375 
Preliminary estimate of spawning 
frequency and batch fecundity 
of striped weakfish, 
Cynoscion striatus, 
in coastal waters off 
Buenos Aires province* 
Gustavo J. JVIacchif 
Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) 
Instituto Nacional de Investigacion y Desarrollo Pesquero (INIDEP) 
CC. 175, Mar del Plata (7600), Argentina 
E-mail address: gmacchi@inidep.edu. ar 
The striped weakfish, Cynoscion 
striatus, is a demersal species in- 
habiting coastal waters of the 
Southwest Atlantic. It ranges from 
Brazil (22°35'S) to the south of 
Buenos Aires province (Argentina) 
(42°S) (Cordo, 1986). The commer- 
cial catch takes place mainly off 
Buenos Aires province, between 35° 
and 40°S, to 50 m depths. The an- 
nual catch of this species is about 
20,000 metric tons, * 1 corresponding 
to 20% of the total commercial catch 
of coastal species in Argentina. 
Despite a variety of studies de- 
scribing C. striatus life history, such 
as feeding (Ciechomski and Ehr- 
lich, 1977; Cordo, 1986), growth 
(Ciechomski and Cassia, 1978), 
embryonic and larval development 
(Ciechomski and Cassia, 1982), 
length distributions, and sex ratios 
(Cousseau et al., 1986), studies on 
reproductive biology are rare and 
largely incomplete. Only one pre- 
vious report has included histologi- 
cal analysis of the ovaries and fe- 
cundity estimates (Cassia, 1986), 
providing evidence that striped 
weakfish is a multiple spawner. 
In the present study, ovaries of 
C. striatus from the coastal area of 
the Buenos Aires province (Argen- 
tina, Southwest Atlantic) were ex- 
amined histologically, and particu- 
lar attention was paid to evidence 
for multiple spawning and to esti- 
mates of spawning frequency and 
batch fecundity. 
Material and methods 
Cynoscion striatus was colit \ ted in 
the zone known as “El Rincon” 
( Buenos Aires province, Argentina, 
38°50'-40°30'S) during two re- 
search trawl cruises carried out in 
early November 1994 (n=179) and 
September 1995 (n= 224) (Fig. 1). 
Mature females caught near “Punta 
del Este” (Uruguayan coast, 35°10'S- 
55°W) in November 1994 were also 
used to estimate fecundity (n= 26). 
Individuals were measured to the 
nearest centimeter (total length, 
TL) and weighed (total weight, 
TW). Length range of sampled fe- 
males was 31-58 cm TL, which cor- 
responds to 3-15 yr old individu- 
als (Cioffi, 1992). The decision to 
sample only females of C. striatus 
greater than about 30 cm was based 
on the fact that this length is the size 
at maturity (Macchi and Acha 2 ). 
Immature ovaries therefore were 
underrepresented in the samples. 
The ovaries of individuals sampled 
were removed immediately after 
capture and fixed in 10% neutral- 
buffered formalin or in Davidson’s 
fluid for two weeks. Later, fixed 
gonads were weighed (GW), and a 
portion of tissue (about 2.0 g) was 
removed from the center of each 
ovary, dehydrated in methanol, 
cleared in benzol, and embedded in 
paraffin. Tissues were sectioned at 
approximately 5 pm thickness, 
stained with Harris’s hematoxylin 
followed by eosin counterstain. His- 
tological classification of ovaries 
was based on the occurrence and 
relative abundance of five stages of 
oocyte development (Table 1) as 
well as on the occurrence and in- 
tensity of atresia. The terminology 
used in the description of oocyte 
stages was adapted from Forberg 
(1982), and the classification of 
atresia followed that given by 
Hunter and Macewicz ( 1985). Ova- 
ries were classified into eight 
stages: 1) immature, 2) developing 
early, 3) developing late, 4) fully 
developed, 5) gravid, 6) partially 
spent, 7) spent, and 8) resting. This 
classification is a modification of that 
given by Mayer et al. ( 1988). Oocyte 
measurements were taken of the ova- 
ries in different maturity stages (3 
ovaries for each stage). Oocytes with 
visible nuclei showing were mea- 
sured along the longest axes with an 
ocular micrometer. About 10 fields of 
view per histological section were 
chosen at random (Fig. 2). 
To estimate the spawning frac- 
tion, only the samples collected 
during November 1994 were used. 
The percentage of spawning fe- 
* Contribution 1013 of the Instituto Nacio- 
nal de Investigacion y Desarrollo Pes- 
quero, Mar del Plata, Argentina. 
1 Secretaria de Agriculture, Pesca y Alimen- 
tacion. 1996. Flota pesquera Argentina 
(capturas maritimas totales). [Available 
from SAPyA., Paseo Colon 982, Buenos 
Aires, Argentina.] 
2 Macchi, G. J., and M. E. Acha. In press. 
Chapter 4: Aspectos reproductivos de las 
principales especies de peces. In Lasta 
(ed.), Resultados de la campana H-13/94, 
Serie Informes Tecnicos INIDEP. 
Manuscript accepted 9 July 1997. 
Fishery Bulletin 96:375-381 (1998). 
