Size-structured migration and feeding patterns in the banded puffer fish Colomesus psittacus (Tetraodontidae) from north Brazilian mangrove creeks

摘要

Tidal migrations of fishes are influenced by several coincident factors (abiotic and biotic). The interactive effect of these multiple factors has never been analyzed statistically in a model approach. We used proportional hazards analysis to analyze the interactive effect of space (4 creeks) and time (diurnal neap tide cycles in 2 seasons) on patterns in the intertidal migration of 3 size classes of the banded puffer fish Colomesus psittacus (Tetraodontidae) from mangrove creeks and link this to ontogenetic and temporal changes in feeding. The intertidal migration strategy and patterns of vertical resource exploitation changed ontogenetically, thereby reducing intraspecific competition. Juvenile fish entered creeks earlier and left later, which resulted in longer feeding times and fuller intestines than adults. Juveniles fed mainly on barnacles and fiddler crabs from the mid-intertidal, while adults were specialized predators of the mangrove crab Ucides cordatus from the high intertidal. The shape of the migration curves (the proportions of fish leaving a creek at a given ebb tide water level) indicated that the tidal migration took place in close response to creek-specific drainage characteristics and suggests that the fish interact successfully with variable and dynamic creek features in a macrotidal mangrove environment. When ebb tide cycles were completed during daylight hours, the tidal migration was well-structured. When ebb tide overlapped with sunset, juveniles left earlier, and the tidal migration was compressed. We provide a time budget scenario of habitat use by diurnal C. psittacus during a 15 d spring-neap tide cycle according to the changes in interactions of flood and ebb tide with sunset and sunrise.