The Tasmanian Giant Freshwater Crayfish (Astacopsis gouldi) is the world’s largest crayfish species and the biggest known freshwater crustacean. This imposing invertebrate is sometimes referred to as a freshwater lobster due to its immense size.
The World’s Largest Crayfish Species
Historical accounts confirm the Tasmanian Giant Freshwater Crayfish has attained monumental dimensions. The species has been reliably reported to reach weights of up to 6 kilograms (approximately 13 pounds). Record-breaking individuals have also been measured at lengths exceeding 80 centimeters (about 31 inches), though specimens of this magnitude are now exceedingly rare.
The common name is the Giant Freshwater Crayfish, but it is also known locally as the Giant Freshwater Lobster. Due to the sheer scale of the animal, the term “lobster” is often used in casual conversation. However, due to decades of overfishing and habitat degradation, the species has declined significantly. Today, a specimen weighing 2 to 3 kilograms (4.4 to 6.6 pounds) is considered exceptionally large in the wild.
Geographic Range and Unique Habitat
This massive crayfish is found exclusively in the rivers and streams of northern Tasmania, making it an endemic species. Its geographic range is limited to waterways that drain into the Bass Strait, typically below 400 meters above sea level. The species’ survival depends entirely on a highly specific and pristine aquatic environment.
The required habitat must feature high-quality water that is cold, clean, and highly oxygenated, with very low levels of suspended sediment. Adult crayfish prefer deep, slow-moving pools for shelter beneath submerged logs and within stable, undercut riverbanks. The stringent need for clean water means that habitat loss remains one of the greatest threats to its continued existence.
Biology of Extreme Growth
The reason Astacopsis gouldi achieves such impressive size is directly linked to an exceptionally slow growth rate and an extended lifespan. Unlike most smaller crayfish species, this giant can live for a remarkable period, with individuals known to survive for up to 60 years. This longevity provides the necessary time to accumulate the body mass required to reach its maximum size.
The reproductive cycle is also characterized by a slow, deliberate pace, which contributes to its vulnerability. Females do not reach sexual maturity until approximately 14 years old, while males mature around 9 years of age. Females only breed once every two years, carrying the fertilized eggs attached to their tail for about nine months. Growth in crustaceans only occurs after molting, and the largest adults molt very infrequently. This combination of long lifespan, late maturity, and infrequent reproduction places the species in a precarious position, reflected in its classification as Endangered.