School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, Washington, 98195, USA.
Alaska Fisheries Science Center, National Oceanic and Atmospheric Administration, 7600 Sand Point Way NE, Seattle, Washington, 98115, USA.
Ecol Appl. 2017 Oct;27(7):1985-2000. doi: 10.1002/eap.1593.
Many rockfish species are long-lived and thought to be susceptible to being overfished. Hypotheses about the importance of older female rockfish to population persistence have led to arguments that marine reserves are needed to ensure the sustainability of rockfish populations. However, the implications of these hypotheses for rockfish population dynamics are still unclear. We modeled two mechanisms by which reducing the proportion of older fish in a population has been hypothesized to influence sustainability, and explored whether these mechanisms influenced mean population dynamics and recruitment variability. We explored whether populations with these mechanisms could be managed more sustainably with a marine reserve in addition to a constant fishing mortality rate (F) than with a constant F alone. Both hypotheses can be seen as portfolio effects whereby risk of recruitment failure is spread over a "portfolio" of maternal ages. First, we modeled a spawning window effect whereby mothers of different ages spawned in different times or locations (windows) with local environmental conditions. Second, we modeled an offspring size effect whereby older mothers produced larger offspring than younger mothers, where length of a starvation period over which offspring could survive increased with maternal age. Recruitment variability resulting from both models was 55-65% lower than for models without maternal age-related portfolio effects in the absence of fishing and increased with increases in Fs for both models. An offspring size effect caused lower output reproductive rates such that the specified reproductive rate input as a model parameter was no longer the realized rate measured as the reproductive rate observed in model results; this quirk is not addressed in previous analyses of offspring size effects. We conducted a standardization such that offspring size effect and control models had the same observed reproductive rates. A comparison of long-term catch, the probability of falling below a biomass threshold, and recruitment variability over a range of exploitation rates for models with an age-related portfolio effect showed no benefit of a marine reserve implemented in addition to a constant F (as compared to a constant F alone) for populations with sedentary adults and sedentary or mobile larvae.
许多石斑鱼物种寿命长，被认为容易过度捕捞。关于老年雌石斑鱼对种群生存的重要性的假设，导致了人们认为需要建立海洋保护区来确保石斑鱼种群的可持续性。然而，这些假设对石斑鱼种群动态的影响仍不清楚。我们模拟了两种机制，即减少种群中老年鱼类的比例被假设如何影响可持续性，并探讨了这些机制是否影响了种群的平均动态和补充变异性。我们探讨了在除了恒定捕捞死亡率（F）之外还有海洋保护区的情况下，这些机制是否可以使种群更可持续地管理，而不仅仅是恒定的 F。这两个假设都可以看作是投资组合效应，即通过“投资组合”中不同的母体年龄来分散繁殖失败的风险。首先，我们模拟了产卵窗口效应，即不同年龄的母鱼在不同的时间或地点（窗口）产卵，与当地环境条件有关。其次，我们模拟了后代大小效应，即年龄较大的母鱼产生的后代比年龄较小的母鱼大，在饥饿期间能够存活的后代长度随着母鱼年龄的增加而增加。与没有母体年龄相关的投资组合效应的模型相比，两种模型产生的补充变异性降低了 55-65%，而且随着 Fs 的增加，两种模型的补充变异性都增加了。后代大小效应导致生殖率输出降低，使得作为模型参数指定的生殖率输入不再是模型结果中观察到的生殖率，这一怪癖在以前对后代大小效应的分析中没有得到解决。我们进行了标准化，使后代大小效应和对照模型具有相同的观察生殖率。对具有年龄相关投资组合效应的模型在一系列开发率下的长期捕捞量、低于生物量阈值的概率和补充变异性进行比较，结果表明，对于具有静止成年和静止或移动幼虫的种群，除了恒定的 F 之外，实施海洋保护区并没有好处（与单独的恒定 F 相比）。
