Predators often predate on a limited size range of prey, which may or may not overlap with size ranges of same prey targeted by fisheries. When they do overlap, the effect of competition over that prey is immediate, as the predator removes prey, which are at the same time suitable for the fishery. However, if the predator consumes the same prey species as the fishery, but targets smaller prey sizes, this predation on smaller sizes may result in a potential loss of future, rather than current, fishing opportunities. Comparative analyses of predator size preference and fisheries selectivity are scarce, despite their relevance in the context of integrated management of fish populations. We evaluated how size-selective cod predation influences the dynamics of sprat and herring in the Baltic Sea, as well as the competition with pelagic fisheries through immediate and delayed effects. We found a large overlap (30–60%) between prey lengths targeted by cod and fisheries, which was largest in the 1970s–1980s, when cod had higher abundance and was larger in size. Cod generally consumes herring and sprat, which are smaller than those caught by the fisheries, causing both immediate and delayed effects on prey biomass available for the fisheries.

中文翻译：

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鳕鱼和远洋渔业之间的大小选择竞争猎物

捕食者通常捕食有限大小的猎物，这可能与渔业所针对的相同猎物的大小范围重叠，也可能不重叠。当它们确实重叠时，对猎物的竞争效果是立竿见影的，因为捕食者会移除猎物，同时也适合渔业。然而，如果捕食者消耗与渔业相同的猎物种类，但以较小的猎物为目标，这种对较小尺寸的捕食可能会导致未来而不是当前的捕鱼机会的潜在损失。捕食者大小偏好和渔业选择性的比较分析很少，尽管它们在鱼类种群综合管理的背景下具有相关性。我们评估了大小选择性捕食鳕鱼如何影响波罗的海鲱鱼和鲱鱼的动态，以及通过即时和延迟影响与远洋渔业的竞争。我们发现鳕鱼和渔业所针对的猎物长度之间有很大的重叠（30-60%），这在 1970 年代至 1980 年代最大，当时鳕鱼的丰度更高且体型更大。鳕鱼通常消耗鲱鱼和鲱鱼，它们比渔业捕获的要小，对渔业可用的猎物生物量造成即时和延迟影响。