ABSTRACT: Sea urchins are considered the most important grazers in Mediterranean shallow sublittoral rocky reef ecosystems, but fish can also have an important role in overgrazing and the reduction of habitat complexity. In this study, the trophic behavior of fish was recorded when provided access to experimental surfaces with increased macroalgal biomass and associated benthic fauna, created by herbivore exclusion cages. After a sufficient period for substantial algal growth, the cages were removed and the activity of fish on these surfaces was recorded for 3 h by an automated photographic camera system. Control surfaces with no restriction on grazers were defined on similar substrates for comparison. To quantify the effects of fish feeding activity on macroalgal coverage, photographic samples were taken immediately after the opening of the cages and after each 3 h recording. The response of fish when the cages were removed was immediate and intense. Feeding activity by 13 different fish species was recorded in total, of which the most frequent were the omnivores Diplodus vulgaris, Coris julis and Thalassoma pavo, and to a lesser extent the herbivore Sarpa salpa. The coverage of erect algae was substantially decreased on the experimental surfaces due to fish feeding activity. The algae were either directly consumed by the fish or cut off when the fish were feeding on macroinvertebrates. We conclude that in addition to grazing by herbivores, fish of higher trophic levels can also significantly affect macroalgal assemblages and restrict the recovery of erect algae in overgrazed reefs where prey is scarce.

中文翻译：

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杂食性鱼类在地中海岩礁过度放牧中被忽视的作用

摘要：海胆被认为是地中海浅海沿岸岩礁生态系统中最重要的食草动物，但鱼类在过度放牧和栖息地复杂性降低方面也发挥着重要作用。在这项研究中，当提供进入由草食动物排斥笼子产生的大型藻类生物量和相关底栖动物群增加的实验表面时，记录了鱼类的营养行为。在藻类大量生长足够长的时间后，移除网箱，并通过自动摄影摄像系统记录这些表面上鱼的活动 3 小时。对食草动物没有限制的对照表面被定义在类似的基材上以进行比较。为了量化鱼类饲养活动对大型藻类覆盖率的影响，打开笼子后立即拍摄照片样本，每 3 小时记录一次。移除网箱后，鱼的反应是立即而强烈的。总共记录了 13 种不同鱼类的摄食活动，其中最常见的是杂食动物Diplodus vulgaris、Coris julis和Thalassoma pavo，以及较小程度上的食草动物Sarpa salpa。由于鱼类摄食活动，实验表面上直立藻类的覆盖率显着降低。藻类要么直接被鱼吃掉，要么在鱼以大型无脊椎动物为食时被切断。我们得出的结论是，除了食草动物的放牧外，较高营养水平的鱼类也会显着影响大型藻类组合，并限制猎物稀少的过度放牧珊瑚礁中直立藻类的恢复。