JFM 2001 Quarterly Rpt. sidebar
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(Quarterly
Report for Jan-Feb-Mar 2001)
Mussel
Population Response to Decline in Predation
Intensity After Exxon Valdez Oil Spill
Auke Bay Laboratory (ABL) personnel assessed the
relative importance of direct effects of the Exxon
Valdez oil spill in Prince William Sound,
Alaska, and indirect effects of the spill (resulting
from a reduction in predation pressure) on mussel, Mytilus
trossulus, populations. They compared the mussel
population structure 7-8 years after the spill on
Knight Island, where the shore was heavily oiled and
where sea otter numbers were greatly reduced, with
mussel population structure along the northwestern
shore of Montague Island (unoiled), where sea otters
were unaffected by the spill. Mussel populations
were sampled on 1,076 transects in May, June, and
July 1996 and 1997 at the two islands.
The density of all mussels ($5
mm in shell length) at Knight Island exceeded that
at Montague Island in both years of our study, but
the majority of mussels at Knight Island were small,
having recruited to the population in the previous
1-2 yrs. The length-frequency and biomass (ash-free
dry mass (AFDW)) distributions of the mussels at the
oiled location were strongly skewed to the right in
both years. The mean density and biomass of
mussels greater than or equal to 20 mm in shell
length did not differ significantly between study
areas in 1996 but was higher at the unoiled beaches
than at the oiled beaches in 1997. The density
of mussels less than or equal to 40 mm (the size
range preferentially consumed by sea otters) was
very low at both study areas. The density did not
differ between study areas in 1996, but in 1997 was
greater at the unoiled locations than at oiled
beaches. The mean biomass density of mussels greater
than or equal to 40 mm at Knight Island slightly
exceeded that at Montague Island in 1996, but it was
less than 1/6 that at Montague Island in 1997.
The results indicate that a decrease in sea otter
predation on Knight Island after the Exxon Valdez
oil spill did not result in an increase in the
abundance of large mussels there 7-8 yrs after the
spill as would be predicted if sea otters controlled
the size-structure of mussels in Prince William
Sound. There is no evidence that the direct effects
of oil on the mussel population on the oiled beaches
of Knight Island extended beyond 1995. The
mean density of Nucella lima on oiled beaches
exceeded that on unoiled beaches by 2.4 times in
1996 and by 6.6 times in 1997, and the mean density
of N. lamellosa on oiled beaches exceeded
that on unoiled beaches by 80 times in 1996 and by
over 350 times in 1997. Estimates from laboratory
feeding rate studies on N. lima and N.
lamellosa of the total consumption of Mytilus
by Nucella in our study areas were less than
or equal to 0.3% and about 4% of the total mussel
population in the study areas at Montague Island and
Knight Island, respectively. The level of predation
of Nucella on Mytilus at Knight Island
may have contributed to the creation of a bottleneck
in the supply of large mussels in the population
despite the release of the large mussels from sea
otter predation at Knight Island in the 7-8 yrs
after the oil spill.
By Charles O’Clair
Evaluation of Oil in the
Intertidal Zone of Prince William Sound From the Exxon
Valdez Oil Spill
Members of the ABL Exxon Valdez Oil Spill
group have initiated a program to provide a
quantitative estimate of the amount of shoreline
(length, area, sediment, and volume) that remains
contaminated following the March 1989 Exxon
Valdez oil spill. Oil from the spill has been
surprisingly persistent on some beaches. At
the end of the 1992 cleanup season, natural
processes were expected to disperse most of the oil
remaining on shorelines. However, relatively
unweathered oil remains at several locations that
were heavily oiled initially and protected from
dispersion by storm-generated waves. The
extent of the remaining oil is unknown. This
uncertainty has caused public and scientific
concerns about the potential effects the oil may
have on humans and on fauna exposed to the oil
directly or indirectly.
A stratified random sample of shoreline will be
intensively sampled in summer 2001 for surface and
subsurface oil to estimate length of oiled
shoreline, area and volume of oiled sediment, and
volume of oil. Approximately 8 km will be
sampled by digging more than 8,000 pits to discover
and quantify subsurface oil. This estimate
will provide information for any assessment of the
significance of the amount of oil remaining and will
be the basis for further management.
By Mandy Lindeberg.
Effects of Hydraulic
Pumping on Shock Resistance of Pink Salmon Eggs
Good estimates of the survival of salmon eggs in
gravel require accurate discrimination between live
and dead eggs. Dead eggs must not be confused with
eggs mechanically damaged (shocked) by pumping.
To determine the effect of hydraulic pumping
on the shock resistance of eggs over time, pink
salmon (Oncorhynchus gorbuscha) eggs were
pumped from the gravel of the intertidal section of
Lovers Cove Creek, southeastern Alaska, six times
between 27 September and 15 November 2000. Resistance
to shock increased from less than 5% to greater than
95% over the sampling period. We simulated egg
pumping in a stream by pumping known-age pink salmon
eggs from a barrel of stream gravel. Resistance
to shock for the hatchery eggs increased similarly
to that of the eggs in the stream, decreasing from
0% to 92.5% from 1 day to 28 days after
fertilization.
Misclassification of live eggs as dead was rare in
the field because eggs pumped from the stream were
removed from water within 5 minutes of pumping, a
procedure that arrested the color change from pink
to white in shocked eggs. When describing the
condition of eggs in a stream, we recommend that the
condition be described before the effect of
hydraulic pumping on the eggs occurs; thus, shocked
eggs and live eggs should be combined into a single
“live” category, and dead eggs should only
include those that were dead before sampling began.
This philosophy differs from that of some
other researchers, who combined shocked eggs and
dead eggs into a single “dead” category and
reported greater egg death in streams sampled when
eggs are immature than when sampled after the eyed
stage is reached. Our modified method can
alleviate discrimination of egg condition problems
posed by differing egg maturity within and between
streams and over time.
By John Thedinga.
Summary of 2000-2001 Winter
Conditions at Auke Bay
Although there was a brief cold snap in mid-March,
the Auke Bay 2000-2001 winter was milder than
average. Air temperatures were 1.5EC
to 2.8EC
above average. Sea surface temperatures were
generally 1EC
to 2EC
above average through January and February and
slightly below average in March. Precipitation
total for January through March was 32.66 cm, a bit
higher than the average of 30.96 cm. Snowfall
was far below average, with a January-March total of
only 58.8 cm compared to the average of 145.0 cm.
Auke Lake froze over about 14 December 2000,
about 10-14 days later than average. The lake
was open from 23 January 2001 through 15 February
2001. Heavy wet snow in mid-February led to
the lake refreezing until it opened again on 6
April, 10-14 days earlier than average.
By Bruce Wing.
Unusual Invertebrates Added
to ABL Reference Collection
Seventy-one specimens of corals and coral-like
animals were received from the ADF&G Mandatory
Observer Program in February. The specimens
were collected during the golden king crab winter
fisheries in the Aleutian Islands region. The
collection includes one species of sponge, one
species of bryozoan, 11 species of hydrocorals, and
16 species of octocorals. Three hydrocoral
specimens, two Errinopora sp. and a Stylaster
sp., are of undescribed species seen in earlier
collections. Another Errinopora sp. and a Stylaster
sp. may also be an undescribed species. Also
in the collection is a Stenohela sp., a genus
of hydrocoral not previously reported from the North
Pacific Ocean. Among the octocorals were specimens
of three gorgonian genera which have not been
previously recorded in Alaska.
A small collection of Pleistocene mollusks,
bryozoans, and crustaceans was received from Dr.
Anne Pasch, Department of Geology, University of
Alaska Anchorage. It was collected from
deposits uncovered by the Bering Glacier outwash.
The deposits have been dated using C-14 data
at 10,000 years before present. With the exception
of one species of snail, all species are known to be
presently living in near-shore waters of the Gulf of
Alaska and Prince William Sound. One
exceptional specimen is a single Leucosyrnix
kincaidi Dall, 1919. This is the second
specimen ever collected of this species, the first
of which was taken from deep water in Shelikof
Strait by Dall. Although the specimen is badly
eroded, it fits Dall’s description and
illustration.
By Bruce Wing.
Development of
Bering-Aleutian Salmon International Survey
Staff from the ABL Ocean Carrying Capacity program
in conjunction with Kate Myers of the
University of Washington, developed an international
cooperative research initiative, the Bering-Aleutian
Salmon International Survey (BASIS). The
initiative was presented 20 March 2001 to the
Research Planning and Coordination Meeting of the
North Pacific Anadromous Fish Commission (NPAFC) and
was well received by national participants.
The scientific concepts behind the BASIS plan are
simple, but the results should greatly enhance our
understanding of salmon in the Bering Sea. The
plan calls for four synoptic 1-month seasonal
(spring, summer, fall, winter) surveys per year.
The survey area consists of 95 sampling
stations spaced at regular intervals across the
Bering Sea: from the Aleutian Islands north to
64°N, and from the Alaskan to Russian coasts.
Sampling would consist of surface trawls to
capture salmon of all ages, CTD (conductivity-
temperature-depth) casts, plankton tows, and
continuous sampling of ocean conditions (e.g.,
salinity, temperature). Ongoing, long-term
research by Japan in the Bering Sea would also be an
integral part of the sampling effort. Coordination
of sampling from Russian vessels within the Russian
Exclusive Economic Zone (EEZ), U.S. vessels within
the U.S. EEZ, Japanese vessels, and other
countries’ vessels within international waters
would be through the NPAFC.
The plan also calls for in-depth biological and
stock identification analyses to determine growth
and life-history characteristics of regional stock
groups. The stock identification analyses
would be based on genetic, parasite, scale, otolith,
and tag data, and would require review and
enhancement of existing baselines. The BASIS
plan is designed to complement long-term climate,
ocean, and ecosystem monitoring and research
activities by other international organizations such
as the North Pacific Marine Science Organization and
GLOBEC and will yield the first ever synoptic
seasonal information on distribution, abundance, and
stock origins of all species, age, and maturity
groups of salmon in the Bering Sea - information
vital to the fishing industry, fishery managers,
conservation organizations, policy makers, and
others faced with declines in key salmon
populations.
By Steve Ignell.
NPAFC Bulletin Published
The second NPAFC Bulletin entitled “Recent Changes
in Ocean Production of Pacific Salmon” was
published in March 2001. The bulletin
comprises 39 papers given at the NPAFC symposium
held in Juneau, Alaska, on 1-2 November 1999.
Symposium topics were 1) physical and biological
factors affecting ocean production of Pacific
salmon; 2) detection of trends, patterns, and
changes in historical salmon and environmental data;
3) forecasts and models of Pacific salmon dynamics;
and 4) new research methods and techniques in ocean
salmon research. ABL scientists contributing
to the papers were Jack Helle, Don Mortensen, Dick
Carlson, Bruce Wing, Noele Weemes, Michele Masuda,
Chuck Guthrie, Dean Courtney, Ellen Martinson, Ed
Farley, Jim Murphy, Joe Orsi, Mary Auburn-Cook, and
Steve Ignell.
The bulletin is dedicated to Dick Carlson of ABL’s
Ocean Carrying Capacity (OCC) program who passed
away in July 1999.
Seasonality of Prey
Availability in Regions of Contrasting Steller Sea
Lion Abundance Trends
The ABL began research in March 2001 to test the
hypothesis that sea lion prey diversity and
seasonality are related to Steller sea lion
population trends. One hypothesis is that the
decline in the western population of Steller sea
lions may be due to decreased prey availability.
This decrease may be exacerbated by fishery
removals of prey in sea lion habitat. Area-specific
diet diversity and population change of Steller sea
lions also appear to be related, with faster
declines in areas of lower diet diversity (Merrick
et al. 1997). Steller sea lions also may
switch diet seasonally, as different prey become
more available. The purpose of this set of
studies is to test the hypothesis that sea lion prey
diversity and seasonality are related to Steller sea
lion population trends. Our approach is to
measure Steller sea lion prey, prey quality (free
fatty acid analysis), and predator abundance and
fishery removals near selected rookeries and
haulouts, emphasizing seasonal measurements
conducted during critical life stages of Steller sea
lions. Two regional trend areas, southeastern
Alaska and the Kodiak Island area, are being
compared. Study haulouts and rookeries were
selected based on year-round accessibility. Simultaneous
sampling of sea lion abundance, distribution, and
diet (scats) is being done in cooperation with other
researchers. In southeastern Alaska, ABL is
cooperating with the ADF&G, the University of
Alaska, and the North Pacific Universities Marine
Mammal Research Consortium. This study also is being
coordinated with existing University of Alaska
studies on Kodiak Island.
By Mike Sigler
Rockfish Age-structured
Modeling Workshop
A rockfish (Sebastes spp.) modeling workshop
was held at the ABL 20-22 February 2001. The
workshop was attended by stock assessment scientists
from the Center’s REFM Division and from the ABL.
The goal of the workshop was to implement a
common model framework for a number of different
rockfish populations managed by NMFS. A simple
age-structured model (with allowance for size
composition data) was agreed upon as a base model
and constructed with AD Model Builder Software.
The base model was applied to the following
Gulf of Alaska stocks: Pacific ocean perch (POP),
northern rockfish, dusky rockfish, and rougheye
rockfish. Additionally, the model was applied
to the Aleutian Islands and eastern Bering Sea POP
stock and may be applied to the POP stock off the
coast of Washington and Oregon. Because each
stock has particular differences in fishery, survey,
and biology, features were added to the base model
to account for additional data types and special
fishery characteristics. The base models will
be tuned by individual stock assessment scientists
to particular stocks, and the patterns of
information will be compared among the stocks for
the specific common model. The base model will
also be evaluated for sensitivity to assumptions for
the different stocks. Results will be
summarized in a NOAA technical publication.
By Dean Courtney and Jim Ianelli.
2001 Sablefish Longline Survey
The precruise meeting for the 2001 sablefish
longline survey was held 23 March. The meeting
covered topics including vessel operations and
safety; specific sampling protocols, gear, and
special requests, staffing, and survey schedule.
The survey will begin sampling in the Bering
Sea on 2 June and complete the last station in the
Gulf of Alaska 3 September. Eighty-nine
regular stations and three seamounts will be fished,
and a 2-day hooking experiment will be conducted
during the survey. Approximately 130 sablefish will
be tagged and released with internal electronic
tags.
Young-of-the-Year
Sablefish Age and Growth in the Gulf of Alaska
Experiments were conducted to validate the daily
periodicity of otolith increment deposition in
young-of-the-year (YOY) sablefish. The validity of
daily increment formation was tested by chemically
marking the otoliths of YOY sablefish held in
captivity at the ABL. Approximately 30 YOY sablefish
were captured along the continental shelf by NMFS
staff from the Oregon Hatfield Marine Science Center
and returned alive to the ABL on 1 June 2000. The
fish were maintained in seawater tanks at the ABL
for up to 104 days. The water temperature was
elevated and held at a constant 13EC,
and the photo period was lengthened and held at a
constant 16 hrs of light per day. The fish
were split into three groups of roughly equal size.
The otoliths of the fish in each group were
marked twice by immersing the live fish in seawater
with elevated levels of strontium chloride (SrCl2).
For each group, the strontium immersions were
separated by a period of approximately 15 days. The
first group was marked twice in June, the second was
marked twice in July, and the third was marked twice
in August. The fish from each group were
sacrificed approximately 15 days after the second
strontium immersion. The otoliths of marked
fish are being processed into thin sections, and the
strontium markers will be detected with electron
scanning microscopy by staff at the University of
Alaska Fairbanks. For each processed otolith,
the number of micro-increments (alternating light
and dark bands visible under a transmitted-light
compound microscope) between detected strontium
bands will be counted and compared to the number of
days between SrCl2
immersions.
By Dean Courtney.
Young-of-the-Year
Sablefish Abundance, Growth, and Diet in the Gulf of
Alaska
ABL scientists synthesized basic life history
information on YOY sablefish abundance, growth, and
diet to determine whether forecasting year class
abundance based on YOY surveys was practical. Surface
gillnet surveys were conducted annually during the
sablefish longline survey from 1995 to 1999 along
the seaward edge of the continental shelf of Alaska.
Sablefish made up about one-third of the catch
and were caught mostly in the central and eastern
Gulf of Alaska. Growth averaged 1.2 mm per
day. The mean date the first otolith increment
formed, 30 April, implied an average spawning date
of 30 March. Diet was mainly euphausiids.
Growth rate tended to be higher in years when
gillnet catches were higher, but no relationship was
apparent between diet and gillnet catches. Data
for the synthesis was drawn from work conducted in
recent years by AFSC staff. Much of this work
was presented at the Western Groundfish Conference,
held 24-28 April 2000 in Sitka, Alaska. The
results are detailed in a manuscript accepted for
publication by the Alaska Fishery Research Bulletin.
By Dean Courtney.
Otolith Marking and Pink
and Chum Salmon Workshops
Two workshops were held at the University of
Washington on 21-23 March. The first, held on
March 21, was the North Pacific Anadromous Fish
Commission’s (NPAFC) Workshop on Salmonid Otolith
Marking. The workshop was well attended by
scientists from Russia, Japan, Canada and the United
States with several outstanding talks on the
relatively new technology of mass marking juvenile
hatchery salmon otoliths. Otolith marking of
hatchery salmonids is providing a powerful research
tool that is bringing Pacific Rim salmon scientists
together into a cooperative spirit of joint
participation and mutual involvement.
Peter Hagen, Alaska Department of Fish and Game
(ADF&G), and Hiko Urawa, National Salmon
Research Institute of Japan, were principal co-chair
coordinators of the workshop. Eric Volk,
Washington Department of Fish and Wildlife, who is
considered by many as the chief innovator for
otolith marking of Pacific salmon, gave a keynote
overview and history of this technology. Joe
Orsi and Jack Helle from the Auke Bay Laboratory
(ABL) presented papers at the workshop. Orsi’s
paper, coauthored with Don Mortensen of ABL and Dian
Tersteeg and Ric Focht of Douglas Island Pink and
Chum, Inc., a local nonprofit hatchery based in
Juneau, was titled “Early Marine Growth and
Habitat Utilization of Two Major Alaska Chum Salmon
Stocks, Based on Otolith Marks”. Helle’s
talk was “Variations in Proportions of Thermally
Marked Hatchery Pink and Chum Salmon Juveniles in
the Gulf of Alaska, 1996-1998", coauthored with
Ed Farley of ABL and Peter Hagen.
The second workshop was the 20th Biennial Northeast
Pacific Pink and Chum Salmon Workshop held 21-23
March, also at the University of Washington. At this
workshop, Bill Heard from ABL gave the keynote
address “Then, Now, and What Next?” about
pink and chum salmon resources, past, present, and
future research on these fishes, and the workshops
that have focused on them. Alex Wertheimer of ABL
gave a paper, coauthored with Bill Smoker, Tim
Joyce, and Bill Heard on “Hatchery Pink
Salmon in Prince William Sound: Enhancement or
Displacement?” Poster presentations from ABL
were submitted by Joe Orsi, Don Mortensen, Mark
Carls, John Thedinga, Molly Sturdevant, and Mike
Sigler. Auke Bay contractors from the ABL
Ocean Carrying Capacity Program also made oral and
poster presentations at the workshop. Jack
Helle gave the wrap-up talk at the workshop on
“Highlights and Observations of Forty Years of
Workshops.” Holding the two workshops at the
same time allowed major participation by Japanese
and Russian scientists in both workshops.
By Bill Heard.
University of Washington
Oceanographic Seaglider
At a January meeting of the Global Ocean Ecosystem
Dynamics (GLOBEC), Northeast Pacific Coastal Gulf of
Alaska Program, University of Washington
oceanographers gave a preview of the new Seaglider
sampling device they are developing. The
Seaglider is a self propelled, non-tethered vessel
for physical, chemical, and some biological
oceanographic sampling. It is a low watt, low
cost vessel that can sample a large number of
parameters while cruising at depths up to 300 m for
weeks at a time. The vessel, roughly
1.5 m in length can be programmed to sample at
multiple depths, and its position is determined by a
sliding battery pack that tips the glider in an up
or down position. Negative or positive
buoyancy is shifted by slight changes in the
location of oil in a fore-aft reservoir-bladder
system. When the glider is programmed to
return to the surface, a satellite or cell phone
transmitting antenna and GPS receiver is activated
for uploading data or for retrieval by a surface
vessel.
By Bill Heard.
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