Auke Bay Laboratory Report for Alaska Fisheries Science Center Quarterly Report for January-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 AFSC’s 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

ABL’s 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.

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 Alaska’s 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.