Post J R, Persson L, Parkinson E A, van Kooten T
Ecology and Evolutionary Biology, Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
Ecol Appl. 2008 Jun;18(4):1038-49. doi: 10.1890/07-0465.1.
Recreational angling opportunities in lakes are distributed across landscapes and attract anglers based on the combination of angling quality, travel distance, and availability of facilities. The relationship between angler density and fishing quality, as measured by catch rate, represents a numerical response that is analogous to a predator numerical response to variability in prey abundance. We quantified this numerical response of anglers to rainbow trout, Oncorhynchus mykiss, populations distributed over a large lake district in south-central British Columbia, Canada. We developed a harvest dynamics model by linking this empirical description of the spatial numerical response of anglers to a logistic population growth rate model. The model was parameterized for rainbow trout and simulated spatial patterns of angler density and catch rates over a landscape. At locations distant from urban centers, angler density is low and catch rate high, suggesting near pristine conditions; at intermediate distances angler density is higher while catch rates are lower and approximate maximum sustainable levels; and at short distances angler density is sufficiently high to harvest to local extirpation. We extrapolated the model to other lake districts varying in human population size using an empirically derived angling participation rate relationship. Extrapolation to lake districts with one-tenth the human population maintained viable fisheries close to the urban area, and districts with 10 times the human populations could not maintain viable fisheries across much of their lake district. Landscape-scale spatial patterns differed quantitatively for species varying in rates of intrinsic population growth and carrying capacity, but the qualitative spatial patterns were consistent among species, demonstrating the pervasive impacts of the angler numerical response. To achieve a management goal of sustaining fisheries across landscapes, a change in management perspective is necessary, from that of individual lakes to one of dynamic harvest processes across landscapes. This new approach makes it clear that a one-size-fits-all management approach must be replaced with a mosaic of approaches cognizant of landscape-scale processes.
湖泊中的休闲垂钓机会分布于各地，其基于垂钓质量、出行距离和设施可用性的综合因素吸引着垂钓者。以捕获率衡量的垂钓者密度与垂钓质量之间的关系，代表了一种数值响应，类似于捕食者对猎物数量变化的数值响应。我们对加拿大不列颠哥伦比亚省中南部一个大湖区内分布的虹鳟（Oncorhynchus mykiss）种群，量化了垂钓者的这种数值响应。通过将垂钓者空间数值响应的这一经验性描述与逻辑斯谛种群增长率模型相联系，我们开发了一个收获动态模型。该模型针对虹鳟进行了参数化，并模拟了整个区域内垂钓者密度和捕获率的空间格局。在远离城市中心的地点，垂钓者密度低而捕获率高，表明接近原始状态；在中等距离处，垂钓者密度较高而捕获率较低，接近最大可持续水平；在短距离处，垂钓者密度足够高以至于能将当地的鱼捕获至灭绝。我们利用经验推导的垂钓参与率关系，将该模型外推至人口规模不同的其他湖区。外推至人口为十分之一的湖区，能在市区附近维持可行的渔业，而人口为十倍的湖区在其大部分湖区无法维持可行的渔业。对于内在种群增长率和承载能力不同的物种，景观尺度的空间格局在数量上有所不同，但定性的空间格局在物种间是一致的，这表明了垂钓者数值响应的普遍影响。为实现跨区域维持渔业的管理目标，管理视角需要转变，从单个湖泊的管理转变为跨区域动态收获过程的管理。这种新方法明确表明，一刀切的管理方法必须被一系列认识到景观尺度过程的方法所取代。
