Witman Jon D, Sebens Kenneth P
Marine Science Center, Northeastern University, 01908, Nahant, MA, USA.
Oecologia. 1992 Jun;90(3):305-315. doi: 10.1007/BF00317686.
Regional variation in the intensity of fish predation on tethered brittle stars and crabs was measured at 30-33 m depths in the rocky subtidal zone at seven sites representing coastal and offshore regions of the Gulf of Maine, USA. Analysis of covariance comparing the slopes of brittle star survivorship curves followed by multiple comparisons tests revealed five groupings of sites, with significantly greater predation rates in the two offshore than in the three coastal groups. Brittle stars tethered at the three offshore sites were consumed primarily by cod, Gadus morhua, with 60-100% prey mortality occuring in 2.5 h. In striking contrast, only 6-28% of brittle star prey was consumed in the same amount of time at the four coastal sites, which were dominated by cunner, Tautogolabrus adspersus. In several coastal trials, a majority of brittle star prey remained after 24 h. The pattern of higher predation offshore held for rock crabs as well with only 2.7% of tethered crabs consumed (n=36) at coastal sites versus 57.8% of crabs (n=64) consumed at offshore sites. Another important predatory fish, the wolffish, Anarhichas lupus, consumed more tethered crabs than brittle stars. Videos and time-lapse movies indicated that cod and wolffish were significantly more abundant at offshore than at coastal sites. Three hundred years of fishing pressure in New England has severely depleted stocks of at least one important benthic predator, the cod, in coastal waters. We speculate that this human-induced predator removal has lowered predation pressure on crabs and other large mobile epibenthos in deep coastal communities. Transect data indicate that coastal sites with few cod support significantly higher densities of crabs than offshore sites with abundant cod.
在美国缅因湾沿海和近海区域的七个地点，于潮下带岩石区30 - 33米深处测量了鱼类对附着的蛇尾和螃蟹的捕食强度的区域差异。通过协方差分析比较蛇尾存活曲线的斜率，随后进行多重比较测试，结果显示有五个地点分组，其中两个近海地点的捕食率显著高于三个沿海地点组。附着在三个近海地点的蛇尾主要被鳕鱼（Gadus morhua）捕食，在2.5小时内猎物死亡率达到60 - 100%。形成鲜明对比的是，在四个沿海地点，同样时间内只有6 - 28%的蛇尾猎物被消耗，这些沿海地点以康氏躄鱼（Tautogolabrus adspersus）为主。在几次沿海试验中，大部分蛇尾猎物在24小时后仍留存。近海较高捕食率的模式在岩蟹中同样存在，沿海地点附着的螃蟹只有2.7%被消耗（n = 36），而近海地点有57.8%的螃蟹被消耗（n = 64）。另一种重要的捕食性鱼类，狼鱼（Anarhichas lupus），消耗的附着螃蟹比蛇尾更多。视频和延时电影显示，近海的鳕鱼和狼鱼数量明显多于沿海地点。新英格兰地区三百年的捕鱼压力已严重耗尽了沿海水域至少一种重要的底栖捕食者——鳕鱼的种群数量。我们推测，这种人为导致的捕食者移除降低了对沿海深海群落中螃蟹和其他大型移动性表栖生物的捕食压力。横断面数据表明，鳕鱼数量少的沿海地点螃蟹的密度显著高于鳕鱼数量多的近海地点。
