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Dry Tortugas Cruise Day 6 - August 30, 2007
management zones and the interfaces
between bank and shelf. Ten stations
were randomly selected from the
interfaces in three management zones:
Dry Tortugas National Park, Tortugas
Ecological Reserve, and the
U.S. Exclusive Economic Zone
Tortugas Ecological Reserve is a bold attempt to manage our coastal resources in a sustainable way. The Reserve encloses the northern portion of Tortugas Banks, located at the southern margin of the West Florida Shelf and 60 nautical miles west of Key West. The remote location and proximity to ocean currents that merge to form the Florida Current, make the Tortugas an excellent location for a reserve whose biological production can spill over to other areas. It is believed that the reproductive output from the Tortugas can rejuvenate fish populations in the Florida Keys, where intense fishing pressure has reduced most exploited stocks far below their sustainable level.
To evaluate the impact of the Reserve on exploited fishes, we have conducted surveys in three areas that differ in the fishing pressure they receive. Since the Reserve’s establishment in 2001, ten stations have been established and sampled in each of three management areas. The three areas are Tortugas North Ecological Reserve (TNER, where all fishing is prohibited), Dry Tortugas National Park (DTNP, where commercial fishing and spearfishing are prohibited), and the Exclusive Economic Zone (EEZ) of the U.S. (where both commercial and recreational fishing are allowed). By comparing how populations vary over time in these areas, we can gauge the performance of the Reserve. Our sampling is focused on an ecologically sensitive habitat of the benthic landscape, the transition between the coral banks and the sandy shelf, allowing us to monitor both reef and shelf communities. These communities are linked ecologically; many of the fishes that shelter on the reef during the day feed on the sandy shelf during the night.
(Ocyurus chrysurus) from Tortugas
North Ecological Reserve (TNER), Dry
Tortugas National Park (DTNP), and the
Exclusive Economic Zone (EEZ).
(J.S. Burke, NOAA CCFHR, unpublished
data)
our sampling sites.
Photo credit: Brett Harrison.
John Burke, a Research Fisheries
Biologist at the Center for Coastal
Fisheries and Habitat Research, pictured
here preparing to board a small boat
after a fish survey.
Photo credit: Amy Uhrin.
Our results suggest a rapid positive response by commercial species to the protection provided by the Reserve. Yellowtail snapper provide the best evidence for positive impact of the Reserve. This species is common in the area, grows rapidly, matures early, and is specifically targeted by commercial fishermen. Our counts over the five years of this survey show that yellowtail numbers have increased significantly, and that their abundance in the Reserve is significantly greater than in the Park or the EEZ.
This year’s survey indicates that the condition of many commercial fish stocks is improving locally. The abundance and size of exploited species at our survey sites are increasing. Increases are evident for scamp grouper, mutton snapper, red and black groupers, as well as yellowtail snapper. Several rare species absent from previous surveys were observed. The goliath grouper, a threatened species which can reach a length of six feet and 800 pounds, was observed at several of our stations. The threatened Nassau grouper was observed for the first time at two stations.
The full impact of the Reserve is likely to take decades to unfold. It will provide an excellent opportunity to further our knowledge of the workings of marine ecosystems. The Reserve has been designed to protect both reef and shelf habitats while preserving their ecological linkage. Exploited fish populations may be enhanced by improved habitat conditions in their shelf feeding grounds. We hope to determine the contribution of habitat improvement relative to reduction in fishing mortality as determinants of Reserve success. Tortugas Ecological Reserve is an opportune location to find answers to such questions, as monitoring continues to document its long term benefits.