The role of habitat in determining recruitment of juvenile marine fishes: Testing foraging arena theory.
Juanes, Francis*,1, 1 University of Massachusetts-Amherst, Amherst, MA
ABSTRACT- The relative importance of specific early life stages in determining future year-class strength of marine fishes depends on the duration and the respective mortality rates experienced during each stage. The transition phase describes a distinct juvenile stage associated with the recruitment to benthic habitats by pelagic life stages. The habitat shift is often accompanied by feeding shifts and metamorphosis. Density-dependent settlement, growth and mortality are often the major factors controlling recruitment success of this phase and may lead to the evolution of behavioural flexibility during the transition. Habitat use also becomes more pronounced after settlement. During this stage, juvenile fishes generally have spatial refuges from predation, and forage in limited but risky areas near refuges. Models of food density dynamics within such limited foraging areas predict that food availability and feeding rates per time spent feeding should depend strongly on juvenile density and habitat. Selection should act on the time that juveniles spend foraging, so as to strike a balance between growth and predation risk. Because the risk of predation also varies with habitat, we expect variation in foraging times and resulting growth and mortality rates to be habitat-specific and density-dependent. These concepts will be tested by focusing on the early life history of Atlantic cod (Gadus morhua) and cunner (Tautogolabrus adspersus) in the northwest Atlantic. The results suggest that future recruitment studies should include examination of spatial habitat use by juveniles, and the behavioral and physiological mechanisms for adjusting behavior to varying food density and predation risk.
Key words: fish recruitment, habitat use, foraging arena theory, cod and cunner
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