Shrimps, Prawns and Mangroves

Shrimp Farming can lead to Habitat Destruction

Sep 17, 2008 John Blatchford

Mangrove swamps in estuaries are cleared to provide lagoons to raise shrimps.

Farming Giant Tiger Prawns and White-leg Shrimps often involves the destruction of mangrove swamps, while farming the Giant River Prawn appears to have much less environmental impact. The life histories and ecological requirements of these creatures explain this difference.

The Difference Between Shrimps and Prawns

Both shrimps and prawns are decapod crustaceans (see 'Invertebrate Classification'), but the prawns belong to the sub-order Dendrobranchiata, with branched gills, while the shrimps have flattened gills and are in a different sub-order. Common names can be misleading – for example the Giant River Prawn (Macrobrachium rosenbergii) is in fact a shrimp, whereas the White-leg Shrimp (Litopenaeus vannamei) is a prawn! Of the three species discussed here only the Giant Tiger Prawn (Penaeus monodon) is correctly named – being a true prawn.

Environmental Effects of Shrimp and Prawn Farming

Tiger Prawns and White-leg Shrimps (both Prawns) mature and breed only in a marine habitat. In the wild, the developing young migrate into estuaries where they feed in the nutrient-rich water. As they approach adulthood they migrate back into the sea to complete the cycle. Shrimp farms developed during the 1980s and 1990s, and led to the clearing of large areas of mangrove swamp in estuaries (to create brackish water lagoons).

Giant River Prawns (or Malaysian Prawns) live in fresh water, but the young need the brackish water of estuaries. Curiously there are three different types of males. One never grows very big, another grows to full size, and a third grows large and develops blue claws. These ‘blue-claws’ dominate the others, and will often eat them. For this reason Giant River Prawns can only be raised ‘extensively’ – with light stocking levels. Add to this the fact that they are raised in fresh-water lagoons (no clearing of mangroves required) and it becomes clear why their farming has less serious environmental impact. (This shrimp/prawn (Macrobrachium rosenbergii) can be successfully raised in outdoor ponds and, since young are readily available for sale on the Internet, it is often kept by amateurs in the United States.)

Mangrove Swamps

Coral Reefs are in serious trouble, and Mangroves and Seagrasses are important for their wellbeing. Unfortunately many shrimp-farms around the world have been created by clearing large areas of mangrove swamp. July 26th 2003 was ‘International Day of the Mangroves’, and did much to publicise the problem. (See ‘Mangrove Action Project’ for more information about the harmful effects of shrimp-farming.)

The copyright of the article Shrimps, Prawns and Mangroves in Marine Biology & Oceanography is owned by John Blatchford. Permission to republish Shrimps, Prawns and Mangroves in print or online must be granted by the author in writing.

Steamed Shrimp