Fish migration reduces predation

http://rsbl.royalsocietypublishing.org/content/9/2/20121178.short

Migration confers survival benefits against avian predators for partially migratory freshwater fish

1. Christian Skov1⇓, 
2. Ben B. Chapman2, 
3. Henrik Baktoft1,
4. Jakob Brodersen3, 
5. Christer Brönmark2, 
6. Lars-Anders Hansson2,
7. Kaj Hulthén2 and 
8. P. Anders Nilsson2

The importance of predation risk in shaping patterns of animal migration is not well studied, mostly owing to difficulties in accurately quantifying predation risk for migratory versus resident individuals. Here, we present data from an extensive field study, which shows that migration in a freshwater fish (roach,Rutilus rutilus) that commonly migrates from lakes to streams during winter confers a significant survival benefit with respect to bird (cormorant,Phalacrocorax carbo spp.) predation. We tagged over 2000 individual fish in two Scandinavian lakes over 4 years and monitored migratory behaviour using passive telemetry. Next, we calculated the predation vulnerability of fish with differing migration strategies, by recovering data from passive integrated transponder tags of fish eaten by cormorants at communal roosts close to the lakes. We show that fish can reduce their predation risk from cormorants by migrating into streams, and that probability of being preyed upon by cormorants is positively related to the time individuals spend in the lake during winter. Our data add to the growing body of evidence that highlights the importance of predation for migratory dynamics, and, to our knowledge, is one of the first studies to directly quantify a predator avoidance benefit to migrants in the field.

작은 물고기들 조사해 봤더니 잡아먹힐 위험을 줄이기 위해 이동하는 것도 나타났다, 그런 얘기였는데 겨울에 호수에 머무르면 큰가마우지 cormorant 가 잡아먹으니까 하천으로 숨는답니다. 어떻게 생각하면 너무 당연하긴 한데, 그동안 많이 생각해 보지 않았던 부분인가 봅니다 이 연구가 자기들 생각하기엔 최초라고 하는 걸 보니. 지난 번에 상헌씨에게 민물고기 얘기 듣고 너무 재밌어서 자꾸 관심이 가네요. 물고기에 달 수 있을 정도로 태그가 작아졌나 놀랍기도 하고, 여튼 즐거운 주말 다들 되셔요! 

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철새가 많이 날아오는 곳 호수에서 물고기 개체수 조사를 했으면 그러니까 서식지 환경이 나빠서 애들이 없어진 걸로 생각해 왔을 수도 있다. 인터레상트 인터레상트