The quest for cryptic creatures: Impacts of species-focused recreational diving on corals

Coral reefs are popular with ecotourists, but the impact of divers on reefs is cause for concern. In this study, we assessed the damage to corals caused by divers seeking cryptic but charismatic fish such as seahorses (family Syngnathidae) and frogfishes (Antennariidae), which are found on reefs around the world. These fish are closely associated with the reef substratum, thus bringing divers into close proximity to coral. We found that when in the vicinity of frogfish and seahorses, divers made unintentional contact with corals significantly more often and for longer periods than when these species were absent. This change in diver behaviour resulted in a greater frequency of coral breakage and scarring at seahorse/frogfish sites than at ecologically equivalent control sites. However, the spatial extent of damage appeared limited. Beyond 1–3 m from the seahorse or frogfish, coral breakage and scarring rate decreased to levels similar to those of control sites. None of the coral species, which suffered the most damage, was particularly rare, suggesting that the habitat conservation concern of these marked shifts in diver behaviour is limited. Nevertheless, the use of pre-dive briefings and smaller dive group sizes could minimise the damage caused by divers approaching cryptic species of interest near the reef.