Distribution and feeding habitat characterization of whale sharks Rhincodon typus in a protected area in the north Caribbean Sea.

The relationship between the distribution of the whale shark Rhincodon typus and hydrobiological variables in the Caribbean Sea during 2005-2009 was analysed. Monthly trips were made to the R. typus aggregation area during the months when this species is present in the region (May to September) to record sightings and hydrological data and to collect samples to determine nutrients, chlorophyll a (Chl a) and zooplankton biomass. A total of 2104 R. typus were counted and three zones of high abundance were identified: Cabo-Catoche, Contoy (both within the Whale Shark Biosphere Reserve, WSBR) and the zone knows as Afuera. The zones of greatest R. typus density within the WSBR were characterized by high Chl a concentrations (median: 1·1 mg m-3 , interpercentile range: 0·5-1·8 mg m-3 ) and high nutrient concentrations, such as ammonium (median: 2·5 µmol l-1 , interpercentile range: 0·5-6·4 µmol l-1 ), due to the influence of local upwelling. A generalized additive model (GAM) was used to explore the relationship between R. typus distribution and the environmental variables inside WSBR. Zooplankton biomass was the most influential environmental variable, supporting the close relationship between R. typus distribution and biological productivity. Copepods were the dominant zooplankton group within the WSBR. In the Afuera zone, there were large R. typus aggregations (>80 individuals) associated with zooplankton dominated by fish eggs and significantly higher mean ± s.d. biomass (3356·1 ± 1960·8 mg m-3 ) compared with that recorded inside the WSBR (103·5 ± 57·2 mg m-3 ). The differences among zones generated changes in R. typus distribution patterns and provided opportunities to develop local management strategies for this species.