A review of domestication effects on stocked fishes, strategies to improve post stocking survival of fishes and their potential application to threatened fish species recovery programs in the Murray–Darling Basin

Introduction A number of Australian native fish species in the Murray–Darling Basin have declined significantly and are listed as vulnerable or endangered in part of, or across all of their former range within the Basin (Lintermans 2007). These species include large bodied icon species such as Murray cod (Maccullochella peelii), trout cod (Maccullochella macquariensis), Macquarie perch (Macquaria australasica), silver perch (Bidyanus bidyanus) and eel-tailed catfish (Tandanus tandanus), as well as small bodied species like the southern purple spotted gudgeon (Mogurnda adspersa) and the olive perchlet (Ambassis agassizi) (Murray–Darling Basin Commission 2004). The Murray–Darling Basin Commission (now Murray–Darling Basin Authority) has developed a Native Fish Strategy (the Strategy) with the long-term goal of restoring native fish populations to 60% of their pre-European colonisation levels. One of the objectives of the Strategy is to devise and implement recovery plans for threatened fish species. Driving actions of the Strategy include rehabilitating fish habitat, protecting fish habitat, managing riverine structures (barriers to migration), controlling alien fish species, protecting threatened fish species and managing fish translocation and stocking (Murray–Darling Basin Commission 2004). Although all these actions are likely to have positive effects on the recovery of threatened fishes, in some catchments of the Basin these fish have already become locally extinct, or declined so drastically that carefully managed conservation stocking of hatchery-reared fish may become a necessary part of any recovery program. If the driving actions of the Native Fish Strategy are successful, then reintroduced hatchery-reared threatened fish that survive should go on to produce self-sustaining populations. However, conservation stockings are not always successful. Much of this has been attributed to domestication effects of captive rearing. The basis of this review is to investigate why stocking of hatchery-reared fish is not always successful and how to improve the post-stocking survival of hatchery-reared fish. The review also includes an investigation of current hatchery practices in eastern Australia to determine likely domestication effects on threatened Murray–Darling Basin species.