Climate change and Australian marine and freshwater environments, fishes and fisheries: introduction John D. Koehn Arthur Rylah Institute for Environmental Research, Department of Sustainability and Environment, 123 Brown Street, Heidelberg, Vic. 3084, Australia. Email: john.koehn@dse.vic.gov.au Additional keywords: Australia, climate, estuaries, fish, fisheries, freshwater, impacts, Indo-Pacific, marine. Introduction There are worldwide concerns over the effects of climate change on both environments and human communities, with a need to better understand the range of existing and potential impacts. The Earth’s climate has changed rapidly in the past few decades (Steffen 2009), largely caused by human activities (IPCC 2007). Climate change is a global problem that will require global solutions, and these will take time both to achieve and take effect. Until then, there is a need for prioritised management actions in the form of species- and/or site-specific adaptations to changed climatic conditions. Although there is a recognised need to use the best available science to support evidence-based policy and management (Ryder et al. 2010), there is typically a lack of uptake of science into conservation management (Koehn 2004), with the effective translation of scientific findings into policy and on-ground practice still limited, especially in fresh- water science (Lake et al. 2010). The political debate that sur- rounds climate change can cloud scientific findings and there is a need for clear scientific messages to politicians, the public and resource managers on climate change (see Australian Academy of Science 2010) and its impacts (see papers in this Special Issue). Climate change is already affecting many aspects of marine and freshwater ecosystems, their fishes and fisheries, and the human uses of them. This includes commercial and subsis- tence fisheries and the people who rely on them (Bell et al. 2009) as well as non-market benefits such as biodiversity and ecosystem services. These latter benefits are often neglected in economic evaluations. Importantly, these impacts will not only be for today but also into the future. Climate-change impacts are not the only stressors to aquatic ecosystems, and in many cases, will not be the primary threat to fish or fisheries. However, an understanding of how climate change might interact with these other stressors is crucial for management and protection of biodiversity and ecosystem goods and services. Papers in this Special Issue explore these complex inter-relationships for Australian marine, estuarine and fresh- water systems. Climate change, fish and fisheries in Australia Australia is a large, generally dry continent that spans tropical to temperate zones. It has a long continuous coastline but few mountains, limiting opportunities for cool-climate freshwater species to move to higher altitudes to compensate for increasing temperatures (Koehn et al. 2011). Australia has a valuable marine fisheries zone, high levels of tourism in coastal areas (Koehn et al. 2011) and angling is a popular recreational pas- time, particularly in freshwater, estuarine and inshore marine environments (Henry and Lyle 2003). Whereas some attention has been paid to the impacts of climate change on marine areas (Poloczanska et al. 2007), particularly those with high profiles such as corals and the Great Barrier Reef (see Munday et al. 2008; Pratchett et al. 2011), freshwater ecosystems may be more vulnerable. Drought and increased climatic variability, includ- ing intense floods and storms, threaten Australia’s endemic and depauperate freshwater fish communities (Allen et al. 2002; Pusey et al. 2004), which have large numbers of species of conservation concern (Lintermans 2010). Australian rainfall patterns and river flows are highly variable (Walker et al. 1995), complicating predictions of future changes (Lough and Hobday 2011). Australia’s freshwater and estuarine fishes and their habitats have suffered considerable degradation in many regions (Gillanders et al. 2011; Morrongiello et al. 2011; Pratchett et al. 2011) and have been already affected by many other threats that have led to range reductions and reduced and fragmented populations. Some considerations have already been given to climate- change impacts on Australian biodiversity (Lindenmayer et al. 2010), water resources (Bates et al. 2008) and the management of rivers and wetlands (Kingsford 2011). In particular, this has focussed on water management (Lester et al. 2011; Pittock and Finlayson 2011; Pittock and Hartman 2011), setting priorities (Crook et al. 2010) and developing adaptation strategies (Aldous et al. 2011). It is important that prioritisation be given to the management of species, locations and ecosystems judged to be most vulnerable to the impacts of climate change (see Koehn et al. 2011). CSIRO PUBLISHING www.publish.csiro.au/journals/mfr Marine and Freshwater Research, 2011, 62, 981–983 Ó CSIRO 2011 Open Access 10.1071/MF11152 1323-1650/11/090981