THE MIGHTY WHITE!
The white sturgeon is a unique freshwater fish species that plays a significant role in British Columbia's cultural and social heritage, as well as our economy. The white sturgeon (Acipenser transmontanus) belongs to the sturgeon family Acipenseridae. Not only is it the largest sturgeon species in North America, it is also the largest freshwater fish species in North America. The only other sturgeon species found in British Columbia waters is the green sturgeon (Acipenser medirostris Ayres). However, very little is known about this species except that it tends to be found under more marine and coastal conditions.
White Sturgeon are found in 3 major drainages on the west coast of North America including the Sacramento (in California), Columbia (in British Columbia, Idaho and Washington) and Fraser systems. In British Columbia, spawning populations of white sturgeon occur in three rivers: the Fraser/Nechako, Columbia and Kootenay. White sturgeon have also been observed in the mouth of the Cowichan and Somass rivers on Vancouver Island. However, it is likely that these fish represent stray fish from the mainland systems, possibly the Columbia River in Washington, rather than separate spawning populations.
It is difficult to mistake white sturgeon for other species (except close sturgeon relatives). These large fish have been known to grow up to 6 metres long (the length of a small school bus) and over 600 kg. The overall body form is long and cylindrical, usually ranging in colour from greenish grey on the dorsal (back) side to light grey or white on the ventral (belly) side.
The body is covered with large armour-like scutes (bony plates) rather than scales like other fishes.
The nose or rostrum of white sturgeon is flattened. On the underside of the rostrum just in front of the mouth are four barbels or fleshy whisker-like projections that are used as sensory organs to detect food since the water is often murky at the bottom of the river.
Most of the skeleton is made up largely of cartilage rather than bone, and the overall appearance is quite prehistoric, which makes sense since sturgeon have remained virtually unchanged since they first appeared in the fossil record 175 million years ago.
Some variation in colour and morphology (body shape) has been observed in white sturgeon in B.C. For example, snout length differs markedly in the Fraser - short nosed and long-nosed fish are both common.
The body shape and mouth structure of white sturgeon is ideally suited to bottom feeding. Although sturgeon have poor eyesight, they use their highly sensitive barbels to locate prey. Rather than using teeth, sturgeon have a extendible mouth which they can use like a vacuum cleaner to suck up prey.
Small sturgeon feed on chironomids, as well insect larvae, molluscs and other small invertebrates. Larger sturgeon switch to a fish-based diet although chironomids can still make up a significant part of the diet. White sturgeon in the Fraser are known to follow sockeye runs and also feed on eulachon, sculpins and stickleback.
Many of the threats to white sturgeon are specific to the river system in which they live. In general, these threats include over-fishing, hydro-electric dams and associated flow regulation, water diversions and dyking for flood control and irrigation, introduced species including predators and competitors, reduced water quality associated with various land-use practices (e.g. forestry) and loss of habitat from dredging, gravel mining and other industries.
One trait that makes the white sturgeon so unusual is its incredibly long lifespan. Some individuals are over 100 years old - these individuals were around even before British Columbia became part of Canada. Given their long life, they tend to grow slowly and are not ready to spawn until the females are over 18 years of age and males are at least 14 years of age. Unlike many salmon species that spawn once and die, white sturgeon are capable of spawning many times throughout their life.
White sturgeon depend on a number of environmental cues in the spring to spawn - these include water temperature, day length, strength of water current and riverbed material. Adult sturgeon do not build nests but rather the male and female release sperm and eggs together in the water current - called broadcast spawning. A female may release between 100,000 to 3 million eggs but only a small number may actually get fertilized. Once they are fertilized, the eggs become sticky and attach to the river bottom as soon as they come into contact with it. The young embryos mature into larvae in 8-15 days and then spend another 20-30 days nestled in the river bed until they metamorphose into free- swimming young sturgeon.
Tracking studies indicate that sturgeon generally don't move more than a few km during the summer feeding season. However,before spawning or when traveling to over-wintering locations, sturgeon can migrate over 100 km. Adult fish tend to occur in deeper, faster waters of large river mainstems, where they spend most of their time on or near the bottom of the riverbed. Juveniles prefer slow moving sloughs and backwaters. Spawning habitat is usually in turbulent fast water, but locations can range from shallow murky side channels with pebbly and sandy bottoms to deeper, less murky main channels with larger boulders and cobble.
Releasing White Sturgeon The Gentle Way
The majority of white sturgeon populations in British Columbia are listed under the federal Species at Risk Act and are not open to angling. Since populations in the Lower and Middle Fraser River are relatively healthy, they are able to support exciting world class fi sheries. However, these populations are still vulnerable to impacts from angling, habitat destruction, pollution and salmon net fi sheries, and they are still provincially and nationally designated as endangered. In addition to being endangered, white sturgeon mature after 17 to 20 years and can live for more than 100 years, so impacts or injuries can be long lasting. As such, all sturgeon angling in the province is catch and release only, and will be more strictly managed in the future..... read more