Effects of a COVID-19 lockdown-induced pause and resumption of artificial provisioning on blacktip reef sharks (Carcharhinus melanopterus) and pink whiprays (Pateobatis fai) in French Polynesia (East-Pacific)

Abstract

The tourism activities linked to artificial provisioning of blacktip reef sharks (Carcharhinus melanopterus) and pink whiprays (Pateobatis fai) on a specific site in French Polynesia were suddenly and completely stopped due to a COVID-19 lockdown that lasted 6 weeks from March 20 until April 30, 2020. Using both drone footage and underwater counting, we were able to track the abundance of those two species before, during, and after reopening and thus investigate the impact of provisioning on wild shark populations. The absence of any stimulus during this long period resulted in almost total desertion of the site by the elasmobranchs. However, 1 day prior to reopening, some individuals of both species positively reacted to the single acoustic stimulus of an engine boat, showing the resilience of conditioning, and some elasmobranchs reacted to acoustic and olfactive stimuli linked to the provisioning practice from the first day after reopening. During the first 2 weeks after reopening, the abundance of both species remained at reduced levels comparable to those observed between 2008 and 2010 for sharks; i.e., around 9 animals in the presence of local tourists. Pre-lockdown abundance levels, reaching approximatively 15 individuals for sharks and 10 for rays, were considered restored 1 and 2 months after reopening for blacktip reef sharks and pink whiprays, respectively. These findings improve our capacity to better understand the potential effects of artificial provisioning tourism on the abundance of elasmobranchs by showing that conditioning is resilient for several weeks, suggesting that intermittent interruption of elasmobranchs feeding would not really help to decrease its impact on animal welfare.

Keywords: anthropause; conditioned behavior; feeding; memory retention; reconditioning delay.

FIGURE 1

Study area. a: Localization of Moorea, French Polynesia. b: Unmanned Aerial Vehicle (UAV) overflight of the Tiahura marine reserve. C: UAV overflight of a provisioning session involving different tour operators and swimmers interacting with blacktip reef sharks (Cacharhinus melanopterus) and pink whiprays (Pateobatis fai)

FIGURE 2

Photographs from drone surveys showcasing representative abundance of sharks (red circles) and rays (yellow circles) at the Tiahura feeding site on (a) 04/29/2020 (2 days before re‐opening) showing the presence of one shark; (b) 04/30/3030 (1 day before re‐opening) showing the presence of four sharks and three rays; (c) 05/02/2020 (1 day after re‐opening) showing the presence of eleven sharks and five rays; (d) 06/01/2020 (31 day after re‐opening), showing the presence of 20 sharks and 9 rays. All images were taken at 10 a.m. and have been adjusted to optimize shark and ray counts

FIGURE 3

Abundance of blacktip reef sharks (Carcharhinus melanopterus) and pink whiprays (Pateobatis fai) furnished by several studies completed in Tiahura. Boxplots not sharing the same letter are significantly different in pairwise comparisons (p‐value <.05). Purple dots represent mean values of the abundance for the study considered. Note that the y‐axis varies with species

FIGURE 4

Accumulation curve of the individuals photo‐identified at the Tiahura site. The blue line represents the accumulation curve for blacktip reef sharks and the red line for pink whiprays. Colored values on the x‐axis represent samplings collected during early post‐lockdown in green (n = 124) and samplings collected during late post‐lockdown in purple (n = 12). 95% confidence intervals are highlighted for each curve