Scientific research on farmed trout

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Science is the key to an environmentally sustainable trout farming industry. A number of trout and other freshwater aquaculture studies have been undertaken over the past decade to build understanding about trout species, trout-farming production methods, the effects of trout farming on lake ecosystems, and innovative approaches to feed composition and waste management. This includes a multi-year initiative undertaken by Fisheries and Oceans Canada scientists and researchers at the Experimental Lakes Area near Kenora, Ontario, to monitor any fish farm-related changes to one of its lakes, including on native fish species, with the establishment of a small-scale Rainbow Trout farm.

Innovation

The Canadian Model Aqua-Farm in Manitoba uses a simple, yet intensive re-circulating land-based aquaculture system that is intended to be the basis for a standardized approach to freshwater aquaculture production. The Rainbow Trout farm is being heavily monitored to document the economic and environmental performance of the model design, which uses the most current technologies in terms of nutrition and feeding strategy, fish health management, water conservation and utility, waste processing and management, and other operational standards.

  • Canadian Aquaculture R&D Review articles: 2009, 2011

The effectiveness of constructed wetlands to treat aquaculture waste in freshwater is being investigated in Ontario. The project builds on research done in warmer or more moderate climates in equatorial areas and the U.S. and Europe, which showed constructed wetlands were effective at removing or reducing concentrations of nitrogen and phosphorus, pathogens, and other contaminants in wastewater effluent.

  • Canadian Aquaculture R&D Review article: 2009

To meet the regulatory guidelines for the production and use of aerobic compost in Ontario, researchers performed the required chemical analysis and compilation of compost developed by a fish farmer in Northern Ontario. The composting system uses fish processing waste and dead stock, along with locally available waste sawdust, in an aerobic digester to produce the compost.

  • Canadian Aquaculture R&D Review article: 2009

A national selection and breeding program for rainbow trout aquaculture in Canada is being investigated by researchers and other stakeholders. This initiative seeks to enhance performance in rainbow trout, specifically targeting improved fillet yield, enhanced growth rate, and greater tolerance to warm-water conditions.

  • Canadian Aquaculture R&D Review articles: 2009, 2011

Research is currently inventorying the genetic variation in wild, semi-domesticated, and diploid and triploid strains of rainbow trout in British Columbia, as well as a commercial LYNDON strain in Ontario. Building a genetic database for the LYNDON strain will help in monitoring mating success and inbreeding, and could eventually be used to help in pre-selecting broodstock individuals for desired production traits.

  • Canadian Aquaculture R&D Review article: 2011

Trout feed

Researchers are studying the growth coefficient and apparent digestibility of coefficient of nitrogen and phosphorus for various size ranges of rainbow trout and brook trout fed different commercial feeds and exposed to two water temperatures. Based on the results, the study will establish nitrogen, phosphorus and dry matter balances.

  • Canadian Aquaculture R&D Review article: 2011

Following the results of experiments that showed a phosphorus-deficit diet induced multiple vertebral anomalies in farmed Rainbow Trout, scientists are working to identify the role and function of genes involved in bone tissue growth that led to such observations. This is an international research project.

  • Canadian Aquaculture R&D Review articles: 2011, 2013

Potential effects on wild fish and shellfish and/or the freshwater environment

Adding natural or artificial substances, such as nitrates and phosphates, into a body of water has the potential to increase the water’s biomass, which could cause eutrophication and potentially deplete oxygen in the water. A number of trout-farming research initiatives have been undertaken to study whether the presence of trout farms may alter the trophic status of lakes.

Nutrient fluxes from sediments to the water column were quantified in the Experimental Lakes Area to estimate the overall contribution of sediments affected by trout farm fish wastes to soluble phosphorus and nitrate loading, and the contribution of these fluxes (if any) to eutrophication in the water.

Phosphorus is an essential nutrient for skeletal development and growth in fish, which is obtained almost entirely from dietary sources. An inter-provincial research team worked to optimize the formulation of a phosphorus-deficient diet for Rainbow Trout, as well as to determine the alternating sequence of phosphorus-sufficient and phosphorus-deficient diets to maximize growth of the trout and minimize phosphorus discharges.

A multi-disciplinary team of researchers have been tracking interactions between wild and farmed rainbow trout in the North Channel of Lake Huron by following small numbers of farmed rainbow trout outfitted with acoustic/radio telemetry transmitters. The project aims to quantify the range and extent of “escapee” movement and gene flow among fish populations, and to measure the interactions between wild, stocked, and escaped fish. Results of small- and large-scale releases indicated that many of the escaped fish remained in close proximity to the farms or repeated visits to the sites, and were susceptible to predation and angling.

  • Canadian Aquaculture R&D Review articles: 2007, 2009, 2011

The impact of trout cage sites on wild fish and other freshwater species in Lake Huron was studied by an interdisciplinary team of researchers using bottom-grounded gillnets located at farm sites and one-two kilometres away from the sites to capture sample fish and other species. Based on the sampling design, the farms were shown to have no effect on the isotrope rations of the wild fish. However, it was noted that abundances of both small and large fish were greater around the pens for non-food reasons. Researchers suggested the pens may be used for shelter by wild stocks against birds and other predators.

  • Canadian Aquaculture R&D Review article: 2007

Regulations

To assist government regulators in the decision-making processes for licensing and regulating the new freshwater aquaculture sites, researchers are working to develop objective tools. There are five main components of this five-year study: evaluating the particle tracking model DEPOMOD; developing a dispersion model; developing a benthic impacts model, testing particle dispersion and benthic impacts models, and modeling ecological effects. The suitability of DEPOMOD in the freshwater environment is being tested at the largest rainbow trout cage farm in Canada, Wild West Steelhead in Saskatchewan.

A computerized Decision Support Tool was developed to provide a consistent formula to Ontario regulators in the review of aquaculture licence applications. The application has ten worksheets containing the decision criteria and document decision points to rate risk in 10 categories: fish habitat, fish health, fish communities, species at risk, operational practices, water quality, sediment, consultation, navigable waters, and Crown land tenure.

  • Canadian Aquaculture R&D Review article: 2009

Animal health

Bacterial coldwater disease is a primary disease of concern for trout farm raceway operations that use groundwater. To prepare to conduct autogenous vaccine trials for the disease, research was undertaken to identify the strains of the bacteria that cause the disease. The study also involved a treatment trial to determine the efficacy of florfenicol as a therapeutic measure to blunt the impact of the disease.

  • Research abstract, Canadian Aquaculture R&D Review article: 2009

The effectiveness of cinnamaldehyde on a common fungus, in vitro as well as on the eggs and fry of Brook Trout and Rainbow Trout, was tested and compared to malachite green, formaldehyde, and bronopol. The researchers also measured the impact of the treatment (bath or in-feed) on the egg hatching rate, as well as on fry malformation and survival rates.

A multi-disciplinary team of researchers aimed to identify the possible causes of “gastric dilation, air sacculitis” syndrome in farmed steelhead trout in Bay d’Espoir and to suggest possible mitigating measures. Standard diagnostic health testing was performed, as well as histopathological and biochemical indexes during the production cycle.

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