ภาพที่ 1One of the two remaining natural populations of the Australian lungfish (Neoceratodus forsteri) is under threat from a proposed dam, according to a paper to be published in the journal Environmental Biology of Fishes by Angela Arthington.
Natural populations of the Australian lungfish are restricted to the Burnett and the adjacent Mary river drainages in southeast Queensland, Australia (although other populations of lungfishes exist in Australia, these are the results of translocations), and the species is considered Vulnerable under Australian legislation.
The proposed Traveston Crossing Dam on the free-flowing main channel of the upper Mary River could seriously threaten the lungfish, according to the author. Construction of the dam is thought to adversely impact the lungfish population in several ways:
1. Loss of habitat Adult lungfishes typically inhabit stream and river reaches with overhanging riparian vegetation along the banks, woody debris in the water and dense macrophyte beds.
The construction of the dam would not only inundate the preferred main channel and tributary habitat for lungfish but will also spill out of the main channel to flood surrounding low lying terrain.
2. Loss of spawning sites Previous studies have shown that lungfish prefer to spawn in areas with intermediate flow velocities, low turbidity, a broad range of temperatures, high dissolved oxygen levels, depths of 4060 cm and moderate to high densities of aquatic macrophytes 1635 cm in height. The inundation of the river channels caused by the dam would wipe out many such areas.
3. Reduced juvenile recruitment "Dense beds and banks of vegetation provide suitable microhabitat for developing lungfish embryos and newly hatched lungfish, where they feed on small invertebrates such as microcrustaceans, molluscs and worms.
Impoundments with steep profiles and fluctuating water levels typically do not provide suitable nursery habitat and food resources for very young fish and juveniles (<30 cm) which rely on dense macrophyte beds in very shallow water for many months or years after hatching, until they move into deeper water."
4. Restriction of movement The dam will isolate upstream and downstream populations of the lungfish unless effective fish transfer facilities can be provided. Lungfish can also be injured or killed when they pass over the top of dam walls and tidal barrages during high water flows.
5. Increased threat from alien species The creation of a large artificial lake by the dam facilitates the establishment and spread of alien species. There are concerns that alien fishes that have been introduced into the Burnett and Mary river systems could threaten the lungfish.
Although the author discusses several mitigation measures (e.g. building fish transfer facilities into the dam), there is no guarantee that these measures may adequately compensate for the loss of habitat and restriction of movement associated with the dam.
The author concludes that "...building a large storage reservoir on the main channel of the upper Mary River appears highly likely to risk significant decline and fragmentation of important natural populations of the Australian lungfish. This risk seems far too high for a species already declared vulnerable and urgently in need of recovery in its remaining natural habitats."
ภาพที่ 2
1
) 