Predation of the invasive green crab Carcinus maenas on the edible snail Buccinastrum deforme, targeted as the most important nearshore marine gastropod fishery from Patagonia, Argentina

Abstract

Biological invasions constitute one of the main problems for the conservation of marine environments and are among the major causes of biodiversity reduction. The green crabs, Carcinus maenas was first reported on the Patagonian Argentinean coast in 2003 and has rapidly spread northwards along the coast. In 2018, many empty shells of the edible gastropod Buccinastrum deforme were observed at the shoreline, showing scars compatible with those caused by crab-crushing predations. This study aimed to evaluate the effect of C. maenas on the edible gastropod B. deforme, a species of great fishing importance in Patagonia, Argentina. In order to characterize the green crab´s predatory marking patterns observed on the shell of B. deforme, aquarium experiments were conducted. At the same time, field sampling census of shells stranded in the intertidal zone were carried out in three different sites where high densities of B. deforme were previously recorded. Empty shells showing the characterized marking patterns were used as an indicator of predation and were randomly collected from the intertidal to quantify the frequency of each type of predatory mark. Additionally, the abundance of snails and crabs was estimated using baited traps in ten sampling sites. Our results are consistent with the fact that the non-native green crab C. maenas presents a highly aggressive behavior that affects native species´ abundances once established in a new environment. The most frequent pattern of predation marks was the combined crush of the apex and lip, occurring simultaneously in the same individual. A decrease in B. deforme presence was inversely proportional to the increase in C. maenas populations. This is the first work that records the impact of predation of the invasive species C. maenas on Atlantic Patagonia´s sandy bottoms, which negatively affects a fragile species such as the edible snail B. deforme. The dispersal capacity of the green crab, in addition to its predatory strength and voracity, could endanger the artisanal fishery of B. deforme and induce irreversible changes in the coastal ecosystems of Atlantic Patagonia.