Chapters 3.6
3.6 Rainbow Trout
Emma Hardman , University of Guelph, Canada
Suggested citation for this chapter.
Hardman,E. (2022) Fish And Freshwater/Marine Invertebrates. In The Student Encyclopedia of Canadian Indigenous Foods. Editor, M.N. Raizada, University of Guelph, Canada. http://www.firstnationsfoods.org/
Background
Rainbow Trout, also referred to as Oncorhynchus mykiss, are a species of freshwater fish native to the fresh waterways of western northern america (Virginia Department of Game and Inland Fisheries, 2015). These fish naturally reside west of the rocky mountains (Virginia Department of Game and Inland Fisheries, 2015) as seen in figure 1 below, although due to their salmonid status they are capable of surviving in both fresh and saltwater (Behnke, 2002). As seen in figure 2, these fish have been introduced and integrated into ecosystems all over North America. Once entering and living in the salty ocean, these rainbow fish go through a physical transformation into Steelhead trout, a much larger and colourless fish (NRCS/Native Practices Work Group, 2010). Growing between 15-40 centimeters in length, these edible fish are between 1-3kg at market weight (Government of Canada, 2016). Named after their colourful bodies these trout are slim with a pink or red line running down their sides. Freckles completely cover their bodies with the exception of their white bellies and blue backs (Government of Canada, 2016).
Benefits
Benefits of rainbow trout to human and animal nutrition
Rainbow trout are an incredibly nutritious fish for humans and mammals alike. A total of 19.9 grams of protein can be found in only 100 grams of this freshwater creature. Hidden in that same 100 g, are 6.18 g of largely monounsaturated fats, 25 mg of calcium, and 226 mg of phosphorus. This fish is rich with omega-3-fatty acids (U.S. Department of Agriculture, 2009).
Benefits of rainbow trout to society
Rainbow trout farming operations have potential to be successful near any large fresh body of water, for example a lake. This is because the trout are extremely suitable to Canadian waters and have very few requirements outside of feed. In Canada alone aquaculture employs over 3,700 people while employing another 28,000 in the processing and packaging of the seafood (Government of Canada, 2021). Breeding stock, eggs, milt, and feed are all commonly produced in Canada eliminating the need for imports and costly border taxes (ref).
Benefits of rainbow trout to the environment
Rainbow trout farming is incredibly ‘low waste’, benefiting within and outside the farm’s immediate habitat. The waste produced by the trout contains phosphorus that settles on the bottom of the lakes in open net systems. This phosphorus acts as a supplement consumed by phosphorus deficient offshore fish populations to aid in growth (Government of Ontario, 2021). As rainbow trout are a predatory species (Virginia Department of Game and Inland Fisheries, 2015), the popularity of inland hatcheries and open net systems greatly reduce the impact on freshwater ecosystems and protect at-risk prey. Trout farmers find ways to reduce environmental impact at the processing and packing stages by utilizing “wasted fish” in fertilizer and as mink farm food (Cedar Crest Taylor, 2015).
Benefits of rainbow trout to women and children
Mercury is a neurotoxin commonly found in the muscles of fish (Health Canada 2019). This neurotoxin is especially harmful to women and children. Consistent exposure to this toxin can cause tumors, vision impairment, and loss of motor control (United States Environmental Protection Agency, 2021). It is recommended that pregnant or breastfeeding women should consume ¼ the amount of fish that the general public can eat to limit mercury transmission (Health Canada 2019). Rainbow trout, however, have very low levels of mercury in the wild and are therefore not a risk to women or children (United States Environmental Protection Agency, 2021). Fish absorb mercury through water and prey (Heath Canada, 2019), therefore through water quality control and tested prey, it is possible to nearly eliminate mercury in farmed trout.
Indigenous history surrounding rainbow trout
Rainbow Trout was and continues to be a traditional food of the indigenous peoples of North-Western North America. The Lillooet, Okanagan and Secwepemc tribes of British Columbia were particularly known for their hunting and consumption of the fish (Smith, 2009)(Kennedy, 1998).
Historically, Salmonid fish were used as trading chips when Indigenous peoples encountered fur trade era settlers (Smith, 2009). These fish were often dried and stored in the fall to create a storable protein for the cold winter months (Newcomb, 1974).
In present times, the government of Canada has instituted various programs to support the use of Rainbow Trout by indigenous communities in a commercial and personal manner. The government has created business funding and grant initiatives for Indigenous hatcheries and fish farms (Aboriginal Communal Fishing Licences Regulations, 1993). Indigenous communities are also eligible for an Aboriginal Communal Fishing Licence which allows unlimited fishing for food and ceremonial purposes (Aboriginal Communal Fishing Licences Regulations, 1993).
Outside of Rainbow Trout's nutritional value as a food source, it has spiritual value for (Native Languages org., n.d.). Rainbow trout are symbols of the motion, wisdom and change in indigenous beliefs (ref). They are admired for their natural migration patterns from salt to freshwater, of course transforming them into Steelhead trout (Native Languages org., n.d.).
Limitations
As with anything in life, even Rainbow trout has limitations. When discussing the future of the species it is important to consider negative effects the fish may have on wildlife and humans, the difficulties in natural cultivation of the species today, and it’s yield rate. These factors are vital when evaluating Rainbow trout to determine it’s worth as a wild food source and its role in an aquatic ecosystem.
Harmful effects of rainbow trout
While not toxic, Rainbow trout have been known to cause an abundance of issues for aquatic wildlife. Rainbow trout commonly spread whirling disease, a parasitic disease affecting neurological pathways in salmonids (Government of Alberta, 2021). This parasite is microscopic and enters the body through infected worms. The parasite attacks the nervous system of the fish leading to lack of spatial awareness and circling in place, hence the name whirling (ref). While harmless to humans the inability to navigate back to spawning waters and 90% mortality rate quickly destroy any hope of catching wild trout (Government of Alberta, 2021). In addition to parasitic disease, rainbow trout are an invasive predatory species in many waterways. These fish were initially released into north american waterways east of the rocky mountains to encourage recreational fishing (ref). The Rocky Mountain Research Station has begun to launch studies to find the extent to which Rainbow trout have negatively affected native species (U.S. Forest Service, 2014). Rainbow trout are non-harmful to humans and mammals, and have no toxic effects when ingested (ref).
Difficulties in cultivation of rainbow trout
Rainbow trout and their wild cultivation in Canada are threatened. The Athabasca river is one of the major Canadian habitats for rainbow trout, although it’s trout population is currently deemed ‘at-risk’ by the Government of Canada (Government of Canada, 2021). These trout are facing competition from invasive species in the river, and are being poisoned by contaminants from industrial waste dumping (Government of Canada, 2021). Based on the numerous environmental risks that would not only limit trout populations through climate change and predation, pollution in waterways could create health risks when consumed by humans (ref).
Yield of wild rainbow trout
When in the wild, rainbow trout is a reasonably high yielding fish as they grow and mature at rapid rates. These trout grow over an inch a month, making them a solid 2 pounds at approximately 1 year of age (Freshwater-Aquaculture, 2019). Growth predictions are reliant on reasonable temperature conditions within fresh bodies of water. Ideal growth occurs between 10-15 C (Freshwater-Aquaculture, 2019).
References
1.Aboriginal Communal Fishing Licences Regulations, SOR/93-332. (1993). https://laws-lois.justice.gc.ca/eng/regulations/sor-93-332/page-1.html
2. Behnke, Robert J. (2002). "Genus Oncorhynchus". Trout and Salmon of North America. New York: The Free Press. Pp. 10–21. ISBN 978-0-7432-2220-4.
3.Cedar Crest Taylor. (2015, April 13). Ontario Aquaculture-Processing Rainbow Trout [Video]. Youtube. https://www.youtube.com/watch?v=cbOu16K0xGA
4.Ford, R. J. (1984). Norwegian Salmon and Trout Farming. Marine Fisheries Review, 46(3).
5.Freshwater-Aquaculture. (2019, August 26). Trout. National Institute of Food and Agriculture. https://freshwater-aquaculture.extension.org/trout/
6.Fridrikson, S. (2008). [Map]. Canadian Geographic. https://www.canadiangeographic.ca/article/animal-facts-rainbow-trout
7.Government of Alberta. (2021). Whirling Disease. https://www.alberta.ca/whirling-disease.aspx
8.Government of Ontario. (2021, October 22). Packaging, transporting or exporting fish. https://www.ontario.ca/page/packaging-transporting-or-exporting-fish#section-3
9.Government of Canada. (2021, March 29). Fishing and the Canadian Economy: Employment. https://www.dfo-mpo.gc.ca/stats/cfs-spc/tab/cfs-spc-tab2-eng.htm
10.Government of Canada. (2020, November 7). Recovery Strategy for the Rainbow Trout (Oncorhynchus mykiss) in Canada (Athabasca River populations). https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/recovery-strategies/rainbow-trout.html#toc9
11.Government of Canada. (2016, December, 19th). Rainbow Trout. Fisheries and Oceans Canada. Retrieved November, 15th, 2021, from https://www.dfo-mpo.gc.ca/species-especes/profiles-profils/rainbow-trout-truite-arc-en-ciel-eng.html
12.Government of Ontario. (2021, October 22). Packaging, transporting or exporting fish. https://www.ontario.ca/page/packaging-transporting-or-exporting-fish#section-3
13.Health Canada. (2019, November 27). Mercury in Fish. Government of Canada. https://www.canada.ca/en/health-canada/services/food-nutrition/food-safety/chemical-contaminants/environmental-contaminants/mercury/mercury-fish.html
14.Kennedy D, Bouchard RT: Lillooet. In: Handbook of North American Indians, Volume 12: Plateau. Edn. Edited by Walker DE, Jr. Washington, DC: Smithsonian Institution; 1998: 174-190
15.Native Languages Org. (n.d.). Native American Fish Mythology. Native Languages. Retrieved October 20, 2021, from http://www.native-languages.org/legends-fish.htm.
16.Newcomb, W, W. (1974). North American Indians: An Anthropological Perspective. Goodyear Publishing Company, Inc.
17.NRCS/Native Practices Work Group. (2010, August). Indigenous Stewardship Methods and NRCS Conservation Practices .
18.NRCS Wildlife Habitat Management Institute. (n.d.). [Map].
19.Smith, K, D. (2009). Liberalism, Surveillance, and Resistance: Indigenous Communities in Western Canada. AU Press.
20.United States Environmental Protection Agency. (2021, March 3). Health Effects of Exposures to Mercury.
21.U.S. Forest Service. (2014, April 29). Nonnative Trout. United States Department of Agriculture. https://www.fs.fed.us/research/invasive-species/fish-aquatic/nonnative-trout.php
22.U.S. DEPARTMENT OF AGRICULTURE. (2009, April 1st). Fish, trout, rainbow, farmed, raw. Agricultural Research Center. Retrieved November, 13th, 2021, from, https://fdc.nal.usda.gov/fdc-app.html#/food-details/173717/nutrients
.23.Virginia Department of Game and Inland Fisheries. (2015, February 26). Rainbow Trout. National Parks Service. Retrieved October 19, 2021, from https://www.nps.gov/shen/learn/nature/rainbow-trout.htm.