JAS 1999 Quarterly Rpt. sidebar
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(Quarterly Report for Jul-Aug-Sep 1999)
SOCIOECONOMIC
ASSESSMENTS
Economists with the AFSCs Socioeconomic
Asessment Program assisted in preparing the NMFS Fishing Capacity Task Force draft report,
which was presented to the NMFS Science Board and participated in a fishing capacity
training session held at Headquarters in Silver Spring, Maryland, in late September.
The NMFS Fishing Capacity Task Force has recommended data envelopment analysis (DEA)
and stochastic frontier (SF) production functions as two of the primary quantitative
methods of estimating technical fishing capacity. Program staff were instrumental in
identifying four critical issues with respect to assessing the use of these two methods to
estimate fishing capacity:
The circumstances for which it is
appropriate to include efficiency as a component of capacity and the difficulty of doing
so when inputs are heterogeneous.
The ability of these methods to provide
estimates of technical capacity.
Their ability to deal with noisy data.
The usefulness of the concept of technical
capacity for fishery management purposes.
Although both methods can be used to estimate
a production frontier that can in turn be used to estimate a type of capacity of
individual vessels and fleets, their underlying assumptions and method of solving for the
frontier are quite different. One substantial difference is how each model handles noisy
data. An understanding of the implications of this difference is important because random
variation is likely to exist in commercial fishery data.
Dan Holland and Todd Lee have completed the
initial phase of a research project that explores the impacts of noisy data on fishing
capacity estimates made with DEA and SF. Their research uses Monte Carlo simulations to
investigate possible finite sample biases attributable to this type of noisy data.
The results of this research suggest that DEA may give highly biased results, and
the bias increases as either the sample size or level of noise increases. The SF method is
also shown to give biased estimates, but the average bias tends to be much smaller than
that found with DEA. However, the simulations demonstrate that the bias of SF estimates
can be bimodal when the sample size is small or the level of noise in the data
is large; thus, possibly leading to a high occurrence of under- or
overestimates of fishing capacity. Although these results are based on models that predict
efficient output as opposed to maximum potential output for a given capital stock, they
can be expected to carry over to estimates of technical capacity that assume full
utilization of variable inputs. The results of this study should not be interpreted
as an indication of the general superiority of either DEA or SF. While DEA may
confound noise with inefficiency, SF may confound inefficiency with specification error.
Other factors that this study does not address may impact the relative performance
of the two methods.
Lee and Holland have prepared a paper on this
research titled, The Impact of Noisy Catch Data on Estimates of Fishing Capacity
Derived From DEA and Stochastic Frontier Models: A Monte Carlo Comparison
which will be submitted to Marine Resource Economics (MRE). A working paper
detailing some additional work with DEA models that is not discussed in the MRE paper has
also been prepared. Additional research along similar lines is planned. This
new research will focus on using SF and DEA models to estimate technical capacity with
unconstrained use of variable inputs. Lee and Holland also plan to investigate the
factors that lead to negative and positive bias in SF capacity estimates and test the
robustness of alternative distributional assumptions used with the SF model.
By Joe Terry.
STATUS OF STOCKS
AND MULTISPECIES ASSESSMENTS
Evaluation of
Catch Sampling Methods
The Groundfish Forum (a fishing industry
association) and the AFSC collaborated in research to examine species composition and
length frequency sampling methods used by at-sea observers. The research was conducted
under an experimental fishing permit approved by the North Pacific Fishery Management
Council and NMFS in June 1999. Fieldwork was completed in the Bering Sea aboard the
factory trawler American No. 1 between 5 and 23 September 1999. John Gauvin
and John Henderschedt of Groundfish Forum coordinated the fieldwork with assistance from
Craig Rose (RACE Division) and Sarah Gaichas (REFM Division). The experimental
design called for removing six 100-kg subsamples from each of 60 commercial sized (10-12
metric ton) trawl catches, as well as accounting for all production and discards by
species group for each haul. The length frequency sampling portion of the experiment
required deck sorting of halibut to minimize mortality as well as collecting 120 length
samples at specified intervals throughout each haul. The excellent work and
cooperation of the vessels captain, Mike Peterson, factory foreman, Young Ho Chu,
and the entire crew made this labor-intensive experiment a success in the field.
Data analysis will continue throughout fall 1999, and a full report is expected by
February 2000.
By Sarah Gaichas.
Pilot Study
of CPUE Variability for Atka Mackerel
Members of the RACE and REFM Divisions, NMML,
and the Office of Fisheries Information Systems designed, organized, and participated in a
preliminary pilot study of small-scale Atka mackerel distribution and abundances in the
Aleutian Islands region. The study was initiated because of concerns regarding the
efficacy of trawl exclusion zones around Steller sea lion rookeries and haulouts to
maintain prey populations for the endangered Steller sea lion. The pilot study is just one
of several recent collaborative efforts within the Center requiring the collection of
disparate types of data necessary to manage fisheries to reduce Steller sea lion/fishery
interactions.
Data collected during the study will be used
to design a larger-scale experiment for detecting the effects of fishing on prey
distributions and the efficacy of trawl exclusion zones. Trawl exclusion zones were
established around sea lion rookeries as a precautionary measure to protect critical
sea lion habitat, including local populations of such prey as Atka mackerel.
Localized fishing may affect Atka mackerel abundance and distribution near sea lion
rookeries. The larger project is intended to assess such effects. To this end, AFSC
scientists are considering two types of fishery-independent methods to measure changes in
abundance and distribution of Atka mackerel:
Bottom trawl surveys before and after a
fishery. Potential impact of the fishery will be judged by the change in catch per
unit effort (CPUE) where effort is the area swept by the trawl.
Mark and recapture (tagging) experiments to
estimate abundance and movement between areas open and closed to the Atka mackerel
fishery.
This pilot study will help determine design
parameters and feasibility for these two methods. Trawl CPUEs may provide an
adequate index of change in abundance. The preliminary study tested survey
strategies appropriate for estimating change in CPUE. The data collected will be
used to estimate within-station and between-station variances and assess the sample size
required for the larger experiment to detect effects of the local fishery on Atka mackerel
abundance near sea lion rookeries.
Initial research on the feasibility of
tagging Atka mackerel and on mortality of tagged fish was also conducted as part of this
study. The initial tagging work will allow us to estimate tagging mortality, daily tagging
production, and methodologies for tagging aboard a commercial vessel. Results from
this work will help determine the feasibility and design of future mark-recapture research
for estimating abundance and movement of Atka mackerel between areas open and closed to
the commercial fishery.
The vessel factory trawler Seafreeze Alaska, owned and operated by U.S. Seafoods LP, was chartered for 16 days to conduct
Atka mackerel research in the vicinity of Seguam Pass in the Aleutian Islands region.
The charter began on 4 August in Dutch Harbor and ended in the same port on 19
August.
A total of 40 randomly-selected stations
spread amongst the three strata were sampled twice. This constituted the 40 paired
stations for CPUE variance determination. In addition, four stations (two within the
buffer zone and two outside of it) were sampled every 3-4 hours over a 24-36 hour period
to determine diel variations in Atka mackerel abundance at defined locations related to
tides, light, and current. A total of 140 hauls were taken during the 12 days of trawl
operations from 6 to 17 August.
A total of approximately 2,500 tagged Atka
mackerel were released during the cruise. Most of the fish (approximately 1,700)
were tagged and released opportunistically during trawl operations during 6-17 August.
About 10% of the tagged fish were double tagged to estimate tag shedding rates.
During the last 12 hours on station, all time was devoted to tagging.
Approximately 800 mackerel were tagged and released in the area currently open to
the fishery.
The B-season Atka mackerel fishery began on 1
September and was closed on 8 September 1999 when the total allowable catch (TAC) was
reached. During the fishery, six tagged Atka mackerel were caught by the fishing
vessel SeaFisher during operations south of Seguam Island. Four of the tags
were recovered, while two tags were observed by the processing crew but not subsequently
recovered. The four tagged fish recovered were each released outside the trawl
exclusion zone and recaptured 4-7 nmi away from their release point; each was recaptured
15-22 days after release.
The tagging mortality experiment was
conducted during the 12 days of trawl operations 6-17 August. Twenty fish were
placed in each of four tanks; 10 of the fish were tagged (2 double-tagged) and 10 were
untagged. By the end of the 12-day experiment, only three fish had died, one
untagged fish and two tagged fish, resulting in a 97.5% survival rate for untagged fish
and 95% survival rate for tagged fish. Observations of internal injuries and
scale/skin loss suggest that the three fish died not from the tagging procedure, but the
effects of initial trawl capture. On 17 August, all untagged fish in the experiment
were tagged and released, along with all tagged fish.
By Lowell Fritz.
OSCURS Update
The Ocean Surface Current Simulations
(OSCURS) model is available to the public on a Live Access Server via the REFM
Divisions webpages at http://www.afsc.noaa.gov/refm/docs/oscurs/default.htm. The
interactive numerical model allows users to pick their own input by: clicking a
start-point on the graphic chart of the North Pacific Ocean and Bering Sea; selecting any
start-day from January 1980 to July 1999; and selecting a duration (the number of days to
drift). Based on the input, the model generates a chart that appears in about 20 seconds
showing the vectors of daily movement strung together in a trajectory that gives the net
drift trajectory from the start-point.
Development of OSCURS was motivated by the
need in fisheries research for indices that describe variability in ocean surface
currents. These synthetic data, derived through empirical modeling and calibration,
provide insight that far exceeds their accuracy limitations. OSCURS daily surface
current vector fields are computed using empirical functions on a 90-km oceanwide grid
based on daily sea level pressures (1946-97). In addition, long-term mean
geostrophic currents have been incorporated. The model was tuned to reproduce
trajectories of satellite-tracked drifters with shallow drogues from the eastern North
Pacific.
The internet application provides two options
for generating output; 1) a color chart of the North Pacific Ocean and Bering Sea with the
trajectory in red; or 2) an ASCII data file of daily latitude-longitudes of surface water
movement. Trajectories replicate satellite drifter movements quite well on
time-scales of a few months. Up to 1-year-long trajectories can be produced, but
their absolute accuracy diminishes with time. Currently, trajectories after July
1999 simply use the long-term mean pressure fields (but this will be updated as new
pressure field data become available).
Repeating the runs from the same location in
different years can give a time series of surface current patterns. This serves as
one of the main purposes of OSCURS for comparison with fisheries data.
Our most recent experiment compares 90-day
drift starting 1 March from Unimak Pass each year from 1970 to 1999 with year- class
strength of walleye pollock. There is some indication that on-shelf,
northeastward drift of eggs and larvae after spawning favors greater recruitment, whereas
weak or northward drift does not.
By Jim Ingraham and Jim Ianelli.
RESOURCE ECOLOGY
AND ECOSYSTEMS MODELING
Activities
and Research Results
Stomachs collected totaled 6,430 for the
eastern Bering Sea and 3,040 for the Gulf of Alaska. Laboratory analysis was performed on
1,157 groundfish stomachs from the eastern Bering Sea and 1,236 from the Aleutian Islands
region. Three observers returned with 159 stomach samples collected from the eastern
Bering Sea.
Diet Overlap of
Some West Coast Groundfish
The stomach contents of several species of
groundfish were collected off California, Oregon, Washington, and British Columbia during
standard NMFS surveys in 1989, 1991, and 1992. Details of the analysis of our
findings from these samples were recently published in Buckley et al. (1999). One
part of the analysis was the estimation of the amount of diet overlap (calculated from
diet composition in terms of weight) among the groundfish species that were sampled.
Pacific whiting (Merluccius productus), arrowtooth flounder (Atheresthes
stomias) and juvenile sablefish (Anoplopoma fimbria) consumed mostly
euphausiids and other euphausiid consumers. Adult sablefish, shortspine thornyhead
(Sebastolobus alascanus), longspine thornyhead (S. altivelis), Pacific grenadier
(Coryphaenoides acrolepis) and giant grenadier (Albatrossia
pectoralis) were omnivorous,
preying on a wide variety of fishes, crustaceans and other invertebrates, and scavenging
on offal. Most of the prey were benthic or epibenthic. Two small-mouthed
flatfishes, Dover sole (Microstomus pacificus) and deepsea sole (Embassichthys
bathybius), consumed mainly polychaete worms and brittle stars. Spatial trends
in main prey categories consumed by these groundfish species are also shown in the report.
Diets of Groundfish
in the Gulf of Alaska in 1990, 1993, and 1996.
A total of 13,928 stomachs from 13 species
were analyzed to describe the food habits of the major groundfish species in the Gulf of
Alaska in 1990, 1993, and 1996. The analysis emphasized predation on commercially
important fish, crab, and shrimp.
Arrowtooth flounder, Pacific halibut,
sablefish, Pacific cod, and pollock were the main predators that consumed fish. The
main predators that fed on Tanner crabs were Pacific halibut and Pacific cod.
Pollock, shortspine thornyhead, shortraker rockfish, flathead sole, and rougheye
rockfish were the main consumers of pandalid shrimp. Pacific ocean perch, northern
rockfish, dusky rockfish, and Atka mackerel fed mainly on zooplankton such as euphausiids
and calanoid copepods.
Figure 1. Percent weight of dominant prey items
in the diet of major groundfish species in the Gulf of Alaska in summer of 1990, 1993, and
1996.
(prey key: pan = pandalid shrimp, cap = capelin, plk =
pollock)
A significant finding was the degree of predation on pandalid shrimp, capelin,
and pollock by the dominant groundfish species in the Gulf of Alaska (Figure 1 above).
Pollock were the dominant prey fish every year and were consumed mainly by
arrowtooth flounder, Pacific halibut, sablefish, and Pacific cod. Pollock
cannibalism, which accounted for only 2% of the diet by weight in 1990 and 1% in 1993,
increased to 10% in 1996. Other forage fish such as Pacific herring, capelin,
eulachon, Pacific sand lance, and Atka mackerel can be categorized as the next most
important prey fishes in the diet of groundfish. All predators sampled, except
northern rockfish and Atka mackerel, preyed on pandalid shrimp.
Multispecies
Forecasting of the Effects of Fishing
For several years, the groundfish
plan teams of the North Pacific Fishery Management Council have expressed specific
ecosystem concerns with regard to the effects of fishing on species composition. In
particular, the plan teams have noted that large differences exist in the harvest rates of
groundfish species off Alaska. Some groundfish (such as walleye pollock, cod,
sablefish, and rockfish) are harvested at or close to the recommended allowable biological
catch level while other species (such as some flatfish) are harvested at substantially
lower levels. The plan team has requested analysis of the long-term implications of
disproportionate harvest rates.
In order to address this concern, we
have used results from a multispecies virtual population analysis (MSVPA) model for the
eastern Bering Sea, which has been updated to reflect information from the 1998 stock
assessments. The outputs from the MSVPA model have been used to forecast the
possible long-term multispecies effects of harvesting groundfish.
A system of eight species was
defined for the eastern Bering Sea and modeled in the multispecies VPA and the resulting
multispecies forecast. Four species played the role of both predator and prey
including walleye pollock, Pacific cod (Gadus macrocephalus), Greenland turbot
(Reinhardtius
hippoglossoides) and yellowfin sole (Pleuronectes asper). Rock sole
(Lepidopsetta bilineata) and Pacific herring (Clupea harengus
pallasi) were considered only
as prey. Finally, arrowtooth flounder (Atheresthes stomias) and northern fur
seal (Callorhinus ursinus) were considered other predators. Other
predators are considered external predators within the MSVPA because their populations are
not estimated within the MSVPA; instead, they are provided externally from other sources.
For the forecasting of eastern Bering Sea, it was assumed that the northern fur seal
population remained constant. For arrowtooth flounder, we followed the same assumptions on
recruitment and fishing mortality as the rest of the species. Figure 2 below shows
the biomass flow for the system defined for the eastern Bering Sea.
Figure 2. Biomass flow of the
system defined for the eastern Bering Sea.
Deterministic multispecies and
single species forecast models were set up to analyze and contrast the equilibrium
dynamics of the system under three regimes of fishing mortality. The first regime
evaluates the status quo removal rates of groundfish (Fref - calculated as the
average of the last 3 years (1996-98) of the fishing mortality estimates from the MSVPA
models). The second fishing regime examined the effects of fishing at rates that produced
the allowable biological catch levels recommended in the 1998 stock assessments
(FABC).
The final scenario examined the effects of no fishing on the multispecies complex.
Long-term equilibrium forecasts of these scenarios were made using a multispecies
model that took predation interactions into account and single species models that did not
include predation interactions. Results from the multispecies and single species
forecasts predict almost the same trends for the relative changes of yield biomass, total
biomass, and spawning biomass under the FABC regime relative to the Fref
case with the exception of rock sole. For rock sole, the multispecies model predicts a
larger increase in yield and a smaller decrease in total biomass than predicted by the
single species forecast, with the difference presumably caused by predation interactions
(particularly with cod) not taken into account in the single species model.
Under the no-fishing regime, much
larger differences were seen in biomass levels relative to the Fref case in the
single species forecasts than in the multispecies forecasts. The single species
forecasts predicted much larger increases in total biomass of groundfish populations under
a no-fishing regime than in the multispecies no-fishing regime, which included predation
interactions. Although a simple assumption of constant recruitment was implemented,
the multispecies forecasting model provided valuable information on the possible
consequences of fishing regimes and highlighted the importance of including predation. In
the future, more realistic assumptions on recruitment will be added to the model.
By Pat Livingston.
NORTH
PACIFIC GROUNDFISH OBSERVER PROGRAM
During the third quarter of 1999,
241 observers were trained, briefed, and equipped for deployment to fishing and processing
vessels and shoreside plants in the Gulf of Alaska, Bering Sea, and Aleutian Islands
region. They sampled aboard 227 fishing and processing vessels and at 16 shoreside
processing plants. These observers were trained or briefed in various locations.
The AFSC Observer Program in Seattle trained 51 first-time observers and briefed 45
observers who had prior experience, while the University of Alaska Anchorage (UAA)
Observer Training Center briefed 85 observers and trained another 32 first-time observers.
At the Observer Programs field offices in Dutch Harbor and Kodiak, 14 more observers
were briefed and 14 were excused from briefing because they had just completed a cruise
successfully and were returning immediately to the field. The third quarter 1999
observer workforce thus comprised 34% new observers and 66% experienced observers.
The Observer Program conducted a
total of 72 debriefings during the third quarter of 1999. Three debriefings were
held in Dutch Harbor, 18 in Anchorage, and 51 were held in Seattle. No debriefings
are conducted at the UAA.
During the third quarter of 1999,
implementation of an expanded Community Development Quota (CDQ) program and implementation
of provisions of the recently enacted American Fisheries Act (AFA) continued. The
CDQ program was developed for the purpose of allocating fishery resources to eligible
Western Alaska communities to provide the means for starting or supporting commercial
fishery activities that would result in ongoing regionally-based, commercial fishery or
related businesses. The program was initiated in 1992 with walleye pollock and
expanded to include fixed-gear halibut and sablefish in 1995. In 1998, it was
further expanded to include multiple species (MS) of groundfish and crab (MSCDQ). As
of 1999, NMFS is responsible for monitoring the groundfish (including pollock and
sablefish) and halibut CDQs, and the state of Alaska is responsible for monitoring crab
CDQs.
The AFA, enacted by Congress in late
1998, made changes to the pollock fishery in the Bering Sea and Aleutian Islands.
These changes included reallocation of fish among industry segments, provided for
the formation of fishing cooperatives, and increased observer coverage levels on some
components of the fleet. The offshore component of the fleet organized a fishing
cooperative this year and has been receiving increased, mandatory observer coverage.
More recently, the Observer Program has been involved in implementation of aspects
of the AFA related to shoreside pollock. The shoreside component has proven to be
more complex than the offshore component and will involve possible NMFS regulatory actions
and a changing role for the observer.
MSCDQ and AFA catch accounting for
offshore processors is based entirely on data collected by observers and, unlike the open
access fisheries where observer data is used to manage a fleetwide quota, industry
participants in the MSCDQ and AFA fisheries require individual accounting of fish
harvested in each haul or set. This change has required great effort on the part of the
Observer Program to develop special selection criteria and training requirements for
observers, develop new sampling strategies and regulations to enhance the observers
working environment, and implement changes to the data collection and data management
software systems.
An extensive, independent review of
the Observer Program began during the third quarter of 1999. The review is being
carried out by Marine Resources Assessment Group (MRAG) Americas, Inc., an independent
consulting firm, which provides professional advice and services for the management of
marine fisheries throughout the world. Their final report is due sometime next year.
By Bob Maier.
AGE AND
GROWTH PROGRAM
Flathead
sole |
99 |
Rock
sole |
50 |
Rex
sole |
236 |
Alaska
plaice |
419 |
Northern
rock sole |
1,004 |
Yellowfin
sole |
1,257 |
Arrowtooth
flounder |
870 |
Walleye
pollock |
8,908 |
Sablefish |
1,194 |
Atka
mackerel |
245 |
Pacific
whiting |
4,402 |
Pacific
ocean perch |
1,126 |
Northern
rockfish |
514 |
Production figures from 1
January to 30 September 1999 are shown to the right. Total production figures were 20,324
with 7,278 test ages and 190 examined and determined to be unageable.
By Dan Kimura.
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