Fecundity and Length at First Spawning of the Hawaiian Anchovy, or Nehu (Stolephorus purpureus Fowler) in Kaneohe Bay, Oahu

Abstract

Fecundity, length at first spawning, and spawning seasonality of Stolephorus purpureus were determined by examining preserved ovarian eggs and fish captured throughout a 4-year period. Fecundity was estimated from the number of eggs in the most advanced ovarian mode after it was determined that all these eggs hydrated and were spawned. Fecundity (Y) was related to fish weight (X) by the hyperbolic function, Y = X/(0.0049-0.0033X). According to this relationship, a fish having a weight equal to the mean for the population contains 566 eggs/g of fish weight. Large variations in fecundity from year to year were attributed primarily to environmental factors whose influence on reproduction by Stolephorus purpureus has not been studied. Length frequencies of ovarian eggs were bimodal, but the smaller modes remained stationary regardless of the position of the larger modes. This was interpreted as evidence that individual fish spawned only once per year. From data on egg length versus fish length it was estimated that fish were first capable of spawning when 35 mm (standard length); the smallest fish observed to contain hydrated eggs was 37.8 mm. Captured fish containing hydrated eggs were rare, 1.1 percent of 1,735 adult females examined. Spawning occurred year around but the incidence was higher during the spring and summer than during the remainder of the year.