Reproductive biology and spawning strategy of the catadromous percichthyid, Macquaria colonorum (Gunther, 1863)

The reproductive biology and spawning strategy of the iconic catadromous percichthyid, estuary perch Macquaria colonorum was examined from three coastal rivers of south-eastern (SE) Australia. Ovarian and testicular development followed a pattern similar to that of other percichthyids, world-wide. Females were collected in significantly larger sizes and greater numbers from all, and two of the three rivers, respectively. Mean size and age at maturity was greater for females (25.05 cm FL +/- 0.85 and 3.75 yrs +/- 0.08, respectively) than males (22.21 cm FL +/- 0.50 and 3.28 yrs +/- 0.08 respectively), with no significant difference between rivers. Trends in gonadosomatic indices indicated that M. colonorum spawn in the austral winter-spring in SE Australia. However, peak spawning occurred earlier (June-August) in the two most northern rivers (Hawkesbury and Clyde) compared with the Bemm River (September-November) further south. Ripe females were captured only in the lower reaches of estuaries throughout the spawning period in all three rivers. Mature M. colonorum females displayed a group synchronous pattern of oocyte development suggesting a multiple spawning strategy. Mean batch fecundity (F (B) ) was 266 583 +/- 17 821 oocytes per female and relative fecundity was 377 +/- 10 oocytes.g(-1) body weight. There were significant power relationships between F (B) and fork length (FL), weight and age. Similar to other percichthyids, M. colonorum are long-lived, highly fecund and exhibit a flexible spawning strategy which is attuned to the highly variable environments in which they are found.