Do Reef Fish Habituate to Diver Presence? Evidence from Two Reef Sites with Contrasting Historical Levels of SCUBA Intensity in the Bay Islands, Honduras

Abstract

Contact between humans and the marine environment is increasing, but the capacity of communities to adapt to human presence remains largely unknown. The popularization of SCUBA diving has added a new dimension to human impacts in aquatic systems and, although individual-level impacts have been identified, cumulative effects on ecosystem function and community-wide responses are unclear. In principle, habituation may mitigate the consequences of human presence on the biology of an individual and allow the quick resumption of its ecological roles, but this has not been documented in aquatic systems. Here, we investigate the short-term impact of human presence and the long-term habituation potential of reef-fish communities to recreational SCUBA divers by studying symbiotic cleaning interactions on coral reefs with differing levels of historical contact with divers. We show that incidences of human contact result in a smaller decline in ecosystem function and more rapid resumption of baseline services on a reef in Utila, Honduras that has heavy historical levels of SCUBA diver presence, compared to an un-dived reef site in the Cayos Cochinos Marine Protected Area (CCMPA). Nonetheless, despite the generally smaller change in ecosystem function and decades of regular contact with divers, cleaning behavior is suppressed by >50% at Utila when divers are present. We hypothesize that community-wide habituation of reef fish is not fully achievable and may be biologically restricted to only partial habituation. Differential responses to human presence impacts the interpretation and execution of behavioral research where SCUBA is the predominant means of data collection, and provides an important rationale for future research investigating the interplay between human presence, ecosystem function, and community structure on coral reefs.

No persistent behavioural effects of SCUBA diving on reef sharks

“…Ultimately, our findings suggest that SCUBA diving does not have long-term impacts on shark behaviour. This stands in stark contrast to the imme- A possible explanation for our result is that sharks may have become habituated to the presence of SCUBA divers after 15 yr of persistent exposure, which has been observed in other reef-dwelling species (Titus et al 2015). If sharks were habituated to divers, then there would be no immediate behavioural response to SCUBA divers in the water, as well as no permanent change to shark behaviour and space use at dived locations.…”

“…Following intense tourism activity and provisioning, the naturally solitary southern stingray developed shoaling behaviour, changed feeding habits, and experienced a higher rate of injury and larger parasite load resulting in an overall lower body condition than stingrays at non-tourist sites (Shackley 1998, Semeniuk & Rothley 2008. Hawksbill turtles may also decrease time spent eating and breathing in response to an approaching SCUBA diver (Hayes et al 2016), and reef fish may forgo cleaning opportunities in the presence of divers (Titus et al 2015).…”

Temporal patterns of Pederson shrimp (Ancylomenes pedersoni Chace 1958) cleaning interactions on Caribbean coral reefs

“…In rare instances where shrimp disappeared for longer than 15 s and were not observed returning to the host anemone, we assumed the clean was ongoing as long as the client fish remained stationary at the station. Even with these minor limitations, the benefits of using remote cameras for this study far outweigh the benefits of direct diver observations (see Titus et al 2015). First, cameras greatly increase the observation period per station.…”

“…While direct diver observations would provide a maximum observational period of 45-60 min, our cameras routinely recorded for 120-180 min per station. Second, while divers in the water may be able to shift their perspective in situations where the cleaner moves to the far side of the client fish and is obscured from view, additional movement on the part of the observer could magnify the already well-documented effect divers have on fish behavior and community composition (Chapman et al 1974;Kulbicki 1998;Lobel 2005;Fox and Bellwood 2008;Dearden et al 2010;Dickens et al 2011;Januchowski-Hartley et al 2011;Longo and Floeter 2012;Titus et al 2015). Finally, cameras circumvent the complicating factor of understanding the long-term historical use of each reef site by SCUBA divers.…”

“…Finally, cameras circumvent the complicating factor of understanding the long-term historical use of each reef site by SCUBA divers. For example, repeated long-term exposure to SCUBA divers appears to lead to partial habituation of reef fish communities (Titus et al 2015). Using a combination of direct diver observations and remote video, Titus et al (2015) showed that divers recorded significantly more cleaning interactions using direct diver observations at a heavily dived reef than an undived reef.…”