What is a Cutthroat Trout?

Cutthroat trout are salmonids, and are classified in the same genus as Pacific salmon. This group also includes chinook, chum, coho, sockeye and pink salmon as well as steelhead trout. (Some other trout varieties such as the bull, brook and lake trout are actually char.) Cutthroat trout are beautiful, sleek fish with greenish-blue backs, silvery sides, and abundant spots. They are named for the two signature orange-red slashes under the lower jaw. There are several subspecies of cutthroat trout; the one found in the waters of the Victoria area is called the coastal cutthroat (Onchorynchus clarki clarki).

Where do Cutthroat Trout live?

The habitat range of cutthroat trout spans from Northern California to southern Alaska. In freshwater, they live in clear, cool water in coastal streams, pools and tributaries of small rivers.

Trout need healthy freshwater streams characterized by: clear water; abundant oxygen, plenty of shade from streamside vegetation, hiding spaces (e.g. overhanging banks and fallen logs), clean gravel, sufficient nutrients and healthy insect populations. Stream flow is also crucial: insufficient flow can strand sea-run smolts and cause increased competition, while excessive flow can wash juvenile fish out to sea prematurely, and destroy important channel characteristics.

Healthy streamside vegetation (including reeds, sedges, willows, shrubs and trees) helps to absorb water and protect stream banks from erosion in times of high flow. Streamside vegetation also provides nutrients and habitat for the insects that cutthroat prey upon. Large woody debris such as fallen trees helps to create pools and sheltered areas where cutthroat like to live. In the ocean, cutthroat feed and shelter in estuaries, tidal lagoons and marshes. They generally stay close to shore in protected areas. Eelgrass and kelp beds are prime cutthroat trout habitat, as they host a wide variety of prey species, and provide shelter.

Cutthroat trout live in many of the creeks and marine areas around Victoria, such as: the small creeks that drain into Esquimalt Lagoon; Millstream Creek, which flows into Esquimalt Harbour; Colquitz and Craigflower Creeks, which flow into Portage Inlet. Maintaining water quality and habitat (such as wetlands and eelgrass beds) in the creeks and harbours is crucial to ensuring the survival of both the resident and sea-run cutthroat trout.

How do Cutthroat Trout live and reproduce?

There are two varieties of coastal cutthroat trout, resident and sea-run. Resident cutthroat spend their lives in freshwater streams, and are usually no more than 20 cm in length. Sea-run cutthroat are anadromous, meaning they spend part of their lives in the ocean and return to freshwater to spawn. They are larger, up to 50 cm and 2.5 kg. Sea-run cutthroat enter streams in late summer to late fall, and spawn between December and May. Some sea-run trout have become trapped upstream of creek obstructions such as dams, making them resident due to these changes.

Unlike salmon, sea-run cutthroat do not migrate far offshore; instead they remain near stream mouths and in estuaries. They also spawn repeatedly, whereas salmon die almost immediately after they spawn. Resident cutthroat migrate from lakes, pools and sloughs to smaller streams and isolated tributaries to spawn in late winter to early spring.

Once a suitable nesting spot has been found, the female scoops out a redd in the gravel with her tail, and deposits the eggs within it. The male then fertilizes the eggs with milt, and the female covers the eggs with gravel. Larvae with yolk sacs (called alevins) hatch after six to seven weeks, and emerge from the gravel as fry in another one to two weeks. At about two to three years of age, sea-run cutthroat migrate to the ocean as smolts, which are adapted for life in salt water. Most adults return within one year to spawn.

Diet varies slightly between the two varieties of cutthroat. Resident cutthroat eat insects, crustaceans, small fish and occasionally the eggs of other trout and salmon. Sea-run cutthroat eat fish, sandworms, shrimp and squid.

How have people used Cutthroat Trout?

Cutthroat trout was one of the many types of fish used for food by First Nations. Since cutthroat trout do not venture far out to sea, they have not been subject to major commercial fishing. However, cutthroat is popular among anglers, who fish for them in shallow marine areas, rivers and small streams of coastal B.C.

Why are Cutthroat Trout important?

Cutthroat trout are very sensitive to elevated levels of sediment and chemical pollution. Therefore, they are a good indicator species, meaning their presence is a sign that the ecosystem is in good shape. They are also an important link in the coastal food web, since they are both predator and prey. Animals that feed on cutthroat trout include:
  • great blue herons, kingfishers and mink feed on juveniles in freshwater
  • bears, river otters and ospreys feed on adults in freshwater
  • adult salmon, hake, dogfish and harbour seals feed on adults in the ocean
Like Pacific salmon, sea-run cutthroat trout link diverse ecosystems since they live both in the sea and in streams.

What threatens Cutthroat Trout?

Loss of spawning and rearing habitat is a major factor in the decline of some cutthroat trout stocks. This occurs when wetlands and estuaries are filled in for construction of buildings and roads, and when streams are placed in culverts and otherwise modified.

Removal of streamside vegetation is a common consequence of development and has a number of negative effects:
  • banks become more prone to erosion, which can cause excessive sediment to cover gravel spawning beds and clog fish gills
  • water temperatures fluctuate more due to a lack of shade
  • less decaying vegetation is available to nourish cutthroat trout prey
Another form of habitat loss results from shoreline or stream bank armouring, for example with seawalls or large rocks.

Excessive water flows result when large areas of the watershed are paved. Instead of slowly soaking into the ground and filtering through soil and roots, rainwater can then rush straight into the streams with in high volumes. This can contribute to erosion, and destroy stream features that previously provided shelter for young fish, such as calm pools and overhanging banks. This problem is compounded when stream channels are straightened and the banks are armoured (e.g. with cement or rocks); both of these modifications increase the destructive energy of water in the stream.

Degraded water quality in streams and harbours results from pollutants (e.g. oils and gasoline from roads and boats, household wastes disposed of in storm drains, lawn/garden fertilizers and pesticides, industrial chemicals). Some of these pollutants are directly toxic to trout, while others have indirect effects; for example, fertilizers cause excessive algae growth that robs the water of oxygen when algae dies off.

In addition:
  • Activities such as logging and excavation in the watershed (land that drains rainfall to a particular body of water) can introduce sediment into streams and estuaries. This can smother spawning gravel and clog the gills of cutthroat trout
  • Small or large dams can block fish passage for spawning, and reduce stream flows
  • Improperly managed sports fisheries can deplete stocks

How can I help protect Cutthroat Trout?

For information on protecting cutthroat trout, please visit our How Can I Help? section.

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