Predatory fish structure communities through prey pursuit and consumption and, in many marine systems, the gadoids are particularly important. These predators have flexible feeding behaviours and often feed on large prey items. Digestion times of large prey are usually longer than handling times, and gut processing limits feeding rate at high prey density. Optimizing the gut content mix can therefore be an important behavioural strategy. Here, we develop a foraging model that incorporates gut processing and use the model to disentangle internal and external limitations on feeding in the omnivorous cod (Gadus morhua, Gadidae). We extend the traditional definition of prey profitability to consider prey digestive quality, which we quantify for prey of Northeast Atlantic cod populations. We find an important role for gut limitation; within a range of ecologically relevant temperatures and prey densities, predicted feeding rates were strongly reduced compared to feeding constrained by external factors only, and the optimal diet composition under gut limitation differed from predictions from traditional foraging theory. Capelin, a main prey of Northeast Arctic cod, had the highest digestive quality of all prey across ecosystems, but the cold temperatures in the Barents Sea strongly limited feeding rate by slowing down digestion. Baltic cod fed on a higher proportion of poor‐quality prey compared to the other populations, contributing to its slow growth in relation to water temperature. Gut limitation is particularly important to consider in foraging models for fish with many alternative prey species or fish occupying cold waters where digestion is slow.

中文翻译：

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没有甜点的空间：肠道有限的掠食性鱼类的捕食机制选择模型

通过猎物的捕食和消费，掠夺性鱼类结构群落，在许多海洋系统中，类小动物特别重要。这些捕食者具有灵活的喂养行为，通常以大型猎物为食。大猎物的消化时间通常长于处理时间，肠处理会限制高猎物密度下的进食速度。因此，优化肠内容物混合可能是重要的行为策略。在这里，我们开发了一种结合肠道处理的觅食模型，并使用该模型来消除杂食性鳕鱼（Gadus morhua）的内部和外部限制，Gadidae）。我们扩展了对猎物获利能力的传统定义，以考虑猎物的消化质量，从而量化了东北大西洋鳕鱼种群的猎物。我们发现肠道限制的重要作用。在与生态相关的温度和猎物密度范围内，与仅受外部因素限制的饲喂相比，预计的饲喂速度大大降低，并且在肠道限制下的最佳饮食组成与传统觅食理论的预测不同。Capelin是东北北极鳕鱼的主要猎物，在整个生态系统中具有最高的消化质量，但是巴伦支海的寒冷温度通过减慢消化速度而严重限制了进食速度。与其他种群相比，波罗的海鳕以劣质猎物为食，导致其与水温有关的缓慢增长。在具有多种替代捕食物种的鱼类或占据缓慢消化的冷水中的鱼类的觅食模型中，考虑到肠道限制尤其重要。