Species of special interest

Fishes using freshwater habitat

Fishes occur in almost all aquatic habitats and represent the largest group of vertebrates in the world.1 Although freshwater is relatively scarce globally, covering only 1% of the Earth’s surface, about 43% of the 29,000 to 32,000 fish species live in freshwater for at least part of their lives.2, 3 With over 8,500 rivers and two million lakes, covering almost 9% of the total land area,4 Canada has a disproportionate amount of the global freshwater habitat, but only about 200 species of native freshwater and diadromous fish. (Diadromous fishes use both marine and freshwater.2)

Fishes are among the world’s most important natural resources, providing numerous goods and services, including an annual global harvest of 92 million tonnes; 10.1 million tonnes from inland waters, most of which is freshwater.5 The commercial freshwater harvest in Canada is over 32,000 tonnes and valued at almost $68 million.6

This section is further divided into the following four topics:

Globe

Global Trends

An estimated 37% of the world’s freshwater fishes are threatened with extinction.17

Native freshwater and diadromous fishes at risk

Number of Extirpated, Endangered, Threatened, or Special Concern species
Graph: freshwater and diadromous fishes at risk. Click for graphic description (new window).
Note: Diadromous fish use both marine and freshwater. Trends reflect a combination of changes in the condition of species as well as the addition of new information.
Source: data compiled by Hutchings, 20108 from Hutchings and Festa- Bianchet, 20097 and COSEWIC, 20109

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has assessed 18% (35 species) of freshwater and diadromous fishes as Endangered or Threatened throughout all or parts of their ranges. Fifty-eight species (29%) have been assessed as at risk, which includes species assessed as Extirpated and of Special Concern, as well as those that are Endangered or Threatened.7-9 The number of fishes at risk has been growing since the 1980s. The leading causes of declines in Canadian freshwater fishes are habitat loss and habitat fragmentation – caused by dams, weirs, roads and degradation of the riparian zone – and non-native aquatic species.3, 10-12 Overfishing, pollution, climate change, and interactions between wild and farmed species are also linked to declining populations of freshwater fishes.2

Sturgeon, species at risk

Photo: juvenile sturgeon © Traci JensenAll 24 species of sturgeon in the world are at risk, although definitions of “at risk” vary. Two of the five species in Canada are classified as Endangered or Threatened.13 White sturgeon, the largest freshwater fish in Canada, is restricted to the west coast of North America.14 Its size (up to 6 metres), longevity (over 100 years), and late maturity (14 to 30 years), make it especially vulnerable to overexploitation and habitat degradation.15 Of the six B.C. white sturgeon populations, three are declining (Columbia, Kootenay, Nechako), one is now more stable, with some fluctuations (lower Fraser), and two are stable (mid and upper Fraser). Poor juvenile survival, linked to river diversions, changes in sediment quantity and quality, and water flow regulation, associated with dams, are the primary reasons for endangerment of the three declining populations.15, 16

White sturgeon, Nechako River populations
Juvenile production, 1945 to 1990
Graph: juvenile white sturgeon production, Nechako River populations. Click for graphic description (new window).
Source: McAdam et al., 200516

Lake sturgeon once sustained large commercial fisheries. Reductions of 50 to 98% have been observed in western Canadian rivers and lake sturgeon have disappeared from the Red-Assiniboine River and Lake Winnipeg. Great Lakes populations have been reduced to a fraction of their original size, and populations in the Ottawa and St. Lawrence rivers are showing recent declines. Before the turn of the century, overfishing was the main threat to lake sturgeon. In recent years, declines are attributed to habitat fragmentation and degradation in the Great Lakes, as well as overfishing, dams, contaminants, and invasive species elsewhere.13

American eel

American eel in Ontario
Average number (thousands) of eels per day at R.H. Saunders Hydroelectric Dam, 1974 to 2005
Graph: American eel in Ontario. Click for graphic description (new window).
Note: no data are available for 1996.
Source: Ontario Ministry of Natural Resources, 201034

The American eel is an example of a once abundant species that is now listed as Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). Since the 1970s, populations have declined by 99% in the upper St. Lawrence34 and less extreme declines have been observed in both the lower St. Lawrence and Gulf of St. Lawrence.35, 36 The long life span of American eels, combined with their vast migration distances of up to 4,500 km, make them vulnerable to a wide range of stressors, such as mortality in hydroelectric turbines, physical barriers such as dams, overharvesting, and habitat alteration. Climate change, resulting in changes to ocean currents that carry eel larvae from the spawning grounds, may also contribute to population declines. American eels once provided both subsistence and commercial fisheries in Canada.36

Prey fishes in the Great Lakes

Trends in prey fish biomass based on annual bottom trawl surveys
Map and graphs: population trends of prey fishes in the Great Lakes. Click for graphic description (new window).
Source: adapted from Environment Canada and U.S. Environmental Protection Agency, 200937

The term prey fish refers to fish species that are the main food items of popular commercial and sport fish. A fish is considered a prey fish if it remains small in size, usually feeds on zooplankton or bottom-dwelling species, and is abundant enough to feed a predator fish population.38 Prey fish make up the majority of fish biomass and are the foundation of the Great Lakes fishery (see commercial fishing), as they are eaten by predatory fish such as trout, walleye, and bass. Prey fish include native species such as slimy sculpin, trout-perch, cisco, and bloater, and also non-native species such as alewife, rainbow smelt, and round goby. Declines in prey fish populations have been occurring since the 1980s and 1990s. The most likely causes are: stocking of Pacific salmon, which was done to reduce non-native prey fish; reductions in nutrients; and non-native zebra and quagga mussels, which filter nutrients from the water column and reduce food for the invertebrates that prey fish eat.37

Sockeye salmon © iStock.com/RKoopmans
Sockeye salmon

Salmon

Canadian lakes and rivers provide spawning habitat for five species of wild salmon on the West Coast18 and one on the East Coast. Wild salmon are a staple and a cultural foundation species for Aboriginal Peoples.19, 20 They are the basis of commercial, recreational, and Aboriginal food, social, and ceremonial fisheries on both coasts.20, 21 Wild salmon are revered by Canadians, in part because of the mystique of their life cycle – after growing in the ocean they migrate long distances to spawn in freshwater.

Fraser River sockeye returns

Number of returning salmon (millions), 1952 to 2009
Four graphs: Fraser River sockeye returns for four cohorts. Click for graphic description (new window).
Note: it takes four years for most sockeye to return to spawn after hatching.
Source: adapted from Lapointe, 201022
Fraser River sockeye survival
Productivity index (returns/spawner)
4-year running average, 1952 to 2008
Graph: Fraser River sockeye survival. Click for graphic description (new window).
Source: Fisheries and Oceans Canada (DFO), 201023

 

The Fraser River is legendary for its sockeye salmon runs. Since the 1990s, the number of returning sockeye has fluctuated widely, depending on the cohort (see graphs for the four cohorts above), while the survival rate – the proportion of fish that grow to adults and return to spawn – has been declining. In 2009, only 1.5 million adult sockeye returned – the lowest number since 1947. A scientific panel investigating the evidence for declining adult returns concluded that the major cause has been unfavourable physical and biological conditions in the Strait of Georgia, combined with freshwater and marine pathogens.23, 24 In 2010, mid-summer estimates predicted the largest Fraser River sockeye run since 1913.25

In some years, warming water and reduced flows due to climate change have impacted salmon migration, spawning, and rearing success. Sockeye survival and spawning are impaired as river temperatures increase above stock-specific thresholds.26, 27 Since the 1950s, mean summer temperatures in the Fraser River have increased by approximately 1.5°C.26, 28 This trend is likely to continue, increasing the probability of sockeye being exposed to water temperatures that will impair their survival.29

Atlantic salmon population trends

Hundreds of fish, 1970 to 2005
Map and graphs: Atlantic salmon population trends. Click for graphic description (new window).
Source: adapted from Gibson et al., 200630

Returns of Atlantic salmon to many rivers in North America have declined since the 1980s or 1990s, with northern populations increasing and southern populations remaining at low levels.30 For example, in inner Bay of Fundy rivers, runs of 30 to 40 thousand fish in the mid-1980s have been reduced to a few hundred fish, and in southern Nova Scotia, most salmon exist only as remnant populations or have been extirpated.31, 32 Although the factors contributing to low marine survival are largely unknown, freshwater declines are a result of the effects of dams, loss of spawning habitat, invasive species, increases in stream temperatures, siltation, contaminants,33 poaching20 and, in southern Nova Scotia, acid deposition.20, 32

Photo: recreational fishers, interior British Columbia lake © iStock.com/MarvinBeatty
Interior British Columbia lake

Commercial freshwater fishing

Commercial fish production in Lake Winnipeg
Tonnes (thousands), 1883 to 2006
Graph: commercial fish production in Lake Winnipeg. Click for graphic description (new window).
Source: adapted from Manitoba Water Stewardship Fisheries Branch as cited in Shipley and Kling, 201039

Lakes and rivers in Canada support significant commercial fisheries. Lake Winnipeg supports the largest commercial fishery in Manitoba, valued at approximately $20 million per year. Commercial fish production has been highly variable in Lake Winnipeg over the past 125 years, both in the amount of fish and the species harvested. For example, a dramatic decline in fish production from 1940 to the1960s was followed by an increase since the 1970s. Walleye production is now at historical highs and is the most important fishery species. Sauger, on the other hand, have been declining since the 1970s. Walleye are benefitting from the invasion of rainbow smelt and nutrient enrichment. These same factors are believed to be driving the decline in sauger.39, 40

The Great Lakes commercial fishery has an annual dockside value, in Ontario, that fluctuated between $29 and $37.5 million between 2004 and 2008,41 contributing $850 million per year in direct and indirect benefits to the Ontario economy. The overall commercial harvest has been declining since the 1980s. The main species harvested today are walleye and yellow perch, both native species, and rainbow smelt, a non-native species.42 Overfishing and predation by the non-native sea lamprey led to the collapse of lake trout in the late 1950s. Restoration, including stocking, has maintained a fishery, and lake trout are now reproducing in Lake Superior and Lake Huron.37, 43

Recreational freshwater fishing

Number of fish (millions), 1995 to 2005
Graph: recreational freshwater fishing. Click for graphic description (new window). Photo: Recreational fisher © Rob Stenner.
Source: adapted from Orok and Johnson, 200544

Approximately 3.2 million people participated in freshwater recreational fishing, or angling, in 2005, down from 4.2 million in 1995. The reduction in number of anglers has resulted in a reduction in the number of fish caught and the number of fish retained. It has also had an economic impact. Direct expenditures on angling were about $2.5 billion in 1995, 2000, and 2005. Although the dollar value of expenditures has not changed, this represents a 19% decrease in expenditures over 10 years, when adjusted for inflation. Anglers concentrate on some of the same species as the commercial fishery, namely walleye and yellow perch, although other species, such as brook trout, rainbow trout, bass, and northern pike, are also important. In 2000, the Year of the Volunteer, Canadian anglers dedicated over a million days to habitat clean-up and other activities related to improving recreational fishing.44, 45