Fecundity and Length at First Spawning of the Hawaiian Anchovy , or Nehu (

Fecundity, length at first spawning, and spawning seasonality of Stolephorus purpureus were dete~minedby examining preserved ovarian eggs and fish captured throughout a 4-year period. Fecundity was estimated from the numbel 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 = Xj(0.0049-0.0033X). According to this relationship, a fish having a weight equal to the mean for the population contains 566 eggsjg 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. SUCCESS of the fishery for skipjack tuna (Katsuwonus pelamis) in Hawaii, which is the state's most important fish on the basis of tonnage landed and dollar value, depends largely on the use of a live bait fish (anchovy) I Hawaii Institute of Marine Biology contribution no. 457. This study was supported by funds from the National Oceanic and Atmospheric Administration, contract N208-1189-71(N), and from Sea Grant. Manuscript received 5 June 1974. 2 University of Hawaii, Hawaii Institute of Marine Biology, P.O. Box 1346, Kaneohe, Hawaii 96744. Present address: United States Agency for International Development/Philippines, APO San Francisco, California 96528. 3 University ofHawaii : Department ofOceanography and Hawaii Institute of Marine Biology, Honolulu, Hawaii 96822. Present address: Division of Fisheries and Oceanography, CSIRO, P.O. Box 21, Gronulla, New South Wales, Australia. 4 University of Hawaii: Department of Oceanography and Hawaii Institute of Marine Biology, Honolulu, Hawaii 96822. Present address: North Carolina State University, Department of Zoology, P.O. Box 5577, Raleigh, North Carolina 27607. known locally as nehu (Stolephorus purpureus Fowler). Under present fishing practices, the availability of nehu is an important factor limiting expansion of the skipjack fishery in Hawaii and the central Pacific area. Various aspects of the biology of nehu have been studied (Nakamura 1970); however, there are no published reports on their fecundity. This information is essential for estimating the inherent reproductive potential of the fish and, therefore, is an important consideration in managing the bait resource effectively. The objective of this study was to further knowledge of the reproductive biology of nehu by determining their fecundity and the length of females at first spawning. We also examined spawning seasonality to compare our findings with earlier reports. Data were obtained by examining preserved specimens and their ovarian eggs. We would like to thank Michael Palmgren for his assistanc~ in collecting and processing data for this study.