Grey heron, Ardea cinerea L., predation at cage fish farms in Argyll, western Scotland
Grey heron, Ardea cinerea L., predation at cage fish farms in Argyll, western Scotland
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灰鹭 (Ardea cinerea L.) 在苏格兰西部阿盖尔的网箱养鱼场被捕食
DOI：
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
D. Carss
中科院分区：
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作者：
D. Carss
。本研究的目的是确定访问苏格兰西部阿盖尔一个大型淡水网箱养殖场的苍鹭Ardea cinerea L.的数量和年龄结构，并对该地点苍鹭的捕食行为进行量化。1985年9月至1987年8月，在海滨、流动和静止的淡水水体以及鲑鱼养殖场对苍鹭的丰度进行了评估。苍鹭几乎只在晚上或黄昏时造访农场，因此，农场工作人员在冬天比夏天更频繁地看到苍鹭。苍鹭选择装着小鲑鱼(300克)的笼子，站在最上面的网上，穿过网眼捕鱼，把它们从笼子里拿出来。鱼群损失有两种；鲑鱼要么被直接吃掉，要么在操纵过程中被苍鹭丢弃，当时特有的伤口增加了疾病的易感性，或者使鱼滞销。成年苍鹭在取食方面比第一年更成功，尽管年轻的鸟类花在取食上的时间更多，但就它们在农场的总时间而言，它们的采食率仍然低于成年苍鹭。在笼子里，较小的鱼比较大的鱼聚集在离水面更近的地方，因此更容易受到苍鹭的捕食。在许多情况下，被苍鹭攻击的鱼中有很大比例是盲人和/或状况不佳。由于只记录受伤的鱼，养殖场工作人员大大低估了它们对苍鹭的损失。然而，对农民来说，袭击有时看起来很严重。然而，与其他形式的鱼类死亡和损失相比，这种损失很小。
. The aims of the present study were to determine the number and age structure of grey herons, Ardea cinerea L., visiting a large freshwater cage trout farm in a study area in Argyll, western Scotland and to quantify heron predation at the site. Heron abundance was assessed on sea loch shores, running and standing freshwater bodies and at the trout farm between September 1985 and August 1987. Herons visited the farm almost exclusively at night or during twilight periods and, as a consequence, were seen more often by farm staff in winter than in summer. Herons selected cages containing small trout (<300g) and removed them from cages by standing on the top nets and fishing through the mesh. Stock losses were of two kinds; trout were either eaten directly or were dropped by herons during manipulation, when characteristic wounds increased susceptibility to disease or made the fish unmarketable. Adult herons were more successful at feeding than first-years and although younger birds spent more time feeding their intake rates remained lower than those of adults in terms of their total time at the farm. Within a cage, smaller fish aggregated closer to the surface than larger ones and so were more vulnerable to heron predation. In many cases, a high proportion of the fish attacked by herons were blind and/or in poor condition. By recording only wounded fish, farm staff considerably underestimated their losses to herons. Nevertheless, attacks sometimes appeared serious to farmers. However, such losses were small compared with other forms of fish mortality and loss.