(Quarterly Report for Jul-Aug-Sept 1998)
Adaptive Sampling of Rockfishes in the Gulf of Alaska
A cooperative study by the Auke Bay Laboratory (ABL) and the Juneau Center for Fisheries and Ocean Science (JCFOS) of the University of Alaska Fairbanks (UAF) was conducted 5-21 August 1998 aboard the chartered fishing vessel Unimak Enterprise to investigate a new sampling design, adaptive sampling, for slope rockfish (Sebastes spp.). Data were also collected to help determine sampling protocols for the National Marine Fisheries Service (NMFS) fishery observer programs. This was the first year of a 2-year Sea Grant Partnership Grant to the UAF-JCFOS .
Presently, NMFS scientists rely on results from bottom trawl surveys that use stratified random sampling to determine estimates of abundance (biomass) for various groundfish species. Random sampling, however, is believed to do a poor job of estimating abundance of species that aggregate in localized areas. Biomass estimates for rockfish often show large fluctuations from survey to survey that do not seem reasonable, given the slow growth and low natural mortality rates of all Sebastes species. Adaptive sampling is a relatively new technique that, to date, has seldom been used in fisheries applications. It appears to be particularly appropriate, though, for sampling populations with a clustered distribution, such as that observed for many rockfish species. In adaptive sampling, random or systematic sampling is initially used to locate concentrations of the targeted species; then, the area in the vicinity of the concentrations is intensively sampled.
The study focused on three commercially important species of slope rockfish: Pacific ocean perch (S. alutus, also known as POP), shortraker rockfish (S. borealis), and rougheye rockfish (S. aleutianus). The survey net used was equipped with tire gear to facilitate trawling over rough substrate. The vessel was allowed to retain the catch to defray some of the costs of the charter. Ten days were devoted to trawling in POP habitat, followed by 3 days trawling in deeper water where shortraker and rougheye rockfish are more common. The experiment was conducted at two study areas in the central Gulf of Alaska in the vicinity of Portlock Bank, northeast of Kodiak Island. The POP study area was further divided into four subareas, or strata, based on habitat. The shortraker and rougheye rockfish study area was divided into two strata. In each stratum, an initial random sample of 12-15 bottom trawl tows of 15-minute duration was conducted. After the initial sample was taken, the adaptive sampling plan was implemented. The initial stations subjected to adaptive sampling were those with the two or three highest catches in each stratum. Depending on the stratum, either a cross pattern (up, down, left, right) or a linear pattern around the selected initial tows was used for adaptive sampling. A distance of 0.1 nautical mile (nmi) was maintained between all tows in the adaptive phase to avoid depletion effects on catches. A stopping rule was imposed to limit the amount of adaptive sampling.
Of the 121 stations sampled in the POP study area, 45 stations were sampled during the random phase, and 76 stations were sampled during the adaptive phase. Of the 64 stations sampled in the shortraker and rougheye rockfish study area, 37 stations were sampled during the random phase, and 27 stations were sampled during the adaptive phase. Preliminary examination of the data indicates that adaptive sampling may be particularly well suited for POP. During the random sampling phase of the experiment, catch rates of POP were highly variable, and consistently high catches of POP occurred in the vicinity of the stations chosen for adaptive sampling.
By Jon Heifetz and Dave Clausen.
Sablefish Longline Survey Completed
The 1998 sablefish longline survey was conducted 1 June to 5 September. This was the twentieth annual standard longline survey. The survey is conducted by the ABL and Resource Assessment and Conservation Engineering (RACE) Division of the AFSC and covers the Gulf of Alaska annually and the Bering Sea and Aleutian Islands region in alternate years. The survey charter vessel Alaska Leader sampled 86 stations in the Aleutian Islands and Gulf of Alaska. The survey catch rates are critical in the determination of the annual Allowable Biological Catch (ABC) of sablefish (Anoplopoma fimbria). In addition, 2,684 sablefish, 478 shortspine thornyheads (Sebastolobus alascanus), and 66 Greenland turbot (Reinhardtius hippoglossoides) were tagged and released during the survey; when these fish are recaptured, the information will help us better understand the movements, growth, and mortality rates of the species. Further, 195 sablefish were implanted with electronic tags that record temperature, time, and depth. Length-weight data and otoliths were collected from about 2,129 sablefish. During the survey, a surface gill net was deployed to sample juvenile sablefish (ages 0 and 1). The net was set at 32 different stations and caught 954 juvenile sablefish, as well as other fish species, especially juvenile and adult Pacific salmon (Oncorhynchus spp.). Ten juvenile and one adult short-tailed albatross (Diomedea albatrus) were sighted during the cruise. None were taken on the gear.
By Mike Sigler and Tom Rutecki
Sablefish and Rockfish Early Life History
In July 1998, two cruises of the NOAA ship John N. Cobb were allotted to study rockfish. The July 5-9 cruise was devoted to collection of larval rockfish in western Frederick Sound off Alaska. (Andrew Gray (UAF, JCFOS) cooperated on this cruise to take photographs and genetic samples.) Through comparisons of pigment patterns and mitochondrial DNA analyses, we plan to develop keys for routine identification of larval rockfish in zooplankton surveys.
The July 10-14 cruise of the John N. Cobb was devoted primarily to collection of dusky rockfish, (S. ciliatus) for morphometric measurements and mitochondrial DNA analyses. Light- and dark-phase dusky rockfish are suspected of being two separate species. Dark dusky rockfish were collected at the entrance to Cross Sound and in Lisianski Inlet. Both light dusky rockfish and dark dusky rockfish were collected on the west coast of Admiralty Island. Following the John N. Cobb cruise, both color phases from the west Admiralty Island area were collected to be held alive in the ABL aquaria to determine if coloration changes with time and habitat, as has been observed with Pacific ocean perch.
By Bruce Wing.
Effects of Trawling on a Soft-bottomed Marine Ecosystem
In 1986 the North Pacific Fisheries Management Council closed nearshore areas around Kodiak Island, Alaska, to bottom trawling. The closure was intended to assist in rebuilding severely depressed crab stocks. A bottom-trawl fishery occurs adjacent to the closed areas for walleye pollock (Theragra chalcogramma), flathead sole (Hippoglossoides elassodon), butter sole (Isopsetta isolepis), Pacific halibut (Hippoglossus stenolepis), arrowtooth flounder (Atheresthes stomias), Pacific cod (Gadus macrocephalus), and several species of demersal rockfish (Sebastes spp). Consequently, these areas provide a unique opportunity to study the effects of bottom trawling on a productive, soft-bottomed marine ecosystem.
During 4-17 June, ABL staff on board the ADF&G vessel Medeia used the submersible Delta to observe the seafloor and a bottom sampler to sample the substrate. Two study sites were selected 160 km apart at locations where extensive bottom trawling has occurred in the last 5 years. The purpose of the study was to assess changes to the seafloor caused by repeated trawling. Specific objectives were to compare untrawled zones to trawled zones to determine if changes have occurred to populations of infauna, finfish, and invertebrates or to substrate characteristics, including grain-size composition and total organic carbon content.
Twenty four transects were completed, and visual counts and observations were made over 72 km of the seafloor. Each transect was 3,000 m long and bisected the boundary between open and protected areas. The seafloor at both sites was a relatively flat and unstructured bottom comprised of mostly fine sand and silt interrupted only by dense beds of several species of sea whips (Gorgonacea). Evidence of bottom trawling (e.g., trawl door furrows, broken sea whips) were observed at about one-third of the transects. Fish and invertebrates observed from the submersible included adult and juvenile flatfish (Pleuronectidae), weathervane scallops (Patinopecten caurinus), juvenile Tanner crabs (Chionoecetes bairdi), hermit crabs (Paguridae), sea anemones (Actiniaria), sea stars (Asteroidea), and sea whips.
Video footage is currently being analyzed for counts of fish and invertebrates in the trawled and untrawled zones. Infauna composition, sediment grain size, and organic carbon content analyses are near completion. Future studies on the effects of trawling may be planned at these sites, depending on the results of the 1998 study.
By Robert Stone and Ken Krieger.
Waning El Niņo to be Replaced by La Niņa
Meteorologists and oceanographers have made a great issue of the 1997-98 El Niņo because it was one of the strongest on record and because they were able to forecast it well in advance. Now they are forecasting an anti-El Niņo, La Niņa. During strong El Niņos, warm surface waters dominate the eastern North Pacific Ocean. During La Niņas cold surface waters dominate the northeastern Pacific Ocean. La Niņas are not as well understood as El Niņos. La Niņas occur less frequently and have been less studied than El Niņos, and, at least at the higher latitudes, may have less noticeable effects than the El Niņos.
The 1997-98 El Niņo was strongly evident in Alaskan marine waters. Sea surface temperatures recorded at the ABL rose above normal in April 1997 and remained above normal through much of August and September 1998. During the 1997-98 El Niņo, several warm temperate fish species were reported along the southern Alaska coast in either greater abundance than usual (blue shark, Prionace glauca; ocean sunfish, Mola mola; pomfret, Brama japonica; Pacific saury, Cololabis saira; Pacific mackerel, Scomber japonicus; and jack mackerel, Trachurus symmetricus) or farther north and west then usual (green sea turtle, Chelonia mydae; albacore, Thunnus alalunga; pelagic armorhead, Pentaceros richardsoni; northern anchovy, Engraulis mordax; Pacific barracuda, Sphyraena argentea; and Pacific sardine, Sardinops sagax).
September 1998 temperatures at Auke Bay closely match the long-term average, although they have cooled more rapidly than the temperatures of the outer coast. Because Auke Bay and coastal Alaska are at the extreme north of the eastern Pacific Ocean, temperature conditions associated with the El Niņo phenomenon often lag several months to a year behind the more closely monitored areas of the coterminous states. Also, the effects of El Niņos, especially weak ones, may not be evident in Alaska.
By Bruce Wing
Eelgrass: Essential Fish Habitat in Southeast Alaska
In 1998, a study of Essential Fish Habitat (EFH) was conducted at Klawock and Craig, Southeast Alaska, to investigate the role of eelgrass (Zostera marina) habitat for fish and other marine species. The area is a good example of the interaction between urban development and eelgrass habitat because it is the fastest growing area in Alaska and has common eelgrass habitat and many past and proposed fill activities. The NMFS consults on requests for permits under Section 404 of the Clean Water Act for filling subtidal areas, and a major concern is the effect such filling will have on eelgrass habitat, which is thought to be productive nursery habitat for several commercially important species.
Objectives of the project are to 1) determine the role of eelgrass beds as essential fish habitat; 2) assess cumulative effects of 404 permit filling in the vicinity of Craig, Alaska; and 3) provide an updated goegraphic information system (GIS) map of existing eelgrass and other estuarine habitats near Craig. (This information also is used to update the National Wetlands Inventory (NWI) database through a contract with the U.S. Fish and Wildlife Service (USFWS) to inventory eelgrass and other nearshore habitats). The City of Craig and the Prince of Wales Hatchery Association contributed logistical support.
Adjacent eelgrass and noneelgrass habitats were sampled to determine seasonal utilization by commercially important marine species. The seasonal role was examined by seining eelgrass and adjacent noneelgrass sites in April, May, June, and September. A paired-site design was used to compare eelgrass habitat with adjacent noneelgrass habitat. Four site pairs were established from inside Klawock Inlet to its opening at Bucareli Bay. We used a 37-m-long, variable-mesh beach seine to capture fish and decapods at two adjacent beaches (>50 m apart) at each site. All sampling occurred during low spring tides (<0 m elevation). Based on diver observations, seining was more than 95% efficient. Captured fish and decapods were identified to species and enumerated, and a sample of target species, including salmonids, flatfish (Pleuronectidae), gadids, and rockfish (Sebastes spp.), were measured for length. Sites were classified by habitat type, and physical data (e.g., temperature, salinity, substrate composition, depth profile) were also taken. Vegetation cover was estimated each sampling date, and eelgrass was sampled in quadrats to determine seasonal density, height, and biomass.
Preliminary results indicate that eelgrass habitat had higher total fish density and species diversity than noneelgrass habitat. Eelgrass appeared to be important nursery habitat for chum salmon (O. keta) fry in April, but chum fry moved away from eelgrass in May and June. Other salmonids (pink salmon (O. gorbuscha) fry, coho salmon (O. kisutch) smolts) were not significantly associated with eelgrass habitat. Juvenile rockfish (Sebastes spp.) were more abundant in vegetated habitats, both in eelgrass and Laminaria beds.
Cumulative effects of the 404 permitting program are being assessed by inventorying existing eelgrass beds and areas already filled in the vicinity of Craig and Klawock. The habitat inventory was contracted to the USFWS to update the existing NWI database (which currently depicts no eelgrass at all in the vicinity). The USFWS made aerial surveys of the area 2 days in August at low spring tides and reclassified the shoreline. The City of Craig also hired an independent contractor with city funds and a grant from the State of Alaska to map all eelgrass beds within the Craig city limits. With these data and information on previous permitted fills, we will evaluate cumulative effects by calculating the proportion of eelgrass beds that have been lost due to filling.
The last objective of this project is to provide NMFS with updated GIS maps of shoreline habitats near Craig. The contract with the USFWS was to update all shoreline in the USGS quadrangles Craig B4, Craig C4, and the Trocadero Bay portion of Craig B3. Field verification was completed in August for all shoreline, except for part of Craig B4 (Waterfall to Big Bay). The GIS files (digitized maps) for Craig B3 will be available in January 1999, and files for Craig C4 will be completed in March 1999. Field verification for Craig B4 will be completed in spring 1999, and GIS files available in October 1999.
By Michael Murphy.
New Methods for Assessing Nearshore Essential Fish Habitat
Another objective of the EFH study was to develop effective sampling methods for juvenile groundfish in a range of habitats in Southeast Alaska. In 1998, we tested various sampling gear (e.g., traps and seines) in combination with a remotely operated vehicle (ROV) to evaluate sampling methods for capturing groundfish and for quantifying habitat structure.
In April 1998, the John N. Cobb was used as a platform in several bays near Sitka to test an underwater video-sled being developed by scientists with the Centers RACE Division. This system proved ineffective for sampling fish in nearshore habitats. Based on the test, we decided to purchase an ROV which allows close control and live video feedback. In August, a second, 2-week cruise on the John N. Cobb was used to test the ROV in 10 bays comprising a transect across Southeast Alaska from Biorka Island off Sitka to Funter Bay near Juneau. Traps and seines were also used in conjunction with the video on both cruises.
The ROV proved effective for videotaping juvenile groundfish and their habitat at depths to at least 70 m and in moderate current. The ROV was used in different habitat types including eelgrass, kelp forests, Laminaria beds, and rock cliffs. The ROV was operated out of a skiff powered by a portable generator and was controlled via a console in the skiff. Preliminary results show that the ROV works best for epibenthic fish but not as well for pelagic fish and that most fish were not disturbed by the ROV. Video from the ROV also revealed that species abundance and diversity declined sharply from outside waters near Sitka to inside waters near Juneau. Future studies with the ROV will focus on quantifying fish abundance and habitat characteristics in a wider geographic area.
By Michael Murphy.
Natural Hydrocarbon Background in Prince William Sound
The natural hydrocarbon background in benthic sediments of Prince William Sound (PWS), Alaska, has been the focus of collaborative work by scientists at the ABL and the U. S. Geological Survey during the past 2 years. The source of background hydrocarbons in benthic sediments of PWS where the 1989 Exxon Valdez oil spill (EVOS) occurred has been ascribed to oil seeps in coastal areas of the Gulf of Alaska. We present evidence that coal is a more plausible source, including: 1) high concentrations of total polynuclear aromatic hydrocarbons (TPAH) between 1670 and 3070 ng/g in continental shelf sediments adjacent to the coastal region containing extensive coal deposits; 2) PAH composition patterns of sediments along with predictive models that are consistent with coal but not oil; 3) low ratios (<0.2) of triaromatic steranes to methylchrysenes found in sediments and coals, contrasting with the high ratios (11 and 13) found in seep oil; and 4) bioaccumulation of PAH in salmon collected within 100 m of the Katalla oil seeps but not in filter-feeding mussels collected near oil field drainages 9 km from the seeps, indicating negligible transport of bioavailable PAH from Katalla seeps to the Gulf of Alaska. In contrast with PAH in crude oil, PAH in coal are not bioavailable, so presence of coal in these benthic sediments confers no adaptive benefit to biota of the marine ecosystem with respect to PAH contamination from human activities (e.g., oil spills). A paper describing this study has been accepted for publication in Environmental Science and Technology.
By Jeffrey Short.
Exxon Valdez Restoration Studies Continue
ABL scientists continue to monitor the long-term recovery of the environment from the Exxon Valdez oil spill. A total of nine studies of oil contamination exposure and energy flow at the ecosystem level were funded in 1998. Nine field surveys were completed during the summer. The surveys gathered more than 3,000 mussel samples (Mytilus trossulus), 300 sediment samples, and 430 sandlance samples (Ammodytes hexapterus) for size, growth, and fat content measurements or for analysis of hydrocarbon concentrations in tissues and sediments.
Chenega beaches in PWS were cleaned of oil in 1997. Oil contamination was still found in summer 1998, although the quantities of oil were measurably reduced. Some mussel bed sites continue to have high concentrations of oil underlying the beds, with the oil in a relatively unweathered form. However, the distribution of the oil is patchy and the amounts are small at most sites.
The last study on the toxicity of oil to pink salmon was initiated in September 1998 at ABLs Little Port Walter field station. Over 400 pink salmon spawners were used to start the incubation of 500,000 eggs in oiled and unoiled environments. Release of marked fish is scheduled for spring 1999, and evaluation of reproductive fitness from returning adults will be measured in the fall of 2000.
March 1999 marks the 10th anniversary of the Exxon Valdez Oil Spill. A symposium marking the anniversary sponsored by the state/federal Exxon Valdez Oil Spill Trustee Council is scheduled for 23-26 March 1999 in Anchorage, Alaska .
Survey of Juvenile Salmon in the Marine Waters of Southeast Alaska, MayAugust 1998
Twenty-four stations were sampled monthly along a primary marine migration corridor in the northern region of Southeast Alaska to assess the distribution, growth, mortality, and diet of wild and hatchery stocks of juvenile (age -.0) Pacific salmon. Stations were stratified into three different habitatsinshore (Taku Inlet and near Auke Bay), strait (Chatham Strait and Icy Strait), and coastal (Cross Sound, Icy Point, and Cape Edward). Sampling was conducted aboard the John N. Cobb from May to August 1998. At each station, fish, zooplankton, temperature, and salinity data were collected during daylight with a surface rope trawl, conical nets, bongo nets, and a conductivity, temperature, and depth profiler. Surface (2-m) temperatures and salinity during the survey ranged from 7.6E to 14.2EC and 16.4 to 32.0.
A total of 12,817 fishes and squids representing 30 taxa were captured with the rope trawl. All five species of juvenile Pacific salmon and steelhead (O. mykiss) were captured and comprised 85% of the total catch. Of the 10,898 salmonids caught, over 99% were juveniles, and less than 1% were immature or adult. Nonsalmonid species made up more than 1% of the catch and included Pacific herring (Clupea harengus pallasi), capelin (Mallotus villosus), squid (Gonatidae), and sablefish. The highest frequency of occurrence (>25%) in the trawl catches was observed for chum, coho, sockeye, pink, and chinook salmon (O. tshawytscha), and wolf-eels (Anarrhichthys ocellatus). Overall catch rates of juvenile salmon were highest in June and July, intermediate in August, and zero in May. Catch rates of pink, chum, and chinook salmon were highest in June, whereas catch rates of sockeye and coho salmon were highest in July. Catch rates of juvenile salmon except chinook salmon were highest in strait habitat and lowest in inshore habitat; chinook salmon catch rates were highest in inshore habitat. Overall catch rates for juvenile salmon along the offshore transect declined with distance offshore; most juveniles were captured within 25 km of shore, and only one juvenile salmon was found beyond 40 km. Mean fork lengths of juvenile salmon in JuneJulyAugust were pink (94127162 mm), chum (102134164 mm), sockeye (112139153 mm), coho (166213253 mm), and chinook salmon (160166190 mm).
Twenty-four juvenile and immature salmon (13 chinook and 11 coho) containing internally planted coded-wire tags were recovered; 20 originated from Alaska, 3 from the Columbia River Basin, and 1 from Washington state. The recoveries of juvenile chinook salmon from the Columbia River Basin are some of the earliest documented recoveries of these stream-type stocks in Alaska during their first summer at sea.
Onboard stomach analysis of potential predators of juvenile salmon indicated a low level of salmon predation by sablefish, spiny dogfish (Squalus acanthias), and adult coho salmon. Results from this study and further laboratory analysis of otolith-marked fish will be used to assess potential competitive interactions between wild and hatchery stocks and stock-specific life history characteristics.
By Joseph Orsi, James Murphy, and Donald Mortensen.
Third Annual Survey of Juvenile Salmon in the North Pacific Ocean Completed
During 21 July - 12 August 1998, the Ocean Carrying Capacity (OCC) Program conducted a cruise to survey distribution of young Pacific salmon in the Gulf of Alaska for the third consecutive year. The Great Pacific, a chartered 38-m stern trawler, sampled 12 coastal transects from nearshore to 60 miles offshore with a large surface trawl and covered over 3,000 miles from Dixon Entrance to Unimak Pass. Catches included nearly 26,000 juvenile (ocean age-0) salmon, mostly pink salmon, with substantial numbers of chum and sockeye salmon (O. nerka). Over 2,000 immature (2nd ocean year and older) salmon also were takenmostly chum and some sockeye. Juvenile salmon were taken mostly over the continental shelf, and between Dixon Entrance and Shelikof Strait. Immature salmon were taken mostly near the slope (100 fm) zone, and from Cape St. Elias westward. Oceanographic observations were made along selected transects at Cape Ommaney, Cape St. Elias, Cape Chiniak (Kodiak), and Unimak Pass. Sample sizes are sufficient for laboratory analyses of growth rates using scales, incidence of otolith marks from hatchery releases, food habits, and genetic tests for stock identity of wild stocks. Comparisons with locations sampled in 1996 and 1997 are under way and will help define migration patterns for young salmon and address goals of the North Pacific Anadromous Fish Commission for evaluating the status of salmon resources in the North Pacific Ocean.
By Richard Carlson.
Otolith-Marked Salmon Caught in the North Pacific Ocean and Bering Sea
North Pacific Ocean and eastern Bering Sea research cruises conducted by the OCC program during July and August 1997 provided ocean recoveries of 180 pink, 157 chum, and 13 sockeye salmon thermally marked during incubation at Alaskan and Canadian hatcheries. The 180 otolith thermal marks for juvenile (age .0) pink salmon, 101 otolith thermal marks for juvenile chum salmon, and 8 otolith thermal marks for juvenile sockeye salmon represent 22.8%, 31.2%, and 2.5% of our samples, respectively. The 56 otolith thermal marks for immature (age .1+) chum and 5 otolith thermal marks for immature sockeye represent 3.7% and less than 1% of these samples, respectively. The marked juvenile salmon migrated westerly along the coastal waters of the North Pacific Ocean. The marked immature chum salmon from Southeast Alaska and Canadian hatcheries were found in the coastal waters of the North Pacific Ocean from Prince William Sound to the eastern Aleutian Islands and also in the coastal waters of the eastern Bering Sea. The marked immature sockeye salmon from Southeast and Southcentral Alaska were found in the coastal waters of the North Pacific Ocean from the eastern Aleutian Islands to the central Aleutian Islands.
By Ed Farley.
Forecast Models Developed for Bristol Bay Sockeye Salmon
Sockeye salmon forecast models were developed for Egegik, Naknek, and Kvichak Rivers in Bristol Bay, Alaska. The forecasts for each river system contained large errors for 2-ocean fish in 1996 and for all age groups for Naknek and Kvichak in 1997. The forecasts were based on univariate and multivariate time series analysis models that incorporate returns (catch + escapement from 1956 to 1995), return-escapement, and sibling-smolt relationships. Marine environmental influences were included in multivariate time series models when significant cross-correlations between the residuals from the forecast models and residuals from the univariate environmental models occurred. A persistent significant relationship was found between sockeye salmon returns and the annual anomalies of mean (May - August) air temperatures taken at Cold Bay, Alaska, (CBMAT) lagged by 1, 2, or 3 years. The best model and forecast statistics for 2-ocean sockeye salmon consisted of age group returns (1.2 and 2.2) that included CBMAT, whereas, sibling models produced the best model and forecast statistics for most of the 3-ocean sockeye salmon return time series. The only exceptions were for age groups 2.2 and 2.3 in Kvichak where the linear transfer function smolt model and univariate model of returns produced the best overall model and forecast statistics, respectively. Including Cold Bay, Alaska air temperatures did not improve forecast performance in 1996 or 1997. Sibling relationships improved forecast performance in 1997, particularly for 3-ocean sockeye salmon returning to the Egegik River.
By Ed Farley.
Rope Trawl Compared With Gillnet For Capturing Young Salmon and Sablefish
Pelagic fishing gear comparisons were conducted along the coast of Southeast Alaska as part of a cooperative research effort by the Ocean Carrying Capacity and Marine Fisheries Investigation programs at the ABL. Sampling efficiency and catch composition from research gillnet and rope trawl samples were summarized during a 4-day survey near Salisbury Sound. The rope trawl was found to be much more effective in capturing juvenile Pacific salmon (223 juveniles, 2 adults), whereas the gillnet was more effective in capturing adult salmon (36 juveniles, 23 adults). Research gillnets were found to be slightly more effective in capturing juvenile sablefish (25 gillnet, 10 rope trawl). During the survey eight adult Pacific sardines (Sardinops sagax) were captured by rope trawl, which is the northernmost recovery of adult Pacific sardines. The last recovery of Pacific sardines off the coast of Southeast Alaska was in August 1931 by George Rounsefell during port sampling of herring reduction fisheries near Cape Ommaney.
By Jim Murphy.
1998 Radiotagging of Yukon River Salmon
As part of a cooperative international research program between the United States and Canada, the ABL is conducting a large-scale radio telemetry study of Yukon River salmon to provide information on stock composition, abundance, timing, movement patterns, and the location of undocumented spawning areas in the upper Yukon River basin. The cooperative work in 1998 concentrated on four areas: 1) installation of remote tracking stations in the drainage to record and transmit data on the movements of radio-tagged fish, 2) conducting a large-scale spaghetti tagging study of fall chum salmon to collect information on run characteristics and handling response, 3) a feasibility study on radio-tagging of chinook salmon to assess handling response, and 4) development of an automated database and geographical mapping system to summarize telemetry data.
In 1996-97, remote tracking stations were installed (and left in place) near the tagging site (about 900 km downstream from the U.S.-Canada border), at the U.S.-Canada border on the main stem of the Yukon River, at the border on Porcupine River, and in Canada on Fishing Branch River, a upriver tributary of the Porcupine. In 1998, additional stations were installed to record radio-tagged fish traveling the river and entering and leaving spawning index areas. On the U.S. side, stations were installed on the Yukon River main stem near Circle, Alaska; on the Chandalar and Sheenjek rivers (major U.S. tributaries of the Yukon River); on the Black River (a lower river tributary of the Porcupine); and on the lower main stem of the Porcupine River. In Canada, stations were installed at sites on the main stem of the Yukon River and on the Kluane River. In all, sixteen radiotag tracking stations are currently operating within the drainage.
Salmon were captured with fish wheels located about 900 km downriver from the U.S.-Canada border. In 1998, 50 chinook and 530 chum salmon were tagged with radio transmitters. The fish responded well to tagging, with 45 (90%) chinook and 492 (93%) fall chum salmon resuming upriver movement after release. Information on distribution, movement patterns, timing, and handling response are being summarized. Aerial surveys of spawning area will be conducted during mid- to late October.
The automated database-GIS map, developed to assist in summarizing telemetry data, was used effectively during the 1998 season. Although a prototype, the system operated throughout the study and was essential in preparing inseason summaries used by management agencies to assess chum salmon returns. Additional work is being conducted to refine and enhance this systems capabilities.
By John Eiler