Abstract Evans ML, Kohler AE, Griswold RG, Tardy KA, Eaton KR, Ebel JD. Salmon-mediated nutrient flux in Snake River sockeye salmon nursery lakes: the influence of depressed population size and hatchery supplementation. Lake Reserv Manage. 36:75–86. Since the 1970s, Snake River sockeye salmon (Oncorhynchus nerka) have returned in low numbers to nursery lakes in central Idaho, consequently diminishing marine-derived nutrient subsidies to freshwater spawning and rearing environments. In healthy Pacific salmon populations, returning adults generally import more nutrients than juveniles export, resulting in net positive salmon-mediated nutrient fluxes to freshwater ecosystems. To mitigate for declining sockeye salmon returns, Snake River nursery lakes have been stocked with embryos, with captive-reared juveniles and adults, and fertilized with inorganic nutrients. Here, we examine sockeye salmon-mediated nutrient flux in 3 nursery lakes, Alturas, Pettit, and Redfish, across 20 yr of study (1998–2017). In Redfish Lake, sockeye salmon-mediated nutrient flux was positive in all years when imports from the captive-rearing program were considered in our estimates. Without captive-rearing program inputs, Redfish Lake nutrient flux was positive in only 40% and 45% of years for phosphorus and nitrogen, respectively. In Alturas and Pettit lakes, nutrient export by juveniles exceeded nutrient import by adults in 67% and 56% of years for phosphorus and nitrogen, respectively. Overall, our findings suggest that a sufficient number of adult recruits relative to juvenile migrants, corresponding to a smolt-to-adult return rate > 0.78%, is needed to achieve positive salmon-mediated nutrient flux within lakes and that this will depend on both adequate population productivity and enhanced marine and freshwater habitat connectivity.

中文翻译：

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蛇河红鲑鱼苗圃湖泊中鲑鱼介导的营养通量：种群规模下降和孵化场补充的影响

摘要 Evans ML、Kohler AE、Griswold RG、Tardy KA、Eaton KR、Ebel JD。蛇河红鲑鱼苗圃湖泊中鲑鱼介导的营养通量：种群规模下降和孵化场补充的影响。湖泊保护区管理。36:75-86。自 1970 年代以来，蛇河红鲑鱼 (Oncorhynchus nerka) 以少量返回爱达荷州中部的育苗湖，因此减少了对淡水产卵和饲养环境的海洋衍生营养补贴。在健康的太平洋鲑鱼种群中，返回的成鱼通常进口比幼鱼出口更多的营养物质，从而导致鲑鱼介导的淡水生态系统养分通量为净正值。为了减轻红鲑鱼数量下降的影响，蛇河育苗湖已经放养了胚胎、人工饲养的幼鱼和成鱼，并施以无机养分。在这里，我们在 20 年的研究中（1998-2017 年）检查了 3 个育苗湖 Alturas、Pettit 和 Redfish 中红鲑鱼介导的营养通量。在红鱼湖，当我们的估计中考虑到来自圈养饲养计划的进口时，红鲑鱼介导的营养通量在所有年份都是正的。在没有圈养饲养计划投入的情况下，红鱼湖养分通量分别在 40% 和 45% 的年份中磷和氮为正。在 Alturas 和 Pettit 湖中，在磷和氮方面，幼鱼的养分输出量分别在 67% 和 56% 年内超过了成鱼的养分输入量。总体而言，我们的研究结果表明，相对于青少年移民而言，有足够数量的成年新兵，对应于从幼小到成年的返回率 > 0.78%，