In diet studies, stomach contents from predatory fish may be difficult to identify due to digestion. The Gizzard Shad Dorosoma cepedianum is an important prey species for sport fish; thus, determining the size of ingested shad can assist with evaluating competitive interactions, bioenergetic patterns, and niche partitioning and can add precision to predictive models. The gizzard organ of clupeids appears to be more resistant to digestion compared to other tissues and can often be found in the stomachs of predatory fish after other tissues from Gizzard Shad are digested. If the gizzard diameter is proportional to Gizzard Shad weight or length, it could be a useful structure for estimating the size of partially digested Gizzard Shad when other structures that are traditionally used to estimate weight or length (e.g., backbones) are damaged due to advanced digestion. For this reason, we evaluated the allometry relating gizzard diameter and Gizzard Shad weight and TL. We sampled a total of 936 Gizzard Shad from nine Oklahoma reservoirs. Fish were frozen and later thawed; they were measured for weight (±0.01 g) and TL (±1 mm), and the gizzard was then removed. Gizzard diameter was measured (±0.1 mm) at its widest point using calipers. Eight different equations were evaluated to find the best relationship (lowest Akaike’s information criterion) between gizzard diameter and weight or length. The relationship between gizzard diameter and fish weight was best modeled as a second‐order polynomial, whereas the relationship between gizzard diameter and fish TL was best described by a five‐parameter Richard’s equation. Both relationships explained over 80% of the variation in Gizzard Shad size. The 95% CIs for weight (±4–7%) and TL (±2–7%) indicated good overall precision for mean fish size based on gizzard diameter. Therefore, we recommend using gizzard diameter to determine weight and TL from diet samples when advanced digestion of Gizzard Shad limits the use of more traditional metrics (TL, backbone length, etc.).

中文翻译：

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使用食izz直径估计食肉动物饮食中部分消化的食izz的重量和长度

在饮食研究中，由于消化作用，捕食性鱼类的胃内容物可能难以识别。izz ShaDorosoma cepedianum是运动鱼的重要捕食物种；因此，确定摄入的sha鱼的大小可以帮助评估竞争性相互作用，生物能模式和生态位分配，并可以为预测模型增加精度。与其他组织相比，丘比特的izz的器官对消化的抵抗力更强，在消化了G的其他组织后，通常在掠食性鱼类的胃中发现它们。如果the的直径与G的重量或长度成正比，则当传统上用来估计重量或长度的其他结构（例如主干）由于结皮受损而损坏时，izz是估计部分消化的G的尺寸的有用结构。消化。因此，我们评估了与ometry的直径，G的重量和TL有关的异速生长法。我们从俄克拉荷马州的9个水库中总共采样了936个Gizzard Shad。鱼被冷冻后融化；测量它们的重量（±0.01 g）和TL（±1 mm），然后除去izz。使用卡尺在最宽点测量izz的直径（±0.1毫米）。对八个不同的方程进行了评估，以找出g的直径与体重或长度之间的最佳关系（最低的赤池氏信息标准）。g的直径和鱼的重量之间的关系最好用二阶多项式来建模，而best的直径和鱼的TL之间的关系最好用五参数Richard方程来描述。两种关系都解释了Gizzard Shad大小变化的80％以上。重量（±4–7％）和TL（±2–7％）的95％置信区间表明，根据g的直径，平均鱼类大小的总体精度良好。