|Page tools: Print Page RSS Search this Product|
Fishing and the environment
Depletion of marine resources
Although fish are a renewable resource, fisheries production of a number of species has been declining since the late 1980s (Kearney 1995). Reasons for declines in some fisheries include overfishing, use of non-selective fishing gear, loss of habitat, pollution (see Environment), natural disaster, and Australia's marine jurisdictional complexity which hinders management of a fish stock or population. Management of fisheries ecosystems, as opposed to the management of single species, is an important step towards better management of marine resources. The loss of a few key species has the potential to destroy whole ecosystems. For example, krill, 'the world's most abundant crustacean', has a key role in southern waters. Krill is the staple diet of many seals, whales, fish, squid, penguins and other seabirds, making it significant in the conservation of many species. If krill were to disappear, most of the creatures that feed on them would disappear (AAD 2000). There are very few examples in which fisheries management can claim clear success in achieving regulatory goals. The Western Australian Western Rock Lobster Fishery and the Tasmanian Abalone Fishery have managed to rebuild stocks over several years.
Impacts on target species
Species that are particularly vulnerable to fishing activities are usually slow growing, low breeding (it produces a low number of eggs compared to other fish), long-lived marine species that aggregate for their spawning. For example, the 'overfished' Eastern gemfish, taken in the Commonwealth South East Trawl Fishery off southern New South Wales, was fished excessively in the 1970s and 1980s, and as a result it is still vulnerable. A zero catch limit was set from 1993 to 1996. The total allowable catch (TAC) for 1997 was set at 1,000 tonnes, but the catch was only 393 tonnes. Scientific advice was that the TAC for 1998 should be zero, but a total of 500 tonnes was allocated to cover bycatch (see Impacts on non-target species for definition) and reduce discarding. The catch, however, was only 214 tonnes. The 1999 allocated catch for bycatch (see below) was 250 tonnes (actual catch 158 tonnes), and in 2000 the allocated catch for bycatch was reduced to 200 tonnes. Eastern gemfish remain vulnerable to targeted fishing as it congregates for its spawning run (SoE 2001b).
Impacts on non-target species
In some fisheries, large numbers of other species (non-targeted species) are also taken. These are termed 'bycatch', which refers to the species that are taken incidentally in a fishery. Bycatch species are usually of lesser value and of greater quantity than the target species, and are sometimes discarded. Management of bycatch is of particular concern as little is known about the impacts of retained or discarded bycatch on marine ecosystems.
The components of fishing bycatch can be described as:
Attempts to reduce bycatch
As a response to the significant issues and impacts of bycatch on the marine environment, the Commonwealth developed a National Bycatch Policy in 1999 and a Commonwealth Bycatch Policy in 2000. By the end of 2001, Bycatch Action Plans were developed for 14 of the 21 Commonwealth fisheries. Turtle exclusion devices (TEDs) and bycatch reduction devices (BRDs) allow escape and have been trialled in the Northern Prawn Fishery since 1993. They became compulsory in this fishery in 2000. Seal excluder devices are currently being trialled in the South East Trawl Fishery. These projects show that the use of TEDs and BRDs has resulted in a substantial decline in the catches of large animals such as turtles, stingrays and sharks. However, the use of BRDs in this fishery seems to have had little impact on the catch of the smaller, more abundant bycatch. The Commonwealth Government has provided just over $1m from the Natural Heritage Trust to establish the SeaNet extension service. The project is focused on increasing the rate of adoption by the commercial fishing sector of new fishing gear and practices to aid bycatch reduction and to implement environmental best practice (SoE 2001b).
Trawling is one of the most widely used commercial fishing methods in Australia. Demersal trawling makes contact with the sea floor and therefore it can have substantial impacts on seabed habitats and benthic (occurring at or near the bottom of a water body) ecosystems (Harris & Ward 1999). The extent of essentially indiscriminate impacts can be significant, including physical removal, disturbance of organisms and non-living components and increases in water turbidity. The nature of the catch in trawl fisheries other than the target species can include threatened species (e.g. turtles) and invertebrate (e.g. jellyfish) and large amounts of non-target species. Nearly 10,000 turtles are caught accidentally by trawl fishing each year in northern Australia, but an estimated 90% of these are released alive (SoE 2001b). Australia has about 30 of the world's 50 sea snakes, around half of which are endemic. They are quite fragile animals and it has been estimated that between 10% and 40% taken in trawls die once released (Zann 1995b).
Repeated trawling may prevent the recolonisation of benthic species, both sedentary and mobile. Seamounts (sites of highly valued marine biodiversity) have been trawled for orange roughy and some have been damaged by this activity. Trawl nets may dislodge attached species such as sponges and modify the habitat and food chains. Possible effects of trawling also include changes in food webs, such as increased populations of scavengers such as seabirds, fish and crabs. A 1996 study by the CSIRO and the Queensland Department of Primary Industries showed that each pass of the trawl along the sea bed removes about 5% to 25% of the seabed life. However, there is a cumulative effect; seven trawls over the same area of seabed removed about half the seabed life, and 13 trawls removed 70% to 90%. In the far northern Great Barrier Reef Marine Park, for every tonne of prawns harvested, about six to ten tonnes of other species are discarded (SoE 2001b). A study on the environmental effects of prawn trawling (Poiner et al. 1998) found that about one-third of bycatch species were crustaceans and two-thirds fish. Zoning in the Great Barrier Reef Marine Park prohibits trawling on about 20% of the sea floor (Zann 1995a).
There are both Commonwealth and state fisheries laws under which fisheries are managed through general regulations or other statutory methods. There are various methods to manage each fishery such as size and catch limits and gear restrictions. The Environment Protection and Biodiversity Conservation Act 1999 (Cwlth) (the EPBC Act) came into force in July 2000. It requires an assessment and approval process for activities that are likely to have a significant impact on the Commonwealth marine environment, on nationally threatened species and ecological communities, and on internationally protected migratory species. The Act also requires that all Commonwealth managed fisheries have their own environmental impact strategically assessed. One of the most significant legislative changes is the removal of the general exemption of most marine fish from export control regulation under the Wildlife Protection (Regulation of Exports and Imports) Act 1982 (Cwlth). The removal of the exemption makes the taking of marine native species consistent with the taking of terrestrial native species. This change comes into effect in December 2003. Before a fishery can become exempt from the Act, it must show that the fishery is ecologically sustainable in terms of its impact on: target species, non-target species and bycatch, and the ecosystem generally (including habitat) (SoE 2001b).
Longline fishing involves setting baited hooks along a line up to 100 km in length behind a boat. The line is deployed at various depths and is a particular threat to several non-target species, especially seabirds (EA 2000). The death rate of albatross averages 0.4 birds per 1,000 hooks deployed. The number of hooks set annually is high, between 50 and 100 million in the world's southern oceans alone (Robertson 2001). The interaction of sea birds that feed in open waters with longline fishing vessels can be fatal and considerable concern has been raised about the effect of longlining on populations of albatross and on some species of petrels. Species of albatross are particularly at risk, not only because of the number of birds caught, but also because of their breeding patterns. Albatross are now listed as vulnerable by the Commonwealth Government. The Government put in place a threat abatement plan in 1998 with the aim of reducing bycatch to one bird per 20,000 hooks set. This is a reduction of 90% over a five-year period through techniques such as setting baits at night when seabirds are less active (EA 2000).
Ghost fishing refers to the lost, damaged or abandoned fishing nets and traps out at sea that continue to catch fish and other marine creatures. Worldwide, many thousands of marine mammals, turtles and seabirds die each year from swallowing plastic bags and other objects, or get trapped in discarded fishing gear. Fishing litter such as net fragments, ropes and bait straps may entangle marine animals, strangling or drowning them. In southern Australia, seals often get their necks entangled in lost or discarded fishing gear. It is estimated that at any one time around 500 seals in Tasmanian waters and 45 seals at Victoria's Seal Rocks have 'collars' of plastic litter (Zann 1995b). A study by the Bureau of Rural Sciences in 1989-91 of the composition of neck collars on entangled seals shows that trawl nets constitute the highest proportion followed by packaging bands.
Illegal, unreported and unregulated fishing is a growing problem. Illegal fishers generally damage marine ecosystems in a number of ways. They typically remove unsustainable numbers of their target species from the marine environment and often capture large amounts of bycatch due to indiscriminate fishing methods. This contributes significantly to the decline in fish stocks and undermines their sustainable management within the AFZ and worldwide. Illegal fishers also often abandon fishing gear to avoid apprehension, endangering non-target species in the environment (SoE 2001b). Periodically, larger trawlers and longliners of various nationalities are apprehended fishing illegally in Australian waters.
For further information on protection of the marine environment see Environment.
AAD (Australian Antarctic Division) 2000, Looking South: the Australian Antarctic Program into the 21st Century, Australian Antarctic Division, Environment Australia.
ABARE (Australian Bureau of Agricultural and Resource Economics) 2002, Australian Fisheries Statistics 2001, Canberra.
BRS (Bureau of Rural Sciences) nd, Fishery Status Reports.
DEST (Department of the Environment, Sport and Territories) 1993, Biodiversity and its value.
EA (Environment Australia) 2000, Threat Abatement Plan for the Incidental Catch (or Bycatch) of Seabirds During Oceanic Longline Fishing Operations, Biodiversity Group, Environment Australia, Canberra.
Harris ANM & Ward P 1999, Non-Target Species in Australia's Commonwealth Fisheries: A Critical Review, Bureau of Rural Science, Canberra.
Kearney R 1995, Coastal fisheries: a critical review, Fisheries New South Wales.
McLoughlin K, Kailola P, Williams M, Stewart PC, Reichelt RE, McNee A & Grieve C 1993, Australian fisheries resources, Bureau of Resource Sciences and Fisheries Research and Development Corporation.
Poiner I, Glaister J, Pitcher R, Burridge C & Wassenberg T 1998, Final Report on Effects of Trawling in the Far North Section of the Great Barrier Reef Marine Park: 1991-1996, CSIRO Division of Marine Research, Cleveland, Queensland.
Robertson G 2001, Albatross and longline fisheries, Australian Antarctic Division.
SoE (Australian State of the Environment Committee) 1996, Australia State of the Environment Report 1996, State of the Environment Advisory Council, CSIRO Publishing, Melbourne.
SoE 2001a, 'Biodiversity', Australia State of the Environment Report 2001 (Theme Report), CSIRO Publishing on behalf of the Department of the Environment and Heritage, Canberra.
SoE 2001b, 'Coasts and Oceans', Australia State of the Environment Report 2001 (Theme Report), CSIRO Publishing on behalf of the Department of the Environment and Heritage, Canberra.
Zann LP 1995a, The coastal zone, Great Barrier Reef Marine Park Authority.
Zann LP (ed.) 1995b, Our Sea, Our Future: Major Findings of the State of the Marine Environment Report for Australia, Great Barrier Reef Marine Park Authority for the Department of Environment, Sport and Territories, Ocean Rescue 2000 Program, Canberra.
These documents will be presented in a new window.