Assessing composition and diversity of benthic invertebrates in two Patagonian scallop fishing grounds at the shelf-break front of Argentina, Southwestern Atlantic Ocean

Abstract

Long-term time series based on repeated ecological sampling and the continuous collection of biological, environmental, and associated metadata are essential for understanding community dynamics over time. In Argentina, the Patagonian scallop (Zygochlamys patagonica) fishery started in 1996, and the monitoring of the benthic community was one of its main management objectives. This study provides a long-term study of the composition and diversity of the benthic invertebratecommunity in two Fishing Grounds (FG D and FG E) of the Patagonian scallop fishery located in the shelf break front of Argentina in the SW Atlantic Ocean. A total of 254 samples were studied from six stock assessment surveys conducted between 2015 and 2022, using a non-selective dredge. Ninety epibenthic taxa were recorded. No species loss or decrease in biodiversity indexes was detected. The highest biomass and species richness were recorded at FG D, where Poriferadominated, with smaller contributions of Ophiuroidea, Echinoidea, and Ascidiacea. In FG E, Ophiuroidea dominated, and Echinoidea, Porifera, and Polychaeta were the other most important groups depending on the year. Biodiversity, benthic community composition, and species associations only showed small variations. The main assemblages—composed of the Patagonian scallop, Porifera, three Ophiuroidea species, the sea urchin Sterechinus agassizii, and the cnidarian Alcyonium sp.—persisted over time. The lack of significant differences in diversity and biomass values can be interpreted as evidence of ecological stability and resilience, and of the capacity of this benthic community to maintain or recover key properties over years to decades, highlighting that the ecosystem-based management approach applied is being effective.