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Commercial Shark Fishery Observer Program

Final Report Abstracts

1994-1995 Final Report Abstract
Steve Branstetter1 and George Burgess2
1 Gulf and South Atlantic Fisheries Development Foundation, Inc.
2 University of Florida
Report submitted: May 1997

Since 1994, observers have been placed aboard voluntarily participating commercial shark vessels to sample the catch and effort of the southeast U.S. commercial shark longline fishery, and thus enhance the reliability of management strategies. During 1996, this award supported performance leading to documentation of ~1.7% of the large-coastal shark commercial fishery quota; observers logged 150 sea-days on 43 fishing trips documenting 1.2 million hook-hours of effort with a catch of more than 5,600 sharks. Additional information gleaned during the first two months of 1997 was used limitedly for additional comparisons in specific analyses. More importantly, these data contributed to an overall 3-year database representing ~ 4.1 million hook-hours of fishing effort, and a catch of more than 16,500 sharks which resulted in 158 metric tons of landings (2.0% of the quota over the period). Two large coastal shark species, blacktip and sandbar sharks, dominated the catch and landings in the monitored regions.

1996-97(1) results, compared to results for 1994-95, illustrated the need for long-term fishery dependent monitoring to adequately characterize and assess the status of the stock and fishery because of annual variations in fishing effort. For the sandbar shark, each of the three regions surveyed had distinctly different catch patterns according to fish size and depth of capture. There is a size segregation by area; catches of juveniles and adolescents dominated in the North Carolina area, the South Atlantic was dominated by sub-adults and adults with a few juveniles taken in winter, and in Gulf Florida waters, the entire catch was composed of sub-adult and adult fish. Annual catch rates (sharks per 10,000 hook-hr) for the sandbar shark have not shown any consistent trend that would indicate any changes in the stock, except perhaps for North Carolina. 1994-1996 annual sandbar shark catch rates were 24, 27, and 47 for North Carolina; 5, 12, and 10 for the South Atlantic; and 8, 5, and 6 for the eastern Gulf of Mexico. Similarly, length-frequencies of the sandbar shark taken from each region have not shown any truly distinguishable changes over the program period, except for North Carolina. For North Carolina, the increased CPUE and changing length frequency was caused by an increasing number of juvenile and adolescent sharks being taken during the winter fishery.

The 1989-1992 sandbar shark cohorts appear to be recruiting strongly to the fishery, and may represent a substantial contribution to the overfished stock if appropriate management measures are implemented to protect them. Based on the size structure of the catch and the known biological parameters of the sandbar shark, a 140 cm FL minimum size limit is recommended for a management measure which should allow for recovery of this overfished species under continued measured fishing effort. For blacktip sharks, the size distribution is opposite that of the sandbar shark; the North Carolina catch is dominated by adults, there is a greater contribution of juveniles in the South Atlantic, and the Gulf Florida catch is primarily juveniles and adolescents. A catch rate and length-frequency analysis did not indicate any changes in the size structure of the catch over the three year period; the only noticeable trend was a greater contribution by juvenile, adolescent, and sub-adult fish during the summer fishing seasons.

Reprinted from: MARFIN FINAL REPORT Cooperative Agreement NA57FF0286 "Continuation of an observer program to characterize and compare the directed commercial shark fishery in the eastern Gulf of Mexico and South Atlantic," May 1997.