THE BIOLOGICAL ASPECTS OF POND SMELT (HYPOMESUS OLIDUS (PALLAS)) IN THE SHUI FENG RESERVOIR

1. The pond smelt in the Shui Feng Reservoir has more scales along the lateral line, more gill rakers and more vertebrae than those in other parts of the world (North America, Soviet Russia, Japan, and Korea), but less branched rays in the dorsal, anal and pectoral fins than those in Korea.2. The scale has been used for age-determination; annulus on the scale is characterized by a "check". The fish is about 74 mm in fork length (body length measured from tip of snout to the fork of caudal) and 3g in body weight when one year old; 99 mm and 6.5 g at 2 years of age. The regression equation of body weight (W) and fork length (L) may be expressed as log W=2.5306 log L—1.7590.3. The pond smelt is an omnivorous fish which feeds mainly on zooplanktion (Cladocerans and Copepods, etc.); the components of its food vary with habitats.4. First maturity of this fish is reached at 1 year old. The overall sex ratio in 1000 specimens examined was 446 females to 554 males, or 1♀: 1.2♂, but specific ration varied markedly with habitats. The individual absolute fecundity varied from 905 to 19051, with 4330 eggs on average. Its relation to the fork length may be expressed as Y=58.4860 L—402.7606 (Y—absolute fecundity in unit of 100 eggs, L—fork length in cm). The population fecundity index is 1871; the generative rate of population is 1494 females per "primary female". Spawning takes place in littoral areas of the reservoir in April or May. The eggs are adhesive, and hatch in about 12 days when water temperature ranges from 10° to 15℃.5. The structure of population of pond smelt is simple: there are three year classes in all population, the average age of 1321 specimens being 1.15 years. Body-length (fork length) groups ranging from 65.1 to 80 mm were dominant in that batch of sample (65.6%).