Collaborative photo-identification and monitoring of grey nurse sharks (Carcharias taurus) at key aggregation sites along the eastern coast of Australia

Abstract

Before the worldwide decline of the ‘globally vulnerable’ Carcharias taurus may be addressed, an understanding of its migratory patterns and locations, and/or times when sharks may be vulnerable, is required to identify habitats that are critical to its survival. A collaborative framework for photo-identification and monitoring of C. taurus may greatly assist with conservation management initiatives. Images of C. taurus were sourced from public submissions to the www.spotashark.com (verified 12 February 2009) website and during targeted surveys. A computer-assisted program (I3S) was used to match the images of sharks photographically from the database. Research revealed patterns of movement, site utilisation and population structure similar to those in previous tagging studies. With the use of an underwater camera and two laser-scaling devices, 408 individual sharks were identified. Average occupancy times at two locations in New South Wales (NSW), Australia, were 308 days (Fish Rock) and 363 days (Magic Point). Seventeen individuals undertook northward or southward movements, averaging 350 km. The present study showed that a broad-based technique for data acquisition, coupled with rigorous evaluation of photographic identifications can provide support for local research and management programs and may aid with the conservation of the C. taurus species worldwide.