Data from: Temporal constraints on the potential role of fry odors as cues of past reproductive success for spawning lake trout

Deciding where to reproduce is a major challenge for most animals. Many select habitats based upon cues of successful reproduction by conspecifics, such as the presence of offspring from past reproductive events. For example, some fishes select spawning habitat following odors released by juveniles whose rearing habitat overlaps with spawning habitat. However, juveniles may emigrate before adults begin to search for spawning habitat; hence, the efficacy of juvenile cues could be constrained by degradation or dissipation rates. In lake trout (Salvelinus namaycush), odors deposited by the previous year's offspring have been hypothesized to guide adults to spawning reefs. However, in most extant populations, lake trout fry emigrate from spawning reefs during the spring and adults spawn during the fall. Therefore, we postulated that the role of fry odors in guiding habitat selection might be constrained by the time between fry emigration and adult spawning. Time course chemical, physiological, and behavioral assays indicated that the odors deposited by fry likely degrade or dissipate before adults select spawning habitats. Furthermore, fry feces did not attract wild lake trout to constructed spawning reefs in Lake Huron. Taken together, our results indicate fry odors are unlikely to act as cues for lake trout searching for spawning reefs in populations whose juveniles emigrate before the spawning season, and underscore the importance of environmental constraints on social cues.

对于绝大多数动物而言，确定适宜的繁殖场所是一项重大生存挑战。许多动物会依据同种个体成功繁殖的相关线索来选择栖息与繁殖地，比如过往繁殖事件中产生的后代踪迹。例如，部分鱼类会借助幼鱼释放的气味来选择产卵场——这类幼鱼的抚育环境与产卵场存在重叠。然而，幼体可能会在成体开始搜寻产卵场之前就已迁出，因此幼体相关线索的有效性可能会受到气味降解与消散速率的限制。

在湖鳟（lake trout，*Salvelinus namaycush*）中，学界曾假设上年产出的幼体留下的气味会引导成体前往产卵礁。但在绝大多数现存的湖鳟种群中，幼鱼会在春季从产卵礁迁出，而成体的产卵行为则发生在秋季。因此，我们推测幼鱼气味在引导成体选择繁殖栖息地的作用，可能会受到幼体迁出与成体产卵之间的时间间隔的制约。

时程化学分析、生理学实验与行为学检测结果表明，幼鱼释放的气味很可能在成体开始选择产卵场之前就已降解或消散。此外，在休伦湖的人工产卵礁实验中，幼鱼粪便并未吸引野生湖鳟前往产卵区域。

综合来看，本研究结果表明，在幼体在繁殖季前就已迁出的湖鳟种群中，幼鱼气味不太可能作为成体搜寻产卵礁的线索；同时本研究也凸显了环境制约因素对社会交流线索的重要影响。