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Spatial distribution of fishes in a Northwest A tlantic ecosystem in relation to risk of predation by a marine mammal
Author(s) -
Swain Douglas P.,
Benoît Hugues P.,
Hammill Mike O.
Publication year - 2015
Publication title -
journal of animal ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.134
H-Index - 157
eISSN - 1365-2656
pISSN - 0021-8790
DOI - 10.1111/1365-2656.12391
Subject(s) - predation , gadus , ecology , habitat , biology , foraging , fishery , ecosystem , atlantic cod , marine ecosystem , spatial distribution , geography , fish <actinopterygii> , remote sensing
SummaryNumerous studies have shown that, at spatial scales of metres to several kilometres, animals balance the trade‐off between foraging success and predation mortality by increasing their use of safer but less profitable habitats as predation risk increases. However, it is less clear whether prey respond similarly at the larger spatiotemporal scales of many ecosystems. We determine whether this behaviour is evident in a large marine ecosystem, the southern G ulf of S t. L awrence (s GSL , 75 000 km 2 ) over a 42‐year period. This ecosystem is characterized by a recent increase in the abundance of a large marine predator, the grey seal ( H alichoerus grypus F abricius), by more than an order of magnitude. We compared changes in spatial distribution over the 1971–2012 period between important prey of grey seals ( A tlantic cod, G adus morhua L.; white hake, U rophycis tenuis M itchill; and thorny skate, A mblyraja radiata D onovan) and non‐prey fishes. Distribution was modelled using generalized additive models incorporating spatially variable effects of predation risk, density dependence and water temperature. Distributions of cod, hake and skate were strongly related to risk of predation by seals, with distribution shifting into lower risk areas as predation risk increased. Non‐prey species did not show similar changes in habitat use. Spatial variation in fish condition suggests that these low‐risk areas are also less profitable for cod and skate in terms of food availability. The effects of density dependence and water temperature were also important in models, but did not account for the changes in habitat use as the risk of predation increased. These results indicate that these fish are able to assess and respond to spatial variation in predation risk at very large spatial scales. They also suggest that non‐consumptive ‘risk’ effects may be an important component of the declines in productivity of seal prey in this ecosystem, and of the indirect effects at lower trophic levels.