Quantity and quality of prey available for the whale shark (Rhincodon typus, Smith 1828) at the Mexican Caribbean aggregation site

Abstract

Prey availability is the major driver of the presence of whale sharks in the aggregation sites around the world. The northern Mexican Caribbean is one of the most important feeding sites for the whale shark (Rhincodon typus, Smith 1828), at which two sources of food are available. Trophic ecology concepts considers that the organisms should satisfy their energy requirements taking not only abundant food but also of good quality. However, scarce studies have been conducted to explorer trophic preferences. Therefore, the aim was to assess the energy density of zooplankton (quality) and zooplankton biomass (quantity) and its spatial and temporal variation related to the whale shark aggregation. Marine surveys were conducted around the three historic zones of more whale sharks sighted, between June and September 2016 to measure physic-chemical parameters, collect zooplankton samples, record whale shark and calorimetric analysis from zooplankton were performed. The whale shark distribution and abundance were mostly regulated by food quantity composed mainly by fish eggs, evidencing the food quality as a lesser factor. However, analyzing food with whale shark presence, the quality food was relevant around July and September when good quality and quantity food was available. Which jointly allowed the largest aggregation of whale sharks. A relationship between these parameters should be constantly evaluated to better understand the trophic function, as also a thermodynamic approach is recommended to be included in future whale shark monitoring.