[2] - Aquaculture is a growing industry in inland waters of the Great Lakes basin, but lake-based cage culture of salmonids, which began in the mid to late-1980s, occurs only in Georgian Bay and North Channel of Lake Huron.
- Aquaculture is the farming of aquatic organisms. In cage-based systems, cages are suspended in the water, allowing water to pass through. The water brings oxygen in and carries away waste products including feces, uneaten food, and medicines.
- Aquaculture is the fastest growing food production sector in the world. In Ontario, aquaculture production was 4500 tonnes in 2005.
- Rainbow trout is the dominant species produced in Canadian aquaculture systems.
- Approximately 75% of the production comes from eight freshwater cages located in Georgian Bay and the North Channel of Lake Huron.
Impacts of aquaculture on surrounding environment
Aquaculture can be detrimental to its immediate surrounding environment, affecting water quality via food byproducts and excreted waste from fish, leading to organic and nutrient enrichment and eutrophic conditions. Other potential problems include introduced diseases and parasites and antibiotic use. Because rainbow trout, although a non-native species, are already established in the Great Lakes, the most likely impact of trout aquaculture is through degradation of water quality.
Mapping aquaculture as a Great Lakes stressor
Aquaculture locations were derived from Canadian Aquaculture Systems, Inc. and located visually using Google Earth to generate a point file of aquaculture pen locations.1
Spatial distribution of aquacultre as a stressor in the Laurentian Great Lakes. (Inset: North Channel, Lake Huron).
Ontario cage operations are reported to use low-phosphorus, high digestibility feeds and produce both particulate waste from fish feces and feed and dissolved nitrogenous wastes from gill and urinary excretions.2,3 The majority of solids settle to the lake bottom within hundreds of meters of cage locations, whereas ammonium levels have been reported to return to background at distances of 0.5 to 12 km. Water circulation patterns will substantially influence the extent of flushing as well. We represent the water quality impacts from cage aquaculture as local, dissipating to 10% of their initial value within 5 km and to 1% within 10 km.
Data Sources:
1. Canadian Aquaculture Systems, Inc. 2009. Strategy for Sustainable Aquaculture Development in Ontario. Cobourg, Ontario, Canada.
2. Bureau, D.P., S.J. Gunther, and C.Y. Cho. 2003. Chemical composition and preliminary theoretical estimates of waste outputs of rainbow trout reared in commercial cage culture operations in Ontario. North American Journal of Aquaculture 65:33-38.
3. Podemski, C.L. and P.J. Blanchfield. 2006. Overview of the environmental impacts of Canadian freshwater aquaculture. A scientific review of the potential environmental effects of aquaculture in aquatic ecosystems. Canadian Technical Report of Fisheries and Aquatic Sciences 2450: 30–79.