DISCUSSION
The differences in the natural distributional patterns of
prawns and shrimps follow our expectations from the
ecology of the two species, and are matched by the
laboratory-based choice experiments. Unlike prawns,
which readily associated with a group of conspecifics,
shrimps only showed a weak tendency towards active
shoaling behaviour in our experiment. Shrimps also spent
less time shoaling (i.e. in either of the end-zones) than
prawns, suggesting their movements within the test tank
were more limited. The absence of strong sociality in
shrimps is in agreement with our predictions and leads us
to propose that the clumped distribution found in the
field results from indirect factors, such as microhabitat
preferences (Wittman 1976). As suggested by their appearance,
shrimps seem to rely on crypsis to reduce their individual
predation risk, with apparent aggregations in the
DISCUSSIONThe differences in the natural distributional patterns ofprawns and shrimps follow our expectations from theecology of the two species, and are matched by thelaboratory-based choice experiments. Unlike prawns,which readily associated with a group of conspecifics,shrimps only showed a weak tendency towards activeshoaling behaviour in our experiment. Shrimps also spentless time shoaling (i.e. in either of the end-zones) thanprawns, suggesting their movements within the test tankwere more limited. The absence of strong sociality inshrimps is in agreement with our predictions and leads usto propose that the clumped distribution found in thefield results from indirect factors, such as microhabitatpreferences (Wittman 1976). As suggested by their appearance,shrimps seem to rely on crypsis to reduce their individualpredation risk, with apparent aggregations in the
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