Assessment of risks associated with extreme climate events in small-scale bivalve fisheries: conceptual maps for decision-making based on a review of recent studies

Extreme climate events, such as heatwaves and torrential rain, affect the physiology and functioning of marine species, especially in estuarine habitats, producing severe ecological and socioeconomic impacts when the affected species support important fisheries, such as artisanal shellfisheries. Studies of the impact of sudden decreases in salinity and increases in temperature were reviewed with the aim of producing comprehensive conceptual maps to aid the management of fisheries of the native clams Ruditapes decussatus and Venerupis corrugata, the introduced Ruditapes philippinarum, and the cockle Cerastoderma edule in Galicia (NW Spain). The maps show the effects on mortality, scope for growth, ability to burrow, changes in gonad development or predation risk. While V. corrugata will generally be more affected by low salinity (5 to 15) or high temperature (30 °C) during only two tidal cycles, C. edule populations may recover. Both species are also expected to become more vulnerable to predators. The clams R. philippinarum and R. decussatus will be more resistant, unless extreme events occur after massive spawning episodes; however, the presence of the intertidal seagrass Zostera noltei may buffer the negative effects of high sediment temperature on the growth of some species, such as R. decussatus. Finally, recommendations for assessing climate risk and designing management actions for shellfisheries are given.Ministerio de Economía y Competitividad | Ref. CTM2014-51935-RXunta de Galicia-FEDER | Ref. GRC2013 004Xunta de Galicia-FEDER | Ref. ED431C 2021/4

Predation risk increases in estuarine bivalves stressed by low salinity

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGSalinity drops in estuaries after heavy rains are expected to increase in frequency and intensity over the next decades, with physiological and ecological consequences for the inhabitant organisms. It was investigated whether low salinity stress increases predation risk on three relevant commercial bivalves in Europe. In laboratory, juveniles of Venerupis corrugata, Cerastoderma edule, and the introduced Ruditapes philippinarum were subjected to low salinities (5, 10 and control 35) during two consecutive days and, afterwards, exposed to one of two common predators in the shellfish beds: the shore crab Carcinus maenas and the gastropod Bolinus brandaris, a non-indigenous species present in some Galician shellfish beds. Two types of choice experiment were done: one offering each predator one prey species previously exposed to one of the three salinities, and the other offering each predator the three prey species at the same time, previously exposed to one of the three salinities. Consumption of both predators and predatory behaviour of C. maenas (handling time, rejections, consumption rate) were measured. Predation rates and foraging behaviour differed, with B. brandaris being more generalist than C. maenas. Still, both predators consumed significantly more stressed (salinity 5 and 10) than non-stressed prey. The overall consumption of the native species C. edule and V. corrugata was greater than that of R. philippinarum, likely due to their vulnerability to low salinity and physical traits (e.g., thinner shell, valve gape). Increasing precipitations can alter salinity gradients in shellfish beds, and thus affect the population dynamics of harvested bivalves via predator–prey interactions.Ministerio de Economía y Competitividad | Ref. CTM2014-51935-RMinisterio de Economía y Competitividad | Ref. BES-2015-074211Xunta de Galicia | Ref. GRC2013-00