Thompson J N, Beauchamp D A
Washington Cooperative Fish and Wildlife Research Unit, School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, Washington, 98195, U.S.A.
U.S. Geological Survey, Washington Cooperative Fish and Wildlife Research Unit, School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, Washington, 98195, U.S.A.
J Fish Biol. 2016 Sep;89(3):1720-39. doi: 10.1111/jfb.13078. Epub 2016 Jul 10.
Increased freshwater growth of juvenile steelhead Oncorhynchus mykiss improved survival to smolt and adult stages, thus prompting an examination of factors affecting growth during critical periods that influenced survival through subsequent life stages. For three tributaries with contrasting thermal regimes, a bioenergetics model was used to evaluate how feeding rate and energy density of prey influenced seasonal growth and stage-specific survival of juvenile O. mykiss. Sensitivity analysis examined target levels for feeding rate and energy density of prey during the growing season that improved survival to the smolt and adult stages in each tributary. Simulated daily growth was greatest during warmer months (1 July to 30 September), whereas substantial body mass was lost during cooler months (1 December to 31 March). Incremental increases in annual feeding rate or energy density of prey during summer broadened the temperature range at which faster growth occurred and increased the growth of the average juvenile to match those that survived to smolt and adult stages. Survival to later life stages could be improved by increasing feeding rate or energy density of the diet during summer months, when warmer water temperatures accommodated increased growth potential. Higher growth during the summer period in each tributary could improve resiliency during subsequent colder periods that lead to metabolic stress and weight loss. As growth and corresponding survival rates in fresh water are altered by shifting abiotic regimes, it will be increasingly important for fisheries managers to better understand the mechanisms affecting growth limitations in rearing habitats and what measures might maintain or improve growth conditions and survival.
幼年虹鳟（Oncorhynchus mykiss）在淡水中生长加快，提高了其存活至幼鲑和成鱼阶段的几率，因此促使人们对影响关键时期生长的因素进行研究，这些因素会影响其后续生命阶段的存活。对于三条热状况不同的支流，采用生物能量学模型来评估猎物的摄食率和能量密度如何影响幼年虹鳟的季节性生长和特定阶段的存活。敏感性分析考察了生长季节中猎物摄食率和能量密度的目标水平，这些水平能提高各支流中幼年虹鳟存活至幼鲑和成鱼阶段的几率。模拟的日生长量在较温暖的月份（7月1日至9月30日）最大，而在较寒冷的月份（12月1日至3月31日）体重会大幅下降。夏季猎物年摄食率或能量密度的逐渐增加拓宽了生长较快时的温度范围，并增加了幼年虹鳟的平均生长量，使其与存活至幼鲑和成鱼阶段的虹鳟相当。在水温较高、生长潜力增加的夏季，通过提高摄食率或食物的能量密度，可以提高其存活至后期生命阶段的几率。各支流夏季较高的生长量可以提高其在随后导致代谢应激和体重减轻的较寒冷时期的恢复能力。由于非生物环境的变化会改变淡水环境中的生长和相应的存活率，渔业管理人员更好地了解影响养殖栖息地生长限制的机制以及哪些措施可以维持或改善生长条件和存活率将变得越来越重要。
