Macchi and Acha: Spawning frequency and batch fecundity of Brevoortia aurea 



287 



after the loss of the ahgnment of the granulosa layer 

 was used as the main characteristic to distinguish 

 day-0 from day-1 postspawning ovaries, according to 

 Fitzhugh and Hettler (1995). They concluded that 

 this is the most important feature for classification 

 of POFs in Atlantic menhaden spawning at about 

 20°C. Spawning frequency estimated from the average 

 between day-0 and day-1 POF percentages (11.98%, 

 SD=7.53%) indicated that B. aurea spawn once every 

 eight days during the peak of the reproductive season 

 (November). This value should be considered a pre- 

 liminary estimate because we did not have samples 

 during other months in the spawning period. Daily 

 spawning fraction of Brazilian menhaden was similar 

 to that of other clupeoids inhabiting temperate waters, 

 such as Engraulis mordax (Hunter and Goldberg, 

 1980), E. ringens (Alheith et al., 1984), Sardinops 

 sagax (Herrera and Claramunt, 1990), Sardirw pil- 

 chardus (Perez et al., 1992), E. capensis (Melo, 1994), 

 and E. anchoita (Pajaro et al., 1997). 



Cassia et al. (1979) reported Brazilian menhaden 

 fecundity by counts of yolked oocytes (diameter 

 >540 \im) from ovaries in an advanced maturity 

 stage. They estimated a potential fecundity of 120,000 

 oocytes for one 30-cm-FL female but did not con- 

 sider a multiple spawning pattern. Our estimated 

 batch fecundity for females of this length was about 

 60,000 hydrated ooc3^es. During the main reproduc- 

 tive period (September-December), a female Brazil- 

 ian menhaden with a spawning frequency of 8 days 

 would spawn 15 times. Although total fecundity has 

 been calculated for Atlantic menhaden (Higham and 

 Nicholson, 1964; Dietrich, 1979; Lewis et al., 1987) 

 and gulf menhaden (Lewis and Roithmayr, 1980), 



batch fecundity estimates have not been reported, 

 and gravid females in wild population have rarely 

 been observed (Ahrenholz, 1991). 



Batch fecundity was fitted to a power function of 

 fork length and a linear function of ovary-free body 

 weight. Analysis of covariance showed significant 

 differences (P<0.05) in regression coefficients among 

 the three years considered (1994, 1995, and 1997). 

 The low coefficients of determination in regressions 

 were similar to those obtained for Atlantic menha- 

 den (Lewis et al., 1987), possibly as a consequence of 

 different ages occurring within length classes after 

 sexual maturity ( Lopez Cazorla, 1985 ). Mean relative 

 fecundities forS. aurea (107 [in 1994], 135 [in 1995], 

 and 149 [in 1997] oocytes/g ovary-free body weight) 

 were much lower than those for Engraulis anchoita 

 (about 600 oocytes/g ovary-free body weight), the 

 most abundant clupeoid of the Argentine Sea (Pajaro 

 et al., 1997). The difference may reflect the larger 

 egg size of B. aurea (1500-1600 pm), compared 

 with E. anchoita (about 900 ]jm; de Ciechomski and 

 Weiss, 1973). The reproductive strategy of some spe- 

 cies indicates that egg size takes priority over fecun- 

 dity (Kjesbu et al., 1996). The larger eggs may be 

 advantageous during the first days of life because 

 hatchlings have larger yolk reserves, contributing 

 to higher growth rates, and may avoid predation 

 more effectively (Hinckley 1990; Wootton, 1994). 

 Our paper provides the first estimation of spawning 

 frequency and batch fecundity of Brazilian menha- 

 den during the spawning peak. These parameters 

 should also be estimated at the end of the reproduc- 

 tive season to evaluate possible variations and their 

 effect over the annual egg production. Future stud- 



