Acipenser transmontanus Richardson, 1836:white sturgeon

Biological Description

Body elongate, somewhat cylindrical with 5 rows of pointed bony plates; no lateral line. Head large, broad and depressed, without a fontanel; eye small; snout flattened, slightly concave; mouth ventral, protrusible and without teeth; 4 barbels in a transverse row on ventral surface of snout. Dorsal fin single and placed far back on body; caudal fin heterocercal; anal fin short and narrow; pelvic fins near anus; pectoral fins large and rounded. Color grayish, slightly lighter below.

Life History

The white sturgeon is the largest fish found in the fresh waters of North America. Specimens have been reported to reach a length of 20 feet and a weight of 1,800 pounds. In the Columbia River, white sturgeon reach the minimum legal length of 36 inches when they are 8 to 9 years old. This species is long lived. One fish from the Columbia River was determined to be 82 years old. One large female sturgeon from the Columbia River, 12.5 feet long, weighed 1,285 pounds and contained 125 pounds of eggs.

Males may mature at 9 years of age and females at 13 to 16 years. Spawning occurs in the Columbia River from May through July when water temperatures are between 48 and 63 F. A 95.5-pound female contained 1.7 million eggs, but larger fish may produce up to 3 million. In California, sturgeon larvae have been captured in he San Joaquin Delta between the middle of April and late May when water temperatures ranged from 57° to 72° F. Larvae shorter than 0.7 inch still had yolk sacs; when the larvae were about 0.9 inch long they had barbels and an appearance similar to that of the larger fish.

Geographic Distribution

White sturgeon are found in streams and rivers from northern California to Alaska.

Habits and Habitats

In the Columbia and Snake rivers, white sturgeon are found in the deeper holes. Although sturgeon are bottom dwellers, they have been reported to leap occasionally from the water. These fish are frequently found in localized holes in the river that are well known to sturgeon fishermen. In the water below the spillway at Bonneville Dam, little activity of the sturgeon is observed when the spillway has been closed for a time. When the gates are opened and closd, however, sturgeon have been ohserved to leap out of the water. Most activity near the surface apparently occurs in spring. During fall and winter the commercial and sport catch of sturgeon is low, but even then occasional spurts of activity occur. Fishermen say that these fish are most active and bite better after the river has begun to rise and becomes turbid. Sturgeon tagged in San Pablo Bay in California and the Columbia River in Oregon have usually been recaptured in the same area. However, some fish tagged in San Pablo Bay have been recaptured as far as 60 miles upstream, and one traveled some 660 miles to the mouth of the Columbia. Nearly 4,000 were tagged in the Columbia in 1947-50. Most were captured close to the tagging location, and two fish were taken four times each by sportsmen within a few months. A number of white sturgeon were captured at the mouth of the Columbia, some 100 miles downstream from the tagging locality. One migrated at least 200 miles to the Naselle River, Willapa Bay, Washington. This was the only reported recapture of a tagged fish outside the Columbia River system. Sturgeon in the Columbia appear to migrate upstream during fall and downstream in late winter and spring.

White sturgeon that were tracked with radio transmitters in the Columbia River were inactive in mid-winter but exhibited movements in summer and early fall. These fish occupied shallower waters in summer when water temperatures were warm (63° -64° F) and deeper pool areas in winter.

Diet

The stomachs of small white sturgeon in California have been found to contain primarily mysid shrimp and amphipods. Larger sturgeon feed on a variety of organisms such as crustaceans (shrimp, crab, isopods, amphipods), annelid worms, molluks (clams, mussels, snails), and fish (salmon, striped bass, starry flounder, gobies, herring). In the Columbia River this species has been reported to feed on clams, crayfish, smelt, large suckers, squawfish, sockeye salmon, and adult Pacific lampreys; one stomach even contained a house cat.

Idaho Conservation StatusEndangered. Idaho Native or Import

Native. It is found in the Snake River upstream to Shoshone Falls, the lower Salmon River, and the Kootenai River.

Comments

Its numbers in the Snake River have been severely reduced due to destruction of habitat from construction of dams for power and irrigation.

CreditsSimpson and Wallace 1982.Wydoski and Whitney 1979. Image Copyright Joseph Tomelleri. Used by permission.


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Ancipenser Transmontanus:
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