Comparison Of Catch And Bycatch With The Addition Of Escape Holes To Otter Trawl Nets In The Northeast Shrimp Fishery

Project Leader: Bill Lee, F/V Ocean Reporter

Final report

Small escape holes made from cut pieces of 6-inch PVC pipe were sewn into the net in front of the Nordmore grate in a standard shrimp net used in the northeast fishery. Preliminary tests had provided video of fish escaping through these holes during active trawling. A series of tows, with and without these holes in the nets were made from the vessels the Ocean Reporter and the Marina Rose. Seven other participating boats from Rockport, Massachusetts and Hampton, New Hampshire towed standard gear at the same time and in the same general area. Catch and bycatch was weighed and identified to provide a direct quantitative comparison of the percentage bycatch with and without the escape holes.

Mean catch rate for vessels using nets without rings was 235.5 lbs shrimp/hr with a bycatch rate of 16.7 lbs/hr or 6.6%. For the two vessels with escape rings installed in the nets, the catch rate was 228.6 lbs shrimp/hr with a bycatch of 27.5 lbs/hr or 10.7 %. The data was confounded by the large variation in bycatch rates among vessels and the limited number of tows. The experimental vessels encountered schools of pelagics (whiting or herring) on some days which heavily influenced results. One vessel, the Marina Rose appeared to show a significant reduction in bycatch rate from 19.4% without the rings to 9.4% with the escape rings installed. The other vessel, the Ocean Reporter had a bycatch rate of 7.5% without rings and 11.3% with the rings. A high catch of pelagics on several days during the tests with rings influenced results from this vessel.

A further complication to the study was a discrepancy in bycatch rates between vessels operating out of Hampton, New Hampshire and those out of Rockport, Masachusetts. The New Hampshire vessels had lower overall bycatch rates, which could be due to the area trawled, or performance of the gear. A similar study in the previous year had documented a lower catch of pelagics by the New Hampshire vessels. Future studies should involve a larger number of tows from one or two vessels.