Fluvial Migration, Spawning, and Fecundity of Indus River Hilsa, Hilsa ilisha

Abstract Hilsa is a widely distributed anadromous fish occurring from the Persian Gulf to South Vietnam. The Indus is the only river in West Pakistan which supports a run of hilsa. These fish enter the Indus River each year, beginning about the middle of January, and in some years remain in the river as late as November. The bulk of hilsa, however, are found during June, July, and early August. Although increased stream flow does not appear to be the stimulus that attracts hilsa into the Indus, as reported for other streams, the peak of the run does occur during peak flows. Maturing hilsa entering the river range between 25 and 60 cm in length while a few immature fish enter that are as small as 22 cm. Most of the male fish appear to be in their 4th year of life, while the females are represented predominately by two age classes that appear to be their 4th and 5th respectively. Fecundity of hilsa varies between 755,000 and 2,917,000 eggs per female. There is no close correlation between length or weight a...