Commercial Shark Fishery Observer Program
Final Report Abstracts
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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.
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