White Sturgeon

Appearance

The white sturgeon has a slender, long body, head and mouth. This fish has no scales; instead it has large bony scutes that serve as a form of armor. There are 11–14 dorsal scutes, all anterior to the dorsal fin, and 38–48 lateral scutes and 9–12 ventral scutes on each side. The dorsal color of a white sturgeon is gray, pale olive, or gray-brown. The fins are a dusky, opaque gray. The underside is a clean white. It has four barbels, used for sensing food, near its large toothless mouth.

Sturgeons are classified as a bony fish, but actually are more cartilaginous than bony, their internal bone structure being more like a shark’s. Sturgeon have changed very little since they first appeared, over 175 million years ago and thus have the appearance of a very ancient fish.
The fish are indeed white.

Habitat

The white sturgeon lives on the bottom of slow-moving rivers, bays, and estuarine areas, including the brackish water at the mouths of large rivers. Other sturgeon will spend most of its time in a marine environment, only coming into rivers to spawn. They are well-adapted to finding food drifting by with their excellent sense of smell and taste. When there is an insufficient food supply, sturgeon have been known to move into shallow water to eat freshwater clams.

During the spawning season, the white sturgeon moves to clean, fast-moving areas of rivers, such as just below rapids, with gravel or larger rocks along the bottom.


White sturgeon spawn many times in their lives. As they age, the females spawn less often, but produce more eggs in each spawning. In the late spring or early summer, they congregate in areas of rivers with a heavy current, gravel bottom, and a water temperature of 58 °F to 66 °F . The fish broadcast spawn in these areas, with males releasing sperm as the outnumbered females release anywhere from 100,000 to a million eggs. The fertilized eggs then sink and adhere to the gravel at the bottom. The eggs are brown in color and will hatch in about a week, depending on water temperature. Female white sturgeon do not spawn every year.

Upon hatching, the larvae are around 0.5 in. long, with a tadpole-like appearance. They drift downstream with the current until they reach a suitable habitat. When the rearing habitat is reached, the larvae typically take around 25 days for the yolk sac to be absorbed. About a month after hatching, the sturgeon will have a full set of fins, rays, and scutes. As small juveniles, they feed on insects, small fish, and small crustaceans. Maturity is reached between 5 and 11 years, depending on the gender of the fish and the temperature of the water.

White Sturgeon can live to be over 100 years old. The rate of growth is dependent on water temperature. Typically, they reach six feet long around 25 years of age, showing that these fish do not grow as quickly as many other fish. White sturgeon are anadromous meaning they spawn in fresh water and migrate to salt water to mature. Sturgeon may migrate in and out of salt water many times in their lives. However, since the building of many dams along the Columbia and Snake rivers, the populations above the dams have become landlocked.

Unexpected social behavior has been observed in white sturgeon of the lower Columbia River. Up to 60,000 sturgeon massed in a dense "sturgeon ball" at the base of the Bonneville Dam in early 2008. Scientists do not know what the reason for the behavior was, but predator avoidance is one theory.

Food

A sturgeon's taste buds are located on the outside of its mouth. This, along with the barbels, allows it to see if a possible food source is edible before sucking it up into its mouth. As adults, the white sturgeon’s diet somewhat varies. This is dependent upon the river systems it lives in. In the Columbia River system, dead fish, crustaceans, and mollusks are all popular prey. Lampreys, primitive eel-like fish, come into rivers to spawn at the same time as the white sturgeon, and are a popular food source at that time. Smelt is another food that is abundant around spawning time. Shad come into the Columbia River system in throngs of several million each spring. The extremely large shad runs are often cited as an example of why the lower Columbia River has such a large population of Sturgeon. Like the smelt, these fish often die, and the remains are an easy meal for sturgeon.

Defense

The threat of toxin bioaccumulation is especially high in Sturgeon meat. Because of its eating habits, sturgeon accumulate toxins in its flesh as it feeds. They feed on any sort of organic material found while scavenging; this includes raw sewage, dead fish, paper mill wastes, and plants sprayed by pesticides. Dioxins and dioxin-like compounds are unintentional byproducts of paper bleaching and pesticides. It is also one of the most commonly found toxins in fish populations. PCB is also found in fish. It is used as a plasticizor in paint, rubber, and plastic products. Before the government ceased its production in 1977, more than 1,500,000,000 pounds were produced. Mercury is one of the more commonly known toxins found in fish’s flesh. Some have speculated that it is also the most dangerous. Sturgeon and other fish in the Columbia and Willamette rivers have registered 5 to 0.50 parts per million. Although most accumulation in Sturgeon happens in the liver, pancreas, and other organs; the toxins still accumulate in the edible flesh. The Oregon Department of fish and Wildlife has issued warnings on all fish caught in the Willamette River. “Women of childbearing age, children under six, and people with liver and kidney damage should avoid eating fish from these waters. Healthy adults should eat no more than one eight ounce meal per month.” Also for areas with high concentrations of PCBs, dioxins, and pesticides: “All persons should reduce or avoid eating fatty parts of fish. Exposure can be reduced by removing the skin and all fat, eggs, and internal organs.”