283 



Abstract.— The reproductive biology of 

 Brazilian menhaden, Brevoortia aurea, 

 inhabiting the estuarine waters of the 

 Rio de la Plata (Argentina-Uruguay). 

 was studied by using histological anal- 

 ysis of the ovaries. The samples were 

 collected during the peak of the spawn- 

 ing period of this species (November) 

 during 1994, 1995, and 1997. Brevoortia 

 aurea is a multiple spawner with inde- 

 terminate annual fecundity. Spawning 

 frequency, determined from the per- 

 centage of females with postovulatory 

 follicles, was about VZ'-i during Novem- 

 ber 1995. At this frequency, each female 

 on average spawned a new batch of 

 eggs about every 8 days. Batch fecun- 

 dity, estimated from counts of hydrated 

 oocytes, was fitted to a power function 

 of length and a linear function of ovary- 

 free female weight. Batch fecundity esti- 

 mates ranged from 20,000 (27 cm fork 

 length) to 130,000 (34 cm fork length) 

 hydrated oocvtes. Annual differences 

 in the size-fecundity relationship were 

 observed. Relative fecundity estimates 

 obtained from the different years sam- 

 pled ranged from 60 to 212 hydrated 

 oocytes/g of female (ovary-free weight). 



Spawning frequency and batch fecundity 

 of Brazilian menhaden, Brevoortia aurea, 

 in the Rio de la Plata estuary off 

 Argentina and Uruguay* 



Gustavo J. Macchi 



Conseio Nacional de InvesDgaciones Cientificas y Tecnicas (CONICED 



RIvadavIa 1917 



(1033) Buenos Aires, Argentina 



Present address: Institute Nacional de Investigacion y Desarrollo Pesquero (INIDEP) 



Paseo Victona Ocampo No 1 



Mar del Plata (7600), Argentina 

 E-mail address gmacchii&midepeduar 



Eduardo M. Acha 



Dto. Ciencias Mannas 



Universidad Nacional de Mar del Plata 



Funes 3350 



(7600) Mar del Plata, Argentina 



Manuscript accepted 20 October 1999. 

 Fish. Bull. 98:283-289 (2000). 



The Brazilian menhaden {Brevoor- 

 tia aurea I is a pelagic coastal species 

 of the southwest Atlantic ranging 

 from Salvador de Bahia, Brazil 

 (13°S), to the south of Buenos Aires 

 province, Argentina (40°S) (Cous- 

 seau and Diaz de Astarloa, 1993). It 

 is abundant in the estuarine waters 

 of the Rio de la Plata area, where it 

 is caught by the commercial fleets of 

 Argentina and Uruguay, although 

 it is a resource of little economic 

 value (Argentine landings in 1997 

 were 893 metric tons (t); Anony- 

 mous, 1998). Maximum body size is 

 about 41 cm total length ( 36 cm fork 

 length ), which corresponds to an age 

 of 11 years (Lopez Cazorla, 1985). 

 These attributes are similar to those 

 for Atlantic menhaden (Brevoortia 

 tyrannus) from the Atlantic coast 

 of the United States, which attains 

 a maximum body size of 36-37 cm 

 fork length and a maximum age 

 of about 10 years (Powell, 1994). 

 Estimation of size at sexual matu- 

 rity of Brazilian menhaden has not 

 been documented, but the mini- 

 mum length at maturity for female 



is 22.5 cm TL (Cassia et al., 1979). 

 Previous reports on life history 

 attributes include descriptions of 

 embryonic and lai-val development 

 (de Ciechomski, 1968; Weiss and 

 Krug, 1977), growth (Lopez Cazorla, 

 1985), taxonomy (Cousseau and 

 Diaz de Astarloa, 1993; Diaz de As- 

 tarloa and Cousseau, 1993), and 

 feeding (Sanchez, 1989; Giangiobbe 

 and Sanchez, 1993). Comprehensive 

 information on reproduction of Bra- 

 zilian menhaden does not exist. 

 Recently, we reported that major 

 spawning in the Rio de la Plata area 

 occurs from September to Decem- 

 ber, in estuarine waters across a 

 wide range of salinities (Acha and 

 Macchi, 2000). Cassia et al. (1979) 

 reported total fecundity estimates 

 based on the assumption that the 

 number of eggs spawned by a female 

 is fixed prior to the onset of spawn- 

 ing. Brazilian menhaden may be 

 a multiple spawner, in which case 



Contribution 1128 of the Institute Nacio- 

 nal de Investigacion y Desarrollo Pesquero, 

 Mar del Plata, Argentina. 



