest in the NSNE region; by 2004, the
shortest footrope was used in the GOM, and the longest in the MA.
The average footrope length is longer for larger vessels (Table
64), and increased over time for TC2 and TC4 vessels. Gear size appears to have
decreased for TC3 vessels, although this group also has the highest CV values.
v. Environmental and Habitat Characteristics
Fish and marine mammals have particular habitat requirements
which may depend in part on environmental variables such as SST, water/bottom
depth and bottom slope.
a. Sea Surface Temperature
As with the bottom trawl fishery, there was considerable
variability in the mean SST by year for the mid-water trawl fishery (Figure
33A). This similarity suggests that the variation by year was likely due to
inter-annual variability of SST rather than changes in fishing practices.
However, the mid-water trawl annual SST presents a cooler profile than the
bottom trawl fishery, with a low of ~11°C in 1999 and a high of 12°C in 2000
(Figure
33A). The monthly average SST for the mid-water trawl harvest followed
a pattern of declining temperatures from January–March, followed by a period of
warming until August, then a decline for the remainder of the year (Figure
33B). Effort within the fishery shifted north and south with the seasons, with
most effort taking occurring in the SSNE and in the MA in the first quarter (Figure
34A), and in the GOM in other quarters (Figure
34B-D).
When examined by main species, the average SST followed a pattern
similar to that for the entire fishery, with Atlantic mackerel showing a
slightly warmer winter–spring temperature signature than herring (Figure
35).
This is a result of the more southerly harvest areas for mackerel, identified
above.
Between 1996 and 2004, effort in days fished decreased in waters less
than 20°C (Table
65), and was sustained in the colder waters below 10°C. This
resulted in a slight shift in the distribution of effort to colder waters
(Table
65). The relationship between days fished and hauls is highly correlated
for SST groups, resulting in a similar pattern when effort is examined by
number of hauls (Table
66).
b. Bottom depth and slope
Bottom depth and bottom slope are closely related, as illustrated
earlier (Figure
6). In the mid-water trawl fishery, Atlantic herring is caught
primarily south of Rhode Island, along the northern edges of GB, and in the GOM. These areas are relatively shallow, with
a flat to moderate bottom slope. Atlantic mackerel is primarily caught on the
mid-Atlantic shelf, extending north to east of Long Island, especially in the
area of the Hudson Canyon. The majority of
these areas are less than 100 meters deep and have little bottom slope, except
for the localized topography of the Hudson Canyon, where the walls are too
close together to be well represented in the bottom slope data source used.
An examination of effort by bottom depth categories shows that
the majority of effort in days fished is in waters less than 100 meters (Table
67), with about 60% of days fished. This has changed little over the 9-year period.
When effort is measured by number of hauls, we see that effort is slightly more
concentrated in the less than 100 meter categories (Table
68); this suggests
shorter hauls in the more shallow waters.
Days fished by bottom slope categories shows that a vast majority
of effort is concentrated in areas where slope is less than 0.5° (Table
69);
this concentration has been growing. By 2004, 92% of days fished were in the
category of slope less than 0.5° (Table
69), up from 69% in 1996. A very
similar patter is evident when effort is measured based on the number of hauls
(Table
70).
Discussion
Between 1996 and 2004, effort in the bottom trawl fishery
decreased between 15% and 40%, depending on the unit of measured. Despite these
declines, the total harvest kept (live weight) was relatively stable until
2004, when there was a substantial increase in 2004. The nominal value of the
fishery increased by about 9% over this time; however, the inflation-adjusted value
decreased by 5% and the inflation-adjusted value per vessel increased by about
20%. Relative shifts in effort meant that GB became a more important fishing
region, and increased shares of effort were directed to yellowtail flounder,
fluke, haddock, and Loligo squid trips compared to other species. These shifts were accompanied by a larger
share of effort in deeper and warmer waters.
The mid-water trawl fishery data shows a sharp division in 2001,
the year the Atlantic Herring FMP came into effect. The fishery focuses on herring
and mackerel, which are spatially distinct for most of the year. Both landings
and value for the fishery have been increasing, although there is a high degree
of inter-annual variability. In 2004, the value of the fishery was almost evenly
split between herring and mackerel, although landings for herring were
significantly higher. In contrast to the bottom trawl fishery, the GB region
has become less important to the mid-water trawl fishery as the SSNE and MA
regions have increased in importance both in landings and value. Large vessels
(TC4) increasingly dominate the fishery, measured in effort, landings, and value.
In general, the results of this report will not surprise those
who are in close contact with the bottom and mid-water trawl fishery. However,
the members of the ATGTRT represent a broad cross-section of stakeholders
including fishermen, environmental organizations, state agencies, and federal
government representatives. Thus a disparate level of knowledge of the fishery
may exist; even fishermen who are aware of changes within their fishery or
region may be unaware of the broader picture. This report attempted to
create a base level of information for all participants in the process. This
report is presented at a high level of aggregation, and thus is limited in its
ability to determine the potential impact from proposed actions. However, it
does illustrate changes that are occurring within the fisheries that may
help to identify priorities for actions. For example, shifts in effort to different
regions, main species or depths could result in increases in bycatch which may
need to be addressed proactively.
The data also highlight the importance of understanding changes
in FMPs. Effort patterns within the bottom trawl fishery (Figure
8) illustrate
the impact of year-round closures (Figure
3); while the closed areas themselves
are clear of effort, effort is highly concentrated along their edges. The
expansion of areas closed to bottom trawl gear with the creation of essential fish
habitat (EFH) areas could have potential impacts on the location and intensity
of bottom trawl effort, and potential bycatch. Similarly, the mid-water trawl
fishery showed a high concentration of effort (Figure
24) in herring management
area 1A (Figure
4); in the future mid-water trawls will be excluded from this
area. The relocation of this effort could have implications for bycatch. This
report cannot comment on how effort will shift with management actions, but
highlights the need to support existing and future modeling efforts to capture
these shifts.
The data presented in this paper was drawn primarily from VTRs. Because
these trip reports are mandatory, this data source provides a theoretically
complete survey of all bottom and mid-water trawl effort. However, data
accuracy may not always be reliable. This may be due to errors on trip reports,
data entry errors, or purposeful misrepresentation of trip data by the fishers
themselves. We have taken steps to ensure data accuracy, though the true accuracy
is unknown. Checks of gear size, mesh size, tow time, and number of hauls
against reasonable expected values has shown that in most cases 98% of the data
fell within expected limits (Table
1). Comparisons of recent VTR data against
observer data have also shown a good match (Rago et al. 2005). Within the Northeast Fisheries
Science Center
and Regional Office, steps have been taken to improve the accuracy of both
incoming and existing VTR data. Despite these efforts and generally good
comparisons with other data sources, some data fields such as latitude and
longitude were missing values, especially in earlier years, and given the size
of the database some errors are nearly undetectable and unknowable. Given the
available data, we believe that though each trip record may not be exactly
correct, the VTR data are representative as a whole. Upcoming efforts to
compare VTR data to dealer data (Magnusson in prep) and a more detailed
comparison with observer data (Orphanides in prep) should shed light on this
issue and provide a better framework for assessing the VTR data.
Assuming that the VTR data are generally representative, it is
still possible to misrepresent the data. Much of the fisheries information was
summarized according to what was termed the “main species” of a trip. This
meant that if a trip landed more weight of a particular species than any other,
then that trip was assigned to that main species and the trip variables were
analyzed as being part of the group assigned to that particular species. Using
this method each trip is only used once when summarizing variables by species. It
is unclear whether this grouping method best represents trip variables for
species that did not often make up the majority of the catch. An alternate
method would be to summarize trips by all species caught on a particular trip; if
a trip caught mostly haddock, but also contained cod and monkfish, then the
trip would be included when summarizing variables for haddock, cod, and
monkfish. Alternatively, the trips could be categorized based on the species
with the highest value within a trip, based on the economic principle of
revenue maximization. The question of interest however, is which version of
“main species” most closely matches captains’ determination of “target
species”; this requires additional comparisons with observer data.
It is also important to point out that the spatial and temporal
distributions of fish catch shown in this paper may not necessarily reflect
true fish distributions. Numerous regulations limit the times and areas where
fishers can fish, particularly in the Northeast, and these regulations have
changed over time. Regulations also affect the gear characteristics used in
certain locations, times of the year, and target species. For example, the Northeast
Multispecies FMP, perhaps the most important FMP for the bottom trawl fishery, has
resulted in several changes in permitted mesh sizes, with spatial, temporal,
and species exemptions. Limited access areas, days at sea, and trip limits have
all been added to the FMP and changed over time. Several seasonal and
year-round closed areas have been created, removed, and reconfigured resulting
in a patchwork of year-round, seasonal, and rolling closed areas. These
restrictions make it very difficult to determine the true species distribution
from catch data. The ongoing changes in the regulations also make it difficult
to compare catch data across years. In addition, these regulations have played
a role in the decline of effort in trawl fisheries, which also makes it is
difficult to compare across years. Despite all these changes, fishers still
have managed to maintain or increase harvest and value.
The aim of this paper was to provide summary statistics on the
bottom and mid-water trawl, so it lacks in-depth comparative statistical
analysis. Given the size of the fisheries and the wealth of data available, we
felt that this paper would best serve as a basis for subsequent analysis in
other papers. Similarly, the biological and ecological reasons for the
temporal, spatial, and environmental distributions of the fish were not discussed
in this paper. Again, we felt that we had to limit the scope of this paper to
provide baseline information for the take reduction team process and have left
these topics for other possible subsequent papers.
Acknowledgments
First, we would like to thank the fishers for their honest
reporting of their fishing effort, without which this study would not have been
possible. We would also like to thank all who collected, edited, and archived
these mammoth datasets. We would also like to thank D. Palka for her guidance
and reviews during the preparation of this paper, K. Bisack for guidance in
stratifying the data, and R. Merrick, F. Serchuk, and E. Thunberg for their
helpful comments. All errors and omissions remain those of the authors.
References
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Maine.US Fish Wildl Serv, Fish Bull.
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Gabriel WL. 1992. Persistence of demersal fish assemblages
between Cape Hatteras and Nova Scotia, Northwest Atlantic. J Northw Atlant Fish Sci. 14:29-46.
Magnusson GM.[in
prep]. A comparison of VTR and commercial
fisheries landing data for the Atlantic trawl fishery. NOAA NMFS Northeast Fisheries Science Center,
166 Water St, Woods Hole MA 02543.
New England Fisheries Management Council. 1999. Final
Atlantic Herring Fishery Management Plan Incorporating the Environmental Impact
Statement and Regulatory Impact Review (Including the Regulatory Flexibility
Analysis) - Vol I. Saugus (MA): NEFMC; p 376.
New England Fisheries Management Council. 2006. Final
Amendment 1 to the Fishery Management Plan (FMP) for Atlantic Herring Including
a Final Supplemental Environmental Impact Statement (FEIS) and Initial
Regulatory Flexibility Analysis (IRFA) - Vol I. Newburyport (MA): NEFMC; p.
713.
Orphanides, CD. [in prep.] A comparison of observer and VTR
records for the Atlantic trawl fishery. NOAA NMFS Northeast Fisheries Science
Center, 166 Water St, Woods Hole MA 02543.
Palka DL.[in
prep].Mid-water trawl cetacean bycatch
estimate.NOAA/NMFS/Northeast Fisheries
Science Center, 166 Water St., Woods Hole MA 02543.
Rago PJ, Wigley SE, Fogarty MJ. 2005. NEFSC
bycatch estimation methodology: allocation, precision, and accuracy. Northeast Fish Sci Cent Ref Doc. 05-09; p. 44.
Rossman M. [in
prep]. Bottom trawl fishery cetacean
bycatch estimates.NOAA NMFS Northeast
Fisheries Science Center, 166 Water St, Woods Hole MA 02543.
Rountree BP. 1997. Individual
Vessel Behavior in the Northeast Otter Trawl Fleet during 1982-92.NOAA Tech Memo NMFS NE 113; p. 50.
Stevenson D, Chiarella L, Stephan D,
Reid R, Wilhelm K, McCarthy J, Pentony M. 2004. Characterization of the fishing practices and marine benthic
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Footnotes
[1] Sources for these documents include the New England Fishery Management Council
(http://www.nefmc.org) and the Mid-Atlantic Fishery Management Council (http://www.mafmc.org).
[2] Rountree (1997) summarized vessel level data for the otter trawl fishery for 1982-1992,
prior to the availability of VTR data. Thus, her results are based on a
combination of the commercial fisheries data and port agent reports. In 1992, a
total of 1,012 vessels used otter trawl gear.
[3] Stevenson et al. (2004) used VTRs to map total days at sea (days absent) from
1995-2001 by 10-minute square. For the bottom otter trawl (fish) gear type,
activity was concentrated in the western part of the Gulf of Maine, along the
northwest edge of Georges Bank, east of Long Island, and along the shelf edge
south of Rhode Island and Massachusetts.
[4] Target species is defined by the vessel captain prior to a fishing trip and is
recorded in NMFS observer records. This differs from “main species” which is
based on some measure of actual landings (e.g., greatest landed weight).
[5] The bottom trawl analysis focused on those variables that were in both the observer
and VTR or permit records or could be determined from data within those records
(Rossman [in prep])
[6] Variables with an asterisk (*) are available in the VTR or permit databases or
can be derived from information within those databases (e.g. SST is derived
using date, latitude and longitude from VTR records).
[7] For example, regulated minimum mesh sizes may create a truncated distribution when
examined by species, and increases (decreases) in minimum mesh size may shift
the mean value up (down).
[8] If a vessel was using both a monkfish DAS and a multispecies DAS the mesh size must conform
to the multispecies minimum mesh size.
[9] The lobster fishery is an exception.
[10] FMP group was determined by summing landings for all species within a FMP (Appendix
A). If landings for a FMP group of species was greater than or equal to 50% of
landings, the trips was assigned to that FMP.
[11] From an economic perspective, it would be more reasonable to assume that the main
species was that with the largest contribution to trip revenues. Historically,
however, the bycatch analysis does not incorporate economic values, focusing
instead on physical features such as weight. For consistency the same method
was used in this study. This differs from target species, which is recorded in
the observer data based on a vessel captain’s intentions at the beginning of
the trip, but is not available for VTR records.
[12] Additional information on the climatology data source can be found at: http://podaac.jpl.nasa.gov/products/product111.html
[13] Additional information on the satellite data sources can be found at the
following links: AVHRR: http://podaac.jpl.nasa.gov/products/product216.html. MODIS Terra and
Aqua, see products 162 and 184 (http://podaac.jpl.nasa.gov/products/product162.html and http://podaac.jpl.nasa.gov/products/product184.html);
GOES, see product 190 (http://podaac.jpl.nasa.gov/products/product190.html).
[14] Bathymetry data was acquired from ETOPO Global 2’ Elevations CD, available from
the National Geophysical Data Center.
[15] There are also concerns about possible errors in the VTR depth data with regard to units.
[16] Source: http://www.econstats.com; accessed September 1, 2005. This is the same deflator used
in the annual Fisheries of the United States publication by NMFS.
[17] Information on the distribution of the individual species may be found in the
Essential Fish Habitat Source Documents, which are part of the NOAA Technical
Memorandum NMFS NE series. These documents are available through the NEFSC’s “EFH Source Documents: Life History
and Habitat Characteristics” web page (http://www.nefsc.noaa.gov/nefsc/habitat/efh/; accessed July 20, 2007).
[18] Footrope length is also referred to as “sweep length” and is an indication of
the width of the trawl opening.
Acronyms |
| ASMFC |
= |
Atlantic States Marine Fisheries Council |
| ATGTRT |
= |
Atlantic Trawl Gear Take Reduction Team |
| CA |
= |
closed area |
| CFDBS |
= |
Commercial Fisheries Dealer Database |
| CV |
= |
coefficient of variation |
| DAS |
= |
days at sea |
| EFH |
= |
essential fish habitat |
| FMA |
= |
fishery management area |
| FMP |
= |
fishery management plan |
| GB |
= |
Georges Bank |
| GOM |
= |
Gulf of Maine |
| GRT |
= |
gross registered tons |
| MA |
= |
Mid-Atlantic |
| MAFMC |
= |
Mid-Atlantic Fishery Management Council |
| NEFMC |
= |
New England Fishery Management Council |
| NERO |
= |
Northeast Regional Office |
| NMFS |
= |
National Marine Fisheries Service |
| NOAA |
= |
National Oceanic and Atmospheric Administration |
| NSNE |
= |
North Southern New England |
| OTF |
= |
otter trawl fish |
| OTM |
= |
otter trawl mid-water |
| OTO |
= |
otter trawl other |
| PTM |
= |
paired mid-water trawl |
| RMA |
= |
regulated mesh area |
| SNE |
= |
Southern New England |
| SSNE |
= |
South Southern New England |
| TAC |
= |
total allowable catch |
| TRC |
= |
take reduction plan |
| VHP |
= |
vessel horsepower |
| VTR |
= |
vessel trip report |
