Belcher, C. N., and C. A. Jennings. 2009. Use of fishery-independent trawl surveys to evaluate distribution patterns of sub-adult sharks in Georgia. Marine and Coastal Fisheries: Dynamics, Management and Ecosystem Science 1:218-229.
Abstract
We investigated the utility of a fishery–independent trawl survey for assessing a potential multispecies shark nursery in Georgia’s near and inshore waters. A total of 234 sub-adult sharks from six species were captured during 85 of 216 trawls. Catch rates and size distributions for sub-adult sharks, and the ratio of neonates to juveniles were consistent among areas. The highest concentrations of sub-adult sharks occurred in creeks and sounds. Species composition varied among areas. Atlantic sharpnose shark was the most abundant species in the sound and nearshore stations, whereas bonnetheads were the most abundant species in the creeks. The aggregate of other species occurred with higher frequency in the sounds and nearshore. Sampling characteristics of the trawl survey were compared to those from a fishery–independent sub-adult shark longline survey to assess the similarity of the two gears. A total of 193 sub-adult sharks from seven species were captured during 57 of 96 longline sets, whereas 52 sub-adults from four species were captured during 20 of 48 trawls. Selectivity and efficiency differed between the two gears. The trawl had lower catch rates, caught smaller sharks, and encountered a different suite of species than the longline. General seasonal trends in relative abundance also differed between the two gears, with the longline showing an increasing trend in abundance and the trawl showing a stable trend. Although trawls were not found to be efficient for sampling sub-adult sharks from most species, they can be a useful source of supplemental data.