Department of Fish, Wildlife & Conservation Ecology, New Mexico State University, Las Cruces, New Mexico, United States of America.
Water Science & Management Program, New Mexico State University, Las Cruces, New Mexico, United States of America.
PLoS One. 2020 May 12;15(5):e0232872. doi: 10.1371/journal.pone.0232872. eCollection 2020.
Fish populations globally are susceptible to endangerment through exploitation and habitat loss. We present theoretical simulations to explore how reduced adult survival (age truncation) might affect short-lived freshwater fish species in human-altered contemporary environments. Our simulations evaluate two hypothetical "average fish" and five example fish species of age 1 or age 2 maturity. From a population equilibrium baseline representing a natural, unaltered environment we impose systematic reductions in adult survival and quantify how age truncation affects the causes of variation in population growth rate. We estimate the relative contributions to population growth rate arising from simulated temporal variation in age-specific vital rates and population structure. At equilibrium and irrespective of example species, population structure (first adult age class) and survival probability of the first two adult age classes are the most important determinants of population growth. As adult survival decreases, the first reproductive age class becomes increasingly important to variation in population growth. All simulated examples show the same general pattern of change with age truncation as known for exploited, longer-lived fish species in marine and freshwater environments. This implies age truncation is a general potential concern for fish biodiversity across life history strategies and ecosystems. Managers of short-lived, freshwater fishes in contemporary environments often focus on supporting reproduction to ensure population persistence. However, a strong focus on water management to support reproduction may reduce adult survival. Sustainability management needs a focus on mitigating adult mortality in human-altered ecosystems. A watershed spatial extent embracing land and water uses may be necessary to identify and mitigate causes of age truncation in freshwater species. Achieving higher adult survival will require paradigm transformations in society and government about water management priorities.
全球鱼类种群容易受到捕捞和生境丧失的威胁。我们提出了理论模拟，以探讨在人为改变的当代环境中，减少成年鱼存活率（年龄截断）如何影响寿命较短的淡水鱼类。我们的模拟评估了两种假设的“平均鱼类”和五种 1 龄或 2 龄成熟的示例鱼类。从代表自然、未受干扰环境的种群平衡基线开始，我们系统地降低成年鱼的存活率，并量化年龄截断如何影响种群增长率变化的原因。我们估计了由于模拟的特定年龄生命率和种群结构的时间变化而导致的种群增长率的相对贡献。在平衡状态下，无论示例物种如何，种群结构（第一成年年龄组）和前两个成年年龄组的存活率是决定种群增长率的最重要因素。随着成年鱼存活率的降低，第一繁殖年龄组对种群增长率的变化变得越来越重要。所有模拟的例子都表现出与海洋和淡水环境中受捕捞影响的、寿命较长的鱼类物种相同的一般年龄截断变化模式。这意味着年龄截断是整个生命史策略和生态系统中鱼类生物多样性的一个普遍潜在问题。当代环境中短寿命淡水鱼类的管理者通常侧重于支持繁殖以确保种群的持续存在。然而，为支持繁殖而大力关注水管理可能会降低成年鱼的存活率。可持续性管理需要将重点放在减轻人为改变的生态系统中的成年鱼死亡率上。一个包含土地和水利用的流域空间范围可能是识别和减轻淡水物种年龄截断原因所必需的。要实现更高的成年鱼存活率，需要在社会和政府对水管理重点方面进行范式转变。
