Vertical distribution of Pacific hake eggs in relation to stage of development and temperature

ABSTRACT The vertical distribution of eggs of Pacific hake (Muluccius pvoductus) was determined from 27 MOCNESS samples taken on cruises off southern and central California in March 1995 and February 1996. In 1995, and 250-300 m) were sampled. In 1996, nine 25-ni depth strata were sampled down to 225 m. In 1995 Pacific hake eggs were taken in all strata down to 250-300 ni; most of the eggs were found between 50 and 150 m, with the highest densities in the 50-75-and 75-100-ni strata. Average temperatures for developing Pacific hake eggs were estimated to be 10.2"-11.3"C. Early-stage eggs were generally deeper in the water column than later-stage eggs. Most early-stage eggs were found between 75 and 150 m, with highest densities in the 125-150-111 stratum. In contrast, mid-and late-stage eggs were most dense in the 50-75-and 75-100-m strata. Early-stage eggs were taken primarily in tows between 2200 and 0600 hrs, suggesting diel periodicity in spawning. O n the 1996 cruise hake eggs had a slightly shallower distribution compared with 1995, and there was more overlap in vertical distribution between stages. Methods are given for separating Pacific hake eggs from similar eggs of other species, and criteria are described for staging Pacific hake eggs