Lake Ohinewai pest fish removal

Abstract

Most riverine lakes in the Waikato region have deteriorated from a macrophyte-dominated state to an algal-dominated state. Pest fish have further compounded water quality issues by resuspending nutrient-rich sediment and are believed to be a major barrier to water quality improvements. The University of Waikato has an ongoing programme funded by the Ministry of Business, Innovation and Environment, to produce pest fish management tools for end users that include removing pest fish from five lakes as an objective. The goal of the fish removals is to test the assumption that removing pest fish will improve water quality. Lake Ohinewai was selected as one of the five lakes to attempt a pest fish removal in 2009 and the removal operation was scheduled for January 2011. The Department of Conservation agreed to assist with funding for consumables and the construction of an experimental barrier to assist with the Lake Ohinewai removal project. University of Waikato staff began removing pest fish from Lake Ohinewai in January 2011 with the assistance of the Department of Conservation and volunteers. A one-way fish barrier was designed and installed during May 2011 to prevent adult pest fish from recolonising the lake.