The Seasonal Aggregation of Whale Sharks at Ningaloo Reef, Western Australia: Currents, Migrations and the El Niño/ Southern Oscillation
- 823 Downloads
Whale sharks, Rhincodon typus, seasonally aggregate in coastal waters off Ningaloo Reef, Western Australia. We review the oceanographic setting of the region and present evidence that such aggregations form as a result of migratory behavior associated with climatic and oceanographic processes. We utilise records of whale shark abundance collected at Ningaloo Reef from dedicated searches by boat and aircraft and from log sheets recorded by the tourism industry. Measures of whale shark abundance derived from log sheet data sets were moderately correlated with the Southern Oscillation Index and weakly correlated with coastal sea level, an index of the strength of the Leeuwin Current, and sea surface temperature over the period 1993 to 1998. Abundances of whale sharks derived from boat searches from 1983 to 1992 were also correlated with fluctuations in the Southern Oscillation Index, except during a three year period from 1988 to 1990. We conclude that, at least in some years, there appears to be a link between the abundance of aggregating whale sharks and the physical and biological oceanography of the region, with greater whale shark numbers in La Niña years. The lack of correlation in other years may be due to a combination of uneven quality of data and/or aggregations occurring in response to a complex interaction between the physical and biological oceanography of the region.
Unable to display preview. Download preview PDF.