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Biocontrol and Invasive Trout

By Nicole Carpenter, Science Projects Manager at Georgian Bay Forever

Invasive species are species that have been introduced to a new environment, often accidentally, and can cause harm and disrupt the native wildlife in the absence of predators. These species have not chosen to invade ecosystems, outcompete native species, and wipe out populations, but nature is fierce, competitive, and opportunistic - meaning when given the chance to thrive, it will, even if that means knocking things out of balance. Not all species introduced to a new area become invasive, but when they do, they can have significant impacts on fisheries, agriculture, biodiversity, and even human safety.

Brook trout

Routine boat checks, clean equipment protocols, herbicides, lampricide, boot brushes, and barriers are all examples of tools and techniques designed specifically for early detection of and rapid response to invasives in the Great Lakes watershed. Some are found to be more successful than others, and some are more widely accepted than others depending on their overall impact.

Biocontrol is the use of a predator, parasite, or pathogen of a species to decrease and manage the population, often used to control invasive species. Biocontrol is a controversial method as it involves the release of another non-native species, and has become problematic in the past. Scientists have discovered another type of biocontrol that does not involve introducing a new species, known as genetic biocontrol. According to Teem et al. (2020), this technique is used to control invasive species by altering the genetic material of an organism to disrupt reproduction of invasive populations. An example can be found at the New Mexico State University where students research the invasive brook trout, Salvelinus fontinalis, which is native to eastern North America. Unfortunately, since its arrival, the native Rio Grande cutthroat trout, Oncorhynchus clarki virginalis, is now only found across 10% of its historical range in freshwater rivers and streams across northern New Mexico and southern Colorado (Miller, J., 2022).

The Rio Grande cutthroat trout

Currently, genetic biocontrol is being tested and used as a way to shift the sex ratio to all males. Male broodstock of invasive brook trout are being created in a fish hatchery, released into the Leandro Creek and shifting the population to become all male, resulting in zero reproduction. These brook trout are called Trojan brook trout. Brook trout will no longer be able to reproduce over time, but these Trojan brook trout have been found to produce viable hybrid offspring with the bull trout, Salvelinus confluentus. Thus, this method may prevent future generations of the invasive brook trout, but depending on the other species using the same habitat, it could create an entirely new problem with invasive hybrids of brook trout and bull trout.

A lone brook trout

Over time, people have developed incredible ways to manage and control invasives in an attempt to limit the spread and harm throughout the ecosystem, however, more research needs to be done to better understand where, when, and how to best manage invasive species.


Miller, J. (2022). Trojan Trout: could turning an invasive fish into a ‘super-male’ save a native species? The Guardian. April 21, 2022.

Teem, J. et al. (2020). Genetic Biocontrol for Invasive Species. Front Bioeng. Biotechnol. 2020; 8(452)


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