INFLUENCE OF ENVIRONMENTAL-FACTORS ON THE POPULATION-DYNAMICS OF APHANIUS-FASCIATUS (NARDO, 1827) (PISCES, CYPRINODONTIDAE) IN THE LAGOONS MESSOLONGI AND ETOLIKON (W GREECE)

Age frequency, growth, and mortality of Aphanius fasciatus were studie d using 1084 specimens collected from three locations in the Messolong i and Etolikon lagoons. The three sampling stations, Rebakia, Astrovit sa, and Alykes, differed in terms of physicochemical parameters of the water, composition of the bottom, depth of the water, and presence of predators. The caudal fm was longer in males than females. Specimens from the station with a high salinity regime (Alykes) had longer cauda l fins than those from the other stations. The region with rich vegeta tion of shallow waters (Rebakia station) had the highest number of age classes. The Rebakia specimens were also heavier than those of the ot her stations. At Alykes, females were heavier than males for fish of t he same length. Females, and specimens from Rebakia had longer observe d and back-calculated total lengths at each age class, than males and specimens from Astrovitsa (area with deep waters and fish predators pr esent) and Alykes, respectively. The values of total mortality were hi gher for males than females. At Rebakia the mortality rate of both sex es was lower than at Astrovitsa and Alykes.