3.1.4 Population monitoring protocols for whale sharks

Description

This report reviewed current monitoring methods, highlighted viable data collection and analysis techniques, and developed new protocols for genetic analysis to assist in understanding the population structure of whale sharks at Ningaloo Reef.

Outcomes from demographic analysis based on photo-identification were presented, along with new techniques for individual identification and validation.

Ongoing results and analysis of satellite tagging that describes migration pathways and behaviour of whale sharks participating in the Ningaloo aggregation was described. The results have been placed in context by analysing historical records of whale shark sightings.

The overarching aim was to provide researchers and managers with the necessary context, information and tools to manage the Australian population of whale sharks on a regional and global scale.

Aims

• Review current monitoring methods and highlight viable data collection and analysis techniques.
• Develop new protocols for genetic analysis to assist in understanding the population structure of whale sharks at Ningaloo Reef.
• Use photo-identification techniques as a basis for mark-recapture and demographic analyses of population and stock structure.
• Use satellite tagging techniques to document migration and diving patterns and to compare these to environmental variables such as water temperature and ocean productivity
• Analyse historical databases of whale shark sightings provided by ecotourism operators to determine how abundances of sharks are influenced by oceanographic phenomena and trends in population composition and abundance through time.

Methods

• Conventional fish tags
• Photo identification, computer assisted image identification matching
• Tissue sampling; faecal material, Biopsy spear, microplane skins sampling,
• Satellite tracking; satellite tags, Fin tags, Pop-up Archival Satellite Tags (PSAT),
• Genetic sampling, microsatellite library construction
• Genomic analysis for population genetic structure research
• Population size estimates and demographic modelling
• Splash tags recording; maximum depth, dive duration, time at temperature and time at depth

Outcomes

• The limited knowledge and fragile status of whale sharks necessitates the monitoring of populations with a variety of techniques to ensure that information pertinent to their survival is collected reliably and accurately. Current methods of observation are providing valuable information on the biology and ecology of whale sharks, which is essential for estimating population demographics. These studies then act as the scientific underpinning for informed and effective management strategies.
• mark-recapture analysis based on photo-identification is possibly the simplest and most reliable means of collecting extensive demographic data for population monitoring.
• The majority of the decline of whale sharks at Ningaloo is driven by reductions in the number of large individuals in the population
• Reductions in whale shark populations have occurred despite the total protection of whale sharks in Australian waters
• Despite the vital information about long distance migrations obtained by splash tags , satellite tagging does have limitations arising from the short period tags are deployed for.
• Ongoing work that uses photo-identification libraries to compare the extent of interchange among major whale shark aggregations in the Indian Ocean is also essential
• Genetic information confirms the long-distance dispersal of whale sharks.
• The global pattern of shared haplotypes in whale sharks, long distance patterns of dispersal and declines in abundance of sharks at Ningaloo despite their complete protection in Australian waters are compelling arguments for development of broad international approaches for management and conservation of whale sharks.