Exploring freshwater fish assemblages and population structure in three Tunisian reservoirs for better fishery management

The study of fish populations is essential for sustainable management of the ichthyic resources. This paper aims to assess the state and structure of freshwater fish populations in three Tunisian reservoirs in order to monitor and optimize fishing and stock enhancement for an effective management. The Technical Center of Aquaculture in cooperation with the Higher Institute of Fisheries and Aquaculture of Bizerte has implemented a sampling technique using fish nets inspired by the European standard CEN pr EN 14757. In this study, 3 reservoirs were prospected: Kasseb, Seliana (in March 2016) and Lahjar (in March 2017). The implementation of the sampling protocol allowed the capture of 5 species of freshwater fish. The yields observed are more important in terms of weight than number at the Lahjar reservoir (637.5 in d/1000m2 and 73008.3 g/1000m2) average at Seliana (240 in d/1000m2 and 45191.67 g/1000m2) and quite low at the Kasseb reservoir (25.49 in d/1000m2 and 6750 g/1000m2). The majority of the catches were obtained in the 0-3 and 3-6m strata. An alarming decline of the pike-perch stock was detected in these dams with the absence of carp and eel in all the reservoirs surveyed. It is worth mentioning that overexploitation of fish resources at the level of the explored reservoirs was also observed.