Engen Steinar, Cao Francisco J, Sæther Bernt-Erik
Department of Mathematical Sciences, Centre for Biodiversity Dynamics, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
Departamento de Estructura de la Materia, Física Térmica y Electrónica, Universidad Complutense de Madrid, Plaza de Ciencias, 1, 28040 Madrid, Spain; Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia, Calle Faraday, 9, 28049 Madrid, Spain.
Theor Popul Biol. 2018 Sep;123:28-34. doi: 10.1016/j.tpb.2018.05.001. Epub 2018 May 31.
Harvesting in space affects, in general, the spatial scale of the synchrony in the population fluctuations, which determines the size of the areas subjected to simultaneous quasi-extinction risk. Here we show that harvesting reduces the population synchrony scale if it depends more strongly on population fluctuations than the density dependence of the growth rate in the absence of harvesting. We show that constant and proportional harvesting always increases the spatial scale, using a theta-logistic model for density regulation. We also provide exact scaling results under harvesting for the Beverton-Holt and the Ricker stock-recruitment models that are commonly applied, e.g. in fisheries. Our results indicate that harvest in areas with large abundances should be encouraged to avoid increase of the spatial scale of synchrony in the population fluctuations that can lead to unexpected quasi-extinction of populations over large areas. Our results quantify this harvesting impact giving the resulting scales of spatial synchrony of population fluctuations. This emphasizes the importance of estimating the form of density dependence as well as the dependency of harvest upon population density of exploited populations, in order to get reliable predictions of the size of areas that can undergo simultaneous quasi-extinction.
一般而言，在空间中的捕捞会影响种群波动同步性的空间尺度，而这一尺度决定了同时面临准灭绝风险的区域大小。在此我们表明，如果捕捞对种群波动的依赖程度强于在无捕捞情况下增长率的密度依赖程度，那么捕捞会减小种群同步性尺度。我们使用密度调节的θ - 逻辑斯谛模型表明，恒定捕捞和比例捕捞总是会增大空间尺度。我们还给出了在捕捞情况下，常用于例如渔业的贝弗顿 - 霍尔特模型和里克种群补充模型的精确尺度结果。我们的结果表明，应鼓励在丰度高的区域进行捕捞，以避免种群波动同步性的空间尺度增大，这种增大可能导致大面积种群意外地准灭绝。我们的结果量化了这种捕捞影响，给出了种群波动空间同步性的最终尺度。这强调了估计密度依赖形式以及捕捞对被开发种群种群密度的依赖性的重要性，以便可靠地预测可能同时经历准灭绝的区域大小。
