Identification of hairy, smooth and hybrid marron (decapoda: parastacidae) in the Margaret River: morphology and allozymes

The critically endangered hairy marron, Cherax tenuimanus, is endemic to the Margaret River, Western Australia, and is under the threat of extinction due to its rapid replacement by the introduced smooth marron, Cherax cainii. Cherax tenuimanus now only occurs in sympatry with C. cainii and is almost exclusively found in pools in the forested upper reaches of the Margaret River. An important component of the conservation effort to preserve the hairy marron involves the removal of smooth and hybrid marron, which in turn requires accurate identification. Four allozyme markers (esterase, and three peptidase loci) that can genetically distinguish hairy, smooth, and hybrid marron were used to test the accuracy of field identifications based on diagnostic morphology of individuals (principally the nature of the median carina and the setae on the carapace). Results show that C. tenuimanus can be readily distinguished from hybrids (F1 and backcrosses) and C. cainii using morphology alone. Consistently distinguishing between C. cainii and hybrids was more difficult in the field, but this will be of lesser importance for management operations. A field guide for marron in the Margaret River can be produced to ensure correct identification of C. tenuimanus and permit community involvement in conservation efforts aimed at removing C. cainii and hybrids, and assisting the recovery of the C. tenuimanus population.