Native fish species, such as bull trout, Athabasca rainbow trout and westslope cutthroat trout, have been calling Alberta’s eastern slopes home for thousands of years.
Native fish populations are threatened by many different activities that take place in and around their waters, with the greatest threats being habitat destruction or alteration, hybridization and competition with non-native fish species and fishing pressure.
Why do recovery stocking?
Recovery (or restoration) stocking is a tool that can be used to maintain genetic diversity by supplementing populations and expanding the range of native fish into streams where suitable habitats exist but have no fish living in them.
As populations decline in size and connectivity, genetic variability within a population can become limited. A larger gene pool supports population growth and sustainability, while also providing more resiliency to these threats. Hybridization with non-native species, such as rainbow trout, is a greater risk as non-native fish move into native trout habitat ranges. Hybridization further depletes the gene pools of native trout populations, typically resulting in lower population resiliency. Learn more about hybridization in westslope cutthroat trout.
How does recovery stocking work?
Nearest neighbour populations
Remote site incubation is one method of recovery stocking where fish are introduced into a new habitat from the nearest neighbouring population. It can also be used to supplement populations within the same stream where eggs were collected. Biologists collect eggs and milt from wild mature fish during their spawning season and fertilize the eggs with milt from male fish within the same stream. Fertilized eggs are moved to a quarantine facility at the hatchery until the eyed stage.
Eyed eggs are placed into a remote site incubation unit, which improves survival rates by providing them consistent conditions to develop in. The alevin (young trout) hatch and swim out of the remote site incubation unit into their new habitat and imprint on the stream so they will return there to spawn in the future.
In Alberta, remote site incubation has been used to support westslope cutthroat trout populations. Westslope cutthroat trout prefer habitats with cold, clean, clear and connected waters, and feed on aquatic invertebrates. Biologists have successfully introduced westslope cutthroat trout alevin into sites outside of their current range to support a larger, more connected and genetically pure population.
Read more on remote site incubation: Can buckets bring ‘em back? (Page 14 and 15).
Watch: A new approach to Westslope Cutthroat Trout recovery
Composite brood stock population
Recovery stocking can also be achieved using a composite broodstock raised in fish culture facilities. Composite broodstock are hatchery raised fish that originate from genetically diverse populations within the species native range.
Since 2021, we have worked closely with partners to collect eggs and milt from genetically appropriate, wild-caught westslope cutthroat trout. During each collection year, eggs are cross-fertilized in the field and brought to a quarantine hatchery facility until disease and genetic testing is completed.
Once those eggs hatch, the fish are then transferred to the Allison Creek Brood Trout Station where they are raised until maturity. Their eggs are collected and then cross-fertilized again to further enhance genetic diversity. The offspring of the broodstock can be used in some applications of recovery stocking, particularly when large numbers of fish are needed and nearby native populations are not healthy enough to support translocation efforts.
Read more here: Westslope Cutthroat Trout Composite Broodstock
Where do we complete recovery stocking?
Recovery stocking typically occurs in waterbodies within the species’ native range in Alberta. Locations are chosen based on where fish have the best chance to survive, such as above barriers like waterfalls where hybridization is not an issue and where habitat is intact. Waterbodies are specifically chosen based on where wild populations are limited in size and abundance, or where large-scale habitat recovery and non-native removal projects to restore or re-connect native habitat have occurred.
Related
Updated: Apr 15, 2025