Reproductive biology of the freshwater catfish, Tandanus tandanus Mitchell, in the Gwydir River, Australia. II. Gonadal cycle and fecundity

Abstract

All male and female T. tandanus in the Gwydir River were mature at age V and at a weight of 1200 g, although some females matured at an earlier age and lower weight than males. The seasonal gonadal cycle as indicated by gonad weight, egg size and maturity stages revealed that the spawning period in the Gwydir River extended from January to the beginning of March.

Egg diameter increased linearly with fish length and weight. Ripe eggs ranged from 2.28 to 3.05 mm while fish weight ranged from 675 to 2275 g.

Fecundity increased linearly with fish weight and exponentially with fish length. Egg numbers per female ranged from 2000 to 20 600 eggs while fish weight ranged from 675 to 2275 g. Egg size also increased with increasing fecundity.

Temperature in excess of 24ºC appeared to be the primary factor stimulating spawning. Flooding was not required as a stimulus for spawning.