Census Information

Census 2008

2008

The goals of the 2008 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 2008 we conducted a research cruise to the Dry Tortugas that resulted in 1,710 scientific dives in the region monitoring reef fish, benthic habitats, and spiny lobster.

Also during the period of 2007 – 2008 we continued with our acoustic telemetry project. Theory suggests that as fish biomass in the Research Natural Area  (RNA) builds due to reduced exploitation, directed density-dependent movements of adults from the RNA will supplement adjacent fisheries to quantify spatial requirements of reef fish and their flux rates across RNA boundaries, we determined home range, activity patterns, site fidelity and habitat preferences for 65 acoustically-tagged reef fish representing 11 species using an array of omnidirectional hydroacoustic receivers deployed in the RNA’s diverse coral reef environments.

Our observations clearly demonstrated that exploited-phase red grouper and a variety of other species are capable of, and occasionally do, cross RNA boundaries, and are more likely to do so where boundaries overlay contiguous reef. In general, our estimated home ranges for groupers and snappers were significantly larger than those estimated by other researchers for other coral reef fish, which may be attributed to the unique sizes and life histories of the species we tagged as well as the expanded spatial and temporal scale of our passive acoustic tracking approach. Nevertheless, the home range sizes estimated for red grouper, black grouper, and yellowtail snapper were small relative to the size of the reserve, and indicate that the RNA is probably effective at protecting these species within the size ranges observed. Frequent utilization of the reef habitats within the RNA by more mobile species suggests that the RNA may afford important protection for these species on a daily basis.

Please click here for a complete report of the 2008 Dry Tortugas Expedition.