Department of Environment, Land, Water and Planning, Arthur Rylah Institute for Environmental Research, 123 Brown Street, Heidelberg, Victoria, 3084, Australia.
Department of Fisheries and Oceans, NorthWest Atlantic Fisheries Centre, St. John's, NL A1C 5X1, Canada.
Ecol Appl. 2021 Dec;31(8):e02430. doi: 10.1002/eap.2430. Epub 2021 Aug 23.
Understanding how and why the size of populations varies is critical knowledge for conservation and management. While considerable work has explored how different demographic parameters affect population growth, less is known the drivers of variability in these parameters. Long-term time series tracking population size that are coupled with empirical data to examine the relative importance of different drivers are rare, especially in freshwater systems. Even rarer are studies that collect this information concurrently from multiple species with contrasting life history strategies in the same system to assess whether population size and the relative importance of drivers also vary. We studied changes in the abundance and size structure of four native freshwater fish species in the Murray River, southeastern Australia, over a continuous 19-yr period. Two species with traits typical of "equilibrium" species (Murray cod Maccullochella peelii and trout cod Maccullochella macquariensis) and two with traits of "periodic" species (golden perch Macquaria ambigua and silver perch Bidyanus bidyanus) were sampled annually and capture-mark-recapture modeling was used to ask (1) how did population size change during this period, (2) how were changes in population size related to variability in hydrology, and (3) how were changes in population size driven by different processes (local recruitment or migration events)? Populations of all four species varied throughout the study, and our results are consistent with the notion that local recruitment is an important driver of this variability for Murray cod and trout cod, whereas immigration is more important for the two other species. Increases in spring river discharge strongly influenced these responses for trout cod and golden perch. Our study provides fundamental insights into the population dynamics of these valued species, and how management strategies might differ based on their life histories. Management should focus on allowing connectivity for golden and silver perch, and on promoting local scale recruitment and survival for Murray cod and trout cod. More generally, our study highlights the importance of understanding the processes underpinning population persistence, how these processes may vary for different species, and ultimately how this knowledge can inform targeted management actions.
了解人口规模变化的方式和原因是保护和管理的关键知识。虽然已经有大量工作探讨了不同的人口统计参数如何影响人口增长，但对于这些参数变化的驱动因素知之甚少。长期跟踪人口规模的时间序列，结合经验数据来检验不同驱动因素的相对重要性的研究很少见，特别是在淡水系统中。更罕见的是，在同一系统中从具有不同生活史策略的多个物种中同时收集这些信息的研究，以评估种群规模和驱动因素的相对重要性是否也会发生变化。我们研究了澳大利亚东南部墨累河的四种本地淡水鱼类的丰度和大小结构在连续 19 年期间的变化。两种具有“平衡”物种特征的物种（穆雷鳕鱼 Maccullochella peelii 和鳟鱼鳕鱼 Maccullochella macquariensis）和两种具有“周期性”物种特征的物种（金鲈 Macquaria ambigua 和银鲈 Bidyanus bidyanus）每年都被采样，并使用捕获-标记-重捕模型来回答以下问题：(1) 在此期间种群规模如何变化，(2) 种群规模的变化与水文学的可变性有何关系，以及 (3) 种群规模的变化是由哪些不同的过程（本地繁殖或迁移事件）驱动的？所有四个物种的种群在整个研究过程中都有变化，我们的结果与以下观点一致，即本地繁殖是 Murray cod 和 trout cod 这种变异性的重要驱动因素，而对于另外两个物种，移民更为重要。春季河流流量的增加强烈影响了 trout cod 和 golden perch 的这些反应。我们的研究为这些有价值的物种的种群动态以及基于其生活史的管理策略可能存在的差异提供了基本的见解。管理应侧重于为金鲈和银鲈提供连通性，并促进 Murray cod 和 trout cod 的本地规模繁殖和生存。更广泛地说，我们的研究强调了了解支撑种群生存的过程的重要性，以及这些过程可能因不同物种而异，以及最终如何将这些知识转化为有针对性的管理行动。
