Fisheries Behavioral Ecology - Abstracts
Hurst, T.P., C.H. Ryer, J.M. Ramsey, S.A. Haines. 2007. Divergent foraging strategies of three co-occurring north Pacific flatfishes. Marine Biology 151:1087-1098.
Abstract
Despite facing similar constraints imposed by the environment, significant variation in life history traits frequently exists among species generally considered to comprise a single ecological guild. For juvenile flatfishes, constraints on foraging activity include variation in light and prey availability, as well as predation risk. This paper describes the visual constraints on, and divergent foraging strategies of three co-occurring north Pacific flatfish species, northern rock sole (Lepidopsetta polyxystra), Pacific halibut (Hippoglossus stenolepis), and English sole (Pleuronectes vetulus). Visual foraging abilities measured in the laboratory decreased rapidly below 10−4 μmol photons·m−2 s−1, and were similar among species. Despite similar sensory constraints, field sampling in August 2004 at a Kodiak Island nursery site (Holiday Beach, 57o41.2' N, 152o27.7' W) identified species differences in diets, diel foraging patterns, and within-nursery depth distributions. Northern rock sole and English sole fed primarily on bivalve siphons and polychaetes, whereas mysids dominated the diets of Pacific halibut. Northern rock sole were geographically the most widespread but feeding activity was temporally restricted to the dusk period. Pacific halibut were rare in shallow depths
(<5 m) and fed most intensively prior to dusk. English
sole fed throughout the daylight hours and were abundant
only in the shallowest (<5 m) habitats. These
differences in diets, foraging times, and habitat use
appear related to previously documented species-specific
behavioral characteristics as well as general spatial
(increasing with depth) and temporal (increasing during
foraging activity) variations in predation risk. At
one extreme, the conservative behavioral strategy of
northern rock sole may permit use of a broader range
of foraging habitats, whereas English sole may be
restricted to shallow water by limited behavioral responses to predation threat. These observations
demonstrate that the appearance of habitat partitioning
is not due to differences in sensory ability, but reflects
multi-faceted, species-specific responses to the
ecological tradeoffs between foraging and predation
risks.
Last updated
10 May, 2007
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