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首页> 外文期刊>ICES Journal of Marine Science >Predicting sustainable shark harvests when stock assessments are lacking
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Predicting sustainable shark harvests when stock assessments are lacking

机译：在缺乏种群评估的情况下预测可持续的鲨鱼收获

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Effective fisheries management generally requires reliable data describing the target species' life-history characteristics, the size of its harvested populations, and overall catch estimates, to set sustainable quotas and management regulations. However, stock assessments are often not available for long-lived marine species such as sharks, making predictions of the long-term population impacts of variable catch rates difficult. Fortunately, stage-or age-structured population models can assist if sufficient information exists to estimate survival and fertility rates. Using data collected from the bronze whaler (Carcharhinus brachyurus) fishery in South Australia as a case study, we estimated survival probabilities from life tables of harvested individuals, as well as calculated natural mortalities based on allometric predictions. Fertility data (litter size, proportion mature) from previous studies allowed us to build a fertility vector. Deterministic matrices built using estimates of life-table data or natural mortality (i.e. harvested-augmented and natural mortality) produced instantaneous rates of change of 0.006 and 0.025, respectively. Assuming an incrementing total catch at multiples of current rates, stochastic simulations suggest the relative rate of population decline starts to become precipitous around 25% beyond current harvest rates. This is supported by a sharp increase in weighted mean age of the population around 25% increase on current catches. If the catch is assumed to be proportional (i.e. a constant proportion of the previous year's population size), the relative r declines approximately linearly with incrementing harvest beyond the current rate. A global sensitivity analysis based on a Latin-hypercube sampling design of seven parameters revealed that variation in the survival estimates derived from the life tables was by far the dominant (boosted-regression tree relative influence score = 91.14%) determinant of model performance (measured as variation in the long-term average rate of population change r). While current harvest rates therefore appear to be sustainable, we recommend that fisheries-management authorities attempt to sample a broader size range of individuals (especially older animals) and pursue stock assessments. Our models provide a framework for assessing the relative susceptibility of long-lived fishes to harvest pressure when detailed stock data are missing.
机译：有效的渔业管理通常需要可靠的数据来描述目标物种的生活史特征，其捕捞种群的规模以及总体捕捞估计数，以设定可持续的配额和管理法规。但是，对于鲨鱼等长寿命海洋物种而言，通常无法进行种群评估，因此难以预测可变捕捞率对长期种群的影响。幸运的是，如果存在足够的信息来估计生存率和生育率，则阶段或年龄结构的人口模型可以提供帮助。使用从南澳大利亚州的青铜捕鲸者（Carcharhinus brachyurus）捕捞中获得的数据作为案例研究，我们从收获的个体的生命表中估算了生存概率，并根据异速预报预测了自然死亡率。先前研究的生育力数据（产仔数，成熟比例）使我们能够建立生育力载体。使用生命表数据或自然死亡率（即收获的增重和自然死亡率）的估计值建立的确定性矩阵分别产生0.006和0.025的瞬时变化率。假设总捕捞量是当前水平的倍数，则随机模拟表明，人口相对下降速度开始比目前的收成率高25％左右。人口加权平均年龄的急剧增加支持了这一点，目前的渔获量增加了25％。如果假定产量是成比例的（即前一年人口数量的恒定比例），则相对r随收获量增加超过当前水平而线性下降。基于七个参数的拉丁超立方体抽样设计的全球敏感性分析表明，从寿命表得出的生存估计的变化是决定模型性能（测得）的主要因素（增强回归树相对影响力分数= 91.14％）。作为长期平均人口变化率的变化r）。因此，尽管目前的收成率看来是可持续的，但我们建议渔业管理当局尝试对更大范围的个体（尤其是年长动物）进行抽样，并进行种群评估。当缺少详细的种群数据时，我们的模型提供了一个框架，用于评估长寿鱼类对收获压力的相对敏感性。

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