Originally, Edgar Riek described two giant spiny crayfish species, firstly in 1956 E. spinosus from the upper reaches of the Hastings River, New South Wales, then secondly in 1969 E. clydensis, from a side stream of the Clyde River near Brooman, and paratypes from near Conjola, New South Wales.

Euastacus clydensis
Clyde Giant Spiny Crayfish Euastacus clydensis

Morgan (1997) revised the taxonomy of Euastacus; more recent sampling indicated continuous morphological variation between E. spinosus, E. spinifer and E. clydensis, this led to Morgan considering all three species to be synonymous. In 1997 he syonymised E. clydensis into Euastacus spinifer (Heller, 1865).

Euastacus clydensis
Euastacus clydensis from tributary of Clyde River

Fortuitously, we had done a huge amount of surveying of both the Shoalhaven and Clyde river basins as well as the more unusual sites like Beecroft Peninsular. This surveying as part of the Australian Crayfish Project supplied a broad Euastacus spinifer sample from this southern region for genetic analysis.

Euastacus clydensis from Clyde River
Snorkelling surveys for Euastacus in the Clyde River

An extensive molecular phylogenetic and population genomic analysis of Euastacus spinifer sensu lato from across its geographical range revealed strong population structure corresponding to several major geographically correlated clades, the southernmost clade being the most genetically divergent (Van Der Wal et al. 2022).

In Van Der Wal et al. 2022, we formally remove E. clydensis from the synonymy of E. spinifer, increasing the recognised number of species of Euastacus. With formal recognition of E. clydensis as a valid species separate from E. spinifer, we increase the number of Euastacus species to 54

Euastacus clydensis
Euastacus clydensis is a giant group crayfish with females breeding 4-5 times over a 5 year period

Euastacus clydensis ranges from the Southern Highlands in the vicinity of Moss Vale (~35°S), south to the vicinity of Batemans Bay (~35.6°S) in the southern Shoalhaven and Clyde River drainages

Euastacus clydensis habitat
Typical Euastacus clydensis habitat (clear flowing streams)

For Further Information see:

Wal, Cara Van Der, Ahyong, Shane T., Lo, Nathan, Ho, Simon Y. W. & McCormack, Robert B., 2022, Redescription of Euastacus clydensis Riek, 1969 (Crustacea: Parastacidae), a valid species of spiny crayfish from southern New South Wales, Australia, pp. 285-297 in Zootaxa 5222 (3): https://doi.org/10.11646/zootaxa.5222.3.6




Robert McCormack is the Research and Aquaculture Director for Australian Aquatic Biological P/L. He is a Research Associate with the Carnegie Museum in Pittsburgh, USA, is Secretary of the Aqua Association Incorporated https://www.aqua.asn.au/ and the team leader of the privately funded Australian Crayfish Project, which conducts biological studies of every creek and stream in Australia, collecting and identifying crustaceans. Robert has a passion for freshwater crayfish traveling across Australia to find and photograph them.