Harvesting in seasonal environments
Harvesting in seasonal environments
复制标题
DOI：
10.1007/s00285-004-0303-5
复制
发表时间：
2005-06
影响因子：
1.9
通讯作者：
Cailin Xu;M. Boyce;D. Daley
中科院分区：
文献类型：
--
作者：
Cailin Xu;M. Boyce;D. Daley
大多数收获理论都是基于恒定或随机环境的假设，但大多数人群都会经历某种形式的环境季节性。假设种群遵循逻辑增长，我们研究季节性环境下的收获，重点关注五种常用收获策略下的最大年产量（M.A.Y.）和种群持久性。我们表明，最优策略很大程度上取决于人口的内在增长率和季节性的大小。这些替代收获策略的有序有效性是针对内在增长率和季节性的不同组合给出的。此外，对于分段连续时间收获策略（即开放/封闭收获和脉冲收获），收获时机对于年产量至关重要。最佳收获时机与季节性波动承载能力的最大下降率一致。对于较大的内在增长率和较小的环境变化，几种策略（即恒定的开采率、线性开采率和时间依赖性收获）非常有效，以至于 M.A.Y.非常接近最大可持续产量（M.S.Y.）。可能。豆类收获量甚至可以比 M.S.Y 还要大。因为在季节性环境中，一年中的人口规模变化很大，而人口规模相对于承载能力的变化决定了相对于最佳收获率的价值。然而，对于内在增长率较小但季节性较大的人群来说，这些策略对于 M.A.Y 来说都不是特别有效。远低于 M.S.Y。为这种情况找到最佳的收获策略，并探索遵循其他增长模型（例如，涉及捕食或年龄结构）的种群的收获将是一个有趣但具有挑战性的问题。
Most harvest theory is based on an assumption of a constant or stochastic environment, yet most populations experience some form of environmental seasonality. Assuming that a population follows logistic growth we investigate harvesting in seasonal environments, focusing on maximum annual yield (M.A.Y.) and population persistence under five commonly used harvest strategies. We show that the optimal strategy depends dramatically on the intrinsic growth rate of population and the magnitude of seasonality. The ordered effectiveness of these alternative harvest strategies is given for different combinations of intrinsic growth rate and seasonality. Also, for piecewise continuous-time harvest strategies (i.e., open / closed harvest, and pulse harvest) harvest timing is of crucial importance to annual yield. Optimal timing for harvests coincides with maximal rate of decline in the seasonally fluctuating carrying capacity. For large intrinsic growth rate and small environmental variability several strategies (i.e., constant exploitation rate, linear exploitation rate, and time-dependent harvest) are so effective that M.A.Y. is very close to maximum sustainable yield (M.S.Y.). M.A.Y. of pulse harvest can be even larger than M.S.Y. because in seasonal environments population size varies substantially during the course of the year and how it varies relative to the carrying capacity is what determines the value relative to optimal harvest rate. However, for populations with small intrinsic growth rate but subject to large seasonality none of these strategies is particularly effective with M.A.Y. much lower than M.S.Y. Finding an optimal harvest strategy for this case and to explore harvesting in populations that follow other growth models (e.g., involving predation or age structure) will be an interesting but challenging problem.