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首页> 外文期刊>Aquatic Sciences >Bottom-up control of whitefish populations in ultra-oligotrophic Lake Brienz
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Bottom-up control of whitefish populations in ultra-oligotrophic Lake Brienz

机译：自下而上控制超营养化的布里恩茨湖白鲑种群

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Lake Brienz, an oligotrophic pre-alpine Swiss lake, went through a mesotrophic period between around 1960 and 1990. The lake is moderately turbid caused by fine suspended solids from glaciers. In 1999, yield of the economically important whitefish collapsed to about 10 % of preceding years. Age and growth analysis of the two whitefish types examined - small and large type - revealed an almost complete halt of growth from 1999 until June 2000, paralleled by poor condition. Zooplankton data showed that cladocerans, the preferred food of white-fish, were rare from January 1999 until June 2000. In order to elucidate the trophic relationships between zooplankton and fish, the «Wisconsin Bioenergetics Model 3.0» was applied. The analysis showed that poor growth and condition of whitefish in 1999 and 2000 were caused by the scarcity of primary food organisms. The relatively small and slender fish could not be caught by legal gillnets, which resulted in poor fishing yield. Evidence is presented that cladoceran biomass governs food consumption by the fish («bot-tom-up effect»), while the effect of fish predation on cladocerans was found to be negligible, most likely also during the period of poor growth. Turbidity did not appear to significantly interfere with the feeding of whitefish. Growth, condition and commercial yield of whitefish partly increased again after 2000, but due to the very low productivity of Lake Brienz, fishing yield will remain low. Food chains in such oligotrophic systems are fragile. It is likely that a future collapse of the cladoceran population and, thus, the whitefish fishery will happen again.
机译：布里恩茨湖是一种贫营养的瑞士前高山湖泊，在1960年至1990年之间经历了中营养时期。该湖为中等程度的浑浊，这是由于冰川中细微的悬浮物引起的。 1999年，具有经济意义的白鲑的产量下降至前几年的10％左右。对两种被检查的白鲑类型（大小型）的年龄和生长分析表明，从1999年到2000年6月，几乎完全停止了生长，同时条件较差。浮游动物的数据显示，从1999年1月至2000年6月，作为白鱼首选食物的锁骨鱼类很少见。为了阐明浮游动物与鱼类之间的营养关系，应用了“威斯康星州生物能源模型3.0”。分析表明，1999年和2000年白鱼的生长和状况不佳是由于主要食物生物的缺乏造成的。相对较小和纤细的鱼无法被合法的刺网捕捞，这导致捕鱼产量低下。有证据表明，锁骨的生物量控制着鱼类的食物消耗（“自下而上效应”），而鱼类捕食对锁骨的影响却可以忽略不计，最有可能在生长不良的时期。浊度似乎并未显着干扰白鱼的摄食。 2000年后，白鱼的生长，状况和商业产量再次部分增加，但是由于布里恩茨湖的生产力非常低，捕捞产量将保持较低水平。这种贫营养系统中的食物链很脆弱。锁骨种群的未来可能崩溃，因此白鱼捕捞将再次发生。

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