Imre I, Grant J W A, Keeley E R
Department of Biology, Concordia University, 7141 Sherbrooke St. West, Montreal, Quebec, H4B 1R6, Canada.
Oecologia. 2004 Feb;138(3):371-8. doi: 10.1007/s00442-003-1432-z. Epub 2003 Dec 11.
Optimal territory size models predict a decrease in territory size with increasing food abundance. However, most of these models may not be applicable to juvenile salmonids in streams, because they defend contiguous territories at high densities. The optimal size of a contiguous territory is predicted to (1) be independent of food abundance when food is rare and (2) decrease only when food abundance is high enough to induce a reduction in territory size below the contiguous optimum. To test these predictions, we raised equal densities of juvenile steelhead trout in outdoor stream channels over a 32-fold range of food abundance in the absence of emigration for 25 days. Increasing competition for scarce food resulted in increasing mortality, higher willingness to emigrate, higher variance in body mass, lower growth, lower population density and lower biomass. The size of territories decreased with increasing local population density, and increased with increasing body size. However, territory size did not change with food abundance, a result consistent with the prediction of a contiguous territory size model. On average, total salmonid biomass increased 5.7 times in response to the 32-fold increase in food abundance. Our data provide strong support for an earlier quantitative relationship between the abundance of stream salmonids and their food.
最佳领地大小模型预测，随着食物丰富度的增加，领地大小会减小。然而，这些模型中的大多数可能不适用于溪流中的幼年鲑科鱼类，因为它们在高密度时会保卫相邻的领地。相邻领地的最佳大小预计为：（1）当食物稀缺时，与食物丰富度无关；（2）只有当食物丰富度足够高，导致领地大小减小到低于相邻最优值时，才会减小。为了验证这些预测，我们在室外溪流渠道中饲养了密度相同的幼年虹鳟，食物丰富度范围为32倍，在25天内没有出现洄游情况。对稀缺食物的竞争加剧导致死亡率上升、洄游意愿增强、体重差异增大、生长减缓、种群密度降低和生物量减少。领地大小随着当地种群密度的增加而减小，随着体型的增大而增大。然而，领地大小并未随食物丰富度而变化，这一结果与相邻领地大小模型的预测一致。平均而言，鲑科鱼类的总生物量随着食物丰富度增加32倍而增加了5.7倍。我们的数据为溪流鲑科鱼类的数量与其食物之间的早期定量关系提供了有力支持。
