Discrimination of coastal fish species based on morphology and DNA sequencing

The classification of species is essential in structuring our understanding of the world, but the existence of competing species concepts and diagnostic criteria makes the separation of similar species difficult.

These difficulties can be resolved through integrative taxonomy. Integrative taxonomy involves using multiple complimentary techniques to determine species boundaries and often includes a combination of phenotypic and genetic evidence. This integrated approach is crucial in discerning cryptic species, which are closely related species whose morphological forms are almost impossible to distinguish. Determining the presence of and boundaries between cryptic species is important as different species with different life history traits and strategies may require different conservation tactics.

This project aims to create an integrative taxonomic framework, using DNA barcoding and morphology of the body and otolith (earbone), to distinguish between cryptic species of fish. This framework will then be applied to the closely related species Hyporhamphus australis and Hyporhamphus melanochir, and subsequently used to assess whether H. melanochir is present in NSW landings. These species are two commercially harvested garfish from temperate Australian coastal waters whose distributions intersect in southern NSW. At present they can only be distinguished by variation in their numbers of gill rakers, making fishery identification and management difficult. Differences in their age and size at maturity makes finding more characters to distinguish these two species essential, as this will allow fisheries management to be tailored to the needs of both species and ensure stock sustainability.

NSW DPI-Fisheries has provided around 200 tissue & otolith samples and 100 whole fish for analysis from Western Australia, South Australia, Victoria, and New South Wales. Over the next few months, we will be working hard to photograph and quantify the shapes of otoliths, extract DNA for barcoding, and measure morphometric and meristic characters from these samples.

This study is being conducted by Indiana Riley under the supervision of Prof Iain Suthers from UNSW, John Stewart from NSW DPI, and Joseph DiBattista from the Australian Museum.