Matte Jean-Michel O, Fraser Dylan J, Grant James W A
Department of Biology, Concordia University, Montreal, Quebec, Canada.
J Fish Biol. 2024 Jul;105(1):10-22. doi: 10.1111/jfb.15748. Epub 2024 Apr 10.
Understanding recruitment, the process by which individuals are added to a population or to a fishery, is critical for understanding population dynamics and facilitating sustainable fisheries management. Important variation in recruitment dynamics is observed among populations, wherein some populations exhibit asymptotic productivity and others exhibit overcompensation (i.e., compensatory density-dependence in recruitment). Our ability to understand this interpopulation variability in recruitment patterns is limited by a poor understanding of the underlying mechanisms, such as the complex interactions between density dependence, recruitment, and environment. Furthermore, most studies on recruitment are conducted using an observational design with long time series that are seldom replicated across populations in an experimentally controlled fashion. Without proper replication, extrapolations between populations are tenuous, and the underlying environmental trends are challenging to quantify. To address these issues, we conducted a field experiment manipulating stocking densities of juvenile brook trout Salvelinus fontinalis in three wild populations to show that these neighboring populations-which exhibit divergent patterns of density dependence due to environmental conditions-also have important differences in recruitment dynamics. Testing against four stock-recruitment models (density independent, linear, Beverton-Holt, and Ricker), populations exhibited ~twofold variation in asymptotic productivity, with no overcompensation following a Beverton-Holt model. Although environmental variables (e.g., temperature, pH, depth, substrate) correlated with population differences in recruitment, they did not improve the predictive power in individual populations. Comparing our patterns of recruitment with classic salmonid case studies revealed that despite differences in the shape and parameters of the curves (i.e., Ricker vs. Beverton-Holt), a maximum stocking density of about five YOY fish/m emerged. Higher densities resulted in very marginal increases in recruitment (Beverton-Holt) or reduced recruitment due to overcompensation (Ricker).
了解补充过程（即个体加入种群或渔场的过程）对于理解种群动态和促进可持续渔业管理至关重要。在不同种群中观察到补充动态存在重要差异，其中一些种群表现出渐近生产力，而另一些则表现出超补偿（即补充中的补偿性密度依赖）。我们对补充模式中这种种群间变异性的理解能力受到对潜在机制理解不足的限制，例如密度依赖、补充和环境之间的复杂相互作用。此外，大多数关于补充的研究是使用具有长时间序列的观测设计进行的，很少以实验控制的方式在不同种群中重复。没有适当的重复，种群之间的推断就很薄弱，并且潜在的环境趋势难以量化。为了解决这些问题，我们进行了一项野外实验，操纵了三个野生种群中幼年溪鳟（Salvelinus fontinalis）的放养密度，以表明这些相邻种群——由于环境条件而表现出不同的密度依赖模式——在补充动态方面也存在重要差异。通过对四种种群补充模型（密度独立、线性、Beverton-Holt 和 Ricker）进行测试，种群在渐近生产力方面表现出约两倍的差异，遵循 Beverton-Holt 模型时没有超补偿现象。尽管环境变量（如温度、pH 值、深度、底物）与种群补充差异相关，但它们并没有提高单个种群的预测能力。将我们的补充模式与经典鲑科鱼类案例研究进行比较发现，尽管曲线的形状和参数存在差异（即 Ricker 模型与 Beverton-Holt 模型），但出现了约五条幼鱼/平方米的最大放养密度。更高的密度导致补充量非常微小的增加（Beverton-Holt 模型）或由于超补偿而导致补充量减少（Ricker 模型）。
