Unwedging the Secrets: Species and Genetic Diversity of Wedgefishes (Rhinidae) in Malaysian Waters

Abstract

The wedgefishes (Rhinidae) stand out as one of the most endangered marine lineages due to the conjunction of shallow coastal habitats, slow growth, low fecundity and high fishing pressure. The Indo-West Pacific region, including Malaysia, is of particular interest as it hosts a large share of the wedgefish diversity. Here, we shed light on the species and genetic diversity of wedgefishes found in Malaysian waters. A total of 85 Rhynchobatus samples were collected at 15 locations over 7 years across Malaysia and were identified using both morphological characters and genetics. We highlight the difficulty in identifying species based on morphological characters alone, and that molecular confirmation was needed for ambiguous specimens. Rhynchobatus australiae, broadly distributed across coastal Malaysia, represented a large fraction of the samples (87%), followed by R. palpebratus (11%) and a single R. springeri individual. The occurrence of R. palpebratus is a new record for this species in Malaysia and indicates a wider distribution than previously thought. Population genetic analysis within R. australiae revealed fine-scale structuring within the Strait of Malacca, notwithstanding the fact that this is a relatively small and shallow waterway that does not obviously hinder the movement of R. australiae along the coast. These results reinforce the importance to manage and protect these species and populations in Malaysian waters.