Prawns are aquatic crustaceans found globally in a wide variety of aquatic environments. Their habitat is incredibly diverse, depending on the specific species.
Marine Environments
Many prawn species inhabit saltwater environments across the globe. They are found from shallow coastal waters, such as seagrass beds, sandy flats, and rocky shores, to the deep sea, including abyssal plains and hydrothermal vents. These marine prawns occupy diverse substrates, including muddy bottoms, sandy seabeds, rocky crevices, and vibrant coral reefs.
Tiger prawns, for example, are found in tropical and subtropical waters, often inhabiting coastal areas down to 200 meters, with adults preferring coarse sediments. The Pacific coast of North America, from Alaska to Southern California, also hosts significant prawn populations, typically at depths of at least 70 meters.
Freshwater Environments
Some prawn species live solely in non-saline conditions, making freshwater bodies their home. These crustaceans are found in rivers, lakes, streams, ponds, and even certain freshwater swamps. They tolerate a wide range of environmental conditions, with some preferring clear, flowing water while others thrive in more stagnant settings.
The Giant River Prawn, Macrobrachium rosenbergii, is native to tropical and subtropical Indo-Pacific regions. While primarily freshwater inhabitants, some species within the Macrobrachium genus can tolerate brackish water conditions during certain life stages. These prawns are often nocturnal and omnivorous, feeding on algae, detritus, and small invertebrates.
Brackish Water Environments
Brackish water environments, where freshwater and saltwater mix, are important habitats for many prawn species. These areas include estuaries, river deltas, mangrove forests, and coastal lagoons. Such environments offer fluctuating salinity levels and rich nutrient content, supporting diverse prawn populations.
Many marine prawn species utilize these transitional zones as nursery grounds during their juvenile stages before migrating to the open ocean. Some prawn species spend their entire lives in brackish water, demonstrating a high tolerance for salinity changes. Black tiger prawns, for instance, grow optimally in warm brackish waters with salinities between 15-20 parts per thousand, though they can survive briefly in freshwater.
Factors Influencing Prawn Distribution
Prawn distribution is determined by environmental and biological factors that vary among species. Substrate preference is a key factor, as different prawns require specific seafloor or riverbed types for burrowing, hiding, or clinging to vegetation. For example, adult brown tiger prawns prefer coarse sediments, while grooved tiger prawns favor fine mud.
Water parameters, including temperature, salinity, dissolved oxygen, and pH, are important in defining where prawns can thrive. Black tiger prawns, a tropical species, achieve optimal growth in water temperatures ranging from 25-30°C. Food availability, such as the presence of algae, detritus, or small invertebrates, directly influences where prawns are found. Predator avoidance and the need for shelter also drive habitat selection, with prawns often seeking refuge in dense vegetation or sediment.