Skeletal anomalies in big-scale sand smelt (Atherina boyeri, Risso 1810, Teleostei) as a complementary tool for the assessment of the ecological status of coastal lagoons

This study tested the validity of a lagoon resident species, the big-scale sand smelt Atherina boyeri as an indicator of ecological quality of coastal lagoons. The study approach was based on the use of skeletal anomalies as a metric [1], to formulate a preliminary assessment of the environmental state of four lagoons: Fogliano, Caprolace, Sabaudia, in the province of Latina (Central Italy), and Cabras in the province of Oristano (Sardinia, Italy). A total of 451 fish were analysed for skeletal anomalies frequencies and typologies, after a whole-mount staining procedure specific for ossified tissues. The results yielded a ranking of the four lagoons based on indices such as malformation charge, ratio severe anomalies/total anomalies, and rate of severely deformed fish. In Cabras the highest values for all the indices were found, in Caprolace the lowest values, while Fogliano and Sabaudia showed intermediate values. The ranking of lagoons yielded by anomalies analysis was compared with the Total Pressure Index (TPI) obtained by an assessment based on the measure of anthropogenic pressures [2], evaluated and grouped in three categories: “Morphologic and Hydrology Changes”, “Land and Resource Use” and “Water Quality”. Results indicate Sabaudia as the lagoon with the highest TPI. Fogliano and Cabras show similar, moderate, TPIs originating from intermediate values for the three categories. Caprolace showed the lowest TPI. The two approaches give results that are not completely coherent. The indicators used to quantify anthropogenic pressures aim at a comparative assessment of the ecological status of lagoons. Skeletal anomalies in sand smelt on the other hand might result from some environmental stressor whose weight is not effectively represented in TPI. This points to the possible usefulness of indices based on fish malformations as a complementary tool to evaluate the ecological status of coastal lagoons, in the perspective of an integrated approach.