BIOLOGY OF AMUR SLEEPER (PERCCOTTUS-GLEHNI) IN THE DELTA OF THE SELENGA RIVER, BURYATIA, RUSSIA

We determined the fecundity, growth, diet, and density of the Amur sle eper (Perccottus glehni) in the Selenga River Delta on Lake Baikal dur ing 1986-1991 to better understand how this invading exotic will affec t Baikal's endemic fishes. we also compared the Amur sleeper's diet wi th that of other fishes living in the delta. The largest Amur sleepers were about 200 mm long and weighed 200 g; the oldest were age 7. All females were mature at age 2. Fecundity ranged from 884 eggs at age 1 to 37,056 eggs at age 7. Highest densities of Amur sleepers were found in oxbow lakes where densities sometimes exceeded 4,000 fish per ha. The bulk of the diet of amur sleeper age 2 and older was chironomids, fish, an fish eggs. Chironomids were also important in the diet of the commercially valuable. Siberian roach (Rutilus rutilus lacustris) and Siberian dace (Leuciscus leuciscus baicalensis). Thus the Amur sleepe r may cause population declines of these important endemic fishes thro ugh resource competition and predation on their juvenile life stages. However, Amur sleepers were the species of fish most frequently eaten by Eurasian perch (Perca fluviatilis) and northern pike (Esox lucius). So, maintaining vigorous populations of these two predators may well be an effective strategy for limiting the size of Amur sleeper populat ions.