Fresh Insights into Freshwater Whiprays:
Reproductive Biology and Spatial Ecology of the Freshwater Whipray (Urogymnus dalyensis)

Although most elasmobranchs are marine, approximately 56 species (~5% of all described elasmobranchs) regularly utilise freshwater environments. Despite occupying habitats distinct from their marine counterparts, they exhibit similarly slow life-history strategies, such as late maturity and low fecundity, which can constrain recovery potential. This is further compounded by fragmented distributions, high endemism, and increasing anthropogenic threats. Consequently, ~64% of assessed species are listed as threatened on the IUCN Red List, yet critical gaps remain in the biological and ecological data required for effective conservation.

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Reproductive biology remains one of the least understood aspects of these species. Key traits such as size at sexual maturity are essential inputs for demographic models used to estimate extinction risk and recovery potential. However, traditional methods for assessing female maturity rely on lethal sampling. Although advances in non-lethal approaches, including hormone analysis and ultrasonography, offer promising alternatives, their application across freshwater and euryhaline elasmobranchs remains limited.

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The freshwater whipray (Urogymnus dalyensis) is the only Australian stingray known to inhabit both freshwater and estuarine environments. Despite its Least Concern classification, published data on its reproductive biology remain limited, and its spatial ecology has been examined in only a single study. This presents an opportunity to establish baseline data for U. dalyensis, whilst assessing the feasibility of non-lethal techniques, with applications for conserving threatened freshwater and euryhaline elasmobranchs globally.

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Therefore, this project aims to estimate size at sexual maturity using non-lethal techniques and integrate these thresholds into species distribution models to predict habitat suitability across reproductive stages.