NAME: Acipenser spp. - Sturgeons
Data provided courtesy of Aquaculture/Fisheries Center, University of Arkansas at Pine Bluff - (Dr. Peter Perschbacher)
Sturgeons are found throughout the northern hemisphere. Most of them are anadromous, while eight species live in fresh water. However, their marine migrations are of a shorter distance than are those of species such as the Atlantic salmon.
Owing to their great size (to nearly 3 m in length and over 120 kg in weight for the American lake sturgeon, Acipenser fulvescens), populations of sturgeon are never very great in number, compared to those of other fishes. Sturgeon grow very slowly; few of any species enter the breeding population before they are at least 6 years old. Sturgeon are unusual among very large fishes in preferring shallow water where they are very vulnerable to man. Exposure to human predation is particularly severe during spawning, which takes place in shallow riffles.
In the wild, sturgeon do not spawn each year, except for the sterlet, Acipenser ruthenis in the Danube, but they do spawn several times in their life. As with many species, males reach sexual maturity earlier and at a lower weight than females. Spawning takes place in rivers where water is 5-10 m deep and the current 1 m/s. The river bed must be small pebbles or large gravel. Spawning extends from the start of spring into summer according to species and geographical areas. A short time after fertilization the eggs develop an adhesive coating which allows them to stick to the gravel. Depending on the species, the diameter of the eggs is between 1.8 - 4 mm. Eggs are demersal, and after fertilization, cleavage is of the complete and irregular pattern.
Larvae are around 10 mm long at hatching and have large yolk reserves. The larval stage is short and is taken as ending when the rostrum and the lateral plates appear which is around 20 days for Acipenser transmontanus. For anadromous species, juveniles stay in freshwater from one to three years according to species before migrating to coastal sea waters where they remain until they are sexually mature. Freshwater sturgeon migrate to downstream areas of rivers or lakes where they grow. At the beginning of the larval phase young sturgeon can eat pelagic zooplankton, but the fry quickly develop a benthic mode of life. Diet preference varies with species but is based on a combination of worms, crustaceans, mollusks, and, rarely, fish.
In Russia and other European countries, sturgeon have been prized for centuries not only for their flesh but especially for their roe, which constitutes the true caviar, the gourmet food par excellence. However, Americans did not have a favorable opinion of the edibility of sturgeon until 1855, when the first American caviar began to be produced. In 1860, smoked lake sturgeon entered the market, and the flesh of sturgeon, which had once been unsalable, began to increase in price until today it bring the highest price of any freshwater fish in the United States and Canada.
Sturgeon farming began in the USSR and is mainly concerned with the production of alevins for restocking. Farming for food has developed only recently, firstly in the USSR and more recently in various countries such as the USA and France. Culture of the sturgeon starts with the capture of ripe females. Sturgeon can be brought to maturity in specially built ponds with a relatively strong current moving through them. Hormones also have been used for stimulating both male and female sturgeon. Because the fish are so large and therefore difficult to handle, they are killed for stripping. Several million eggs may be obtained from a female; hatching takes place in incubators. Incubation is short, usually 90-degree days or less. The yolk sac is absorbed in 5 to 10 days. The sturgeon can be released at this point, but survival is so low that culture is often extended for a short period (2 to 3 weeks), a slightly longer period (4 to 6 weeks), or an extended period (2 years or more).
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