Tests of Trawl Footrope Modifications to Reduce the Bycatch of Eulachon (Thaleichthys pacificus) and Other Small Demersal Fishes in the Ocean Shrimp (Pandalus jordani) Trawl Fishery, Information Report 2013-02

Identification Information

Citation

Originator: Hannah, Robert W. and Stephen A. Jones

Publish Date: 2013

Online Link: None

BPA Project #:

Contact Information

Agency: Oregon Department of Fish and Wildlife

Name: Cedric Cooney

Job Position: Natural Resources Data and Systems Manager

Telephone: 503-947-6094

E-Mail Address: cedric.x.cooney@odfw.oregon.gov

Description

Abstract: Three field experiments were conducted to determine if modifying shrimp trawl footropes could be an effective strategy for reducing fish bycatch in the ocean shrimp (Pandalus jordani) fishery. Of particular interest was reducing the trawl bycatch of eulachon (Thaleichthys pacificus), an anadromous smelt that is considered threatened under the United States Endangered Species Act. The experimental design compared catches between two double-rigged, semi-pelagic shrimp trawl nets equipped with rigid-grate bycatch reduction devices, fished simultaneously, with one net incorporating the modified footrope and the other serving as a control. Recording inclinometers were used to control for differences in fishing line height (FLH) between the nets and a specially divided hopper was used to keep catches from the port and starboard nets separate for sorting and weighing. Experiment 1 tested a footrope from which the entire central section of groundline had been removed to allow fish to pass under the trawl, but that was also rigged with reduced FLH to help minimize shrimp loss. Experiments 2 and 3 tested a footrope from which a small (1.5 m) section of the central groundline had been removed to create an “escape window” for fish to pass under the trawl net. In all 3 experiments, large reductions in the bycatch of small flatfish and juvenile rockfish were obtained, however, the reduction in eulachon bycatch was of similar magnitude to the shrimp loss created by the modifications, suggesting minimal effectiveness for eulachon. Comparison of the results from these experiments and other published research showed that smaller escape windows were more effective at maintaining shrimp catch rates and reducing fish bycatch than removing larger sections of the groundline.

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