Howard, K. G.

Community structure, life history, and movement patterns of parrotfishes: Large protogynous fishery species

2008

University of Hawaii

120

Ph.D. Dissertation

"Populations of large protogynous coral reef fishes such as parrotfish are diminishing worldwide. Management strategies to mitigate anthropogenic stressors on these fish are hampered by a paucity of basic biological data, and reproductive and population dynamics models that are inadequate for the complex socio-sexual systems exhibited by these fish. This study provides critical biological information on community dynamics, life history and movement patterns of parrotfishes, and provides input on more effective management strategies. Fishing pressure and habitat degradation are important stressors on parrotfish communities in Oahu, Hawaii. Parrotfish communities were dominated by small, unfished species and smaller size classes of all species. Good quality reef habitat, characterized by higher proportions of live coral cover and more rugose benthic topography, were positively associated with scarid communities. Oahu parrotfish populations, particularly fished species, are stressed, and current management strategies should be modified to better mitigate anthropogenic stressors. Life history characteristics of parrotfish also indicate that current management regimes in Hawaii should be modified. The current minimum size limit of parrotfish catch in Hawaii is 12 inches in fork length, yet 50% of Scarus rubroviolaceus are immature until they reach almost 13.5 inches in fork length. Life history data suggest that management strategies should be employed to protect large female and male parrotfish, so as to prevent reductions I egg production or sperm limitation. Current reproductive and population dynamics models ignore alternative mating strategies as indicated by the presence of non-sex-changed males. These males may be important to sex rations and reproductive dynamics, and the degree to which these males occur in a population may be an indicator of overexploitation. Movement and behavioral patterns of Scarus rubroviolaceus suggest that marine reserves may be an effective management strategy to complement the current management regime in Hawaii. Individuals have discrete home ranges and are site attached. However, individuals make long distance forays from their home ranges (at least 400 m), indicating that small reserves may not fully protect all individuals. There may also be sex-specific biases I movement patterns and in reproductive and sleeping site locations, which should be considered in marine reserve design."

FY2010 Hawaii Coral Reef Management grant NA10NOS4190062; PI: Alan Friedlander

NA10NOS4190062