Tilapias in Aquaculture: The Need for Invasion Science in Decision Making to Protect and Sustain Biodiversity
Aquaculture—generally defined as the farming of fish, shellfish, or aquatic plants—is widely considered a sustainable replacement for wild-caught fish stocks and a means to meet the demand for many fish commodities. During the 1960s and 1970s, international development agencies promoted aquaculture as a protein production method that could improve food security for developing countries without the environmental problems associated with terrestrial agriculture. In the early 1980s, these agencies and others called for a “blue revolution”—suggestive of the earlier “green revolution” that promised to alleviate hunger through agriculture—and funded research into aquaculture practices, including selection for disease-resistant, growth-enhanced fish through conventional breeding methods (McGinn 1998).
Tilapias are subtropical to tropical freshwater fishes of the family Cichlidae that are native to parts of Africa and the southwestern Middle East (Trewavas 1983) and are of increasing importance for aquaculture in both the developed and developing worlds. They are sometimes referred to as the “aquatic chicken” due to their versatility and adaptability for culture in a range of environments (Coward and Little 2001). The term “tilapias” refers to species of three genera, grouped according to parental care patterns (Trewavas 1983): Oreochromis (arena-spawning maternal mouthbrooders), Sarotherodon (paternal or biparental mouthbrooders), and Tilapia (substrate spawners).
A body of literature is emerging that documents the establishment of tilapia populations in areas where they are not native and their subsequent impacts on native biodiversity. The literature demonstrates that owing to such attributes as their adaptability to various water conditions, prolific breeding habits and territoriality, and ability to feed at a range of trophic levels, tilapias can outcompete native species for food, habitat, and spawning sites and displace native species in rivers, lakes, and estuaries. This chapter considers the impacts of introduced tilapias in their host environments, the importance of determining potential for invasiveness when planning aquaculture programs, and the need for additional science related to impacts and management of invasive species in aquaculture. Of particular concern is the promotion of tilapia aquaculture worldwide, its potential as a pathway for invasive species, and the management of tilapia culture practices to avoid negative impacts on native biodiversity.