3.2.1 Diversity, abundance and habitat of sharks and rays

Description

This research project aims to characterise the diversity, abundance and spatial dynamics of sharks and rays within different habitats and zones in the Ningaloo Marine Park (NMP) to provide a baseline for developing management strategies and assessing ecotourism potential for these species.

It has identified critical habitat and aggregation sites and examined habitat use through movement patterns and activity space. This has allowed assessment of the adequacy and representativeness of zoning and development of management targets for sharks and rays.

This aligns directly with specified priorities of the Ningaloo Research Program under A1.4 ‘Large marine fauna biodiversity assessments’ and requirements of the Ningaloo Marine Park Research and Monitoring Plan under sharks and rays.

Aims

• To investigate elasmobranch faunal composition of the Ningaloo Marine Park and determine the distributions and abundances of species
• Determine habitat requirements of species and identify those habitats critical to potentially vulnerable species
• Compare the species composition, abundance and size structure between adjacent management zones
• Examine the habitat utilisation, movement patterns and activity space of selected key species
• Determine times and sites where certain species aggregate, with particular reference to existing and proposed management zones
• Identify candidate sites and species for ecotourism development

Methods

• Snorkel and SCUBA underwater visual surveys were conducted as part of for field trips to Ningaloo
• Between 1- 4 swimmers spread equally at a distance based on water visibility swam in one area and the swept area was calculated by recording start and finish positions via GPS and time as well as visibility and depth.
• Sites were chosen to cover major habitat types and different management zones (sanctuary versus non-sanctuary)

Outcomes

• Forty two species (25 sharks, 17 rays) were documented from the Park, 118 species are estimated to be present in the NMP at certain times making it an area of high diversity
• Although mangrove areas are limited at NMP, the sand and mangrove habitat had the highest sighting rate for elasmobranchs of any of the 11 habitat types.
• Sightings in the lagoon and at the reef edge of all elasmobranchs combined, and of nine out of the ten most commonly seen species, were higher in sanctuary zones than in non-sanctuary zones
• Aggregation sites were documented for one shark (C. melanopterus) at Pelican Point in April, and two ray (G. typus and P. atrus) species at Mangrove Bay, Point Cloates, Pelican and Winderabandi Point, all in sanctuary zones. The C. melanopterus, and two of the G. typus,aggregations were of neonatal fish suggesting that these may be nursery areas. However, further work is needed to determine the consistency of these aggregation events.

Reports

Cerutti-Pereyra F., Thums M., Austin C. M., Bradshaw C. J. A., Stevens J. D., Babcock R. C., Pillans R. D., Meekan M. G. (2014) Restricted movements of juvenile rays in the lagoon of Ningaloo Reef, Western Australia – evidence for the existence of a nursery. Environ Biol Fish 97, 371–383. .doi.org/10.1007/s10641-013-0158-y