No persistent behavioural effects of SCUBA diving on reef sharks

Abstract

Despite rapid growth in the marine tourism sector, the impacts of recreation on the marine environment are generally not well understood. Most existing studies of marine recreation ecology have focused on behavioural changes resulting from direct interactions between humans and wildlife including provisioning. However, non-consumptive, non-provisioning human impacts may also result in persistent behavioural impacts to shark populations. In this study, we examined differences in residency, abundance, and behaviour of reef sharks at Palmyra Atoll in response to long-term SCUBA diving activity, using a combination of survey techniques including baited remote underwater video systems and multi-year passive acoustic monitoring. In most locations with recreational diving operations, some level of human impact is pervasive, but on Palmyra, extractive fishing is prohibited, and scientific diving activities are concentrated on just a few sites that house long-term monitoring projects. These sites experience relatively intensive diving, while the majority of the island is entirely undived. Evidence from elsewhere has shown that sharks behaviourally respond to people in the water over short time scales, but our results indicate that this response may not persist. We did not detect differences in reef shark abundance or behaviour between heavily dived and undived locations, nor were there differences in shark residency patterns at dived and undived sites in a year with substantial diving activity and a year without any diving. Our results suggest that humans can interact with reef sharks without persistent behavioural impacts, and that well-regulated shark diving tourism can be accomplished without undermining conservation goals.

Reef accessibility impairs the protection of sharks

“…For instance, fishing shark preys and human disturbance can impact shark fitness, richness and abundance (Bejder et al., ; Williams, Lusseau, & Hammond, ). The increase in the number of recreational users in no‐take areas within the south‐west lagoon in the past 10 years supports the human disturbance hypothesis (Gonson et al., ), even though Bradley, Papastamatiou, and Caselle () suggest that shark behaviour is not affected by SCUBA divers.…”

“…Shark fishing is historically absent in New Caledonia with almost no reported commercial catch in the last 14 years so recreational shark fishing is considered unlikely ( Hammond, 2006). The increase in the number of recreational users in no-take areas within the south-west lagoon in the past 10 years supports the human disturbance hypothesis (Gonson et al, 2016), even though Bradley, Papastamatiou, and Caselle (2017) (Maire et al, 2016).…”

Drivers of reef shark abundance and biomass in the Solomon Islands

“…remote areas of New Caledonia >2.5 sharks per hour [ 33 ] and Palmyra Atoll; C . melanopterus >2 sharks per hour [ 62 ]). Combined, these results suggest that reef shark populations in the Solomon Islands are relatively healthy when compared to nearby countries, yet likely to have been impacted by fishing given they are not comparable to remote areas without fishing pressure.…”

Dermal denticle assemblages in coral reef sediments correlate with conventional shark surveys

“…Baited remote underwater video (BRUV) surveys were used to obtain video‐based measurements of relative shark abundance. GoPro™ Hero4 cameras mounted on PVC or metal frames were deployed for 120 min at depths between 1 and 7 m at seven sites corresponding with the sediment collection sites (Figure ), with one to three replicate surveys conducted at each site (Bradley, Papastamatiou, & Caselle, ). Each BRUV system was baited with 0.5 kg mackerel.…”