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Keeping Out Exotic Fish Improves Endangered Hawaiian Waterbird Habitat

Photo of Fish screen installed in a wetland unit at the Hanalai National Wildlife Refuge on Kauai. Fish are removed from the water as it flows through the screen. The fish-free water is then used to flood the wetland unit behind the screen. Richard MacKenzie, USDA Forest ServiceFish screen installed in a wetland unit at the Hanalai National Wildlife Refuge on Kauai. Fish are removed from the water as it flows through the screen. The fish-free water is then used to flood the wetland unit behind the screen. Richard MacKenzie, USDA Forest ServiceSnapshot : Exotic tilapia and mosquito fish are found in aquatic ecosystems throughout the Hawaiian Islands where they degrade native fish and waterbird habitat. A prototype fish screen installed in a wetland unit managed for the preservation of endangered Hawaiian waterbirds kept nuisance fish out and increased aquatic insect densities for the native birds to feed on. Additional larger screens have been installed in other wetland units and are under consideration for stream restoration projects.

Principal Investigators(s) :
Mackenzie, Richard A. 
Research Location : USFWS Hanalei National Wildlife Refuge
Research Station : Pacific Southwest Research Station (PSW)
Year : 2014
Highlight ID : 684

Summary

Exotic tilapia and mosquito fish were introduced to aquatic ecosystems in Hawaii and throughout the western Pacific in the early 1900s. Some were intentionally introduced to control mosquitoes, and some were unwanted aquarium pets or escaped aquaculture specimens. Since their introduction, these fish have become well established in wetlands and streams throughout the Pacific, negatively impacting native fish and waterbird habitat. Forest Service scientists monitored exotic fish populations in the Hanalei National Wildlife Refuge and tested the effectiveness of a prototype fish screen designed to keep these fish out of wetland units managed for threatened and endangered Hawaiian waterbirds. As a result, they saw a significant increase in aquatic insect production (native waterbird food) compared to an adjacent unit where these fish were present. The success of the screen resulted in the installation of larger fish screens in other units across the refuge, and land managers are considering using it as a restoration tool for Hawaiian streams.

Forest Service Partners

External Partners

 
  • US Fish and Wildlife Service