Abstract
Predation by invasive exotic catfish (Ictalurus punctatus) on fish and shrimp catches inside large set-nets is considered a serious problem in inland fisheries in temperate Japan. The effects on fish and shrimp catches following the installation of a grid to exclude the catfish from a large set-net were determined by sampling using bag-nets with and without such grid inside the set-net in the littoral zone in Nishiura, Lake Kasumigaura system each month from October 2015 to September 2017. A total of 926 catfish individuals [3.8–69.0 cm in standard length (SL)] were collected during the study period, individuals smaller than ca. 10 cm SL being abundantly caught by bag-nets with and without grid, and individuals larger than 20 cm SL only by bag-nets without grid. Small fishes and shrimp, including commercially important species, were more abundant in nets with grid installed, whereas larger commercially important species, such as crucian carp (Carassius sp.), were more abundant in nets without grid. While the exclusion grid appeared to be an effective tool for excluding larger catfish individuals, their overall usefulness is dependent upon the sizes of other target species.
https://ror.org/00sjd5653 
