Catch-and-release (C&R) is a common practice in recreational angling for northern pike (), whereby the angler releases the fish back into the water after capture with the expectation that it will survive with negligible stress and physical injuries. This may not always be the case, as hooking in critical anatomical locations, such as gills, esophagus, and stomach, increases the frequency of bleeding at the hook wound and has been recognized as a key determinant of post-release mortality in pike. Several factors (e.g. bait type and size, hook characteristics, and fish length) can influence the risk of hooking in critical locations, and the fish’s willingness to strike the fishing lure/bait may largely depend on previous feeding history and associated motivation to feed. In this respect, food deprivation and greater feeding motivation can be expected to result in an intensified response and more forceful attacks on fishing lures/baits, which could increase the risk of hooking injuries in sensitive tissues, as the fish may ingest the hook more deeply. Here, we assess the hooking location and bleeding occurrence in pike caught on soft plastic shads and baitfish in a shallow eutrophic lake. The prey fish density of this lake, primarily common roach (), has been substantially reduced by seining as part of a lake restoration project. Experimental angling sessions took place at the end of 2020 and 2022, approximately 1–2 months and 25–26 months after the initial reduction in prey fish density, respectively. Removal of roach from the lake was also done regularly by seining after the angling sessions in 2020. Pike angled in 2022 had significantly lower body condition than individuals caught in 2020, indicating that mass removal of roach from the lake resulted in food shortage. The risk of hooking in critical locations (herein defined as hooking in gills and back of mouth) was not associated to angling year, body condition, or length of the pike. However, across the two angling years, the incidence of hooking in critical locations was higher for soft plastic shads compared to baitfish (24.2% versus 7.4%). Pike caught on soft plastic shads also bled more frequently than individuals caught on baitfish (19.7% versus 6.2%), most likely due to the fact that hooking in the gills almost exclusively occurred with soft plastic shads. Bleeding propensity was also not related to angling year, body condition, or fish length. Hence, the present study found no evidence that long-term reductions in food availability and resulting declines in body condition influence how pike strike and ingest fishing lures/baits, at least not in a manner that increases the risk of hooking injuries in sensitive locations. Instead, bait type seems to play the largest role for the observed bleeding patterns. We recommend that future studies investigate the potential effects of C&R angling on the post-release survival of pike with reduced body condition due to limited food availability.

中文翻译：

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在猎物鱼可用性减少的湖中进行休闲性捕获和释放钓鱼时捕获的白斑狗鱼（Esox lucius）的解剖钩位置和出血发生情况

捕获并释放 (C&R) 是休闲钓鱼北梭子鱼的常见做法，钓鱼者在捕获后将鱼放回水中，期望它能够在压力和身体伤害微不足道的情况下生存。情况可能并非总是如此，因为在关键的解剖位置（例如鳃、食道和胃）进行钩挂会增加钩伤处出血的频率，并且已被认为是梭子鱼放生后死亡率的关键决定因素。有几个因素（例如饵料类型和大小、鱼钩特征和鱼长度）会影响关键位置上钩的风险，并且鱼撞击鱼饵/饵料的意愿可能很大程度上取决于以前的进食历史和相关的进食动机。在这方面，食物匮乏和更大的进食动机预计会导致对鱼饵/鱼饵的强烈反应和更强烈的攻击，这可能会增加敏感组织中鱼钩受伤的风险，因为鱼可能会更深地吞下鱼钩。在这里，我们评估了软塑料鲥鱼捕获的梭子鱼和富营养化浅湖中的饵鱼的上钩位置和出血情况。作为湖泊恢复项目的一部分，通过围网捕捞，该湖的被捕食鱼密度（主要是普通蟑螂）已大大减少。实验性钓鱼活动于 2020 年底和 2022 年进行，分别在被捕食鱼密度最初降低后约 1-2 个月和 25-26 个月。2020 年钓鱼活动结束后，还定期通过围网将蟑螂从湖中清除。2022 年捕获的梭子鱼的身体状况明显低于 2020 年捕获的个体，这表明从湖中大规模清除蟑螂导致了食物短缺。关键位置钩住的风险（本文定义为钩住鳃和嘴后部）与钓鱼年份、身体状况或梭子鱼的长度无关。然而，在这两个钓鱼年中，与饵鱼相比，软塑料鲥鱼在关键位置上钩的发生率更高（24.2% 比 7.4%）。用软塑料鲥鱼捕获的梭子鱼也比用饵鱼捕获的梭子鱼流血更频繁（19.7％对6.2％），很可能是因为钩住鳃几乎只发生在软塑料鲥鱼身上。出血倾向也与钓鱼年份、身体状况或鱼的长度无关。因此，本研究发现没有证据表明食物供应的长期减少以及由此导致的身体状况下降会影响梭子鱼的攻击和摄入鱼饵/鱼饵的方式，至少不会增加敏感地点钩伤的风险。相反，诱饵类型似乎对观察到的出血模式起着最大的作用。