Benthic Habitats and the Effects of Fishing

Symposium Abstract: Effect of Shrimp Trawling on Snow Crab Resource in the Northern Atlantic

G. Brothers and J. J. Foster


The decline of the Northern Atlantic Cod stock and favorable environmental factors have led to an increase in the Northern Pink Shrimp (Pandalus borealis) Total Allowable Catch from 37,000 MT in 1996 to 112,000 in 2002. As well, an additional 365 new, <20 meter vessels have been added to the existing fleet of 13, >50 meter vessels involved in harvesting the resource. Shrimp and Snow Crab (Chionoecetes opeilio) are known to cohabit the same area, and as such, many crab fishers have expressed concern that shrimp trawling may be having a negative impact on the crab resource. In 2001, a two-phase study was begun to determine the interaction between shrimp trawling and the crab resource. Phase one of the study was conducted in a small area (0.5 x 4 miles) cohabited by crab and shrimp. The experimental design called for three fishing trips to be undertaken, the first directing for snow crab, the second directing for shrimp, and the third directing for crab. Crabs sampled were examined to determine ‘new’ and ‘old’ leg losses and then released 10 miles from the study area. Phase two of the study which was undertaken in 2002, consisted of three, five-day shrimp trawling trips carried out in an area 5 x 10 miles where shrimp and crab cohabit. The shrimp trawl had three retainer bags attached underneath the trawl and behind the footrope to capture the crab that passed over and under the trawl footrope. 12,000 crab captured in the retainer bags were examined for ‘new’ and ‘old’ leg losses and then released 10-miles from the study area. Analysis of ‘old’ and ‘new’ leg losses were compared before and after trawling (phase I) and after trawling and at various times of the year (phase II), and phase one and two data were also compared. Results presented (with confidence limits) that cover both phases indicate a low percentage of recent leg loss, suggesting that shrimp trawling did not adversely impact crab encountered during the two-phase study.