Appropriate management system for invasive fish species to protect water areas and fisheries

Environmental conservation and biodiversity field20230403

This system is used to efficiently ascertain the status of invasive fish species inhabiting dams, reservoirs, and other bodies of water, and to appropriately manage the population in order to reduce and eradicate the invasive fish.

Field:: Environmental business ＞ Environmental conservation and biodiversity field

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Overview
Features

Overview

It is said that about 40,000 species go extinct every year throughout the world. This breaks down to more than 100 species every day. Unless countermeasures are taken, the speed of extinction will accelerate, which could eventually affect the survival of society. In dams, agricultural reservoirs, and other bodies of water which are indispensable to our daily lives, invasive fish species brought in by humans destroy the ecosystem and affect marine resources. Ultimately, the invasive fish may eliminate the native fish. For example, research shows that a largemouth bass weighing 100 grams eats 400 grams of fish per year. The four main species of invasive fish that pose a problem in these waters are largemouth bass, smallmouth bass, bluegills, and channel catfish. Efforts are underway throughout Japan to eradicate these species.
However, the conventional methods of exterminating invasive fish (cast nets, gill nets, set nets, dragnets, drive-in nets, drying ponds, destroying and drying spawning beds, etc.) had many problems; for example, they were inefficient and had a significant impact on existing native fish.

OYO Corporation's system for appropriate management of invasive fish species

In order to eradicate invasive fish that have invaded dams, reservoirs, etc., it is effective to start by aiming for low-density management, not aiming for eradication from the very beginning.
Through periodic catching of invasive fish and predictions for the future number of fish, low-density management is a critical period for systematic management and reduction of numbers toward eradication.
Effective methods for conducting low-density management are using electrofishing boats to efficiently and selectively capture invasive fish species, and using environmental DNA technology to monitor habitat types and population numbers. By applying these methods, it will be possible to review the extermination method at the stage when the number of invasive fish populations has decreased. This makes it possible to promote further efforts for eradication, and will lead to the reduction of invasive species and the recovery of native fish populations.
OYO Corporation provides one-stop services ranging from surveys of habitat conditions to proposals of effective countermeasures for appropriate management and simulations of extermination effects.

Features

Use of electrofishing boat

An electrofishing boat is a partitioned boat equipped with an electric shocker device. This device uses electricity to temporarily paralyze fish so that they can be caught after floating to the surface. Electrofishing boats can be used to efficiently catch only invasive fish, so there is less impact on native fish compared to conventional gill nets. The partitioned design of the boat makes it easy to transport. This kind of boat is suitable for ascertaining habitat conditions along the entire lake shore and catching fish. The electrofishing boat is a technology that can be applied to a wide range of applications, from understanding the habitat conditions of invasive alien fish, preventing invasion, conducting low-density management, and eradicating invasive fish.

Application of environmental DNA technology

Environmental DNA technology is a method for simply ascertaining the types and numbers of organisms inhabiting water areas.
Environmental DNA is a fragment of DNA that exists in water derived from mucus, feces, etc. By analyzing environmental DNA, it is possible to roughly ascertain the types and numbers of organisms inhabiting an area. Specifically, one liter or more of water is sampled at the survey point, reagents are used to extract DNA, and a dedicated device is used to analyze the DNA. Compared to conventional capture surveys, it is possible to more efficiently ascertain the species and numbers of organisms inhabiting an area. Furthermore, even for bodies of water that invasive fish have yet to invade, this method can be used to confirm that a body of water is not inhabited by invasive fish by conducting periodic surveys.

Simulating future population numbers

Based on the number of fish exterminated by methods such as electrofishing boats, it is possible to estimate the number of fish inhabiting an area and simulate the future population. Efforts to eradicate invasive alien fish can be effectively promoted by examining the effect of extermination, reviewing extermination methods, or changing the combination of methods based on future predictions.

Example of implementing proper management through extermination

In a case of catching invasive fish using an electrofishing boat in a swamp in the Tohoku region, more than 300 largemouth bass were exterminated in four hours. By combining such electrofishing boats with existing extermination methods such as drive-in nets and the destruction of spawning beds, it is possible to maintain low populations and propose management plans aimed at future eradication.