The brown trout, Salmo trutta L., population in River Skjern, a major tributary stream to the Danish lagoon Ringkøbing Fjord, is reduced despite various efforts towards its recovery. This study investigated if bycatch of migratory trout in the commercial whitefish, Coregonus lavaretus L., fishery in the lagoon might be a significant cause. Experimental surveys were carried out to examine bycatch levels using different fishing protocols and gear types. Data were also collected through an observer fishery, questionnaires and from a database on local fisheries statistics. Trout occurred as bycatch in low numbers in the observer fishery (mean of 0.2 trout per km gillnet). The whitefish fishing protocols examined in the experimental surveys revealed a significantly lower bycatch of trout when fishing with sinking gillnets than floating gillnets. However, few fishers use floating gillnets in the present-day fishery. The other fishing practices examined revealed no alternatives that would reduce trout bycatch markedly. The results indicated that the whitefish fishery in the lagoon is not the major reason for the lack of recovery of the trout population in River Skjern.

中文翻译：

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商业刺网渔业中兼捕的褐鳟 Salmo trutta，针对白鲑 Coregonus lavaretus

丹麦环礁湖林克宾峡湾的主要支流斯凯恩河中的褐鳟 ( Salmo trutta L.) 种群数量有所减少，尽管为恢复其所做的各种努力而有所减少。本研究调查是否在商业白鲑Coregonus lavaretus中兼捕洄游鳟鱼L.，泻湖中的渔业可能是一个重要原因。进行了实验调查，以检查使用不同捕鱼协议和渔具类型的兼捕水平。还通过观察员渔业、问卷调查和当地渔业统计数据库收集数据。在观察员渔业中，鳟鱼作为兼捕的数量很少（平均每公里刺网 0.2 条鳟鱼）。在实验调查中检查的白鲑捕捞协议显示，使用下沉刺网捕鱼时，鳟鱼的兼捕量明显低于浮动刺网。然而，在当今的渔业中，很少有渔民使用浮动刺网。所检查的其他捕捞方法表明没有其他方法可以显着减少鳟鱼兼捕。