Reproductive pattern and some biological features of anadromous fish <i style="">tenualosa ilisha</i> (family: clupeidae) from Pakistan.

Abstract

This study is the first to describe the reproductive pattern of anadroumous fish <i style="">Tenualosa ilisha </i>based on the<i style=""> </i>histological examination of male and female gonads. The overall sex-ratio was close to 1:1 ratio. The five stages of oogenesis, nearly ripe, fully developed, running ripe, partially spent and spent and four distinct phases of ovarian atresis alpha, beta, gamma and delta were observed. Five stages of spermatogenesis developing, nearly ripe, ripe, partially spent and spent were identified. The male and female specimens in ripe and partially spent stages were considered to be in spawning condition. The spawning males were encountered during the period from May to October with the highest in July, August and October. While spawning females were also observed during the period from May to October, with almost all females being in spawning condition. The length-weight relationship in females of <i>T. ilisha</i> was nearly isometric and in males was allometric. The relationship between fecundity and other variables i.e. total length, body weight, girth and ovary weight in this species was significant. The age estimated on the basis of scales radii and length of the scales showed that the age classes comprised of 1+ to 3+ years. The mean scale length in different length groups was 7.5 to 11.5 mm.