New records of sea snakes at mid-shelf shoals of Australia’s North West Shelf

Abstract

Offshore reefs of the North West Shelf of Australia support the most diverse and abundant sea snake communities in the world. Ashmore Reef (12° 17′S, 123° 02′ E) is the regional centre of diversity hosting 17 species, including two endemics (Rasmussen et al. 2011; Elfes et al. 2013). However, over the last decade the diversity and abundance of sea snakes at Ashmore Reef have declined drastically. In 2010, only two species (Aipysurus laevis, Astrotia stokesii) were observed and at least five species are now presumed locally extinct (Lukoschek et al. 2013). Here we report on a 2013 survey of Ashmore Reef where, despite extensive boatbased searches over nine days and SCUBA-surveys encompassing 12 ha of reef and lagoonal habitat, no sea snakes were encountered. Identifying the causes of sea snake declines at Ashmore Reef is hampered by a lack of distributional data. To address this, we recorded sea snakes at four previously unsurveyed North West Shelf shoals, namely Echuca, Eugene McDermott, Heywood, and Vulcan, which occur approximately 150–200 km SSE of Ashmore (Fig. 1). Three species were observed (Fig. 1): Aipysurus laevis at Heywood, EugeneMcDermott and Vulcan (one individual at each); Emydocephalus annulatus at Echuca (two individuals) and Heyward (one individual); and the Australasian endemic Aipysurus duboisii at Vulcan (two individuals). These shoals are permanently subtidal (20 m+deep) of consolidated low-relief coral and calcareous algae interspersed with extensive rubble fields. Snakes were seen feeding or resting at 20–25 m or ascending/descending. All three species were also sighted at Hibernia Reef (~30 km NE of Ashmore). Given local extinctions at Ashmore and the demonstrated potential for introgressive hybridisation among Aipysurus spp. in the Timor Sea (Sanders et al. 2014),