Movements, distribution and growth rates of the white goatfish Mulloides flavolineatus in a fisheries conservation zone

The movements, growth rates and distribution ofa population of white goatfish Mul/oides flavolineatus were investigated using a combination of tag-and-release and sonic tracking techniques. The study site was a 137 km2 patch reef which has been a no-fishing conservation zone for over 30 years. The population showed high site fidelity; 93% of recaptures occurred at the release site, with times at liberty of up to 531 days. Tracking revealed crepuscular movements away from daytime schooling sites to consistent nighttime foraging grounds 'up to 600 m away. The route taken between daytime and nighttime habitats was the same each night. Suround-net quadrats were used to measure goatfish densities on the nighttime feeding grounds. The high site fidelity and limited range of diel movements of these fish indicate that quite small harvest refugia can serve to effectively protect populations of mature adults, and that for most of the year, emigration of adults into adjacent fisheries was minimal. The white goatfish Mulloides jlavolineatus is widely distributed throughout the Indo-Pacific region. In Hawaii, it is one of several mullid species that are important food fishes, and juvenile M. jlavolineatus are highly prized as bait. Despite their cultural and commercial importance and widespread distribution, little is known about their growth rates, age, habitat utilization, or dispersal patterns. Age and growth parameters have been described for an exploited population found in the Red Sea (AI-Absey, 1987), but similar data are not available for populations in the Pacific. Much of the existing ecological data on Hawaiian goatfishes concerns food preferences (Mahi, 1968; Holland, 1978; Sorden, 1982), which are of particular interest because several mullid species appear to be sympatric on Hawaiian reefs. Unlike the M.jlavolineatus population studied in the Red Sea, the data presented here were obtained from animals living within a marine conservation zone. There is increasing discussion of using fisheries conservation zones (harvest refugia) as tools for managing tropical fisheries (Randall, 1982; Russ, 1985; Davis and Dodrill, 1989; Davis, 1989; Alcala and Russ, 1990; Bohnsack, 1990; Roberts and Polunin, 1991), but very few data are available to evaluate their utility. Theoretically, harvest refugia could serve to protect reproductive adults (which can supply eggs and larvae to repopulate other areas), and could provide recruitment areas for juvenile fish which may grow and eventually emigrate into adjacent fisheries. The appropriate size of a conservation zone would be dictated by the habitat preferences, ranges of movement and degree of site fidelity exhibited by the target species. The current data were collected from a virtually unfished population, and the stock structure, diel movement, and distributional data were analyzed with respect to evaluating conservation zones as a management strategy for this species. STUDY AREA AND METHODS Coconut Island is situated in the middle of a patch reef in Kaneohe Bay, Oahu, Hawaii. The reef flat is comprised primarily of sand and coral rubble under water 0.25 to 1.5 m deep. The reef edge and sand flats are interspersed with sand-bottomed pools, lagoons and inlets varying in depth between