Ault, J. S., Smith, S. G.
Methods to evaluate marine reserve impacts
University of Miami RSMAS
Type Period Note:
Final Report, 10/1/05 9/30/06
The Florida Keys is a unique tropical marine environment of national significance, renown for its productive coral reef ecosystem, diverse natural resources, broad recreational fishing opportunities, and spectacular scenic beauty. Due to severe overfishing, research to assess changes in abundance of reef fish populations resulting from establishment of a network of notake? marine protected areas (MPAs) in the Dry Tortugas region of the Florida Keys is a high priority item for the NOAA Fisheries, Florida Keys National Marine Sanctuary, National Park Service, and State of Florida Fish and Wildlife Commission. The goal of this was to identify and evaluate robust metrics that defined fish community changes in marine protected areas. This was accomplished by through the following tasks: (1) conducting a thorough literature review and synthesis to identify metrics and models to assess population- and community-level changes within marine protected areas, and to assess their application to marine fishery ecosystems; (2) organizing and assimilating our spatially synoptic, long-term fishery-independent database from the Florida Keys on coral reef fish abundance, size structure, species composition, and environmental covariates to facilitate analysis of fish community dynamics in relation to physical and biological habitats, exploitation, and spatial zoning; (3) development of a robust statistical estimation framework to objectively assess differences in the metrics, and to discriminate between changes due to reserve establishment versus other processes or confounding factors; and, (4) applying the quantitative metrics, models and statistical framework identified in (1-3) to our database, particularly emphasizing the Dry Tortugas region of the Florida Keys. In November 2006, the Florida governor and cabinet approved implementation of a management plan for a Research Natural Area (RNA) or no-take marine reserve in the Dry Tortugas National Park (DTNP) to become effective in January 2007. The Florida Fish and Wildlife Conservation Commission also concurred with the proposed National Park Service regulations related to marine fishing in the park. In 2001 no-take marine reserves (NTMRs) covering approximately 566 km2 were established in Florida Keys National Marine Sanctuary waters near Dry Tortugas National Park. The parks new RNA, coupled with marine reserves in the Florida Keys National Marine Sanctuary, is designed to protect precious coral reefs, fishery, and cultural resources, and to ensure sustainability of intensely exploited regional reef fisheries resources - benefiting the Tortugas, the Florida Keys and beyond. The primary objective of fishery-independent monitoring was to conduct a synoptic visual census survey using SCUBA/nitrox to assess the resource status (occurrence, abundance, and spatial distribution), and MPA performance for the reef fish community in Dry Tortugas National Park. The goals of the 2006 Tortugas research expedition were: (1) to conduct a quantitative visual census assessment of coral reef fishery and habitat resources in the Tortugas region five years after implementation of the Tortugas Ecological Reserve (TER); (2) to sample all fish species and sizes in all representative coral reef habitats both inside and outside reserve areas; and, (3) to monitor trends in coral reef fish populations and the effectiveness of current management practices. Using a sampling design-based approach in 2006 we conducted a research cruise to the Dry Tortugas that resulted in 1,344 scientific dives in the region monitoring reef fish, benthic habitats, and spiny lobster. We compared these data to a series of synoptic research cruises with over 4,000 research dives to survey reef fish populations and habitats in the Dry Tortugas before and three years after the NTMRs were implemented. We recorded the presence, abundance and size of 267 fish species from eight reef habitats in three management areas offering different levels of resource protection: the Tortugas North Ecological Reserve (a NTMR), Dry Tortugas National Park (recreational angling only), and southern Tortugas Bank (open to all fishing under regional regulations). Species richness and composition remained stable between 1999-2000, 2004, and 2006, within the overall survey domain. Greatest reef fish biodiversity was found in the more rugose habitats. We detected significant domain-wide increases in abundance for several exploited and non-exploited species, while no declines were detected. In the Tortugas Bank NTMR, we found significantly greater abundances and shifts in length composition structures towards a higher proportion of exploited phase animals in 2004 and 2006 compared to 1999-2000 for some species (e.g., black grouper and red grouper). Consistent with predictions from marine reserve theory, we did not detect any declines for exploited species in the NTMR, while for non-target species we detected both increases and declines in population abundance in the NTMR for non-target species. The observed upsurge in exploited populations, however, may have also been influenced by other factors including past or recent fishery management actions that increased minimum sizes or reduced fishing mortality rates; the passage of recent hurricanes; and, the occurrence of good recruitment year classes. Although still early in the recovery process, our results after five years are encouraging and suggest that NTMRs, in conjunction with traditional management, can potentially help build sustainable fisheries while protecting the Florida Keys coral reef ecosystem. The project outcomes provide a suite of metrics and procedures for assessing MPA impacts that are statistically robust and readily interpretable for the Florida Keys ecosystem as well as applicable to MPA assessment throughout US marine waters.
FY2005 CRCP Project ID 1413; Project Title: General Coral Conservation Grants; Principal Investigator: Andy Bruckner; NA05NMF4631044