A brief history of the Pacific Whiteleg Shrimp
The Whiteleg shrimp (Litopenaeus vannamei) is also known as Pacific white shrimp (or King prawn), and is a variety of prawn from the eastern Pacific Ocean.
The first spawning of was achieved in Florida in 1973 following the spawning of a wild-caught mated female from Panama. Following good results, its commercial culture began in South and Central America. Subsequent development of intensive breeding and rearing techniques led to its culture in Hawaii, mainland USA and much of Central and South America.
Habitat and Biology
The Whiteleg shrimp is native to the Eastern Pacific coast from Sonora, Mexico through Central and South America to as far South as Tumbes in Peru. It lives in tropical marine habitats and thrives in areas where water temperatures are normally >20 °C throughout the year. The adults live and spawn in the open ocean, while post-larvae migrate inshore to spend their juvenile, adolescent and sub-adult stages are in coastal estuaries, lagoons or mangrove areas. Males mature from 20g and females from 28g onwards at the age of 6–7 months. A female weighing 30–45g will spawn 100,000 to 250,000 eggs of approximately 0.22 mm in diameter. Hatching occurs about 16 hours after spawning and fertilisation. The first stage larvae, termed nauplii, live on their yolk reserves. The next larval stages eat phytoplankton and zooplankton, and are carried towards the shore by tidal currents. The post-larvae change their planktonic habit about 5 days after moulting into their post-larval stage, move inshore and begin feeding on worms, bivalves and crustaceans.
The recent expansion of prawn culture has generated many public debates over its impact on the environment and its sustainability:
- The use of protective mangrove ecosystems for pond construction.
- ‘Slash and burn’ style use of ponds for a few years before moving to new areas.
- Salinization of groundwater and agricultural land.
- Pollution of coastal waters by pond effluents.
- Overuse of marine meals leading to inefficient use of vital protein sources and the disruption of marine ecosystems.
- Biodiversity issues arising from collection of wild seed and broodstock and the introduction of non-native species and their attendant pathogens.
- Social conflicts with other resource users.
- Farm discharges, causing self-pollution in prawn growing areas.
Governments along with the prawn industry are trying to mitigate these impacts. New intensive systems that don’t require the use of tidal mangrove areas have allows some mangroves to be replanted. Culture technology in inland areas has been improved using minimal seawater and closed, lined systems to prevent salinization. Closed systems, together with better management practices are being utilised to prevent the pollution of coastal waters. Overfishing of wild seed and broodstock has been alleviated through domesticated stocking of Whiteleg shrimp.