"Surrounded by the Arctic, Atlantic and Pacific Oceans, and home to the Great Lakes, Canada is one of the foremost maritime nations on the planet." ⁽¹⁾

Fisheries are both economically and culturally important to Canada. Canada has the world's longest coastline, largest offshore economic zone and largest freshwater system.⁽²⁾ Over 7 million people live in Canada's coastal areas, and the fisheries industry provided more than 144 000 Canadians with jobs in 1999.⁽²⁾ For many small coastal and aboriginal communities, fishing is more than just a livelihood; it is a way of life.

Canadian fisheries encompass the three oceans (Atlantic, Pacific and Arctic), as well as the freshwater system. Within each region, commercial, recreational and subsistence fisheries play a significant, though varying, role. Overall, marine fisheries account for the greatest landed value of fish ($1.92 billion), with shellfish currently the most valuable catch (Table 1). Salmon had landed values of more than $56 million in 2001,⁽³⁾ and is a vital component of many subsistence and recreational fisheries. Aquaculture, first introduced to enhance natural stocks, and is now one of the fastest growing food production activities in Canada, accounting for 22.5% of Canadian fish and seafood production, worth $557.9 million in 1999.⁽²⁾ Recreational fisheries are also economically important to Canada, contributing $2.4 billion in direct expenditures and $6.7 billion in indirect expenditures in 2000.⁽²⁾

Table 1: Landed value of fish by species; examples given represent the top two types in the category⁽⁴⁾

Climatic factors, such as air and water temperature, and precipitation and wind patterns, strongly influence fish health, productivity and distribution. Changes such as those associated with a 1.4-5.8°C increase in global temperature, as have been projected by the Intergovernmental Panel on Climate Change (IPCC) for the current century,⁽⁵⁾ could have significant impacts on fish populations (e.g., references 6, 7). This is because most fish species have a distinct set of environmental conditions under which they experience optimal growth, reproduction and survival. If these conditions change in response to a changing climate, fish could be impacted both directly and indirectly. Some potential impacts include shifts in species distributions, reduced or enhanced growth, increased competition from exotic species, greater susceptibility to disease and/or parasites, and altered ecosystem function. These changes could eliminate species from all or part of their present ranges^{(8, 9)} and would affect sustainable harvests of fish.

Evidence suggests that, in some regions, fisheries may already be experiencing the effects of climate change. For example, climate change has been identified as a potential contributor to declining salmon stocks on the Pacific coast.⁽¹⁰⁾ In the Arctic, reports of sockeye and pink salmon captured well outside their known range may be related to recent warming trends.⁽¹¹⁾ Furthermore, recent shifts in river flows consistent with climate change projections (see Water Resources chapter) have been linked to changes in fish populations in various regions of the country.

However, marine and freshwater ecosystems are complex, and are influenced by a range of climatic and non climatic parameters. For example, short-term climatic fluctuations, such as El Niño events, as well as stressors, including overfishing, pollution and land-use change, all affect fish physiology, distribution and production. This makes it difficult to isolate the potential impacts of climate change on fisheries.⁽¹²⁾ Further complicating the situation are the potential effects of changing environmental conditions on species interactions, such as predator-prey and parasite-host relationships, food web structure and competition for resources.⁽⁸⁾ How climate change will affect these relationships is poorly understood,⁽⁶⁾ and adds considerable uncertainty to impact assessments.

Any thorough assessment of the vulnerability of fisheries must account for adaptations that would occur either in response to, or in anticipation of, climate change. The fisheries sector has demonstrated its ability to adapt to change in the past, through adjustments in capture methods, marketing strategies and target species. There is, however, a limited understanding of both the adaptive capacity of the fisheries sector with respect to climate change, and the range and feasibility of potential adaptation options.⁽²⁾ Successful adaptation will be key in minimizing the negative impacts of climate change, while taking advantage of any new opportunities that may arise.