The sex ratio of Glossogobius giuris studied for over one year period, shows the male to female ratio as 1: 0.59. Seven maturity stages have been recognized and the size at first maturity is observed at 103 mm in females and at 114 mm in males. GSI values and ova diameter polygons suggest prolonged breeding season from August to January with its peak in the month of September. The logarithmic relationship between fecundity and total length, body weight and ovary weight have also been established. Fecundity varies from 9,380 to 293,664, and the mean fecundity is 113,030 in fish of 76 mm to 273 mm total length.
The knowledge of reproductive parameters like sex ratio, size at maturity, spawning period
and frequency, and fecundity are of greater importance to scientists for fishery prediction
and formulation of conservative measures by understanding the annual regeneration of their
stock. The gobiid Glossogobius giuris forms an important commercial fishery in Gosthani
estuary and contributes considerably throughout the year. The investigations on reproductive
cycle and spawning periodicity of G. giuris from Hooghly estuary by Bhowmick (1965) and
the spawning behavior and spawning season of the same species by Willey (1911), Hora
(1935), Pannikkar et al. (1939), Alikunhi et al. (1951), Tandon (1962), and David et al.
(1979) are worth mentioning. The present paper deals with the gross characteristics of sex
ratio, maturity stages, ova diameter, gonado somatic index, size at first maturity and fecundity
of G. giuris from Gosthani estuary near Visakhapatnam.
The fish samples were collected once a week from Gosthani estuary with the help of local
fishermen, using cast nets and gill nets for a period of one year. A total number of 1264
specimens were analyzed. The sexes can be identified externally in matured specimens by
observing the genital papilla which is straight, thin, and pointed in males, and short, fleshy
and circular in females. In immature specimens, as it was difficult to identify the sexes externally,
the belly was cut open to record the sex, color, and general appearance of gonads, and then
weighed to nearest 0.10 mg, and preserved in 5% formalin in labeled bottles. |
