| Author |
antipodi
Site Admin
Joined: 25 Jan 2006
Posts: 1141
Karma: +6 (6)
Mon Feb 13, 2006 9:39 am
|
|
| Message |
 Australian Marine Turtles..endangered?
|
   |
|
Australian MARINE TURTLES
STATE
Of the world's seven species of marine turtles,  six are found in the waters of the Australian Great Barrier Reef. They are the green, hawksbill, loggerhead, flatback, olive Ridley and leatherback turtles. One of these, the flatback, nests only on Australian beaches. Out of the six species, four (green, loggerhead, hawksbill and flatback) have internationally significant populations in the World Heritage Area. The Great Barrier Reef is one of the few remaining havens for marine turtles in the world.
Marine turtles aggregate for breeding at a limited number of nesting beaches, with individual females always returning to nest at beaches in the same area where they were born. Examples from the World Heritage Area include Raine and Heron islands which are internationally significant green turtle nesting beaches, and Wreck Island, a major loggerhead nesting beach. Marine turtles can migrate as much as 2600 km between nesting beaches and feeding areas, but show great fidelity to both feeding and nesting sites.
Most marine turtles are slow growing and take decades to reach sexual maturity. Females do not breed every year with periods between breeding episodes of five to eight years for green turtles and two to three years for flatback turtles having been measured. Marine turtles require high annual survivorship of adults and near-adults in order for populations to be maintained.
On a global scale, marine turtle populations are under threat. The hawksbill is listed as 'critically endangered' on the 1996 IUCN Red List of Threatened Animals. This means that this species is at 'extremely high risk of extinction in the immediate future'. Green, olive Ridley, loggerhead and leatherback turtles are listed as 'endangered', meaning that they are at 'high risk of extinction in the near future'. Flatback turtles are listed as 'vulnerable', meaning that this species is at 'high risk of extinction in the medium-term future'.
In Australia, marine turtles are also in a vulnerable position. Apart from the flatback turtle, all species of marine turtles found in Australian waters are listed in the Endangered Species Protection Act 1992. The loggerhead turtle is listed as 'endangered' and the four other species as 'vulnerable'.
Turtle Surveys
In the Great Barrier Reef World Heritage Area most scientific studies of turtle populations have concentrated on green and loggerhead turtles. The loggerhead is of particular concern. Since surveys began in the late 1970s the number of nesting females has steadily declined. The east Australian population of loggerhead turtles used to represent the bulk of the South Pacific stock (one of about eight loggerhead stocks globally). If this population disappears, it will represent the effective removal of the South Pacific stock. Because female turtles nest in the area where they hatched, it is highly unlikely that a stock that has died out would be recolonised by turtles from another stock somewhere else in the world.
Although the trends for green and hawksbill turtles are not as clear as those for loggerheads, there is evidence that populations of these species are also declining in the Great Barrier Reef World Heritage Area. There are no indications that flatback turtles are in decline.
Olive Ridley and leatherback turtles are uncommon in the Great Barrier Reef and have been the subject of little scientific research. The long-term trends in the populations of these species are unknown.
PRESSURE
Inside the Great Barrier Reef World Heritage Area, turtle populations are subjected to several sources of human impact. For some turtle species, the greatest pressures occur in overseas waters. Because turtles can regularly make migrations of up to thousands of kilometres, they can spend part of their time relatively well protected in Australian waters, but are exposed to significant pressures in overseas waters.
Although today turtles are protected from commercial exploitation in Australian waters, this has not always been the case. Commercial exploitation of turtles in eastern Australia was permitted until 1968.
Current human pressures on turtle populations in Australian waters include bycatch in trawl nets, traditional hunting, habitat degradation, bycatch in shark control programs, floating rubbish such as plastic and fishing line which can block guts after being eaten, and boat strike. Another human-related pressure is predation of turtle eggs and young by introduced species such as pigs and foxes.
Conservation status of the six species of marine turtles found in the Great Barrier Reef
An estimated 1769 (+/- standard error of 960) turtles are caught in trawl nets in the Great Barrier Reef World Heritage Area each year. Between 29 and 138 of these captured turtles are estimated to drown. The most commonly caught species are flatback turtles and green turtles. Although loggerheads make up only 14% of the turtles caught, they are three times more likely to drown in a trawl net than flatback turtles. Most of the mortality that has led to the decline in the South Pacific population of loggerhead turtles occurs in Australian waters and is thought to be due to drowning in trawl nets.
The direct take of turtles in the Great Barrier Reef Marine Park is restricted to traditional hunting by indigenous communities living adjacent to the Marine Park. Turtle meat and eggs are an important traditional element of the diet of Australia's indigenous peoples, particularly for celebrations and family gatherings. However there are few statistics available for how many turtles are killed. One of the biggest problems with turtle hunting is that turtles targeted by hunters are mature females and, unfortunately, these are most critical to the reproductive success of the species.
Although turtles (almost entirely green turtles) are hunted in the Great Barrier Reef World Heritage Area, the numbers killed are small in comparison to those killed in neighbouring countries. Because turtles migrate over such large distances (up to 2600 km) hunting in neighbouring countries also affects populations in the Great Barrier Reef World Heritage Area. The combined hunting mortality in Australia and neighbouring countries is thought to exceed the capacity to replace losses. This is particularly true for green and hawksbill turtles.
A variety of human activities remove or degrade beach habitats which are nesting sites for turtles. Development may totally remove beach sand or restrict access to nesting areas, as has occurred along part of the beach at Heron Island. Lights from development (particularly street lights) can confuse new turtle hatchlings, causing them to move inland from their nest, instead of moving out to sea.
Between their introduction in the 1960s and about 1996, shark nets caught 2140 turtles in the World Heritage Area. Only 37% of these were released alive, the rest drowned.
RESPONSE
In Australia, marine turtles are protected under Commonwealth and State legislation. The Commonwealth is preparing a recovery plan for marine turtle species. A national Marine Turtle Recovery team consisting of representatives from relevant Commonwealth and State nature conservation and fishery agencies and other stakeholders has been convened. The team has developed a draft Recovery Plan for Marine Turtles in Australia, which identifies the objectives, criteria and actions for recovery of these turtle species.
The Plan identifies the loggerhead turtle as a species of particular concern and urges lead conservation and fisheries management agencies to reduce loggerhead mortality to almost zero.
All turtle species found in the Great Barrier Reef World Heritage Area are protected under Appendix I of the Convention on International Trade in Endangered Species. This means that international trade in turtle products (such as shells or items made from turtle shell) is heavily regulated and illegal without special permits.
Because of long migrations between feeding and breeding grounds, most turtles swim through the waters of more than one country during their lives. Consequently, conservation efforts for turtles must be coordinated at an international level if they are to be successful. An international agreement between Australia, Indonesia, New Caledonia, Papua New Guinea, Solomon Islands and Vanuatu addressing the conservation of marine turtles is needed urgently.
Almost all major turtle nesting areas in and around the Great Barrier Reef World Heritage Area are in protected areas.
Although some turtle hunting is allowed within the World Heritage Area, it can only be carried out by indigenous peoples with an appropriate permit. Even with a permit, hunting is not allowed in preservation zones of the Marine Park.
In recognition of the problem of turtles being caught as bycatch in trawl nets, the Queensland Department of Primary Industries & Fisheries and the Queensland Commercial Fishermen's Organisation have developed guidelines for the release of turtles taken by trawlers.
One of the major issues under consideration in the ongoing development of a new management plan for the east coast otter trawl fishery is bycatch of endangered species, particularly turtles. The Trawl Fishery Management Advisory Committee, Queensland Fisheries Management Authority and Great Barrier Reef Marine Park Authority have all identified the introduction of turtle excluder devices to minimise, if not eliminate, bycatch of turtles as an urgently required measure. The Queensland Fisheries Management Authority has proposed the target of reducing trawl-induced turtle deaths to negligible levels by 2000. Further details of management arrangements for the east coast trawl fishery can be found in Management Status - Fisheries.
Concern over bycatch of shark nets has led to some nets being replaced with baited hooks. Shark nets are now only deployed at ten locations in the World Heritage Area, near Cairns, Townsville and Mackay. Replacement of nets with hooks has not eliminated bycatch of turtles, with loggerhead turtles still being caught on drum lines in southern Queensland.
A major tool for management is ongoing monitoring of turtle populations to provide information that allows informed management decisions. Annual monitoring of green, loggerhead, flatback and hawksbill turtle nesting populations is carried out.
Until there is robust demographic data for marine turtle populations in the Great Barrier Reef World Heritage Area, the management approach is a precautionary one which focuses on managing human activities which may impact on turtle populations
Recovery Plan Map of Australia URL www.deh.gov.au/.../turtle-recovery/map.html
|
|
Search
