• Biochemical and microbiological assessments of dried Alaska pink salmon, red salmon and Pacific cod heads

      Biceroglu, Huseyin; Smiley, Scott; Crapo, Charles; Bechtel, Peter J. (2012-05)
      Fish heads are generally considered as unsuitable byproducts for human consumption in the United States. The initial objective was to compare the moisture content and water activity levels on dried pink salmon (Oncorhynchus gorbuscha) and dried red salmon (O. nerka) using different temperature and time integration. The secondary objective was to compare shelf life characteristics, rancidity and mold growth, between dried pink dried salmon and dried Pacific cod (Gadus macrocephalus) heads stored for up to 180 days at the ambient temperature (21°C) for East African seafood markets. The third objective was to assess the antioxidant effects for frozen and dried pink salmon heads stored for up to 60 days. In a preliminary experiment, dried red salmon heads were found unsuitable due to the water activity levels above 0.6. The critical moisture contents were detected around 10% for pink salmon heads and were around 15% for Pacific cod heads to reduce water activity levels below 0.6 in these products. The applicable drying temperatures of 50°C lasting over 50 hours for pink salmon heads and 50°C for over 24 hours followed by 30°C for over 24 hours for Pacific cod heads were found optimal. Dried Pacific cod heads showed shelf stability as a potential dried seafood product. Frozen pink salmon heads had 60 days shelf life, while heads with antioxidant glazing retarded oxidation levels (p <0.05). The antioxidant treatment in dried pink salmon heads kept oxidation levels lower than the acceptable limit up to 60 days. This study provided essential information to improve the utilization of these Alaskan seafood byproducts.
    • Determining the effects of Asian pink and chum salmon on Western Alaska chum salmon growth

      Minicucci, Tessa J.; McPhee, Megan V.; Yasumiishi, Ellen M.; Adkison, Milo; Beckman, Brian (2018-08)
      Increased hatchery production and favorable ocean conditions have resulted in historically high abundances of Pacific salmon (Oncorhynchus spp.) in the North Pacific Ocean. Despite these conditions, chum salmon (O. keta) have experienced reductions in growth, body size, and increases in age at maturity throughout their range. In western Alaska, dramatic declines in the abundance of chum salmon between 1997-2001 resulted in numerous fishery and economic disasters among commercial and subsistence users. Chapter 1 reviews existing data on salmon diet and ocean distribution to address the potential for competition between western Alaska chum salmon and Asian pink (O. gorbuscha) and chum salmon in the Bering Sea. Western Alaska chum salmon reside in the Bering Sea during their summer foraging months where they overlap with abundant populations of Russian pink salmon (primarily wild origin) and Japanese chum salmon (primarily hatchery origin). Chum and pink salmon occupy a similar feeding niche, and during years of high pink salmon abundance chum salmon have been observed to alter their ocean distribution and rely more heavily on gelatinous zooplankton species as a primary food source. This spatial and diet overlap suggests that inter- and intra-specific competition might contribute to reduced growth and increased age at maturity of western Alaska chum salmon. Chapter 2 uses retrospective scale analysis coupled with linear mixed-effects modeling to investigate the potential for such competition between Asian pink and chum salmon abundance and the growth of chum salmon that rear in the Bering Sea. Chum salmon scale samples were collected through in-river fisheries on the Kuskokwim River during 1973-2014 and from incidental catches of chum salmon in the Bering Sea Aleutian Island walleye pollock (Gadus chalcogrammus) fishery during 2001-2016. Linear mixed-effects models demonstrated a strong negative relationship between Bethel chum salmon growth and the abundance of Japanese hatchery chum salmon. Chum salmon intercepted in the Bering Sea did not exhibit increased growth during 2012-2014 despite reductions in Japanese hatchery releases of chum salmon in 2011 as a result of the Tōhoku Earthquake and tsunami. We did not observe a relationship between Bethel chum salmon growth and the abundance of wild Russian pink salmon. Understanding how salmon populations interact while at sea will assist fishery managers in conserving threatened salmon stocks, particularly as Pacific Rim nations consider increasing production of hatchery salmon.
    • First-generation effects on development time of outcrossing between geographically isolated and seasonally isolated populations of pink salmon (Oncorhynchus gorbuscha)

      Echave, Jesse D.; Gharrett, Anthony; Smoker, William; Adkison, Milo (2010-12)
      Bootstrap analyses of hatch data collected during two independent experiments revealed that hybridization between pink salmon (Oncorhynchus gorbuscha) breeding populations separated at either a large geographic scale or a fine temporal scale can influence development time. Restricted maximum likelihood estimators also revealed that sire, dam, cross, and parental interaction can influence genetic variance associated with development time at either scale. Few studies have investigated the extent of local adaptation that results from fine-scale ecological variation, the genetic underpinnings of that adaptation, or the potential impacts outbreeding at that level may have on fitness. We tested whether or not local adaptation contributed to genetic divergence among subpopulations of pink salmon that overlap temporally within the same spawning habitat (early-run fish and late-run fish within Auke Creek, near Juneau, Alaska) by determining whether or not outbreeding influenced development time (a fitness-related trait) in first-generation hybrids. We examined genetic divergence among populations isolated at a much broader scale (Pillar Creek on Kodiak Island, Alaska, and Auke Creek, 1,000 km great circle distance) as a more extreme reference to local adaptation. Results provide evidence that development time is locally adapted and expressed primarily in a locus-by-locus manner.