Bioprospecting for biological control agents for invasive tilapia in Australia

•Mozambique tilapia is listed in the top 100 of the world’s worst invasive species.•We used a robust framework to assess the safety and efficacy of viral biocontrol.•Tilapia lake virus has been considered as the most promising biocontrol agent.•We have identified the essential information required for biocontrol of tilapia. Originating in Africa, tilapia (Pisces, Cichlidae) now have a worldwide distribution and are both a prime model system for evolutionary biology and an important aquaculture species in over 135 countries. In contrast, Mozambique tilapia (Oreochromis mossambicus) is also listed in the top 100 of the world’s worst invasive alien species and has been documented to have severe impacts on freshwater ecosystems primarily through displacement of native species and habitat alteration. In Australia, both O. mossambicus and the lesser-known spotted tilapia (Tilapia mariae) have established significant populations within Queensland waters, and recent incursions into northern New South Wales are of great concern. Eradication attempts using a combination of electrofishing and piscicide (poison) are rarely successful in open waterways, and given their invasive nature, there is a lack of demonstrated broad-scale effective control mechanisms for tilapia. Biological control (biocontrol), where it is feasible can be a cost-effective, a safe (species specific) and practical solution to managing invasive species because it does not require reapplication of chemicals or poisons, and once established should be self-sustaining. Based on the development of previous viral biocontrol strategies for rabbits and carp, we used a robust assessment framework for bioprospecting of biocontrol agents and found that tilapia lake virus (TiLV), and possibly tilapia parvovirus (TiPV), may offer the potential for biocontrol for invasive tilapia in Australia. TiLV causes high mortality in wild and cultured tilapia, but not in other species, and spreads through a waterborne route - an important transmission pathway for a successful viral biocontrol of fish. However, safety and efficacy, two major concerns for a successful biocontrol virus, need to be taken into consideration before the use of any exotic biocontrol virus is considered. Herein, we describe a systematic approach to assess known pathogens for their suitability as potential agents for biological control of tilapia and outline the possible next steps to further investigate the top candidates.