Structural and functional variations in macrobenthic assemblages impacted by fishing dredges in the soft bottoms of the southern Adriatic Sea during the COVID-19 lockdown

Abstract

Macrobenthic assemblages on shallow soft bottoms exploited by fishing hydraulic dredges in the Gulf of Manfredonia (Southern Adriatic Sea) were investigated before the COVID-19 lockdown (2018–2019) and during the fishing closure caused by lockdown restrictions (June 2020). Standardized abundance data (N/100m 2 ) of benthic species from fishery-independent monitoring surveys were analysed. Fishing effort and environmental variables were obtained from fishermen’s reports and the Copernicus Marine Service, respectively. Temporal changes in diversity, structural and functional traits were analysed through alpha diversity indices and Biological Trait Analysis. Benthic diversity increased in 2020, while the total abundance declined over time. Fishing effort influenced the macrobenthic assemblage in 2018 and 2019, while flooding and related environmental changes impacted soft bottoms in 2020, masking effects expected from the fishing ban due to COVID-19 restrictions, such as the recovery of commercial stocks. Species without protective structures were abundant in 2018, while shell-protected ones increased in 2019. By 2020, small and short-lived species were prevalent, while bioturbators, sessile species and suspension feeders declined. Overall, sudden and impactful natural events affecting seabed sediments appear to shape macrobenthic assemblages more than forced fishing closures, highlighting the need for an ecosystem-based management approach in the management of fishing benthic resources.

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