Salmon Research Department, Fisheries Resources Institute, Japan Fisheries Research and Education Agency, Sapporo, Hokkaido, Japan.
PLoS One. 2024 Jul 19;19(7):e0307552. doi: 10.1371/journal.pone.0307552. eCollection 2024.
In Japan, stocked chum salmon (Oncorhynchus keta) fry may have become the perfect prey for non-native brown trout (Salmo trutta), which are popular targets of anglers. If this is the case, fry stocking which is intended to boost commercial fishing may be helping to sustain the populations of an invasive predator. We used dietary and biochemical analyses to examine whether brown trout quickly restore their nutritional status following wintertime declines by preying upon chum salmon fry that are stocked in spring. We targeted six rivers in Hokkaido, Japan, three with fry stocking and three without. Changes in brown trout condition factor, triglyceride contents in muscle and serum, serum insulin-like growth factor-1 (IGF-1; an indicator of short-term growth), and docosahexaenoic acid (DHA; an essential fatty acid abundant in fish) content in muscle were examined between before stocking and during the stocking period in the six rivers. Dietary analysis showed that brown trout preyed on fry during the stocking period in all stocked rivers. Their nutritional status tended to be higher during the stocking period than before stocking in stocked rivers, but not in unstocked rivers. These results suggest that the massive stocking of chum salmon fry provides brown trout with the perfect prey to quickly restore their nutritional status and fuel increased growth; this may therefore be a controversial issue among stakeholders.
在日本，养殖的秋鲑（Oncorhynchus keta）鱼苗可能已成为非本地虹鳟（Salmo trutta）的完美猎物，虹鳟是垂钓者的热门目标。如果情况属实，旨在促进商业捕鱼的鱼苗放养可能有助于维持入侵捕食者的种群。我们使用饮食和生化分析来研究虹鳟是否会通过捕食春季放养的秋鲑鱼苗来快速恢复冬季下降后的营养状况。我们针对日本北海道的六条河流进行了研究，其中三条有鱼苗放养，三条没有。在六条河流中，我们检查了在放养前和放养期间，虹鳟的条件因子、肌肉和血清中的甘油三酯含量、血清胰岛素样生长因子-1（IGF-1；短期生长的指标）和肌肉中的二十二碳六烯酸（DHA；鱼类中丰富的必需脂肪酸）含量的变化。饮食分析表明，在所有放养鱼苗的河流中，虹鳟在放养期间捕食了鱼苗。在放养河流中，它们的营养状况在放养期间往往高于放养前，而在未放养河流中则不然。这些结果表明，大量放养秋鲑鱼苗为虹鳟提供了完美的猎物，使其能够快速恢复营养状况并促进生长；因此，这可能是利益相关者之间有争议的问题。
