Some Aspects of the Biology of the Micronektonic Fish Cyclothone pallida and C. acclinidens

Abstract

Some aspects of the biology of the micronektonic fishes Cyclothone pallida and C. acclinidens are described on the basis of samples taken during a series of 20 cruises from December 1982 to November 1985 at a fixed station near the center of Sagami Bay, Central Japan. C. pallida is a regular component of the Cyclothone population in Sagami Bay, being found in more than 90% of the samples. On the other hand, C. acclinidens was encountered sporadically, being found in less than 25% of the samples. The depth range of C. pallida is estimated to be about 400-1, 000m. It spawns mainly during the spring and summer in Sagami Bay. C. pallida releases about 1, 000-3, 000 eggs and may spawn several times during its life span. On the average, it reaches 18.5mm standard length (SL) in one year, 24mm SL in two years and 29.5mm SL in three years during its subadult stage. Extrapolation of the growth curve suggests that males and females attain first sexual maturity in three to four years at 30-35mm and five to six years at 40-45 mm SL, respectively. Cyclothone pallida is concluded to have a regular life cycle in Sagami Bay. It remains uncertain whether or not C. acclinidens reproduces in this area.