A Stepwise Approach to Investigating the Movement Patterns and Habitat Utilization of Goliath Grouper, Epinephelus itajara, Using Conventional Tagging, Acoustic Telemetry and Satellite Tracking

Abstract

Goliath grouper,1 Epinephelus itajara, the largest grouper in the western North Atlantic, has been protected from all harvest in U.S. waters since 1990, after years of overexploitation at its spawning aggregations. We are currently assessing this species’ recovery by using a variety of tagging methods, including conventional tagging and acoustic telemetry. We have been monitoring the adult populations at offshore spawning aggregations and the juveniles at their nursery areas along mangrove shorelines. Conventional mark/recapture studies enabled us to predict juvenile goliath grouper population densities, growth rates and survival rates. Conventional tagging and recaptures of both adults and juveniles have given information on habitat use and movement patterns, while manually tracking acoustically tagged fish provided fine-scale habitat use and seasonal movements. Continuous data-logging hydrophones provided long-term data on site residency of both juveniles and adults. Future studies will include the use of satellite tracking to define large scale ontogenetic and spawning migrations to previously undescribed habitats. Each method of tagging has provided answers to key questions regarding goliath grouper population biology, but every method also has had its limitations. By starting with the most economical and simplest methods, we have built upon each study by adding complexity as it is warranted.