Crayfish, also known as crawfish, crawdads, or freshwater lobsters, are crustaceans resembling small lobsters. They inhabit a variety of aquatic environments across the globe and play crucial roles in maintaining the health and balance of freshwater ecosystems, though some species can also be found in brackish and saltwater. Current estimates indicate the existence of upwards of 650 species of crayfish worldwide.
For the most part, crayfish live in freshwater habitats such as streams, rivers, lakes, ponds, and marshes. They are widely distributed across the world, with crayfish species being found on every continent except Antarctica and mainland Africa. Families like Astacidae and Cambaridae are prevalent in the northern hemisphere, with particularly concentrated populations in North America. The southeastern United States, for instance, is home to over 330 species across 15 genera. Australia, meanwhile, is home to some of the world’s largest freshwater crayfish species, such as the Tasmanian giant freshwater crayfish (Astacopsis gouldi), which can weigh more than 5 kilograms.
Crayfish are integral components of freshwater ecosystems, as they function both as predators and prey. They are omnivorous and thus consume a wide range of organic materials, including detritus, aquatic vegetation, and small invertebrates. Their feeding behaviours support nutrient cycling and the decomposition process, both of which improve water quality in their habitats.
In addition, crayfish act as ecosystem engineers. They are frequent burrowers, and their digging can influence sediment composition and water flow, which can eventually create microhabitats for other aquatic organisms. In this way, healthy crayfish populations promote greater biodiversity within their environments.
Crayfish populations are vulnerable to a range of human-induced and ecological threats, such as:
Crayfish are valued highly in many places for economic, culinary, and cultural reasons. In the United States and parts of Europe, they are a regional delicacy and feature prominently in festivals and traditional dishes. Both freshwater and marine crayfish (often referred to as rock lobsters) support valuable commercial fisheries in Australia and New Zealand. Crayfish are also used in scientific research and education as model organisms due to their manageable size and behaviour.
In addition to their commercial value, crayfish play an important ecological role. For instance, in northern Aotearoa, New Zealand, the decline of crayfish populations has been linked to the spread of the invasive long-spined sea urchin (Centrostephanus rodgersii). This species is rapidly degrading kelp forests, which serve as critical habitats for a range of marine life.
Crayfish contribute to nutrient cycling, water quality, and the overall stability of the food web—all of which are vital for keeping freshwater ecosystems healthy. Many crayfish species are accurate indicators of the health of the surrounding environment; declining crayfish populations are often telltale signs of broader ecological stress. Conservation also helps preserve the cultural and economic value of crayfish in regions where they are an important resource.
Because many freshwater systems flow into estuaries and coastal waters, protecting crayfish and their habitats also contributes to the health of connected marine environments. Efforts to maintain the integrity of these upstream systems help reduce sedimentation, nutrient runoff, and other pressures that compromise ocean health. Advances in environmental monitoring—such as Dr. Arie Spyksma’s use of Seascape technology to capture 3D models of the seafloor in Aotearoa, New Zealand—are helping scientists better understand changing ecosystems, which is key to safeguarding species like crayfish and the habitats they depend on.
Individuals and communities can support crayfish conservation by working to reduce threats to freshwater and marine ecosystems and participating in science-led restoration efforts. Advocating for more policies on sustainable water use, control of invasive species, and pollution reduction are all helpful places to start. In New Zealand, for instance, New Zealand Geographic is currently working with Live Ocean and the BLAKE Trust to lobby for more extensive protections for the Hauraki Gulf, where crayfish were once among its most abundant species but where they are now functionally extinct. The primary goal of this partnership is to convince the national government to increase no-take marine protection in the country to 30% by 2030. Read more about what’s at stake here.
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