Rainbow Trout

The Canadian Fisheries and Oceans Aquaculture R&D division conducts trout aquaculture studies to increase human understanding about the species, farming production methods, effect of trout farming on lake ecosystems, feed composition, and waste management. They are also investigating the changes made to one lake at the Experimental Lakes Area near Kenora, Ontario due to the establishment of a small-scale rainbow trout farm.

Fisheries biologists from the Grand Mesa, Uncompahgre, and Gunnison National Forests (GMUG) assessed the biology and population status of rainbow trout in the GMUG Forests in 2008 to summarize past and present publications, providing an objective overview of the status of the species. Limited funds restricted their access to collect a full inventory and monitoring across the landscape. Past studies have focused on native species, therefore not identifying the exact distribution and abundance of rainbow trout populations in the GMUG Forests. Permanent sampling sites and long term monitoring will provide the most accurate description of rainbow trout populations in the area. Gaining a better understanding of rainbow trout habitat requirements, locations of fish barriers, and overall stream conditions will help with managing fisheries resources in maintaining existing rainbow trout populations while meeting Forest Plan standards to protect native fish.

Oregon State University found in 2011 that the health of wild steelhead populations rely on freshwater rainbow trout productivity. Based on a 15-year analysis of over 12,000 steelhead trout, researchers found that up to 40 percent of the genes in returning steelhead came from rainbow trout. Rainbow trout act as a genetic reservoir for when ocean conditions are unfavorable to steelhead survival. The offspring of rainbow trout may migrate to the ocean, and return as a larger, more robust steelhead. The results raise challenges for fishery managers to include the health, stability, and habitat of freshwater rainbow trout in their assessments. 

Scientists are unclear as to why certain rainbow trout remain in the streams while others become anadromous. Based on a study published in 2014 in the Canadian Journal of Fisheries and Aquatic Sciences, they hypothesize that it has to do with the conditions of the individual fish’s size and behavioral tactics, as well as gender, as males more frequently remain in streams while females more frequently become anadromous. Although they found a number of correlations, the scientists suggest studying the effects of water temperature, impact of food supply, the cost of freshwater migration and marine survival, and the effects of overcrowding to better understand the metamorphose. Direct tests are scarce, and little data exists on the extent of residency and anadromy. Data gaps were identified for future research.