Schmitt Russell J, Holbrook Sally J
Department of Biological Sciences and the Marine Science Institute, University of California, 93106, Santa Barbara, CA, USA.
Oecologia. 1986 Apr;69(1):1-11. doi: 10.1007/BF00399030.
The influence of seasonal availability of two critical resources (food and substrates from which food was harvested) on interspecific competition between striped surfperch (Embiotoca lateralis) and black surfperch (Embiotoca jacksoni) was examined. There was a strong depth-related gradient in density of prey and in cover of foliose algae; both declined with increasing bottom depth. Density of prey was reduced 5-10 fold during the winter season, but cover of substrates remained constant throughout the year. Although both fishes co-occurred throughout the same depth range, striped surfperch were more common in shallow habitats and black surfperch were more abundant deeper. Local abundance and distribution patterns of both surfperch species did not change seasonally. Stepwise regression analyses suggested that availability of favored substrates was a proximate influence on local patterns of surfperch distribution and abundance, and that interspecific competition depressed abundance of the two species to the same degree. Removal experiments conducted during the cold-water season revealed that interspecific competition influenced depth distribution of black surfperch but not striped surfperch. Seasonal change in density of prey was accompanied by marked changes in overlap in use of foraging substrates by the surfperches. The pattern of change in interspecific overlap suggested that surfperch competed for food only when prey were seasonally scarce. There was no difference in the agonistic tendencies of the two fishes, and the absolute and relative frequency of interspecific chases was independent of food level. These results have important implications regarding the impact of temporal variability of interspecific competition in natural communities. In the surfperch system, competition was characterized by constant and time-varying elements that had symmetrical and asymmetrical effects and involved both interference and exploitation mechanisms.
研究了两种关键资源（食物以及获取食物的基质）的季节性可利用性对条纹海鲫（Embiotoca lateralis）和黑海鲫（Embiotoca jacksoni）种间竞争的影响。猎物密度和叶状藻覆盖度存在与深度密切相关的强烈梯度变化；二者均随海底深度增加而下降。冬季猎物密度降低了5至10倍，但基质覆盖度全年保持恒定。尽管两种鱼在相同深度范围内共存，但条纹海鲫在浅水区更为常见，而黑海鲫在较深水域更为丰富。两种海鲫的局部丰度和分布模式没有季节性变化。逐步回归分析表明，偏好基质的可利用性是影响海鲫局部分布和丰度模式的直接因素，种间竞争对两种海鲫丰度的抑制程度相同。在冷水季节进行的移除实验表明，种间竞争影响黑海鲫的深度分布，但不影响条纹海鲫的深度分布。猎物密度的季节性变化伴随着海鲫觅食基质利用重叠的显著变化。种间重叠的变化模式表明，海鲫仅在猎物季节性稀缺时才会竞争食物。两种鱼的争斗倾向没有差异，种间追逐的绝对频率和相对频率与食物水平无关。这些结果对于自然群落中种间竞争时间变异性的影响具有重要意义。在海鲫系统中，竞争具有恒定和随时间变化的因素，这些因素具有对称和不对称的影响，并且涉及干扰和利用机制。
