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1. The invasion of carp (Cyprinus carpio L.) in Australia illustrates how quickly an introduced fish species can spread and dominate fish communities. This species has become the most abundant large freshwater fish in south-east Australia, now distributed over more than 1 million km 2 . 2. Carp exhibit most of the traits predicted for a successful invasive fish species. In addition, degradation of aquatic environments in south-east Australia has given them a relative advantage over native species. 3. Derivation of relative measures of 13 species-specific attributes allowed a quantitative comparison between carp and abundant native fish species across five major Australian drainage divisions. In four of six geographical regions analysed, carp differed clearly from native species in their behaviour, resource use and population dynamics. 4. Climate matching was used to predict future range expansion of carp in Australia. All Australian surface waters appear to be climatically suitable for carp. 5. This assessment strongly reinforces the need for immediate management of carp in Australia to include targeted control of human-assisted dispersal, such as use of carp as bait by anglers, distribution to new locations by anglers and the use of the 'Koi' strain in the aquarium industry. 6. Given their historical spread, dispersal mechanisms and ecological requirements, the expansion of carp across most of the remainder of Australia is to be expected.

The Native Fish Strategy (NFS) for the Murray-Darling Basin, southeastern Australia, provides a whole-of-fish-community approach and coordinated direction for the rehabilitation of its severely degraded native fish populations. Together with actions outlined in recovery plans for threatened species, the NFS addresses priority threats identified for native fishes with the aim to rehabilitate native fish populations to 60% (current populations are estimated to be at about 10%) of the levels that existed prior to European settlement. The NFS has a 50 yr time frame and coordinates actions across 6 different management jurisdictions. A key component of the NFS is the engagement of communities and stakeholders, with this being undertaken, in particular, by the use of dedicated coordinators and the development of 'demonstration reaches' where rehabilitation can be undertaken using multiple actions, with community involvement. The NFS is supported by targeted research projects and monitoring within an adaptive management framework. The NFS provides an effective partnership model where central coordination, coupled with focused jurisdictional actions, can deliver benefits to all governments. It synthesises and disseminates knowledge, integrates research and management and catalyses actions for priority problems. The need, objectives, evolution and development, achievements, strengths and weaknesses of the NFS are presented. The NFS approach would be suitable for many large river basins throughout the world.

This study of Murray cod (Maccullochella peelii peelii) movements in a large lowland river in south-eastern Australia indicated that the species was not sedentary, but undertook complex movements that followed a seasonal pattern. While there were sedentary periods with limited home ranges and high site fidelity, Murray cod also under took larger movements for considerable portions of the year coinciding with its spawning schedule. This generally comprised movements (up to 130 km) from a home location in late winter and early spring to a new upstream position, followed by a rapid downstream migration typically back to the same river reach. Timing of movements was not synchronous amongst individuals and variation in the scale of movements was observed between individuals, fish size, original location and years.

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Abstract. Anthropogenic climate change is already apparent and will have significant, ongoing impacts on Australian fishes and their habitats. Even with immediate actions to reduce greenhouse gases, there will be sustained environmental changes. Therefore, it is necessary to consider appropriate adaptations to minimise detrimental impacts for both fishes and the human populations that utilise them. Climate change will have a range of direct effects on the physiology, fitness, and survivorship of Australia's marine, estuarine and freshwater fishes, but also indirect effects via habitat degradation and changes to ecosystems. Effects will differ across populations, species and ecosystems, with some impacts being complex and causing unexpected outcomes. The range of adaptation options and necessary levels of intervention to maintain populations and ecosystem function will largely depend on the vulnerability of species and habitats. Climate change will also have an impact on people who depend on fishes for food or livelihoods; adapting to a new climate regime will mean trade-offs between biological assets and socioeconomic drivers. Models can be used to help predict trends and set priorities; however, they must be based on the best available science and data, and include fisheries, environmental, socioeconomic and political layers to support management actions for adaptation.

The environmental conditions and timing of spawning of Murray cod and trout cod were investigated over three successive years in the regulated Murray River and in the nearby, unregulated Ovens River. Larvae were collected in drift samples from early November. Murray cod larvae were present for up to ten weeks, but trout cod larvae were present for only about two weeks. Cod larvae were collected in both rivers in each year sampled, despite a range of flow conditions. Spawning periods, estimated by back-calculating larval ages and egg incubation times, were in part, concurrent for the two species, beginning in October when water temperatures had exceeded 15 C, allowing the occasional hybridization that has been noted between these two species. Trout cod larvae (10.0-18.2 mm) were significantly larger than Murray cod larvae (9.5-14.8 mm) in both years and the larvae of both species were significantly larger in 1995/6 than in 1994/5 in the Murray River. There was no relationship between larval size and water temperature, but later spawning times at the upper Murray River site coincided with lower water temperatures. Larval abundance varied significantly between sites, samples and years, with peak larval abundances occurring in November. Murray cod larval abundance was best explained by the explanatory variables of year, day length and change in flow over the previous 7 d. Environmental conditions for the spawning of Murray cod and trout cod are similar, and both species exhibit a similar larval dispersal strategy by emergence into the drift. Spawning occurred regularly under a range of flow conditions and it is likely that recruitment of these species in these rivers is driven by the subsequent survival of larvae and juveniles.