Alaska Fishery Research Bulletin Issues, Vol.11 No. 1 - Summer 2005

Catch Estimation Algorithm for the Walleye Pollock Theragra chalcogramma Fishery and Comparison to Similar National Marine Fisheries Service Databases

Brian Battaile, Terrance J. Quinn II, David Ackley, and Galen Tromble - Vol. 11(1):1-14. 2005.

As fisheries management entertains more complex objectives to ensure sustainable fisheries and ecosystems, reexamination of all aspects of data collection, data analysis, and management actions is needed. In particular, focus on fine spatial and temporal scales is becoming more common. A new spatially and temporally explicit database was constructed with this focus for the total walleye pollock (Theragra chalcogramma) catch in the waters off Alaska. Three sources provide information about pollock catches: the National Marine Fisheries Service observer program data, weekly processor reports to the National Marine Fisheries Service, and Alaska Department of Fish and Game fish tickets. The observer program database contains exact locations by longitude and latitude and dates. Fish tickets and weekly processor reports are much coarser in time (by cruise and week, respectively) and space (by Alaska Department of Fish and Game and federal reporting areas, respectively). Hence, obtaining spatiotemporal data at the finest scale requires maximum use of observer data. However, a significant portion of pollock catch is unobserved, so that it was necessary to combine the three data sources to provide a full accounting of catch. Comparisons were made to two National Marine Fisheries Service algorithms, the Catch By Vessel and Blend, presently used for fisheries management and analysis purposes. Estimated total catch was similar among the three systems, but the new database makes best use of the observer data and consequently is preferred for addressing fine-scale questions about pollock management.

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Distribution, Migration Pathways, and Size of Western Alaska Juvenile Salmon Along the Eastern Bering Sea Shelf

Edward V. Farley, Jr., James M. Murphy, Bruce W. Wing, Jamal H. Moss, and Angela Middleton - Vol. 11(1):15-26. 2005.

The size, condition, distribution, and migration pathways of juvenile Pacific salmon (pink, chum, sockeye, coho, and Chinook salmon) were examined along the eastern Bering Sea shelf during August through October 2002. Juvenile salmon were widely distributed across the eastern Bering Sea shelf, but species-specific distributional patterns were found. Juvenile sockeye and chum salmon were large during 2002, suggesting that growth rates were high during their first summer at sea. Seaward migratory pathways for juvenile salmon from Bristol Bay and the Kuskokwim and Yukon rivers were inferred from their size distributions along the eastern Bering Sea shelf, and differ from earlier migration models.

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Faunal Assemblage Structure on the Patton Seamount (Gulf of Alaska, USA)

Gerald R. Hoff and Bradley Stevens- Vol. 11(1):27-36. 2005.

Epibenthic and demersal assemblages of fish and invertebrates on the Patton Seamount in the Gulf of Alaska, U.S.A., were studied in July 1999 using the Deep Sea Research Vehicle Alvin. Faunal associations with depth were described using video analysis of 8 dives from 151 to 3,375 m. A cluster analysis applied to the observations suggests three benthic faunal communities based on depth: 1) a shallow-water community (151–950 m) consisting mainly of rockfishes, flatfishes, sea stars, and attached suspension feeders, 2) a mid-depth community (400–1500 m) also consisting of numerous attached suspension-feeding organisms such as corals, sponges, crinoids, sea anemones, and sea cucumbers and fish such as the sablefish Anoplopoma fimbria and the giant grenadier Albatrossia pectoralis both of which were aggregated over a relatively narrow depth range, and 3) a deep-water community (500–3,375 m) consisting of fewer attached suspension feeders and more highly mobile species such as the Pacific grenadier Coryphaenoides acrolepis, popeye grenadier C. cinereus, Pacific flatnose Antimora microlepis, and large mobile crabs Macroregonia macrochira and Chionoecetes spp. that were less aggregated and covered a much greater depth range. Bottom depth was highly correlated with temperature and bottom substratum type where the upper 1,300 m was primarily a mixed habitat of boulders and large cobbles. The bottom substratum types were less diverse from 1,300 m to 3,300 m, which was composed of gravels and smaller sized particles. The absence of many near shore species on the Patton Seamount suggests this seamount is a unique subset of the near shore fauna but maintains distinct assemblage characteristics.

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Resistance of Naturally Spawned Pink Salmon Eggs to Mechanical Shock

John F. Thedinga, Mark G. Carls, Jacek M. Maselko, Ronald A. Heintz, and Stanley D. Rice - Vol. 11(1):37-43. 2005.

Routine hydraulic sampling of pink salmon eggs Oncorhynchus gorbuscha is the subject of a longrunning dispute over impacts of the Exxon Valdez oil spill on embryo survival in Prince William Sound, Alaska, because relationships between the time of spawning, sensitivity of eggs to mechanical damage, and sample timing were unclear. Previous laboratory and hatchery studies demonstrate that resistance of eggs to mechanical damage increases with maturity, but natural populations require estimates of embryo age distributions and the ability to discriminate between sampler-induced and natural egg mortality. Resistance of naturally-spawned eggs to hydraulic shock, determined 6 times between late September and mid-November in a southeastern Alaska stream, increased sigmoidally from < 2% to 98%. In contrast, the number of eggs that died from natural causes was unrelated to sample time. Rapid removal of all eggs from the water allowed accurate discrimination between eggs shocked and killed by sampling and eggs dead prior to sampling. We caution that combining shocked and dead eggs into a single “dead” category does not accurately describe natural mortality, and recommend use of our method for future studies. Our study showed the rate of mortality resistance to the same hydraulic shock was slower in populations of naturally spawned, mixed-age eggs than in artificially cultured uniform-age eggs.

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United States and Canadian Chinook Salmon Populations in the Yukon River Can Be Segregated Based on Genetic Characteristics

William D. Templin, Richard L. Wilmot, Charles M. Guthrie III, and Lisa W. Seeb - Vol. 11(1):44-60. 2005.

Chinook salmon (Oncorhynchus tshawytscha) spawn throughout the Yukon River drainage, supporting fisheries in both the United States and Canada. To achieve management goals set under international agreements, it is vital to know the proportion of Canadian-origin Chinook salmon harvested in United States fisheries. Currently this proportion is estimated using scale pattern analysis, but this method has several weaknesses, including limited resolution and the necessity for annual sampling. We analyzed samples collected from representative spawning populations throughout the drainage and mixtures from inriver fisheries to investigate the utility of genetic stock identification for applications based on allozyme loci in the Yukon River. Populations demonstrated a strong association between genetic differences and geographic location and could be combined into 6 regional groups. Simulations showed that these regions could be identified in mixtures with a high degree of accuracy and precision.

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Quillfish Ptilichthys goodei, Filiform Prey for Small Coho and Chinook Salmon

Laurie A. Weitkamp - Vol. 11(1):61-65. 2005.

Juvenile quillfish Ptilichthys goodei were identified in the stomachs of nine juvenile coho Oncorhynchus kisutch and two juvenile Chinook O. tshawytscha salmon captured in marine waters of Southeast Alaska in June and July of 1999 and 2000. These extremely elongate prey were nearly as long (maximum 82.3%, mean 65.2%) as their salmon predators, providing the highest prey-predator length ratio reported for juvenile Pacific salmon. Despite this disproportionately high length ratio, however, the mean weight of quillfish consumed per salmon (0.287 g) represented only 35.4% of the total stomach content weight, or 0.5% (range .02–1.76%) of the salmon’s total body weight. While prey length is clearly an important metric for determining which prey a predator will potentially consume, this study emphasizes that it is not the only determinant.

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