Prawns are aquatic organisms belonging to the order Decapoda. Characterized by ten legs and segmented bodies, these crustaceans are found across the globe in a wide range of aquatic environments. Exploring their diverse habitats reveals a complex life history tied to the salinity and physical characteristics of both marine and freshwater systems.
Defining Prawns and Their Primary Environments
The terms “prawn” and “shrimp” are often used interchangeably in commercial and culinary contexts. Scientifically, they are distinct: true prawns belong to the suborder Dendrobranchiata, while most shrimp are classified in the suborder Pleocyemata. This taxonomic difference is marked by anatomical features, such as branching gills and the way their body segments overlap. Prawns typically have a straight body compared to the shrimp’s curled shape.
Despite biological distinctions, both prawns and shrimp share broad environmental niches, found in both saltwater and freshwater. Prawns are distributed across two primary environmental types: marine (saltwater) and inland (freshwater) habitats. Most true prawn species live in marine environments, though a significant number, including the commercially relevant giant river prawn, spend their adult lives in non-saline waters.
Saltwater Habitats and Global Distribution
The majority of commercially harvested prawns are saltwater species, belonging to the family Penaeidae, which dictates their residence in coastal and oceanic zones. These species primarily occupy the benthic, or bottom, environment, preferring soft substrates such as sand and mud, where they can burrow for protection and forage for food. Their distribution spans the globe, particularly in tropical and subtropical regions where warmer waters support faster growth.
Major prawn fishing grounds are concentrated in areas with broad continental shelves and nutrient-rich waters. For instance, the Indo-West Pacific, which includes the coasts of Southeast Asia and Northern Australia, is a hotspot for species like the giant tiger prawn (Penaeus monodon). In the Americas, the Gulf of Mexico is known for its populations of brown, white, and pink prawns, which inhabit depths from shallow coastal areas to the edge of the continental shelf.
Prawns occupy a range of marine zones, from shallow intertidal areas to deep-sea environments. Deep-sea species, such as the royal red prawn, are demersal, living near the seafloor at depths reaching several hundred meters. Coastal areas and estuaries are important habitats. These mixing zones serve as nursery grounds for many juvenile marine species, utilizing lower salinity and protective mangrove roots before they migrate to the open ocean as adults.
Freshwater Prawn Environments
A distinct group of species, primarily those in the genus Macrobrachium, are known as freshwater prawns because they spend their adult lives exclusively in non-saline environments. The most prominent example is the giant river prawn (Macrobrachium rosenbergii), which is native to the Indo-Pacific region, from India to northern Australia. These prawns inhabit a variety of inland water bodies, including large tropical and subtropical rivers, lakes, and streams.
These freshwater species are often found in turbid conditions, preferring areas with dense vegetation or ample cover, such as submerged logs and rocky substrates. They are also widely cultivated in aquaculture ponds across the world, which mimics their natural, calmer water habitats. This reflects their preference for stable, warm water conditions outside the influence of strong ocean currents.
Habitat Requirements and Life Cycle Movement
Prawn habitation is influenced by substrate type, water temperature, and clarity. Most species thrive in warmer waters, which accelerates growth. However, certain commercial species, like the Northern prawn (Pandalus borealis), are adapted to the cold waters of the North Atlantic and Arctic Ocean. Substrate is a determining factor, as many prawns are burrowing organisms requiring fine, silty, or sandy bottoms for shelter.
The location of many prawn species is not static but changes throughout their life cycle, a process known as diadromy. Many species exhibit an amphidromous pattern: adults live and breed in freshwater rivers, but the newly hatched larvae require brackish or full-salinity saltwater to complete development. The giant river prawn exemplifies this. Gravid females migrate downstream to the estuary to release their eggs, and the post-larvae then migrate back upstream to mature into adults. This movement connects freshwater systems with the marine environment, making estuaries and river mouths a temporary but important location for many prawn populations.