Population structures, length-weight relationships and growth parameters of three resident species from the coastal lagoons of Lesina and Varano (Italy, Mediterranean Sea)

Aphanius fasciatus (Valenciennes), Atherina boyeri Risso and Knipowitschia panizzae (Verga) are considered resident fish species in Italian coastal lagoons, which spend their entire life cycle within the brackish waters. They are short-lived species, with a small size, and a rapid growth and attainment of sexual maturity. All these fish species are included in the IUCN Red List with the status of Least Concern. A. fasciatus and K. panizzae are additionally listed in the Appendix III of the Bern Convention and in the Annex II of the European Union Habitat Directive. The aim of this study was to determine the population structures, to assess the length-weight relationships (LWRs) and to estimate the growth parameters of the target species in the lagoons of Lesina and Varano. This information is necessary for population assessments, which provide information that may be used in the management of fish populations in lagoon systems. Sampling of specimens was seasonally conducted in the two lagoons from May 2008 to February 2010. Fishes were caught at eleven stations by fyke nets with 6 mm mesh size at the end. In the laboratory, all specimens were identified to species, measured for total length and weighted. Sex was macroscopically determined. A total of 3,242 specimens of A. fasciatus, 1,664 specimens of A. boyeri and 1,060 specimens of K. panizzae were analyzed. The length frequency distribution, the LWR and the growth parameters were derived for each species in each lagoon. LWRs were estimated by linear regression analysis of the log-converted weight and total length data. Parameters of the von Bertalanffy growth function were determined through the ELEFAN-I software, using length frequency distribution. This study presents the first estimation for K. panizzae of LWRs and von Bertalanffy growth model parameters. Comparisons of the results were performed in relation to the lagoon environments and considering the knowledge about the species.