Catch Efficiency of Great Northern Tellin Hydraulic Jet Dredge

Abstract

An attempt was made to estimate the catch efficiency of the great northern tellin hydraulic jet dredges that are being used in the Shiriuchi sea area. In the dredging survey, 2 dredges, one towed behind the other at a distance of 2 meters apart, were used simultaneously in the same fishing ground. The number of shells caught by each dredge were counted and their lengths were measured.
Under the condition of this dredging survey, the catch efficiency is considered to be a function of the ratio of the number of shells caught by the dredge in the first position to the number of those caught behind it, using shells of the same length.
In this way, the fishing performance for hydraulic jet dredge was evaluated. Mean relative catching effciency due to fishing selectivity of dredge was 0.82, and coefficient proportion to catch-ing rate was 0.68. The average catch efficiency was 0.56 which was estimated from these values.
It was found that the catch efficiency of the hydraulic jet dredge for great northern tellin is higher than the common dredge for ark shell and Japanese surf clams.