• 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.
    • Feeding ecology of larval and juvenile walleye pollock (Theragra chalcogramma) and Pacific cod (Gadus macrocephalus) in the Southeastern Bering Sea

      Strasburger, Wesley Wayne; Hillgruber, Nicola; Pinchuk, Alexei; Mueter, Franz (2012-08)
      Poor recruitment success during warm years (e.g., 2001-2005) was hypothesized to lead to reduced gadid recruitment in the southeastern Bering Sea. These groundfishes are of particular importance, both commercially and ecologically in the southeastern Bering Sea. The spatial and temporal overlap of early life stages of walleye pollock and Pacific cod may explain their strongly correlated recruitment trends in the southeastern Bering Sea. The goal of this study was to compare feeding patterns of larval and juvenile walleye pollock (Theragra chalcogramma) and Pacific cod (Gadus macrocephalus) in the southeastern Bering Sea, and to assess the possibility of prey resource competition. Larvae and juveniles from both species collected between May and September 2008, an exceptionally cold year, were used to analyze stomach contents. Fish body size was most consistently related to diet composition within species, however, spatial and depth factors also had an influence. Feeding success and diet composition of these two gadid species were consistently different throughout the spring, summer, and especially fall seasons. Pacific cod larvae and juveniles consistently consumed larger prey items in every season and progressively fewer prey items, especially in the fall. This data suggests that competition for prey resources was unlikely during cold 2008.