MATURATION AND SPAWNING OF THE ANCHOVY THRYSSA MYSTAX IN THE NORTHERN ARABIAN SEA

Abstract

Maturity studies carried out on Thryssa mystax (Bloch & Schneider),
collected from commercial landings at Karachi Fish Harbour, from January to
December, 1977, show that the female-male ratio is 1.26 : 1, and, as revealed byova-
diameter polygons, S'pawnmg occurs twice a year. There are two peak spawning
seasons, in January-March and June-July, as borne out by the close approximation
of GSI and relative condition coefficient. The minimum size at sexual maturity
was about 140 mm TL for both sexes. The relations between total length of fish
and length and breadth of gonads, and between fish weight and gonad weight have
been determined. The logarithmic relationships between fecundity and total length
and body weight and ovary weight have also been eatablished