Abstract Grouping behavior occurs across a wide variety of taxa, both within and between species. While members are thought to obtain foraging and antipredator advantages, they can also experience costs in the forms of competition or increased conspicuity to predators. The mechanisms behind these costs and benefits can vary depending on group composition, ultimately influencing the choice of which groups to join. Mixed-species fish shoals are common in shallow nearshore habitats, where research has shown that juvenile bonefish (Albula vulpes) occur among similarly-sized mojarras (Eucinostomus spp.) at a rate far exceeding that predicted given the fishes overlapping habitat use, suggesting that bonefish may actively select to join mojarras. To evaluate this hypothesis experimentally, we assessed the shoaling preferences of bonefish when presented with shoals of conspecifics, mojarras, or another gregarious co-occurring fish (pilchard; Harengula jaguana) in a laboratory setting. Focal juvenile bonefish (n = 25) were given the choice between: (i) conspecifics or mojarra, and (ii) conspecifics or pilchard, tested in shoal sizes of one, two, four, and eight. Bonefish were also given the choice between a mixed shoal (two conspecifics, two mojarra) as an alternative to single species shoals of either: (iii) four conspecifics, or (iv) four mojarra. Juvenile bonefish exhibited a strong association with mojarra, spending significantly more time with them than conspecifics in all but one treatment. Moreover, focal fish showed no detectable preference between conspecifics or pilchard, regardless of shoal size. In mixed shoal treatments, focal fish spent significantly more time wherever there was a higher proportion of mojarra. These findings imply that the co-occurrence of bonefish and mojarra in nature is largely a product of bonefish shoal choice behavior, and likewise that any costs that bonefish might incur by joining mojarras (i.e., oddity effects) are likely outweighed by the putative benefits of doing so, which potentially include access to social information and/or reduced intraspecific competition.

中文翻译：

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幼年骨鱼（Albula vulpes）在同种和另一种群居的共生物种存在的情况下表现出偏爱与mojarra（Eucinostomus spp.）的浅滩

摘要 分组行为发生在种类繁多的分类群中，包括物种内部和物种之间。虽然成员被认为获得了觅食和反捕食者的优势，但他们也可能以竞争或增加对捕食者的显眼性的形式承受成本。这些成本和收益背后的机制可能因群体组成而异，最终影响加入哪些群体的选择。混种鱼群在浅海近岸栖息地很常见，研究表明，幼年骨鱼（Albula vulpes）出现在类似大小的莫哈拉（Eucinostomus spp.）中的速度远远超过预测的鱼类重叠栖息地，这表明骨鱼可能会主动选择加入mojarras。为了通过实验评估这个假设，我们评估了在实验室环境中与同种、mojarras 或其他群居性共生鱼（沙丁鱼；Harengula jaguana）成群结队的鲽鱼的成群偏好。焦点幼年骨鱼 (n = 25) 可以选择：(i) 同种或 mojarra，和 (ii) 同种或沙丁鱼，在大小为 1、2、4 和 8 的浅滩中进行测试。也给了北梭鱼选择混合浅滩（两个同种，两个 mojarra）作为单一物种浅滩的替代：（iii）四个同种，或（iv）四个 mojarra。幼年骨鱼与 mojarra 表现出很强的关联，在除一种处理外的所有处理中，与它们相处的时间明显多于同种。此外，无论浅滩大小如何，焦点鱼在同种或沙丁鱼之间都没有明显的偏好。在混合浅滩处理中，在mojarra比例较高的地方，焦点鱼花费的时间明显更多。这些发现意味着，骨鱼和 mojarra 在自然界中的共同出现在很大程度上是骨鱼浅滩选择行为的产物，同样，骨鱼加入 mojarras 可能产生的任何成本（即奇怪效应）可能被推定的好处所抵消。这样做，这可能包括获得社会信息和/或减少种内竞争。