OND99 Quarterly Rpt. sidebar
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(Quarterly Report for Jan-Feb-March 1998)
Essential
Fish Habitat Studies
A new provision of the
Magnuson-Stevens Fishery Conservation and Management Act of 1996 requires NMFS to
describe, identify, conserve, and enhance essential fish habitat (EFH). Currently, NMFS
lacks information needed to identify and describe EFH for several species of fish
that inhabit the North Pacific Ocean. For example, the EFH Technical Team for North
Pacific Groundfish designated the knowledge currently available on habitat requirements
for egg, larval, and juvenile stages of most groundfish species as insufficient to
determine species distributions or to describe the types of habitat where a species might
occur. Thus, basic life history information is needed to carry out the mandate of the Act
to identify and conserve EFH. Recently, NMFS headquarters allocated funding to its
different regional offices, and the EFH Core Team in each region determined the spending
plan for these funds. The ABL received funding for four studies, two of which will
begin in spring 1998.
The first project will study
nearshore habitat use by juvenile groundfish. An underwater video system will be
used in conjunction with traps, nets, and other gear to evaluate methods for capturing
juvenile groundfish in nearshore marine habitats as well as for characterizing structure
of that habitat. In following years, these methods could be used to characterize EFH
according to physical and biological parameters and to develop indices of relative
abundance of groundfish.
The second project will study urban
development-related effects on eelgrass habitat. The most significant consultation
activity of NMFS in Alaska concerns Clean Water Act Section 404 permits for filling
nearshore areas associated with urban development. Frequently, NMFS has recommended
to deny or modify 404 permits. Of primary concern are the effects of nearshore development
on eelgrass habitat, which is thought to be important rearing habitat for juvenile salmon
during their critical early-ocean period. The ramifications of
widespread approval of 404 permits could significantly impact the population levels
of anadromous salmonids. The focus of the EFH study is to 1) assess cumulative
effects of the 404 permitting program by inventorying existing eelgrass and areas already
filled in the vicinity of Craig, Alaska; 2) provide updated digital GIS (geographical
information systems) maps of existing eelgrass and other estuarine habitats near Craig;
and 3) determine the role of eelgrass and other estuarine habitats as essential fish
habitat for anadromous salmonids.
By Mike Murphy and Scott
Johnson.
Duck
Creek Salmon Habitat Restoration Project
The Duck Creek Salmon Habitat
Restoration Project is a community-based program designed to maintain and
restore salmon habitat in urban streams near Juneau, Alaska. Ongoing projects led by
ABL staff include evaluation and monitoring of existing habitat quality, evaluation
of restored salmon spawning habitat, and creation of a storm water treatment marsh.
In 1997, ABL staff received funding
from the NOAA Restoration Center to restore the channel and clean spawning gravel in a
300-m reach of Duck Creek, an impaired urban stream. Before restoration, salmon eggs that
had been placed in hatch boxes and buried in Duck Creek died almost immediately.
Mortality was attributed to large amounts of fine sediment and low dissolved oxygen
in the intergravel water. In February 1998 after restoration of the Duck Creek reach,
84 Whitlock-Vibert hatch boxes containing eyed coho salmon eggs and a standardized
substrate were buried in selected reaches of Duck, Jordan, Steep, and Vanderbilt creeks.
University students and community members are helping to monitor and gather samples
from the sites. Egg-to-fry survival will be compared over time and between streams.
As the boxes are removed from the streams, sediment retained in the hatch boxes and
spawning gravel in the immediate area are collected and sieved to compare survival with
substrate composition. Water samples are also taken periodically from each box and
measured for dissolved oxygen levels. The stages of the developing embryos or fry
when the boxes are removed will be compared to control groups incubating at the Auke Creek
Hatchery and also in aerated Duck Creek water.
Coho salmon eggs and fry incubated
in urban stream treatments in 1996 have been dissected and photographed with a digital
camera. The images are being downloaded into a digitizing program in which the
larvae yolk sac and length can be measured. The ratio of yolk sac to body length will be
used to compare the effects of various restoration methods on salmonid embryo development.
A 2-acre storm-water treatment marsh
designed by ABL staff is under construction in cooperation with local landowners and the
City and Borough of Juneau. Project staff expect that the marsh will filter storm
water and poor quality ground water, thereby improving water quality downstream of the
project and providing better rearing habitat for anadromous fish. Previously, the pond
provided little fish habitat because it intercepted ground water high in minerals, such as
iron and manganese and with almost no dissolved oxygen. The pond also contained many
urban pollutants from the storm water that was routed to it. Much of the pond has
now been filled to levels that will support marsh and aquatic vegetation. Sandy
material supplied from municipal construction projects makes up the bulk of the fill and
is topped with 6-12 inches of peat and organic soil. Over 1,000 starts of plants
such as sedges, horsetail, and marsh marigold have been gathered from local marshes and
planted in the constructed marsh.
By Mitch Lorenz.
Adaptive
Sampling of Rockfish in the Gulf of Alaska
AFSC scientists have relied heavily
on results of research trawl surveys to assess stock condition of rockfish (Sebastes
spp.) that live along the continental slope (slope rockfish). However, these surveys
are believed to be inadequate for estimating rockfish abundance. Biomass estimates
for rockfish often show large fluctuations from survey to survey, which do not seem
reasonable given the slow growth and low natural mortality rates of all Sebastes
species. Several factors may contribute to the surveys performance regarding
rockfish assessment. 1) The surveys are multispecies in design and attempt to determine
abundance of all groundfish species residing on the continental shelf and upper
continental slope, not just rockfish. Because of the large survey area necessary to
sample species residing on the shelf, relatively little sampling effort is directed toward
the habitat occupied by slope rockfish. 2) The standard survey net is designed for a
relatively smooth seafloor and cannot be fished at many of the rough-bottom
locations where rockfish are often found. 3) The surveys use a stratified random
methodology to select their pattern of trawl stations. This approach may be
inappropriate for many slope rockfish species that are known to have a highly clustered
distribution, such as Pacific ocean perch (Sebastes alutus).
In cooperation with the Juneau
Center, School of Fisheries and Ocean Sciences at the University of Alaska Fairbanks
(UAF), ABL scientists have initiated a 2-year study to evaluate a new survey method
specifically designed for slope rockfish. This study was selected for funding under the
Sea Grant-NOAA Partnership National Strategic Initiative competition. The study will
focus on three commercially important species of slope rockfish: Pacific ocean perch,
shortraker rockfish, and rougheye rockfish. The net used will be equipped with tire
gear to facilitate trawling over rough substrate, and a new survey design, adaptive
sampling, will be investigated. Scientists from the AFSCs ABL and Resource
Assessment and Conservation Engineering (RACE) and Resource Ecology and Fisheries
Management (REFM) Divisions are participating in the planning and field data collection
for this study. For the 1998 study, a chartered commercial trawling vessel will be used
for a period of 17 days in August in waters near Kodiak Island, Alaska.
Adaptive sampling is a relatively
new technique that has been rarely used in fisheries applications. However, this
sampling method appears to be particularly appropriate for populations with a clustered
distribution, such as that observed for Pacific ocean perch. An application of adaptive
sampling to larval fish populations by scientists at the Southwest Fisheries Science
Center resulted in increased survey precision as well as information about the dimension
of egg and larval patches. In adaptive sampling, random or systematic sampling is
initially used to locate concentrations of the targeted species and is then followed by
intensive sampling in the vicinity of the concentrations. A brief adaptive sampling
experiment for Pacific ocean perch was conducted in April 1996 using the NOAA ship
Miller
Freeman, and it indicated that adaptive sampling may have benefits over random
sampling in assessment surveys for rockfish. The 1998 study will be a follow-up to
the 1996 work but will be expanded in duration and area so that a comprehensive evaluation
of the adaptive sampling methodology can be made.
By Jon Heifetz and Dave Clausen.
ABL
Sablefish Tag Recovery Program
The sablefish tag recovery and
reward program continued during 1997. Data entry and production of tag reward
letters were streamlined further by the development of Oracle forms and reports more
suited to a UNIX environment. The database for sablefish tagged and released in Alaska
waters now contains 288,910 release records and 20,192 recovery records. The number
of recoveries per year (about 700 in 1997) continued to decline due to low numbers of tags
released since the final Japan-U.S. cooperative longline survey in 1994. Over 38% of
fish recovered in 1997 had been at liberty for more than 10 years, and five of those fish
had been out for more than 24 years. Tagging was resumed in 1997, with 3,847 adult
sablefish tagged and released during the annual longline survey.
Otoliths from 7 known-age sablefish
(i.e., fish tagged as juveniles) were recovered during 1997, bringing the total otolith
collection of these fish to 81. These otoliths will be used to evaluate ageing
criteria for sablefish. In another study, some tagged sablefish were injected with
oxytetracycline (OTC), a chemical which is taken up by bony tissues, including otoliths,
and leaves a distinctive mark. Otoliths from three more OTC-tagged fish were recovered
during 1997; in all, otoliths have been collected from 68 of the OTC-tagged fish.
Some OTC-marked otoliths have been collected in each of the 9 years since the
tagging was carried out. To date, most of these otoliths have not been examined.
By Nancy Maloney.
Early Marine
Growth Affects Interannual Variability in Production of Southeast Alaska Pink Salmon
Scales were collected from the
late-run adult pink salmon (Oncorhynchus gorbuscha) returning to the Auke Creek
weir in the northern region of Southeast Alaska from 1979 to 1996, and scale circuli
distances (C) were used as an index of body growth. Approximately 50 scales were selected
each year, and a Calcomp Digitizing Tablet was used to count circuli and measure distances
between circuli along an axis 20 degrees from the anterolateral line. Commercial
catch data were used to estimate Southeast Alaska pink salmon production (data provided by
the Alaska Department of Fish and Game). Spawning escapement data were excluded from
the estimate of production because escapement data are derived mostly from peak counts of
salmon in index spawning streams and the actual numbers of spawners are unknown.
We found differences in scale growth
between years of high and low production of Southeast Alaska pink salmon. The
largest difference in growth occurred at the earliest circuli (C), and the difference in
growth persisted through C8. Little difference in scale growth was observed between
years of high and low production levels from C8 to C15, which coincides with the scale
circuli associated with the supplmentary check typically found on pink salmon scales.
Scale growth was again higher during years of higher production from C18 to C19,
during the later coastal residency in pink salmon.
Year-to-year changes in early marine
scale growth (C1-C6) were highly correlated (p < 0.001) with production
(commercial catch) of pink salmon in Southeast Alaska. This association remained
significant even after differencing both time series to remove trends, and when early
marine scale growth was included in a spawner-recruit model. However, scale growth
during later coastal ocean residency (C15-C19) was not significantly correlated with
production. These findings are consistent with previous studies on chum salmon (O.
keta) that found that production was most significantly related to scale growth from
C2 to C4.
This relationship between growth and
production supports the concept that growth during the early marine life of Southeast
Alaska pink salmon may be particularly important in determining their survival to
adulthood. Changes in climate, therefore, might affect salmon production by
affecting growth and size-selective mortality, where the risk of predation for young
salmon is greater for slower growing and smaller individuals. Although, predation
during the residency of young pink salmon in coastal waters may be important, the size of
the salmon may not be as important in determining predation risk in coastal waters as it
is during early residency in the ocean.
By Jim Murphy.
Spring
Cruise of the NOAA Ship Miller Freeman Finds Ocean Chum and Sockeye Salmon
ABLs Ocean Carrying Capacity
(OCC) program used the Miller Freeman between 27 March and 3 April 1998 to 1)
collect oceanographic data for characterizing ocean conditions during the current el Niño
event, 2) evaluate the effectiveness of two midwater trawls in capturing Pacific salmon,
and 3) locate immature and maturing salmon in the Gulf of Alaska during early spring.
Temperature, salinity, and plankton data were collected along the Cape Chiniak
transect, a 60-nautical mile (nmi) transect beginning at Cape Chiniak, outside Kodiak,
and ending beyond the edge of the continental shelf. This transect is one of
several coastal monitoring transects established by OCC and Canadian high-seas salmon
researchers. Additional temperature and salinity data were at 60-nmi intervals as
the vessel moved south in search of salmon.
The principal goal of the cruise was
to look at the winter distribution of immature and maturing salmon in the Gulf of Alaska.
Two trawls were used: a Canadian rope trawl rigged to fish near the surface (headrope
depth of less than 20 m) and an Aleutian wing trawl that fished at depths from 20 m to the
deep scattering layer, which ranged from 320 to 390 m. The Canadian trawl was used
during the day, at dusk, and before sunrise; the Aleutian trawl was used both day and
night.
Repeated weather fronts restricted
the number of trawl samplings to 16 and limited the southward extent of the survey.
Overall, we captured 14 chum salmon and 7 sockeye salmon, all near the Jones,
Gibson, and Hecht seamount areas located about 288-360 nmi south southeast of Cape
Chiniak. The salmon were generally caught near the surface and appeared to be in
small and widely scattered schools.
One immature chum salmon with a fork
length (FL) of 265 mm and weight of 167 g was from the 1995 brood year. The
remaining chum salmon were maturing (eight were from the 1994 brood year and five
from the 1993 brood year); of these, lengths ranged from 570 to 612 mm (average 594 mm)
and weights ranged from 2.0 to 2.9 kg (average 2.4 kg). The brood years of the seven
sockeye were 1992 (two individuals), 1993 (one individual), 1994 (four individuals).
One of the 1992 brood year sockeye salmon had two freshwater annuli, and all of the
other sockeye had just one freshwater annulus each. Fork lengths were 426-547 mm
(average 504 mm), and weights were 0.9-1.9 kg (average 1.5 kg). Eight chum salmon
had from one to three newly formed circuli after the last annulus, and in six chum salmon
the annulus was in the process of forming with no new circuli present. All of the sockeye
salmon scales had from two to four circuli after the last annulus, indicating new spring
growth.
By Dick Haight.
Feeding
Interactions of Nearshore Forage Fish in Single-species and Multi-Species
Aggregations in Prince William Sound, Summer 1996
One component of the Alaska Predator
Ecosystem Experiment (APEX) investigates feeding competition among forage fish (food for
seabirds and marine mammals) in Prince William Sound (PWS), Alaska. Evidence for
competition among forage fish may help to explain changes in their populations and the
lack of recovery of predatory seabird populations affected by the Exxon Valdez oil
spill.
We compared the stomach contents of
juvenile herring, pink salmon, and sandlance to each other and to zooplankton samples
collected at the same time to investigate whether food habits were different when any of
these species occurred together compared to when they occurred alone. Sandlance and herring both ate smaller proportions of their principal prey
when they occurred together or with pink salmon, and the total amount of food eaten
decreased for all three species when they occurred with each other (Figure 1 below).
The feeding declines also may have been related to lower zooplankton abundance in
areas where these fish species occurred together. These changes suggest that
when fish interact in common feeding areas they individually eat less. If these
forage species regularly compete for food in areas where zooplankton are less available,
then seabird and mammal populations could continue to beaffected because fewer or smaller
forage fish would be available as food.
![abl.jpg (29560 bytes)](images/abl.jpg)
Figure 1. Decline in prey consumed by
juvenile pink salmon, herring, or sandlance occurring together compared to each species
occurring alone.
By Molly Sturdevant, Leland Hulbert,
and Audra Brase.
Feeding
Variation of Walleye Pollock and Pacific Herring in Prince William Sound, Fall 1994-95
The composition of forage fish in
PWS has changed dramatically since the early 1970s. Various monitoring studies have
observed that schooling forage fishes such as capelin, sandlance, and Pacific herring have
been in a decline, and demersal species such as walleye pollock and Pacific cod have been
increasing. This shift has been attributed to many stressing factors, such as an
increase in El Niño events leading to increased sea surface temperatures, a herring
virus, and the Exxon Valdez oil spill. While it is unclear which events
caused the shift, it is clear from catch data that the interaction of walleye pollock and
Pacific herring is increasing and therefore the potential for food competition has
increased as well. An APEX study has focused on determining 1) the effect the increased
interactions may have on walleye pollock and Pacific herring and 2) the effect these
changes in forage fish might have on the marine birds and mammals of PWS.
Forage fish and their prey were
collected from PWS in November 1994 and October 1995 with midwater trawls and vertical
plankton nets. The contents of the fish stomachs and the available food organisms
caught in the plankton nets were then examined in the laboratory to compare feeding
between single species and multispecies aggregations of walleye pollock and Pacific
herring. The conclusions of the study were that young-of the-year (YOY) walleye pollock
and YOY Pacific herring occur together during at least part of the year in PWS. They
consume similar prey, and they do not selectively feed upon dramatically different prey.
Therefore, these species may be in direct competition for food, which may result in one
species having a competitive advantage over the other. Walleye pollock have a lower
caloric value than herring. Thus, if pollock are able to take over a space in the food
chain previously occupied by herring, the marine birds and mammals dependent on these
forage fish may face a decline in food quality and may have to allocate more resources
towards foraging rather than breeding or brooding activities.
By Audra Brase, Molly Sturdevant,
and Leland Hulbert.
ABL Reference
Collection
Curator of the ABL reference
collections lent specimens of Gymnocanthus to the RACE Division for studies on Alaskan
sculpins and specimens of the black-spined sea star (Lethasterias
nanimensis) to
the British Columbia Royal Museum for studies on echinoderms of British Columbia and
Alaska. He also received 133 specimens of snailfish (Liparis spp.), that had
been on an extended loan to the Royal Museum, and he received from the NMFS
Enforcement Sitka Office the carapace of a Pacific Ridley turtle that had been found on a
beach near Ketchikan, Alaska in 1991. This is the first confirmed Pacific Ridley turtle
found in Alaska.
By Bruce Wing.
Seabird
Avoidance in Longline Fisheries
A draft of Test Plan to
Evaluate Effectiveness of Seabird Avoidance Measures Required in Alaskas
Hook-and-Line Groundfish Fisheries was prepared in late March by staff of the ABL,
the Protected Resources Division and Sustainable Fisheries Division, and the NMFS Alaska
Regional Office (RO). The plan consolidates an earlier plan drafted by the ABL and
RO with significant contributions by staff of the U.S. Fish and Wildlife Service
(USFWS), International Pacific Halibut Commission, and Washington Sea Grant Program.
The Food and Agricultural
Organization (FAO) of the United Nations, Japan, and the United States have agreed to
organize an FAO consultation on incidental catch of seabirds in longline fisheries to be
held in Rome, Italy, in October-November 1998. In preparation for the FAO consultation,
the Seabird Technical Working Group (STWG) was established and is preparing three
background papers which 1) describe the pelagic and demersal longline fisheries (areas,
catches, technology and fishing effort), 2) review the incidental catch of seabird in
specific longline fisheries, and 3) review seabird bycatch mitigation measures and their
effect on other marine species. Mike Sigler prepared a description of longline fisheries
for groundfish in Alaska for the first report. The principal author of this report is
Svein Lokkeborg, Institute of Marine Resources, Norway.
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