Caribbean Fisheries Management and Conservation Genomics: Population Demographics and Stock Connectivity of Data-Poor Fishes

The primary goal of fisheries management is to ensure the long-term sustainable harvest of species and minimizing the ecological impacts while at the same time balance the cultural, economic, and food security needs of a jurisdiction. This is often achieved through a relatively complex and scientifically rigorous stock assessment process that results in management recommendations. Although Puerto Rico, St. Thomas/St. John, and St. Croix share many species of fishes, the underlying geology of the three areas and the impacts of currents and other oceanographic forces differ. Understanding potential differences in genetic stock structure and connectivity of populations for commercial and recreational fisheries species is critical to fisheries assessment and allocation. Knowledge of geographical differences in population demography, reproductive biology, and genetic stock structure for exploited species affords insights into differences that correlate with larval recruitment potential and adaptability that ultimately could affect the long-term sustainability of specific populations. Specifically, my research focused on the following objectives related to queen triggerfish Balistes vetula: 1. Determine the age structure and growth rate for queen triggerfish from north Caribbean waters; 2. Document age at sexual maturity for queen triggerfish from across the U.S. Caribbean. For parrotfish species I focused on the following objectives: 1. Validate age estimation of parrotfish species from the U.S. Caribbean using bomb radiocarbon; 2. Determine the age structure and growth rates for queen parrotfish Scarus vetula and stoplight parrotfish Sparisoma viride from north Caribbean waters; 3. Document size and age at sexual maturity and size and age at sexual transition for queen parrotfish and stoplight parrotfish; 4. Determine the population structure and connectivity for stoplight parrotfish, redtail parrotfish Sp. chrysopterum, princess parrotfish Sc. taeniopterus, and redband parrotfish Sp. aurofrenatum, across U.S. Caribbean and south Florida waters. For management efforts to succeed in Caribbean fisheries, local fishers must support and be willing to comply with fishing regulations. This is more likely when fishers are included in a stock assessment process that utilizes robust scientific evidence, collected in collaboration with fishers, to evaluate the health of fish stocks. Queen triggerfish is an important reef-associated species for commercial fisheries in the U.S. Caribbean. It exhibits a relatively unique reproductive strategy as a nesting benthic spawner, investing substantial energy in territorial defense, building and maintaining nests, and caring for fertilized eggs during the reproductive season. Prior to this study, no comprehensive life history information existed in the literature for queen triggerfish. My dissertation efforts provided the first comprehensive documentation of age, growth, size/age at sexual maturity, reproductive seasonality, and reproductive output for a Balistes species in the Caribbean. Caribbean parrotfishes are important contributors to coral reef ecosystem health while also contributing to local fisheries. Scientifically robust stock assessments require regional species-specific information on age-based key life history parameters, derived from fish age estimates. Evaluation of the accuracy of age estimation methods for fish species is a critical initial step in managing species for long-term sustainable harvest. The current study resulted from a collaborative research program between fish biologists and local fishers investigating age, growth, and reproductive biology of the seven parrotfish species landed in U.S. Caribbean fisheries. This is the first study to directly validate age estimation for any parrotfish species through analysis of radiocarbon from eye lens cores. Our age estimation validation results show that enumeration of opaque zones from thin sections of sagittal otoliths for Sparisoma and Scarus species provides accurate age estimates. Queen parrotfish Scarus vetula and stoplight parrotfish Sparisoma viride are widely distributed throughout the subtropical/tropical regions of the northwestern Atlantic, play important ecological roles in reef ecosystems, and contribute to small-scale commercial landings within several Caribbean management jurisdictions. Prior to this work, no comprehensive life history information existed for either species that combined otolith analysis and gonad histology. The life history information documented in the current study will provide essential information for stock assessments and informed management in the U.S. Caribbean for these two important parrotfish species. The genetic approach we used was next-generation sequencing of double digest restriction-site associated DNA (ddRAD) for my parrotfish population genetics study. None of the parrotfish species exhibited significant genetic heterogeneity between sampling areas within the Caribbean or between Florida Keys and Caribbean areas. For stoplight parrotfish and princess parrotfish, based on multivariate analyses and results from isolation by distance analyses, some amount of genetic heterogeneity and/or barriers to gene flow may occur between the U.S. Caribbean and the Florida Keys.