Incidence of spinal deformities in natural populations of Aphanius fasciatus Nardo, 1827 from the Gulf of Gabes, Tunisia

Spinal deformities in Aphanius fasciatus were observed in fish collected from polluted (S1) and non-polluted (S2) areas in the Gulf of Gabes in Tunisia. Kyphosis, scoliosis and lordosis were detected and these basic deformities frequently co-occur in varying degrees of severity. A total of 612 specimens of A. fasciatus were caught and 54 were found to be deformed, which represents 8.82%. Deformed fish were eight times more frequent in S1 than in S2, possibly indicating a relationship between pollution levels and skeletal malformation. In both sexes, variation of deformities incidence with length was very similar. The highest occurrence of deformities was observed in fish with total length <25 mm and decreasing thereafter with fish length. The possible causes for such deformities as well as the suitability of this kind of study for environmental monitoring are discussed.