• Early marine growth patterns of Situk River steelhead, Oncorhynchus mykiss

      Catterson, Matthew R.; McPhee, Megan; Love, David; Sutton, Trent (2017-08)
      Steelhead Oncorhynchus mykiss exhibit complex life-history patterns described by variable freshwater and marine residency periods, maturation patterns, and reproductive characteristics. Over 300 small populations of Steelhead are present in Southeast Alaska, and similar trends in abundance among these populations suggest the influence of population-regulating forces operating on a regional scale. The Situk River, near Yakutat, Alaska, supports the largest known population of Steelhead in Alaska. Stock assessment studies on this river have collected the longest set of biological data and scale samples for Steelhead in the state. For this study, retrospective scale pattern analysis of samples from Situk River Steelhead was synthesized with regional abundance information to investigate patterns in early marine growth among different life-history and demographic groups, as well as to explore linkages between growth, abundance, and marine environmental variables. Positive correlations were identified between freshwater growth, first ocean-year growth, and adult length, while first ocean-year growth was negatively correlated with second ocean-year growth. Early maturing Steelhead were found to have increased first ocean-year growth and reduced adult length relative to later maturing Steelhead, confirming connections between growth and maturation. Correlations in abundance among Southeast Alaska Steelhead populations suggest that marine and climatic drivers may impact these populations in a regionally coherent manner. Correlations among patterns in abundance also varied along a distance gradient: populations located closer to the Situk River were more correlated with the Situk River than more distant populations. Positive relationships between Gulf of Alaska sea surface temperature, North Pacific Gyre Oscillation, and Situk River Steelhead abundance further supported the importance of climate-driven marine conditions to Steelhead productivity. While conservation concerns for Steelhead in Southeast Alaska are currently minimal, proactive investigations into life-history diversity and population linkages may become more relevant with increased marine ecosystem variability related to climate change.
    • Evaluation of growth and migration trends on the survival and recruitment of chinook salmon in Southeastern Alaska rivers

      Berkman, Stephanie; Sutton, Trent; Adkison, Milo; Mueter, Franz (2017-12)
      Highly variable recruitment and declines in productivity and abundance of Chinook Salmon Oncorhynchus tshawytscha have created economic and cultural hardships for communities throughout Alaska. Although pre- and post-smolt growth are important for determining brood-year (BY) survival and productivity for Pacific salmon through size-mediated mortality, these relationships remain unclear for Chinook Salmon. As a result, it is necessary to better understand the relationships between environmental and biological factors that influence freshwater and marine growth, smolt outmigrations, and recruitment success. This study used retrospective growth to identify the importance of annual growth in determining BY survival and recruitment, determine if growth dependency between growth zones was present, and examine growth differences among age classes for Chinook Salmon in the Chilkat (BYs 1985 - 2007) and Stikine (BYs 1991 - 1998 and 2000 - 2007) rivers. Biological and environmental factors were also assessed to determine their influence on freshwater smolt production, smolt outmigration, and marine survival. Greater first-year marine growth was correlated with higher BY total return and productivity for Chinook Salmon from the Chilkat River and higher BY marine survival for Chinook Salmon from the Stikine River. Daily smolt outmigration of Chilkat River Chinook Salmon was positively correlated to water temperature and negatively correlated to discharge (Deviance explained = 68.5%), while timing of the start of outmigration was influenced by nearshore sea surface temperatures (R² = 0.57) and timing of the mid and end points were positively related to smolt length (R² = 0.72 and 0.34, respectively). Freshwater smolt production was negatively correlated to parr length and fall discharge and positively correlated to spring temperature and discharge (R²adj= 0.52). Marine survival of Stikine River Chinook Salmon was significantly related to smolt size (R² = 0.26), while Chilkat River Chinook Salmon were positively related to migration timing and smolt length and negatively related to discharge (R² = 0.5). These results support the importance of the early marine period in determining year-class strength and highlight the variation in mechanisms that influence recruitment success of Chinook Salmon stocks.
    • Growth and post-harvest quality of selected Pacific oysters (Crassostrea gigas) cultured in Kachemak Bay, Alaska, and Puget Sound, Washington, in October of 2009 and June of 2010

      Thomas, Stuart Rendell; Oliveira, Alexandra; RaLonde, Ray; Eckert, Ginny; Langdon, Chris (2012-05)
      The primary objective of this project was to evaluate the growth, biochemical and fatty acid composition, physical and shell characteristics, and basic reproductive development of families of Pacific oysters (Crassostrea gigas) from the USDA-funded Molluscan Broodstock Program (MBP) planted in suspended culture in Kachemak Bay (KB), Alaska, and at an intertidal site in Thorndyke Bay (TB), Puget Sound, Washington. The MBP selects oysters to improve yields, growth, and survival, but little is known about the effects of selective breeding on other biological characteristics of selected oysters. Shell and meat characteristics of oysters from each of the seven highest-yielding MBP families were compared with those from non-selected control families at each site, which were sampled in October of 2009 and in June of 2010. Biometric and growth data, proximate compositions, fatty acid compositions, and basic degree of reproductive development were measured and compared by family, site, and sampling time. Selection improved yield, growth, and survival in MBP Cohort 20 oysters over three years of growout at KB. Colder water temperatures at KB relative to TB inhibited reproductive development, altering the biochemical composition of oysters within sites and between sampling times. Oysters grown at KB were slower growing and smaller when compared to TB, but higher in glycogen, Omega-3, and Omega-6 fatty acids (particularly docosahexaenoic acid: 22:6 Omega 3). Different latitudes and culture types were contributing factors for observed differences in growth, physiology, and composition, resulting in characteristically unique oysters from either site.
    • Inter-decadal change in sablefish, Anoplopoma fimbria, growth and maturity in the Northeast Pacific Ocean

      Howard, Katy B.; Adkison, Milo D.; Hillgruber, Nicola; Sigler, Michael F. (2008-08)
      Errors in growth and maturity estimates can drastically affect the spawner-per-recruit threshold used to recommend commercial fish catch quotas. Growth and maturity parameters for Alaskan sablefish, Anoplopoma fimbria, have not been updated for stock assessment purposes for 20 years, even though sablefish aging has continued. In this study, the old length-stratified data set (1981-1993) was updated and corrected for bias. In addition, newer, randomly collected samples (1996-2004) were analyzed, and new length-at-age, weight-at-age, and maturity-at-age and length parameters were estimated. A comparison of the two datasets showed that in recent years, sablefish are growing larger and maturing later and that growth and maturity differ somewhat among regions. The updated growth information improves data fits in the sablefish stock assessment model. It also provides results that are biologically reasonable. These updated and improved estimates of sablefish growth and maturity help ensure the continued proper management of this commercially important species in Alaskan waters.
    • Lake trout (Salvelinus namaycush) otoliths as indicators of past climate patterns and growth in Arctic lakes

      Torvinen, Eric S.; Falke, Jeffrey; Arp, Christopher; Zimmerman, Christian; Sutton, Trent (2017-05)