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Technical annual report 2000-01



Technical annual report 2000-01


Dept. of Regional Development, Primary Industry, Fisheries and Resources technical annual report; Department of Regional Development, Primary Industry, Fisheries and Resources technical and annual report; Reports; PublicationNT; Technical bulletin (Northern Territory. Dept. of Primary Industry and Fisheries) ; no. 295




Made available via the Publications (Legal Deposit) Act 2004 (NT).






Agriculture -- Northern Territory -- Periodicals; Fisheries -- Northern Territory -- Periodicals

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Dept. of Primary Industry and Fisheries

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Technical bulletin (Northern Territory. Dept. of Primary Industry and Fisheries) ; no. 295



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Department of Primary Industry and Fisheries 290 PROJECT: Freshwater Pest Species Project Officers: A. Marshall, S. Sly and T. Williams Location: Northern Territory Objective: To protect Northern Territory inland waters by preventing the establishment of exotic aquatic pest species through legislation, public awareness and eradication operations. Justification: During 1999/2000 three exotic species were recognised as a threat to biological diversity in Northern Territory freshwaters. As a consequence the issue of freshwater pests is emerging as an additional responsibility of the Aquatic Pest Management Program (APMP). APMP accepts the role of coordination in the event of a requirement for small-scale control of invasive fresh water and marine species; however the program relies on the cooperation of the Fisheries Division as a whole in addressing aquatic pest incursions. The control and eradication component of the APMP represents the first level of response to a pest infestation. Background: Prior to the establishment of APMP, staff from Fisheries Research undertook the eradication of exotic fish. Since its inception, the role of APMP has incorporated the management of exotic freshwater species both faunal and floral. In this capacity, APMP has been instrumental in the eradication of at least three established populations of exotic freshwater species: the jewel cichlid, guppies and mosquito fish. Eradication of the Jewel Cichlid The jewel cichlid (Hemechromis bimaculatas) is a native of Africa and a prohibited import to Australia. The exotic fish is a prolific breeder and highly competitive and effective at displacing native species. Destruction of the population was essential to ensure maintenance of native biological diversity and discourage translocation by inquisitive individuals. The cichlid population was resident in the drainage channel of the Royal Darwin Turf Club, known locally as Racecourse Creek. It is thought that the original fish may have been introduced to the water body by some well meaning member of the public who did not realise they were in possession of an illegal fish. The individual would no doubt have been ignorant of the potential harm the exotic species could cause to the pristine natural waterways of the Northern Territory. In October 2000 DPIF staff, in collaboration with the Turf Club and staff from the Museum and Art Gallery of the Northern Territory, used the biodegradable natural pesticide rotenone to kill all fish in Racecourse Creek. An estimated total of 1 500 dead fish were removed from the 4-km length of waterway. Approximately 30% of the fish were native species: oxeye herring (Megalops cyprinoides), empire gudgeon (Hypseleotris compressa) and red-tailed rainbow fish (Melanotaenia splendida australis) accounting for about 10% of the biomass of fish removed. The remaining 70% of fish, which accounted for approximately 90% of biomass, were estimated 1000 jewel cichlids (H. bimaculatus) and 200 guppies (Poecilia reticulata). Although jewel cichlids were the target species, it was an extra bonus to eradicate the guppies from the waterway. In February 2001 APMP restocked Racecourse Creek with native red-tailed rainbow fish and emprire gudgeons, sourced from a genetically similar population, to assist the establishment of a natural food web and thus keep mosquito numbers under control. No further populations of exotic freshwater fishes have been recognised in Racecourse Creek.