Use of a marine reserve in Kaneohe Bay, Hawaii by the giant trevally, Caranx ignobilis

Abstract

Movement patterns, site fidelity and growth were studied for giant trevally ( Caranx ignobilis) inhabiting a marine reserve surrounding Coconut Island in Kaneohe Bay, off the Island of Oahu, Hawaii. Short-term movements of fish were determined by acoustic telemetry and long-term movements and growth were investigated with conventional tag and release methods. Giant trevally appear to move to the Coconut Island marine reserve from the adjacent bay floor upon attaining a size of approximately 20–25 cm fork length. After several years spent frequenting the reserve, giant trevally move out of the bay into deeper water. Tracked fish spent considerable time within the marine reserve moving along the reef slope, but frequently ventured outside of the reserve boundaries. The recapture rate for tagged fish was 11%, with an average time at liberty of 346 days. Nearly one-third of recaptured fish were caught at distances greater than 3 km from the tagging site with maximum values demonstrating long-term (more than 7 years) and long-distance (30 km) movements. The protective function of the Coconut Island marine reserve for giant trevally is limited because the reserve is utilized by only a portion of the population, and even these fish regularly move outside of the refuge.