Can Changing Cod End Mesh Size and Mesh Shape Affect the Nearshore Trawl Fishery off the West Coast of the United States?

摘要

A study, spanning the years 1988-1990, on the impact of trawl cod end mesh size and mesh shape was undertaken onboard nearshore bottom trawl vessels operating underproduction conditions off the west coast of the United States. Short-term impacts withexperimental cod ends were analyzed. Six cod ends were used as treatments: 76-, 114-, 127-, and 140-mm diamond mesh, and 114- and 127-mm square mesh. Three response variables were used to compare these cod ends: utilized catch weight (weight of marketable-sized fish), size-discard catch weight (weight of fish discarded due to small size), and giller weight (weight of fish wedged between meshes). Species composition differed between the "inner nearshore" area (0-91 m depth) and the "outer nearshore" area(>91-183 m depth). For all cod ends, the inner nearshore had a consistently greater percent total discard than the outer nearshore. The individual cod end results showed that the 76-mm diamond gave excessively high size-discard rates for both areas. The114-mm square mesh performed well in the outer nearshore, giving high utilized weight per hour and low size-discard weight per hour. The 114-mm diamond mesh did better in the inner nearshore, where a larger percentage of flatfish were utilized, giving a reasonable utilized weight per hour and also a low size-discard weight per hour.