DeFilippo Lukas B, Schindler Daniel E, Ohlberger Jan, Schaberg Kevin L, Foster Matt Birch, Ruhl Darin, Punt André E
School of Aquatic and Fishery Sciences University of Washington Seattle Washington.
Alaska Department of Fish and Game Division of Commercial Fisheries Westward Region Office Kodiak Alaska.
Evol Appl. 2018 Dec 1;12(2):214-229. doi: 10.1111/eva.12709. eCollection 2019 Feb.
Males of many fish species exhibit alternative reproductive tactics, which can influence the maturation schedules, fishery productivity, and resilience to harvest of exploited populations. While alternative mating phenotypes can persist in stable equilibria through frequency-dependent selection, shifts in tactic frequencies have been observed and can have substantial consequences for fisheries. Here, we examine the dynamics of precocious sneaker males called "jacks" in a population of sockeye salmon () from Frazer Lake, Alaska. Jacks, which are of little commercial value due to their small body sizes, have recently been observed at unusually high levels in this stock, degrading the value of regional fisheries. To inform future strategies for managing the prevalence of jacks, we used long-term monitoring data to identify what regulates the frequencies of alternative male phenotypes in the population over time. Expression of the jack life history could not be explained by environmental factors expected to influence juvenile body condition and maturation probability. Instead, we found a strong positive association between the proportion of individuals maturing as jacks within a cohort and the prevalence of jacks among the males that sired that cohort. Moreover, due to differences in age-at-maturity between male phenotypes, and large interannual variability in recruitment strength, jacks from strong year-classes often spawn among older males from the weaker recruitments of earlier cohorts. Through such "cohort mismatches," which are amplified by size-selective harvest on older males, jacks frequently achieve substantial representation in the breeding population, and likely high total fertilizations. The repeated occurrence of these cohort mismatches appears to disrupt the stabilizing influence of frequency-dependent selection, allowing the prevalence of jacks to exceed what might be expected under equilibrium conditions. These results emphasize that the dynamics of alternative life histories can profoundly influence fishery performance and should be explicitly considered in the management of exploited populations.
许多鱼类的雄性表现出不同的繁殖策略，这可能会影响成熟时间表、渔业生产力以及被开发种群对捕捞的恢复能力。虽然通过频率依赖选择，不同的交配表型可以在稳定的平衡中持续存在，但已观察到策略频率的变化，这可能对渔业产生重大影响。在此，我们研究了阿拉斯加弗雷泽湖红大马哈鱼种群中被称为“雄鱼”的早熟偷腥雄鱼的动态变化。雄鱼由于体型小，商业价值不大，但最近在该种群中被观察到处于异常高的水平，降低了区域渔业的价值。为了为未来管理雄鱼数量的策略提供依据，我们利用长期监测数据来确定随着时间的推移，是什么调节了种群中不同雄性表型的频率。雄鱼生活史的表达无法用预期会影响幼鱼身体状况和成熟概率的环境因素来解释。相反，我们发现一个同龄组中成熟为雄鱼的个体比例与该同龄组父本雄鱼中雄鱼的比例之间存在很强的正相关关系。此外，由于雄性表型之间成熟年龄的差异，以及补充强度的年际变化很大，来自强繁殖群体的雄鱼经常在来自早期较弱补充群体的老龄雄鱼中产卵。通过这种“同龄组错配”，由于对老龄雄鱼的大小选择性捕捞而被放大，雄鱼经常在繁殖种群中获得大量代表，并且可能实现高总受精率。这些同龄组错配的反复出现似乎破坏了频率依赖选择的稳定影响，使得雄鱼的数量超过了平衡条件下可能预期的数量。这些结果强调，不同生活史的动态变化会深刻影响渔业表现，在被开发种群的管理中应明确加以考虑。
