Not-So-Rosy Minnows
By Nick Carter, Marketing and Communications Volunteer
February 25, 2025
If you’ve ever visited the fish section at a pet store, you’ve probably seen rosy red minnows. These small golden-orange fish are commonly sold as food for larger aquarium species, and are sometimes used as bait by anglers. Rosy reds, as they’re often called, are really just a variety of the fathead minnow developed in captivity.
While popular in the aquarium trade, the rosy red is causing fish biologists some concerns. In North America and Europe, captive rosy reds have been released into natural water bodies where they’ve started breeding and become an invasive species. These minnows are tougher than they look, and are competing for food and space with native fish species. It’s already happening as near as British Columbia.
Alberta is home to native populations of “wild type” fathead minnows, and invasive rosy reds could interbreed with our wild fatheads and really mess up the local gene pool. And in addition to unwanted competition, rosy reds could introduce new diseases to a variety of native fish species. So if there are rosy reds invading Alberta’s water bodies, biologists want to know about it and, hopefully, stop the problem before it gets worse.
Photo via Alberta.ca
A recent study co-authored by RAM Assistant Curator of Non-avian Vertebrates Sean McFadden (Morris et al., 2024) reveals some important findings. In 2022 apparent rosy reds were found in Edmonton’s Whitemud Creek and Calgary’s Fish Creek. When compared to known specimens of this breed in the RAM collections, their identity was confirmed. Rosy reds have indeed found their way into Alberta’s waterways.
To find out how long these fish have been swimming around under our noses, the research team looked into written and photographic records of rosy reds in the province from sources including government biologists, Freshwater Conservation Canada, and iNaturalist users. 20 records of findings now indicate that rosy red minnows have been loose in Alberta since at least 2011, with most occurrences coming from 2022-2023. Not only that, but rosy reds have been found in the Athabasca, North Saskatchewan, and South Saskatchewan River Basins, most commonly from the major urban centres in these drainage basins.
The authors reasoned that it’s unlikely that what we’re seeing here is native fathead minnows naturally acquiring the “rosy red” gene mutation in the wild, given how recent most rosy red sightings are, and how close they’re occurring to urban areas. The more likely case is that these rosy red findings were pet store fish bred in captivity and released into the wild.
Photo via Alberta.ca
This is, of course, concerning for our wild fathead minnows as well as other native fish species. We need to learn more about the full effects of invasive rosy red minnows on native fish populations. In the meantime, you can help biologists by reporting any rosy reds you see to the Government of Alberta by calling 1-855-336-2628. You can find more information, including how to identify rosy reds, on Alberta.ca. Uploading a photo on the iNaturalist app helps biologists gather more data on where invasive rosy reds are showing up. Make sure to never release aquarium fish into the wild as well. If you have rosy reds at home that you can’t take care of, contact your local pet store or aquarium retailer for help. Many businesses will accept unwanted aquarium fish. This way, we can all contribute to keeping Alberta’s waterways and native fish species healthy.
Reference
Morris, M.R.J., S. Derlukewich, and S. McFadden. 2024. The occurrence of introduced rosy red minnows (Pimephales promelas) in Alberta, Canada. Canadian Field-Naturalist 138(1): 1–9. https://doi.org/10.22621/cfn.v138i1.3253