The functional trophic role of whale shark (Rhincodon typus) in the northern Mexican Caribbean: network analysis and ecosystem development

Abstract

The whale shark (Rhincodon typus) has a high value to tourism, fishing, and pharmaceutical industry, but this species is considered as vulnerable and with potential extinction. The largest aggregation of whale sharks occurs in an upwelling system (Holbox) at northeastern Mexican Caribbean, where we analyzed the trophic role of whale shark. A mass-balanced trophic model was built to: (1) analyze the ecosystem emergent or macroscopic properties; (2) estimate the system recovery time (resilience); (3) assess the fishery effects on different target species; and (4) evaluate the whale shark systemic role in this system. The results showed that the macroscopic properties of the Holbox ecosystem were similar to other upwelling systems with high rates of primary productivity and accumulated biomass in lower trophic levels. Even so, the food web was more like the structure of coral reefs. On the other hand, Holbox system had a lower maturity and development level than coral reefs, suggesting an increased resistance to disturbances. The mixed trophic impacts and short-term dynamic simulation showed that species like snook, sharks, groupers, benthic autotrophs, small benthic epifauna, and phytoplankton had the largest direct and indirect effects. The most significant systemic role of whale sharks is to provide the resilience of the system.