For further information, see Chapter 6: Marine environment.
Pressures from commercial and recreational fishing are important outcomes of coastal urban development, growth in the Australian and global populations, and a range of economic drivers. Aquaculture in coastal waters is one of the fastest growing commercial sectors in Australia.
Pressures from fishing are decreasing overall. However, in some areas of the south-east, east and south-west regions, pressures are widespread and causing serious degradation. Pressures from the development of aquaculture continue to increase in the south-east region, where the worst areas are already suffering serious degradation.
Sea surface temperatures have increased since the early 20th century—by 0.7 °C from 1910–29 to 1989–2008. As mentioned in Section 2.1.2, increases in sea surface temperature, which are particularly marked in the south-west, east and south-east regions, are likely to affect commercial and recreational fishing, aquaculture and a wide range of coastal activities that are part of the social and economic fabric of coastal communities.
Changing ocean temperature directly affects the distribution and abundance of many species and habitats, including seagrasses, macroalgae, phytoplankton, coral reefs, tropical and temperate fish, pelagic fish, marine reptiles and seabirds. The general trend is that habitats and distributions of species are moving southward. Further declines in seagrass meadows and algal beds, due to storms, turbidity and warmer water, are expected in the future. A loss of diversity in coral fish and other coral-dependent organisms is also expected.
For species that require shallow and cool coastal waters, such as for breeding or nursery grounds, this southward forcing by the changing temperature will eventually result in major population reductions as habitats become less available, and finally become unavailable south of the mainland and Tasmania. Changing temperature is likely to create the greatest set of ecological changes in shallow-water marine ecosystems in the coming decades.
An emerging concern in the marine environment is the threat from pathogens and viruses, which are spread by people, cargo, fishing gear and boats, and are difficult to detect. Introduced marine pests can enter Australia by a variety of routes, including ships’ ballast water, biofouling on ships’ hulls and equipment, and the aquarium trade and aquaculture. Around 97% of the volume of Australia’s trade is moved through the network of ports. In 2008–09, approximately 800 million tonnes of cargo were moved through Australian wharves by 4200 vessels that made 26 700 port calls. Further introductions of marine pests in coastal waters represent a significant economic and environmental threat.
Translocation of introduced marine pests within Australian waters occurs through the same means, as well as through natural processes. More than 100 introduced species and marine pests have been identified in Australian coastal waters.
Governments are working together to develop and implement a national system to prevent and manage marine pest incursions.c