Mesh Modification of Commercial Drop Nets for Yellow Perch in Southern Green Bay, Lake Michigan
Parsley, Michael J.
University of Wisconsin-Stevens Point, College of Natural Resources
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Commercial drop nets were modified in one of three ways to reduce catches of sublegal (<191 mm) yellow perch (Perca flavescens) in Green Bay, Lake Michigan. In drop net pots modified with windows of larger mesh (61 & 10-mm stretched mesh), the percent of legal-sized yellow perch and the mean length of perch increased significantly from values obtained from the control pots (46-mm stretched mesh, the size used by most commercial fishermen). But catch per unit of effort of legal-sized perch (CPUE) was the same in the control and modified pots. The increase in percent legal composition of the catch was not sufficient to warrant further investigation. Drop nets modified with larger mesh throughout the pot (51, 60, & 64-mm stretched mesh), and larger mesh covering only the last 2 hoops (57, 58, 62, and 65-mm stretched mesh) resulted in significant increases in percent of legal-sized yellow perch and mean length of perch captured, whereas CPUE declined significantly. Drop nets with larger mesh throughout the pot allowed more sublegal perch to escape than nets with an equal-size mesh covering the last 2 hoops, but CPUE's were the same. Selection curves indicated that legal-sized perch escaped from the experimental meshes. Management options that would require 55-mm stretched mesh throughout the pot along with the current minimum size length of 191 mm, or require 57-mm stretched mesh throughout the pot and retention of all perch captured by commercial fishermen would result in catches of 80 – 90% legal-sized perch, and would reduce handling mortality associated with the fishery, allowing more perch to reach harvestable size.