JAS 2000 Quarterly Rpt. sidebar
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(Quarterly
Report for Jul-Aug-Sep 2000)
Distribution
and Habitat of Rockfish in Nearshore Waters of
Southeast Alaska
From 1998 to 2000, a remotely operated vehicle (ROV)
was used to record in situ observations of juvenile
and adult rockfish (Sebastes spp.) in
nearshore waters (<90 m deep) of Southeast
Alaska; 210 ROV dives were completed at 37 sites.
Habitat types sampled included eelgrass
meadows, kelp beds, vertical bedrock walls,
soft-bottom basins, and complex bottoms of boulder
or rock. Of the 32 species of rockfish found
in the Gulf of Alaska, 13 species were observed in
this study. Most observations of rockfish were
at sites closer to the outer coast. Quillback
rockfish (S. maliger) were observed at more
sites than any other rockfish species, whereas China
rockfish were observed at only one site. Most
observations (>70%) of rockfish were in complex
and vertical wall habitats with numerous ledges,
holes, and crevices for cover. No rockfish
were observed over soft bottoms with no relief.
Black, copper, and unidentified juvenile
rockfish were commonly observed in or near
vegetation (e.g., eelgrass). Median depth of
observations ranged from 16 m for black rockfish (S.
melanops) to 62 m for rosethorn rockfish (S.
helvomaculatus). Information from this
study will help managers identify and protect
essential fish habitat. This is especially
important because nearshore habitats are susceptible
to impacts from shoreline development.
By Scott Johnson.
Residence, Diet, Growth, And Condition of
Juvenile Rockfish in Subtidal Vegetated Habitats of
Southeast Alaska
A 2-year study on juvenile rockfish was completed in
September 2000. In summer 1999, movement of age-1
copper rockfish (S. caurinus) and quillback
rockfish was investigated in Sitka Sound, Alaska, to
determine residence time in eelgrass and kelp
habitats (Habitat
Areas of Particular Concern). Results from a
mark-recapture experiment in the first year of the
study showed that juvenile rockfish move into
shallow eelgrass and kelp habitats in May and remain
in the same local area through late summer.
In summer 2000, growth and diet of age-1 copper and
quillback rockfish within two small semi-enclosed
bays sampled in 1999 were investigated by
mark-recapture methods. Eelgrass and understory kelp
sites from each bay were sampled with a beach seine
monthly from May to September 2000. Fish were marked
with injected elastomer tags to distinguish month
and site and with sequential coded wire tags (CWT)
to obtain unique identification. A total of 4,636
juvenile rockfish were captured, of which 2,969 were
tagged, and 720 were recaptured. In addition,
64 age-2+ copper, quillback, and brown rockfish were
recaptured from fish marked the previous year, 72%
of which were recaptured at the same site where they
were tagged. Growth rates will be compared
between the two habitat types. Also, fish were
collected for diet description and diel sampling to
calculate diet ration within each habitat.
By Scott Johnson.
Study of Spot Shrimp Decline in Prince William
Sound
The goal of the ABL’s Prince William Sound (PWS)
spot shrimp (Pandalus platyceros) project
is to determine the extent to which spot
shrimp abundance in western PWS has recovered since
the population decline which began just prior to
1989. Our objectives in FY2000 were:
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to estimate the abundance of
spot shrimp at 12 sites in western PWS
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to determine the sex and size
composition of spot shrimp at the study sites
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to estimate spot shrimp
fecundity and relative number of egg-bearing
females at the study sites
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to compare abundance data and
data on population structure obtained for this
project with that collected by the Alaska
Department of Fish and Game (ADF&G).
We accomplished
these objectives by sampling six sites traditionally
included in ADF&G’s annual survey using a
methodology similar to ADF&G’s. In addition,
we added six new sites selected during a preliminary
cruise in August 1999. We sampled spot shrimp using
two strings of 11 pots each at each site in October
1999. Our methods differed from those of ADF&G
only in the type of pot used. We used a conical pot
identical to that used by ADF&G in southeastern
Alaska. In PWS ADF&G uses a rectangular pot.
In a side-by-side comparison of the conical and
rectangular pots we found the rectangular pot to be
less effective than the conical pot in catching spot
shrimp. However, our pot was somewhat smaller and
had larger mesh openings in the entrance tunnels.
Subsequent comparison of our data with a summary of
ADF&G’s data at the same sites also collected
in October 1999 revealed no significant difference
between our estimate of the number of spot shrimp
per pot or weight of the shrimp catch per pot and
that of ADF&G. Nevertheless, in the interest of
standardization within the ADF&G as a whole, we
recommended that the ADF&G in Cordova change to
the conical pot as soon as resources become
available to do so. Statistical comparison of the
summarized ADF&G annual survey data from 1998
and 1999 provided to us by ADF&G revealed no
significant increase in the number of spot shrimp
per station or weight of the shrimp catch per
station between 1998 and 1999. Although examination
of the mean values for these variables appeared to
suggest that population recovery may have been
starting in 1999, we do not have the evidence to
indicate an increase in spot shrimp abundance
between 1998 and 1999. We found no significant
differences between ADF&G’s traditional six
sites and our six new sites in October 1999 for
several variables related to the spot shrimp
populations at those sites including: mean number of
spot shrimp per pot, mean weight of spot shrimp per
pot, mean carapace length of males, transitional
shrimp and females, and fecundity. This suggests
that our 6 new sites could be added to the
traditional sites of ADF&G to form a suite of 12
or more sites from which 6 sites could be randomly
chosen for the ADF&G annual survey, thereby
precluding statistical difficulties from lack of
independence that follows from sampling the same
sites each year.
Our estimates of spot shrimp fecundity were
frequently substantially higher than previously
published estimates for the ADF&G traditional
sites from 1989 to1991. We were unable to test the
difference between those estimates and ours because
we lacked the raw data on fecundity used to
calculate the ADF&G estimates. If the
differences were real, they may represent true
interannual differences in the mean fecundity of the
shrimp populations at these sites suggesting that
spot shrimp fecundity may be an important variable
to monitor on a periodic basis.
By Chuck O’Clair.
Examination of Lipid Class and Fatty Acid
Composition of Northern Fur Seals from St. Paul
Island
Lipid and fatty acid analyses provide a basis for
evaluating the nutritional condition of animals by
measuring the relative concentration of
triacylglycerides (TAG). This is a direct index of
the amount of surplus energy stored as lipid in
animal tissues as a result of diet. Otariids
are likely to be especially amenable to these
analyses because their blubber is easily sampled,
metabolically active, and is an important site for
fat storage. Of particular interest is the
northern fur seal (Callorhinus ursinus),
which has been suffering recent population declines
posited to result from changes in the nutritional
quality of their prey. Consequently, lipid class and
fatty acid analysis may offer significant advantages
over existing biased or invasive methods for
examining diet content and quality in these mammals.
However, for blubber to be useful in the
analysis of the nutritional well-being of these
marine mammals, the homogeneity of lipid and fatty
acids must be assessed between specific sites on the
body, as well as between metabolically active
proximate blubber layers and relatively inert distal
layers.
Blubber samples for lipid class and fatty acid
analysis were taken by the National Marine Mammal
Laboratory (NMML) from 3 female and 16 male northern
fur seals harvested on St. Paul Island, Alaska in
1997. Samples were collected from locations
near the neck, shoulder, and pelvis from each seal.
The blubbers were divided longitudinally, and one of
the resulting sections was further divided
latitudinally to provide an inner, outer, and
complete section of blubber from each body location,
for a total of 164 samples. The nonpolar lipid and
fatty acid composition of each sample was evaluated
at the ABL by high performance liquid chromatography
and mass spectrometry, after which ANOVA was used to
compare the nonpolar lipid content and principal
components analysis (PCA) to compare fatty acid
compositions. Comparisons were drawn between samples
to determine if fatty acid and nonpolar lipid
content differed among body locations, blubber
layers, sexes, and individuals.
Nonpolar lipid content varied widely among
individuals ranging from 148 to 1,189 mg/g blubber.
Nonpolar lipid content also varied between the sexes
primarily as a result of the inclusion of a
primiparous female in the data set. Within
individuals, body locations also differed in
nonpolar lipid content, but no body location was
consistently greater than the others. Blubber layers
did not differ in nonpolar lipid content. Comparison
of individuals and sexes revealed large
differences in the 29 fatty acids analyzed. PCA
models could not reliably distinguish differences in
the fatty acid composition of blubber in different
body locations or blubber layers. These data
indicate that individual differences in blubber
fatty acids are a driving feature in the overall
variation of blubber fatty acid composition.
Future sample collections of blubber from fur
seals can be taken from any body location, but that
location should be consistent from individual to
individual. Future studies in cooperation with
the NMML will utilize results presented here to
examine differences in the lipid class and fatty
acid composition of two distinct populations of
northern fur seals, and compare those compositions
to that of potential prey.
By Johanna Vollenweider.
Decomposing Salmon Carcasses are Important
Nutrition Source for Juvenile Salmon
Returning adult salmon are known to represent an
important source of nitrogen and phosphorous to
their natal streams. The arrival of these nutrients
results in increased productivity at lower trophic
levels because the organisms can rapidly assimilate
the nutrients. However, decaying carcasses
also contain macromolecules such as essential fatty
acids, which can be of vital importance to resident
fishes. Top level predators may obtain the
macromolecules by consuming the flesh of decaying
adults or by consuming other scavengers. Consequently,
the annual arrival of adult salmon may have a
quantitative impact on the nutritional status of
resident fish populations. This is likely to be seen
as changes in the amount of stored lipids which are
called triacylglycerides (TAG). In addition, the
composition of the TAG should represent a more
marine signature if the bulk of the stored lipids
are derived from decaying adults.
In a cooperative study with the U.S. Forest
Service, ABL scientists tested these hypotheses by
constructing simulated coho salmon (Oncorhynchus
kisutch) streams, loading them with various
amounts of pink salmon carcasses and, after 60 days,
evaluating the lipid class and fatty acid
composition of resident coho salmon. Carcass
loads in the streams ranged from 0 to 4 carcasses
per square meter. The TAG concentrations in coho
salmon increased with carcass load from 0.78 mg/g
lipid in unloaded streams to 28.9 mg/g in the most
heavily loaded streams. Increases in TAG
resulted from the storage of marine-
derived Omega-3 fatty acids. Juveniles from unloaded
streams averaged one tenth the Omega-3 fatty acid
content of coho salmon from the most heavily loaded
streams. Coho salmon are unable to synthesize
Omega-3 fatty acids but depend on them for
maintaining cell membrane integrity and
osmoregulation during smolting. Thus,
overwinter survival and smolting success of resident
juveniles are influenced by the availability of
these compounds as provided by the biomass of
returning adults.
By Ron Heintz.
Hatchery Pink Salmon in Prince William Sound:
Enhancement or Displacement?
Total pink salmon (O. gorbuscha) production
in Prince William Sound (PWS) is currently at
historic highs; catches over the past decade have
averaged 27.0 million fish annually. Over 85%
of this production is from a system of large
hatcheries. The hatcheries are considered by
some to be a tremendous success; protection of
the hatcheries from oil contamination was one of the
highest priorities in the response to the Exxon
Valdez oil spill in 1989. However, there has
also been concern that hatchery production may have
been deleterious to wild pink salmon in PWS,
complicating the achievement of escapement goals and
reducing productivity. A recent analysis
published in Transactions of the American Fisheries
Society asserts that hatcheries have caused a
decline in the productivity and escapements of wild
pink salmon and that hatchery fish to a large degree
have replaced, not enhanced, pink salmon returns in
PWS, resulting in an average net gain of only 2.0
million pink salmon annually.
The ABL, in collaboration with the University of
Alaska and ADF&G, prepared an alternative
analysis of the changes in pink salmon production in
PWS. By comparing catches from historical and
current peak production regimes, they showed that
numbers of pink salmon in PWS have increased to a
much greater degree than in three other regions of
Alaska: Southeast Alaska, Kodiak, and south Alaska
Peninsula. They did find that wild stock
abundance has declined over a time period in which
wild stock abundances have generally increased in
other regions; hatchery interactions were a possible
contributing factor to this asynchronous decline.
However, they also found asynchrony in
previous increases and declines of wild stock
production in PWS relative to other regions, which
may indicate that other biophysical changes
concurrent with increased hatchery production have
caused density-independent decline in wild stock
productivity in the recent past. Based on
these temporal comparisons, they estimated that
average net gain in catch of pink salmon in PWS due
to hatcheries has been 17.5-23.7 million fish for
the decade of the 1990s. They showed that the
estimates of net gain of only 2.0 million pink
salmon were based on a model that produces highly
unrealistic estimates of wild stock production
potential. They also found that management
resolution for meeting escapement goal ranges has
improved in PWS and is the likely explanation for
the decline in wild stock escapements from a time
period when escapements were chronically above the
escapement goal range, to a time period when
escapements were generally closer to or within the
management range.
By Alex Wertheimer.
Ocean Survival of Wild Coho Salmon
Research at ABL's Auke Creek hatchery and weir is
conducted to evaluate the long-term ocean survival
of wild coho salmon. While ocean survival of
coho salmon throughout much of its southern range
has declined in Southeast Alaska over the
previous three decades, including the Auke Creek
stock, survivals have been in an increasing trend
since at least 1980.
Coho salmon studies at Auke Creek are conducted
under a long-term cooperative project between the
ABL and ADF&G. The Auke Creek coho salmon
stock is one of four wild stocks used as index
systems in Southeast Alaska.. Ocean survival
rates of wild coho salmon at Auke Creek are known
from 1977, when CWTs were first used on smolts
leaving Auke Creek, through 2000, except 1979 (Figure
1). The research at Auke Creek relies
heavily on the permanent fish weir and includes the
annual capture and tagging of seaward-migrant smolts
and capture and enumeration of fish returning
to the creek. Auke Creek is the only index
site where all smolts are captured and marked.
Ocean survival of each smolt cohort is
estimated by summing the fishery harvest of adults
and the number adults that return to the weir.
Fishery harvest is estimated by the ADF&G from
the number of tagged fish recovered during rigorous
sampling of the commercial and sport fisheries.
Although the 2000 coho returns to some areas of
Southeast Alaska were depressed, the ocean survival
of Auke Creek coho was close to the long-term
average of 19%. The ocean survival of the 1999
smolts that returned as adults in 2000 from Auke
Creek was 17 %. The harvest of about 250 coho
in the fishery accounted for a 5% return of smolts,
and the return of 623 coho to the weir represented
12% of the smolts. Scales and size data on the
fish returning to Auke Creek are being collected and
archived. A major retrospective analysis using
the data on scale growth patterns and ocean survival
is being planned. We propose to use data
on Auke Creek coho salmon adults and past and
proposed coastal sampling studies to retrospectively
examine ocean growth and survival. We will
compare interannual marine growth, as reflected in
adult scales, to document the range of scale growth
patterns, and compare theses patterns with marine
survival, smolt-to-adult, for coho salmon at Auke
Creek.
By Jerry Taylor.
Hook Spacing Studies
A sablefish (Anoplopoma fimbria) hook spacing
experiment was conducted in the Gulf of Alaska off
Yakutat Bay 25-26 July 2000 aboard the fishing
vessel Alaskan Leader. Four hook spacings of
0.5, 1, 2, and 4 m were tested using standard survey
longline gear. Results were consistent with two
previous hook spacing experiments conducted by ABL
scientists; catch per hook increased as hook spacing
increased. These data are being used to
improve an equation for standardizing catch rate
differences associated with hook spacing. This
relationship is being used to standardize the catch
rates of commercial longline vessels, and the
standardized rates will be included in the sablefish
stock assessment.
By Chris Lunsford.
Seamounts
NMFS exploratory trawl and trap fishing on nine Gulf
of Alaska seamounts in June and July 1979 found that
sablefish were the dominant finfish on each of the
seamounts. Of the sablefish sampled, nearly
all were ripe, spawning, or recently spent, and
there was a total absence of younger, immature fish,
indicating that the populations of sablefish on
seamounts are maintained by the migration of mature
fish from the continental slope rather than by local
recruitment. Tagged fish released at different areas
of the slope have been recovered on Gulf of Alaska
seamounts, verifying that slope to seamount
migration does occur. It is not known if
emigration from the seamounts or exchange between
seamounts occurs.
Seamount sampling during the annual sablefish
longline survey was initiated in 1999 and continued
in 2000. During the 1999 survey, Giacomini,
Surveyor, and Pratt seamounts were sampled. A
total of 2,400 sablefish were caught. About
800 fish were tagged and released, and otoliths were
taken from 140 fish. Length, sex, and maturity
were recorded for almost all sablefish caught.
During the 2000 longline survey, we revisited
Surveyor and Pratt seamounts and fished Welker
seamount for the first time. Catches were down
slightly from 1999 at Surveyor seamount and about
the same as last year at Pratt. A total of 930
fish were tagged and released from the three
seamounts. Otoliths and length and sex data
were collected as in 1999. Seven tagged fish
were recovered from the same seamounts where they
were released last year, and one tagged fish,
released off Kodiak in 1989, was recovered on Welker
Seamount. Seamount sampling will continue on
the 2001 annual longline survey.
By Nancy Maloney.
Rockfish and Sablefish Stock Assessment
Survey data from the 2000 longline survey have been
processed and incorporation of results into
assessment models are in the preliminary stages.
Work was done to improve the new
age-structured model for northern rockfish, first
previewed at last year’s Groundfish Plan Team
meeting; the model will be finalized in October.
Longline survey data also will be incorporated into
an assessment model for shortraker (Sebastes
borealis) and rougheye (S. aleutianus)
rockfish, and we are developing a preliminary
assessment model for dusky rockfish.
By Jeff Fujioka.
Alaska Longline Survey Completed
The AFSC completed the twenty-second annual
longline survey of the upper continental slope of
the Gulf of Alaska and eastern Aleutian Islands
region on 5 September 2000. One
hundred-forty-eight longline hauls (sets) were
completed. Sablefish was the most
frequently caught species, followed by giant
grenadiers (Albatrossia pectoralis), Pacific
cod (Gadus macrocephalus), arrowtooth
flounder (Atheresthes stomias), and Pacific
halibut (Hippoglossus stenolepis). A
total of 76,351 sablefish were taken during the
survey. A total of 3,098 sablefish, 492
shortspine thornyhead (Sebastolobus alascanus),
and 37 Greenland turbot (Reinhardtius
hippoglossoides) were tagged and released during
the survey. Length-weight data and otoliths
were collected from 2,079 sablefish. Twenty-seven
surface gillnet sets were completed to assess the
abundance of juvenile sablefish. A low number
of sablefish (138 young-of-the year) were caught in
the small mesh gillnets during the 2000 survey.
Killer whales preying on sablefish and
Greenland turbot retrieved on the gear were observed
at one Aleutian Islands station and one Gulf of
Alaska station.
By Mike Sigler.
Rockfish Genetics
Genetic samples of Pacific ocean perch were
collected from the Aleutian Islands region and the
Bering Sea during AFSC trawl surveys to examine the
population structure of Pacific ocean perch
throughout Alaska. An additional study in
under way to examine the potential for a genetic
basis underlying the different color morphs of
rougheye rockfish. Genetic samples of rougheye
rockfish were collected during the 2000 longline
survey. Both light and dark color morphs and
intermediates have been observed, and two quite
different genetic forms have been identified, often
in the same catches. The large genetic differences
suggest the possibility of two species. These
studies are being done under sponsorship of the
AFSC's Rockfish Working Group in cooperation with
the University of Alaska Fairbanks, Juneau Center
School of Fisheries and Ocean Sciences .
By Jon Heifetz.
Growth and Recruitment of Shallow-water Alaskan
Gorgonian
At least 20 species of gorgonian corals inhabit
Alaskan waters. Specimens of all but one species
have been incidentally entangled in fishing gear
(e.g., hook and line, longlines, trawls, crab pots,
and fish traps) and detached from the seafloor.
Several species attain large size and provide
essential habitat in the form of structure and
refuge for species of demersal fishes and
invertebrates. The effects of coral habitat
alteration on benthic communities are unknown but
may be substantial due to the reported longevity and
slow growth rates of cold-water corals. The
North Pacific Fishery Management Council is
considering measures to establish several marine
protected areas where gorgonian corals are abundant.
We examined growth and recruitment of a
shallow-water Alaskan gorgonian (Calcigorgia
spiculifera) in an effort to elucidate the
effects of fishing activities on coral habitat. We
used computer image analysis tools to measure the
linear length of colony branches from digitized
video images collected on tagged specimens in situ.
Length of a branch was measured along the
medial axis from the point opposite its origin.
This method provides a permanent record of
colony morphometry. Highly accurate
measurements are possible with proper colony
orientation with respect to the calibration grid and
parallel alignment of the camera lens with the grid.
Thirty five colonies were tagged at two sites in
July 1999. We relocated 32 (91%) of those
colonies in July 2000. The missing colonies
were presumably detached from the seafloor. Growth
measurements were possible for 16 colonies. Growth
rate was variable for branches from the same colony
and also between colonies. Mean branch growth
rate at both sites ranged from -1.82 to 14.83 mm
yr-1. Growth rates (mean = 5.81 mm yr-1, SD =
4.99) measured during this study were generally much
lower than those reported for other gorgonians
worldwide, including (Primnoa sp.), a
deep-water Alaskan species. Recruitment of new
colonies had not occurred at either study site for a
minimum of several years.
The slow growth rates measured during the first year
of this study, although preliminary, are noteworthy
since shallow-water corals are widely believed to
have faster growth rates and shorter life spans than
deep-water corals. Additionally, recruitment
appears to be a rare, sporadic event. Shallow-water
gorgonian communities may therefore exhibit slow
recovery rates from seafloor perturbations. Our
future research priorities are to focus on growth of
smaller colonies and to establish a third study site
where colonies are more numerous and more variable
in size (i.e., age).
By Robert Stone.
First International Deep Sea Corals Symposium
Robert Stone and Ken Krieger attended The First
International Symposium on Deep Sea Corals held 30
July to 3 August 2000 at Halifax, Nova Scotia,
Canada. Robert presented a poster titled
"Growth and Recruitment of an Alaskan
Shallow-water Gorgonian" and a paper for Jon
Heifetz titled "Coral in Alaska: Distribution,
abundance, and species associations." Ken
Krieger presented a paper titled "Observations
of megafauna that associate with Primnoa spp. and
damage to Primnoa by bottom fishing."
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