Effects of COVID-19 lockdown on the observed density of coral reef fish along coastal habitats of Moorea, French Polynesia

Abstract

During the first COVID-19 lockdown in 2020, levels of coastal activities such as subsistence fishing and marine tourism declined rapidly throughout French Polynesia. Here, we examined whether the reduction in coastal use led to changes in fish density around the island of Moorea. Two natural coastal marine habitats (bare sand and mangrove) and one type of man-made coastal structure (embankment) were monitored on the west coast of the island before and after the first COVID-19 lockdown. At the end of the lockdown (May 2020), significantly higher apparent densities of juvenile and adult fish, including many harvested species, were recorded compared to levels documented in 2019 at the same period (April 2019). Fish densities subsequently declined as coastal activities recovered; however, 2 months after the end of the lockdown (July 2020), densities were still higher than they were in July 2019 with significant family-specific variation across habitats. This study highlights that short-term reductions in human activity can have a positive impact on coastal fish communities and may encourage future management policy that minimizes human impacts on coastline habitats. Supplementary Information The online version contains supplementary material available at 10.1007/s10113-022-02011-0.

Coral reef fish resilience and recovery following major environmental disturbances caused by cyclones and coral bleaching: A case study at Lizard Island

“…Therefore, it is possible that the prolonged lockdown at Lizard Island led to a general increase in fish density due to the large reduction in human activities. Recent studies have shown a significant increase in coral reef fish densities during the lockdown period (Feeney et al, 2022; Bertucci et al, 2023). However, it is also possible that the lockdown affected the fish assemblage, which resulted in higher numbers during surveys, but this could lead to a decline in fish numbers once the lockdown is lifted and human activities resume (Lecchini et al, 2021).…”

Insights from the 2-year-long human confinement experiment in Grand Cayman reveal the resilience of coral reef fish communities

“…The observed increases in fish biomass throughout the period of lockdown restrictions in Grand Cayman can most likely be attributed to two main reasons: (1) behavioural shifts impacting habitat distribution 26 ; and (2) improved fitness leading to increased recruitment. Firstly, cessation of water-based activities would result in reduced ambient sound and physical disturbance in the water leading to immediate changes in the behaviour of fishes that will likely become bolder and less cryptic, thereby encouraging redistribution and habitation of areas previously saturated by boats and people 35 – 38 . Additionally, reductions in stressful conditions caused by water-based activities, such as noise and waste from large boats, also impacts key behaviours including feeding, sociality, reproduction, and subsequently, physiology 21 – 23 , 31 – 33 .…”

“…In summary, lockdown restrictions on water-based activities in response to COVID-19 are associated with increased biomass of coral reef fish, particularly parrotfish and juvenile parrotfish. Given the clear ubiquitous impacts of COVID-19 lockdowns around the world on behaviour and physiology of multiple organisms across multiple ecosystems 27 , 28 , increased biomass of reef fish is not surprising 35 – 38 . However, our study highlights the effect over a longer time-period (2 years) than previous studies 35 – 37 (~ 3 months), indicating increased biomass was likely driven by both altered behaviour and increased ecological fitness owing to lockdown restrictions, which subsequently contributed to fish recruitment.…”

“…Pollution in the form of anthropogenic noise and chemical pollution from sea vessels negatively impacts fish behaviour 31 – 33 and physiology 31 , 33 , 34 thereby influencing community composition. During the short period when tourism and heavy water-based activities were reduced between March and May 2020, coral reef ecosystems in several regions that typically experience high anthropogenetic pressures showed immediate increases in fish species diversity and abundance 35 – 37 , linked to increased recruitment of juvenile fishes 38 . While marked increases immediately following a short respite is positive, studies examining how longer lockdown restrictions on water-based activities influenced the community composition are lacking.…”