Integrating citizen science and telemetry techniques in understanding the movement patterns of the whale shark (Rhincodon typus)

Bradley Michael Norman

Since its inception in 1995, the whale shark photo-identification library that was developed for whale sharks at Ningaloo Reef (Western Australia) has burgeoned, with submissions from over 54 countries throughout the species global range and it has received more than 30000 encounter reports with sighting information and associated photographic images. In recent times, with the assistance of digital techniques, a global campaign to promote the library, and an increase in the number research active organisations utilising the library, has led not only to the identity of the world’s 20 ‘hotspots’ for whale shark aggregations, but to improved conservation measures for this internationally threatened species. The collation and analysis of such data has demonstrated the uniqueness of the different ‘population’ centres, inter-jurisdiction movement patterns within only adjacent sites, an absence of oceanic basin migrations, and has implied that many of the aggregations are comprised of individuals that show a strong affinity to that area, and some individuals return for decades. The population demographics of the various sites may be either homogenous or heterogeneous, including some sites which are seasonally used, while others have year-round residents. Some populations are dominated by juvenile males, while others may be entirely large females. Globally, more than 6000 individual whale sharks have been identified, with over 1000 identified from Ningaloo Reef, a location where contemporary belief was that the aggregation was extremely seasonal, occurring during the Austral autumn and winter. More than 8000 useable images of whale sharks were analysed from Western Australia, and a targeted campaign further assessed whale shark occurrences from 3000 km of the Western Australian coastline. This, coupled with satellite tracking and acoustic tracking, identified that not only are whale sharks found at Ningaloo throughout all months of the year, but the species within Western Australian waters has a strong site fidelity to Ningaloo during the main aggregation period, although individuals may roam north, west or south from Ningaloo and the species ultimately spans much of the State’s immense coast. Acoustic tracking further revealed that at Ningaloo, individuals remain relatively close to the outer reef edge, moving longitudinally. Satellite tracking and citizen science allowed the hypothesis to be tested that in Western Australian waters, individuals may be seeking other areas of high productivity outside of the predictable mass coral spawn at Ningaloo Reef, which has long been thought to be a significant driver of their build up in numbers during the Austral autumn. A number of the whale sharks photo-tagged in Western Australia have been ‘re-captured’ many times over a 21 year period (1995-2015), and these individuals have been studied at a time-scale that exceeds almost all other studies of individual fish. The continuation of the monitoring program of this long-lived species, together with the continued update of citizen science in the region, will in time reveal and help solve additional mysteries (including migration patterns and critical habitats) surrounding this enigmatic species.

Integrating citizen science and telemetry techniques in understanding the movement patterns of the whale shark (Rhincodon typus)

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