Abstract Context The population of saltwater crocodiles, Crocodylus porosus, in the Northern Territory, Australia, has been recovering from a period of intensive, unregulated harvest (1945–1971) since protection in 1971. Consequently, the management goal is shifting from restoring a seriously depleted population to managing an abundant population through controlled harvests for both commercial purposes and public safety. Aims We conducted this study to (1) examine whether the controlled harvest of eggs and adults since protection has had an adverse effect on population size and structure, and (2) explore the effect of future harvest scenarios on population size and structure by adjusting harvest levels of both eggs and adults. Methods On the basis of 40 years of population monitoring data and knowledge of population attributes from previous research, we developed density-dependent, structured matrix population models to explore our aims. Key results The models supported that the depleted population recovered rapidly under protection and that the harvest rates since protection were benign. The model estimated the 2017 harvested population, 46 years after protection, to be ~102 000 non-hatchlings (>0.6 m crocodiles), of which 42.2% are large (>2.1 m total length) individuals. This is similar to the estimated population before the period of intensive, unregulated harvest. Like other crocodilians, the harvest simulations showed that the viability of the population is highly sensitive to adult survival rates. The estimated population should be able to sustain an annual harvest of up to 135 500 eggs if the harvest of large crocodiles remains small (<500 per year). Conclusions Although egg harvest has little impact on population size and structure, population size is sensitive to adult harvest. Implications Crocodile populations are highly sensitive to adult survival, which needs to be taken into account when considering future harvest scenarios.

中文翻译：

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捕食掠食者：模拟种群恢复和控制捕捞咸水鳄鱼 Crocodylus porosus

摘要 背景 澳大利亚北领地的咸水鳄鱼种群 Crocodylus porosus 自 1971 年受到保护以来，一直在从密集、无管制的捕捞时期（1945-1971 年）中恢复。因此，管理目标正在从恢复严重为了商业目的和公共安全，通过控制收获来管理大量人口。目的 我们进行这项研究是为了 (1) 检验自保护以来对鸡蛋和成虫的控制收获是否对种群规模和结构产生不利影响，以及 (2) 通过调整收获来探索未来收获情景对种群规模和结构的影响鸡蛋和成虫的水平。方法 基于 40 年的人口监测数据和先前研究中的人口属性知识，我们开发了密度相关的结构化矩阵人口模型来探索我们的目标。主要结果 模型支持枯竭种群在保护下迅速恢复，并且自保护以来的收获率是良性的。该模型估计，保护后 46 年的 2017 年收获种群为约 102 000 头非幼鱼（> 0.6 m 鳄鱼），其中 42.2% 是大型个体（> 2.1 m 总长度）。这与集约化、不受管制的收获期之前的估计人口相似。与其他鳄鱼一样，收获模拟表明种群的生存能力对成年鳄鱼的存活率高度敏感。如果大型鳄鱼的收获量仍然很少（每年 <500 只），估计种群数量应该能够维持高达 135 500 只蛋的年收获量。结论虽然鸡蛋收获对种群规模和结构的影响不大，但种群规模对成虫收获很敏感。影响 鳄鱼种群对成体存活高度敏感，在考虑未来的收获情景时需要考虑到这一点。