The trout cod (Maccullochella macquariensis) or bluenose cod, is a large predatory freshwater fish of the genus Maccullochella and the family Percichthyidae, closely related to the Murray cod. It was originally widespread in the south-east corner of the Murray-Darling river system in Australia, but is now an endangered species.
Reproduction
Trout cod reach sexual maturity at 3 to 5 years (which corresponds to about 35 cm in males and 43 cm in females). Trout cod reach sexual maturity at a smaller size than Murray cod, which is an adaptation to the rocky, low nutrient and often quite small upland habitats trout cod were found in. Spawning of trout cod has never been observed in the wild and is not well understood. It is believed to be essentially the same as Murray cod but occurs about three weeks earlier and at significantly lower temperatures in waters shared by the two species. Trout cod are believed to spawn at temperatures as low as 15 degrees in upland rivers, using rocks as a spawning substrate; these are also clear adaptations to cool, rocky upland river habitats. Significantly, and unlike Murray cod, trout cod will not breed in earthen dam brood ponds; another indication that trout cod are a more specialised upland species than Murray cod. Artificial breeding programs being conducted for the species recovery use hormone injections to induce ovulation in naturally ripe fish in spring. Trout cod will hybridise with Murray cod and so for recovery projects it is important that Murray cod are not stocked into sites where Trout Cod and Murray cod are not already coexisting sympatrically.
Conservation
Trout cod were once common and abundant throughout the Murray-Darling Basin but are now listed on the IUCN as endangered due to overfishing, degradation of habitat and the introduction of invasive Trout species.