. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MARINE HALFBEAK REPRODUCTION 61 Hemiramphus brasiliensis. JFMAMJJASOND Figure 2. Percent of age-1 Hi'iiiiruiii/>liii* hni.\ilicnxix (ballyhoo), with a whitish, opaque annulus on the margin of the sectioned otolith, by month. Otoliths were collected from July 1997 to June 1998 (n = 1019). and fresh postovulatory follicles could be observed (Figs. 4J. M; 5C). Vitellogenic oocytes not in the final stages of oocyte maturation were observed together with oocytes that had migrating nuclei and with hydrated oocytes (Fig. 4N), wh
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MARINE HALFBEAK REPRODUCTION 61 Hemiramphus brasiliensis. JFMAMJJASOND Figure 2. Percent of age-1 Hi'iiiiruiii/>liii* hni.\ilicnxix (ballyhoo), with a whitish, opaque annulus on the margin of the sectioned otolith, by month. Otoliths were collected from July 1997 to June 1998 (n = 1019). and fresh postovulatory follicles could be observed (Figs. 4J. M; 5C). Vitellogenic oocytes not in the final stages of oocyte maturation were observed together with oocytes that had migrating nuclei and with hydrated oocytes (Fig. 4N), which suggested a fairly rapid turnover of oocytes. The patterns of oocyte development for the two species did not appear to differ, except that the modal diameter of hydrated oocytes was only about mm for H. balao compared to about mm for H. brasiliensis (Fig. 5B, D). In addition, females of H. halao matured (size at 50% maturity = 160 mm FL) at a smaller size than females of H. brasiliensis ( size at 50% maturity == 198 mm FL; Fig. 6). Both species became mature as age-0 fish (, young-of-the- year). There were distinct seasonal trends in maturation, and the seasonal patterns of POP occurrence indicated prolonged, albeit slightly staggered, spawning periods for both species (Figs. 7, 8). During autumn, the incidence of immature and maturing individuals increased because age-0 fish were more frequently caught in the sampling gear; and the gonads of older fish were regressing as winter approached. Spawn- ing frequency peaked in April for H. brasiliensis and in June for H. balao. but spawning by some females was evident year-round based on the continued presence of POFs in older fish. Spawning frequencies were clearly age-specific, even for such short-lived species. All age classes of both species were spawning on a daily, or near-daily, basis, during spring or summer (Fig. 8). In other seasons, age-1 females spawned more frequently than age-0 females did, but age-
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