Microhabitat-scale influences of resources and refuge on habitat selection by an estuarine opportunist fish

We examined how the marine cottid fish Clinocottus acuticeps used vegetated microhabitats within an estuarine system in the Pacific Northwest, USA. C. acuticeps was more abundant and grew faster in microhabitats in algal beds compared with open microhabitats. Furthermore, the condition index (CI) increased in vegetated microhabitats and decreased in open habitats which, combined with the variability in growth measured in both habitats, suggests that fish may regulate their growth more narrowly when food resources and protective cover provided by the algal bed function as complementary resources. Reduced growth in open microhabitats may be a physiological response to increased predation risk. Additionally, giving-up densities (GUDs) were similar in both habitats, in both field and laboratory experiments, where fish foraged in the presence of predators and under different levels of protection by algae. These results, combined with the implications of the growth experiments, suggest that C. acuticeps utilizes a risk-reckless strategy in the face of a tradeoff between food and safety by maximizing food intake despite predation risk. Nevertheless, we maintain that the increased growth and lower predation risk associated with algae microhabitats imply that, ultimately, fitness may be higher in individuals that primarily use vegetated habitats.