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Southeast Alaska Steller Sea Lion Prey Study

As part of an ongoing prey study of Southeast Alaska Steller sea lions (Eumetopias jubatus), two cruises were conducted in 2002 aboard the chartered trawling vessel Viking Storm. The cruises (cruises seven and eight) took place in Lynn Canal on 4-5 December and in Frederick Sound on 6-15 December and mark the second winter assessment of sea lion prey at these study sites. The study tests the hypothesis that diversity and seasonality of prey for juvenile Steller sea lions are related to sea lion population trends.

During the cruises, prey abundance and biomass were measured using echo-integration and midwater trawls. Steller sea lion abundance and distribution were determined from aerial surveys conducted by Jamie Womble of the University of Alaska Fairbanks. To infer sea lion diet, scat was collected during the Frederick Sound leg of the cruise on Sunset, Sail, Southwest Brothers, and West Brothers haulouts. Fish were also collected for proximate and fatty acid analysis. Similar to findings from cruises in December 2001, large concentrations of over-wintering herring (Clupea pallasi) were present in localized areas within both study sites. These large aggregations of mature herring (190-250 mm fork length) are not present at other times of the year. In Lynn Canal, herring were located on the northeast side of Benjamin Island, coincident with approximately 50 sea lions and nearly 10 humpback whales that were foraging. Herring were observed in dense, pelagic, cloud-like schools, filling the majority of the water column from 20 to 80 m (bottom depth = 115 m). In Frederick Sound, the herring were located in the inner bay of Port Houghton. These fish were aggregated in several narrow, vertical, pelagic schools, in depths of 60-115 m (bottom depth = 150 m). Relative to herring from Lynn Canal, the biomass of these herring was smaller.

Port Houghton provided an ideal location for assessing Steller sea lion prey preference. The outer bay contained a large biomass of juvenile pollock (Theragra chalcogramma) (290-330 mm fork length), through which sea lions would have to travel to reach the herring in the inner bay. The pollock formed a continuous, carpet-like layer throughout the bay, at depths from 80 m to the bottom (200 m maximum depth). Supporting the hypothesis that sea lions prefer energy-rich herring over energy-poor pollock, approximately 10 sea lions (as well as several river otters) were observed foraging on the herring in the inner bay. In addition, about 150 sea lions were hauled out on an unnamed rock near Walter Island, located in the outer bay. This haulout has never been previously documented and presumably acts as a seasonal haulout for sea lions utilizing the ephemeral herring aggregation. The haulout is located at 57°18.747' N, 133°17.542' W. Analysis of the scat collected from the haulout may provide further evidence of herring selection. Several weeks prior to the cruises, the Alaska Department of Fish and Game (ADF&G) and the National Marine Mammal Laboratory affixed satellite/VHF tags to five sea lions at each study site. Records of the animal locations will be combined with locations of coincident prey to assess sea lion foraging habits. During the study period, tagged sea lions in Lynn Canal remained near Benjamin Island except for one animal that traveled between study sites and remained at the Brothers thereafter. In Frederick Sound, most sea lions remained within 5-7 km of the Brothers Islands haulouts. However, one animal made short trips to Gambier Bay and Port Houghton, and another visited Gambier Bay. Gambier Bay and Port Houghton were the only areas in which herring were found; however, the magnitude of herring in Gambier Bay was considerably less than in Port Houghton. Two marked sea lions were observed at Walter Island during the trip.

Scientists participating in the cruises included Mike Sigler, Johanna Vollenweider, Dave Csepp, and Lee Hulbert of the Auke Bay Laboratory, as well as Anna Hall of the University of British Columbia. The next cruise is scheduled for March 2003.

By Johanna Vollenweider.

Genetics Laboratory Studies

During the 2000 Ocean Carrying Capacity research survey, juvenile chum salmon were collected in the coastal waters of the Gulf of Alaska and the eastern Bering Sea and analyzed in the laboratory. Since then, protein electrophoresis has been used to determine genotypes for 965 fish for more than 20 allozyme loci. Estimates of origin for the fish will be made using a conditional maximum likelihood model and newer Bayesian model, which compares the genotypes of the sample mixtures with the Pacific Rim chum salmon genetic baseline. Sample sizes are large enough to estimate the regional geographic origin of collections from several transect locations: 1) the Seward Line and Gore Point, south of the Kenai Peninsula; 2) northern and southern Shelikof Strait; and 3) the eastern Bering Sea, near Bristol Bay. The results of this analysis will be compared with results from collections from the same transects in 2001 to investigate interannual differences in migration patterns.

By Chris Kondzela.

U.S. - Japan Aquaculture Panel Meetings

The U.S.-Japan Natural Resources (UJNR) Aquaculture Panel held its 31st annual meeting and associated technical symposia in Japan on 16-24 October 2002. The UJNR is a bilateral cooperative program between the two countries for scientific exchanges in natural resource issues. There are a total of 16 UJNR panels in various disciplines, including 7 marine panels where the U.S. Department of Commerce NOAA serves as the lead U.S. marine agency.

The Aquaculture Panel business meeting and main symposium was held at the National Research Institute of Fisheries Science in Yokohama, where 19 U.S. participants from industry, government, and academia, including 6 NOAA scientists, took part. The main theme of the symposium was "Aquaculture and Stock Enhancement of Algae and Filter Feeders," focusing on the roles macro- and micro-algae and filter feeders play in nutrient cycles of coastal waters. These organisms have an important effect in decreasing deleterious impacts of eutrophication in coastal waters from both point and nonsource pollutants. Point-source nutrient inputs could include fed aquaculture systems near sea pens for growing sea bream, flounders, or salmonids, or agricultural feed-lot systems, where the integration of filter feeders and appropriate algal communities can play an important role in assisting environmental rehabilitation. The same combinations of organisms can also play a similar role in nonsource nutrient input from watershed runoff. Examples of these principles were presented for a number of areas including Hiroshima Bay and Tokyo Bay in Japan, and Chesapeake Bay, Lake Okeechobee, and the Everglades in the United States.

A satellite symposium "Studies on Coastal Fisheries Resources and Aquaculture in the Tohoku Region" was held in Ishinomaki at the Tohoku National Fisheries Research Institute in Miyagi Prefecture. Overviews of Tohoku fisheries and aquaculture included papers on oysters, scallops, seaweed, sea squirt, mysids, clams, anchovy, tuna, flounder, and salmon (both ocean-ranched chum salmon and farmed coho salmon). It should be noted that throughout Japan, capture fisheries and aquaculture are often used interchangeably and are considered synonymous by many Japanese. Of interest to U.S. participants was hearing Japanese fishery scientists speak about problems facing their industries, with themes similar to many in the United States. Topics included 1) cheap prices of imported seafood products, such as seaweeds (wakame and nori) and eels from China and other southeast Asian countries, and coho salmon from Chile, Europe, and Australia; 2) the continuing economic depression in Japan, with reduced government subsidies for seed production and worsening management conditions of public facilities; and 3) increased expenses for fishing and aquaculture activities.

A final satellite symposium was held at the Miyagi Prefectural Freshwater Fisheries Experiment Station. Paper topics included bacterial coldwater disease in Ayu, and studies on sex control methods in salmonids. The latter paper included a hands-on demonstration of producing all-female, triploid, Japanese white-spotted char. These fish, unlike their diploid counterparts, are a commercially viable product on a year-round basis, because they never enter a reproductive cycle and become unfit for market. An important study was a review of the devastating effects on endemic Japanese fish faunas caused by clandestine introductions of largemouth bass into freshwater lakes. Largemouth bass were originally introduced into Japan from the United States in the 1930s and presumably remained essentially unnoticed in one or two lakes on Honshu for several decades. However, following the popular post-war development of bass tournaments in the United States, Japanese sport fishermen and eager fishing tackle producers began secretly planting bass into other Japanese lakes to conduct their own tournaments. Japanese freshwater fish fauna evolved in the absence of any significant fish predators; the sudden presence of a top piscine predator such as largemouth bass has all but eliminated many endemic fishes in several lakes and may have rendered some rare species extinct. Fishery scientists in Japan consider this a serious problem and are working to contain and reverse an apparent lack of concern in some segments of Japanese society for Japan's endemic freshwater fish fauna.

By Bill Heard.

Ocean Survival of Auke Creek Wild Coho Salmon

graph of Auke Creek coho salmon ocean survival
Figure 1.  Ocean survival of Auke Creek coho salmon.

Research at the Auke Creek field station includes studies to evaluate the long-term ocean survival of wild coho salmon. Ocean survival of coho salmon throughout much of their southern range has declined over the past three decades. However, in Southeast Alaska, which includes the Auke Creek stock's range, survival of coho has been increasing since at least 1980.Coho salmon studies at Auke Creek are conducted under cooperative projects between NMFS and the ADF&G. The Auke Creek coho salmon stock is one of four wild stocks used as index systems in Southeast Alaska. Ocean survivals of wild coho salmon at Auke Creek are known for every year from 1977 (when coded wire tags were first used on smolts leaving Auke Creek) through 2002, except for 1979 (Fig. 1 above). The research at Auke Creek relies heavily on the permanent fish weir and includes both the annual capture and tagging of seaward-migrant smolts and the capture and enumeration of fish returning to the creek. Auke Creek is the only index site where all smolts are captured and marked, and all adults are captured and examined for marks and tags. Ocean survival of each smolt cohort is estimated by summing the number of adults that return to the weir and the number of fishery harvests of adults. Fishery harvest is estimated by the ADF&G from the tagged fish recovered during rigorous sampling of the commercial and sport fisheries.

The number of returns of adult coho to Auke Creek in 2002 was 1,112 fish, representing a 19.6% return of the smolts. This was the third highest return on record-the average number of adult coho returning to Auke Creek is 732. The fishery harvest was 401 fish, representing a 7.1% return of the smolts, less than the average of 510 and perhaps due to the low prices for commercially caught coho. Therefore, the estimated ocean survival of Auke Creek coho in 2002 (2001 smolts returning as adults in 2002) was 26.7%. This was greater than the long-term average of 19.8%.

Scales and body size data on fish returning to Auke Creek were collected and archived. A major retrospective analysis using the data on scale growth patterns and ocean survival is currently under way by a University of Alaska Fairbanks graduate student. The project uses data on Auke Creek coho salmon adults and coastal sampling studies to retrospectively examine ocean growth and survival. Interannual marine growth (as reflected in adult scales) will be used to document the range of scale growth patterns and compare these patterns with marine survival, from smolt to adult, for coho salmon at Auke Creek.

By Jerry Taylor.

Whalefest Celebration in Sitka

Scientists from the Marine Salmon Investigations program presented workshops on Southeast Alaska zooplankton ecology in conjunction with the local school curriculum as part of the annual Whalefest Celebration in Sitka, Alaska. Emily Fergusson and Molly Sturdevant led the workshops for five groups of sixth-grade students at Blatchley Middle School during the week of 28 October-1 November 2002. Workshops consisted of classroom, laboratory, and field training sessions. Classroom discussions included PowerPoint presentations on zooplankton communities in Southeast Alaska, displays of research posters, and discussions of ABL's Southeast Alaska Coastal Monitoring Project. Laboratory sessions were held to examine preserved krill, zooplankton, and nekton specimens under the microscope and to become familiar with sampling and processing equipment. After the initial laboratory work, students collected live zooplankton samples, which then were examined in the classroom laboratory. Following the Whalefest curriculum in the schools was a 3-day series of special events on cetaceans with talks by marine scientists from Alaska and the Pacific Northwest.

By M. Sturdevant and E. Fergusson.


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