Fish communities face changes in environmental conditions and fishing that affects the abundances and structures of the populations. Before 1960s there were abundant stocks of both pikeperch () and whitefish () in Lake Oulujärvi, but in 1960s–1970s the stock of pikeperch declined to very low levels while whitefish stock remained abundant. Due to massive re-introductions, pikeperch recovered since 1999 and is again common while whitefish stock has declined. To understand the ecosystem-level changes observed along the recovery of the pikeperch stock, we constructed a food web model capturing the two most recent states of pikeperch abundance in Lake Oulujärvi. We used Allometric Trophic Network (ATN) model to simulate the pelagic food web in the presence and absence of pikeperch and in the presence and absence of fishing. To parametrize ATN model based on body masses and food web interactions, we used data collections of fish cohort analyses, fish individuals, fish stomach contents, zooplankton, and phytoplankton in Lake Oulujärvi. Pikeperch decreased the biomasses of its planktivorous prey. Fishing truncated the age distribution of planktivorous fish. Pikeperch and fishing had synergistic negative effects on vendace () and smelt () percentages of fish biomass, and antagonistic negative effect on whitefish and brown trout () percentages of fish biomass. and other predatory zooplankton, and Cyclopoida zooplankton guilds increased with fishing and pikeperch. Fishing, and pikeperch in the presence of fishing, increased biomass of Crustacean zooplankton guild. There were marked differences between the ATN model simulations and empirically observed time series of fish stock abundances suggesting that the observed changes are partially caused by environmental or fishing-related factors that were not included in the model.

中文翻译：

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顶级捕食者重建和捕捞对模拟食物网的影响：Oulujärvi 湖的异速生长营养网络模型

鱼类群落面临环境条件和捕捞活动的变化，影响种群数量和结构。 1960 年代之前，Oulujärvi 湖中梭鲈 () 和白鲑 () 资源丰富，但在 60 年代至 70 年代，梭鲈资源下降到非常低的水平，而白鲑资源仍然丰富。由于大规模重新引入，梭鲈自 1999 年开始恢复并再次常见，而白鲑鱼群数量则有所下降。为了了解梭鲈种群恢复过程中观察到的生态系统水平变化，我们构建了一个食物网模型，捕捉了 Oulujärvi 湖梭鲈丰度的两个最新状态。我们使用异速生长营养网络（ATN）模型来模拟存在和不存在梭鲈以及存在和不存在捕鱼的情况下的中上层食物网。为了对基于体重和食物网相互作用的 ATN 模型进行参数化，我们使用了 Oulujärvi 湖中鱼类群体分析、鱼类个体、鱼胃内容物、浮游动物和浮游植物的数据收集。梭鲈减少了食浮游生物的猎物的生物量。捕鱼缩短了食浮游生物的年龄分布。梭鲈和捕捞对白鲑 () 和胡瓜鱼 () 鱼类生物量百分比具有协同负面影响，对白鲑和褐鳟 () 鱼类生物量百分比具有拮抗负面影响。和其他捕食性浮游动物以及巨鳍浮游动物群随着捕捞和梭鲈的增加而增加。捕鱼和梭鲈存在下的捕鱼，增加了甲壳类浮游动物协会的生物量。 ATN 模型模拟与经验观察到的鱼类资源丰度时间序列之间存在显着差异，这表明观察到的变化部分是由模型中未包含的环境或捕捞相关因素引起的。