Control of water weeds by grass carp in a drainage ditch in New Zealand

Abstract

Two‐year‐old grass carp Ctenopharyngodon idella Val. were stocked at a rate of 350–650 kg.ha‐1 in a farm drainage ditch in the Bay of Plenty, New Zealand. During the months December to April the fish greatly reduced the standing crop and percentage cover of the weeds Callitriche stagnalis Scop, and Nasturtium officinale R.Br., but had no effect on Polygonum decipiens R.Br. © 1975 Taylor & Francis Ltd.