Flexible responses to predators in a marine fish

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Abstract
The effect of predators on the behavior of signal blennies, Emblemaria hypacanthus (Pisces Chaenopsidae), was examined by comparing populations from two sites in the central Gulf of California that differed significantly in the abundance of predatory fishes. At the low-risk site the sexes differed in habitat use with males and females spending most of their time in shelters and in the open, respectively. At the high-risk site both sexes spent most of their time in shelters and also moved less and retreated into shelters more frequently than they did at the low-risk site. Both sexes fed at similar rates at the two sites, but their feeding efficiency was not measured. Males at the high-risk site courted females less vigorously and exhibited less intense courtship coloration than did males at the low-risk site. Although this difference in coloration was evident in the field over 3 consecutive years, males from both sites exhibited full courtship coloration in aquaria lacking predators. This implies that the color differences of males at these two sites represents a flexible, rather than a genetically-fixed, response to predation risk. Flexible responses are expected to occur where the selective environment of offspring is not correlated with that of their parents, such as in marine fishes with a planktonic dispersal stage.