Eradication of Mozambique Tilapia at Bullyard Creek, Qld a Case Study on the Effectiveness of Using Chemicals to Eradicate Tilapia from Small Water Bodies
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CASE STUDY: Eradication of Mozambique tilapia at Bullyard Creek, Qld A case study on the effectiveness of using chemicals to eradicate tilapia from small water bodies Introduction Fisheries Act 1994), with heavy fines applicable for anyone found in possession Mozambique tilapia (Oreochromis of tilapia. A search warrant was issued mossambicus, ‘tilapia’) is an invasive fish for the suspected farms and the Bullyard species, which was illegally introduced area was extensively surveyed for tilapia to Australia during the 1970s. Since its (see map). Significant numbers of tilapia introduction, the species has spread were discovered in 18 farm dams across throughout Queensland and is also found three properties. Individual tilapia in Western Australia. This has occurred were also found in an irrigation channel partly by natural dispersal and partly associated with these dams. A major through people illegally moving fish concern was that, during periods of between water courses. heavy rain, these dams overflow into the In Australia, management options for adjacent Bullyard Creek, a tributary of tilapia have largely focused on public the Kolan River. These waterways were education campaigns and containment surveyed by electrofishing and netting, of existing populations. There have but evidence of tilapia was not found. also been attempts to eradicate confined populations of tilapia using Aim fish poisons (known as piscicides). These An eradication program using rotenone attempts have had mixed success, with was designed to remove the contained reinfestation of water bodies occurring in populations of Mozambique tilapia and some cases. However, when used under eliminate the spread of from the Bullyard the right conditions, piscicides such as area of central Queensland. rotenone can be useful for stemming the spread of tilapia to new, unaffected Partners and management catchments and watercourses. This eradication effort was managed by In early 2009, Mozambique tilapia were the Fisheries Queensland group of the seen for the first time near Bundaberg Department of Agriculture, Fisheries in central Queensland, by local water and Forestry (DAFF) in cooperation with authority SunWater and members of SunWater, Bundaberg Regional Council, the general public. Reports of sightings the Local Marine Advisory Committee, suggested that local farmers were local stocking and recreational fishing cultivating tilapia in their farm dams groups, the Burnett-Mary Regional Group for personal consumption. This practice (BMRG), Landcare, Oceanwatch, regional is illegal in Queensland (Queensland bait and tackle stores, Bundaberg 1 CASE STUDY: Eradication of Mozambique tilapia at Bullyard Creek, Qld Canegrowers Association, Queensland groups and other government Parks and Wildlife Service, and affected agencies landholders in the Bullyard area. • seeking legal advice about the implications of declared pest fish Process incursions on private property A risk management strategy was (Note: at the time, the landowners developed as a first priority to determine were legally responsible for the what action would be needed to control eradication of pest fish species from the tilapia infestation in the Bullyard their properties at their own cost) area. This strategy was developed in • sending destruction orders to consultation with a wide cross-section the owners of the affected farms of skilled people, including those (Section 108 under the Queensland experienced in fisheries and pest fish Fisheries Act 1994) management, fisheries regulation • identifying experienced personnel, enforcement, media liaison, workplace or those able to become trained and health and safety and human resource accredited in chemical application management. The risk management process considered many factors, • updating Fisheries Queensland including: personnel with the current operating conditions of the Australian • past experiences managing Pesticides and Veterinary Medicines tilapia incursions using different Authority’s (APVMA) ‘Minor use options such as monitoring only, permit for rotenone’ containment, population reduction, Application of rotenone in a • organising timing and cost estimates eradication and/or a combined farm dam at Bullyard. Image: for approved laboratory testing of approach Chris Lupton, DAFF Qld water and soil samples • potential socio-economic and • calculating and ordering the amount environmental impacts of these of rotenone required (1.3–10.5 kg different management options per dam) • opportunities to set up partnerships • organising various logistical issues Fish poisons with community groups and regional such as accommodation, meals, media outlets such as transport, equipment, dead tilapia rotenone can • financial, logistic and geographic disposal, exclusion of livestock opportunities and constraints. and native fauna from the treated be a useful Pest fish eradications are generally very sites, backup irrigation supplies expensive, need a lot of preparation, for landholders, post-eradication tool for and are usually only successful in small- monitoring of dams and the future eradicating scale situations and in shallow and restocking of endemic fish species closed waterbodies. The management back into the treated dams. Mozambique group decided that eradication was the Features of the program tilapia best option in this case, since the tilapia incursion was in a relatively small, To maximise the chances of success, populations contained environment and the water strategies were developed to engage was not used for human consumption. local government, water authorities, under certain state government departments, Onground operations involved: situations industry groups and the local • starting a register of personnel and community. The aims of these strategies resources offered by community were to encourage all stakeholders to 2 pestsmart.org.au participate in ongoing surveillance, and What didn’t work emphasise the point that ‘pest fish are • Feedback from landowners everyone’s problem’. suggested that the information The logistics The pest fish issue was highlighted given to landholders on the likely of pest fish in media releases and in brochures effects of the fish poison rotenone distributed at field days, to local bait was not comprehensive enough. eradications and tackle stores, schools, recreational Science-based literature detailing need to be anglers, and fish stocking groups. Fisheries the impacts of the poison on Queensland gathered information about the environment and on farming thoroughly the presence of pest fish from these practices needs to be distributed investigated and local groups, who were very passionate well before eradication operations about pest fish incursions. begin. methodically Results • The time needed to clean up the site organised. was underestimated — it took about Ideally, the A total of 5900 Mozambique tilapia one week longer than expected. This were eradicated from the 18 farm dams was most likely due to cooler water original source of treated with rotenone. However, as temperatures that prevent the the infestation would be expected with the use of a decomposition (and thus floating) of non-selective poison, large numbers dead fish. needs to be of native fish were also killed. These • Laboratory analysis of residual included rainbow fish (Melanotaenia located and rotenone levels in dam water and duboulayi), gudgeons (Hypseleotris treated surrounding soil returned inaccurate spp. and Mogurnda adspersa), spangled results in a poor timeframe. In perch (Leipotherapon unicolor), long- future, the quality of laboratories finned eels (Anguilla reinhardtii), needs to be verified in advance, to dewfish (Tandanus tandanus), fly- ensure timely and accurate results. speckled hardyhead (Craterocephalus stercusmuscarum), banded grunter What was learnt (Amniataba percoides) and olive perchlet (Ambassis agassizii). • Conflict with property owners during this exercise highlighted the Post-eradication monitoring in November importance of communication with 2009 using boat electrofishing did not all stakeholders. All parties involved detect tilapia in any of the farm dams need to understand their rights and or in the adjacent irrigation channels. responsibilities, and how resources However, tilapia are now known to be and expenses will be shared. present in other parts of the catchment. • Detailed information about the What worked chemicals involved and the • The use of education material and application process needs to be the media proved successful in given to the affected landholders, keeping the community informed. and their agreement sought before • Strategically targeting the farm beginning on-ground activities. dams succeeded in eradicating • Landowners and the public need to resident Mozambique tilapia from be made aware of the limitations these waters. and benefits of planned eradication • Tilapia do not appear to have exercises or other proposed actions. colonised the nearby Bullyard Creek • Pre-eradication fish surveys do not or the adjacent irrigation channel. always give a full picture of the Adult tilapia. Image: Jason Carroll pestsmart.org.au 3 CASE STUDY: Eradication of Mozambique tilapia at Bullyard Creek, Qld The media can be useful allies in pest fish eradications but can sometimes overstate the case Image: Chris Lupton, DAFF Preparing to apply rotenone to a farm dam at Bullyard. Image: Chris Lupton, DAFF Qld extent of an infestation, so they are Where eradication works are to be More info? best considered as a rough