ABSTRACT1. Worldwide, there are concerns about the potential impact of a growing tourism industry on the behaviour and ecology of sharks. Several shark species are key attractions in the scuba diving industry in both the Gala´pagos Marine Reserve (Ecuador) and the Sanctuary of Fauna and Flora Malpelo (Colombia).2. In this study, the reactions of five species of shark to the behaviour of scuba divers were investigated in the Gala´pagos and Malpelo.3. Four discrete categories of shark reaction (evasion, spontaneous approach, alert and no reaction) were identified and analysed against five categories of diver behaviour (direct approach, camera flash, sudden movement, noise and simple presence), two categories of observation strategy (still and movement) and the distance of the focal diver group to the sharks.4. The type of reaction in the sharks was determined by the behaviour of the divers, their distance to the fish and, especially, by their observation strategy. Shark reactions varied between species and locations and divers acted more intrusively towards those species they were not afraid of, and which they could access more easily due to the conditions of their environment.5. 'Direct approach', 'sudden movement', the observation strategy 'moving' and distances closer than 4 m between divers and sharks elicited stronger behavioural responses by the species targeted. Recommendations are given for the preferred actions divers should employ in order to diminish the effects on the target species analysed in this study.

This study focused on the short-term reactions of six key species (Taeniura meyeri, Aetobatus narinari, Triaendon obesus, Chelonia mydas, Phalacrocorax harrisi, and Zalophus californianus) during tourism activities (SCUBA diving, panga-ride, snorkeling, and hiking) at 16 tourist sites on the islands. For each species we recorded its behavior when first encountering tourists and its reaction following this encounter. A Correspondence Analysis revealed that the type of reaction of the species depended significantly on the type of touristic activity, with the exception of the black spotted and eagle rays. Moreover, the analysis showed that, for each species, the different tourist activities were significantly associated with particular animal activities. This suggests that the species analyzed are susceptible to specific tourism activities making it necessary to instate recommendations for management in order to guarantee sustainable ecotourism.