title: Characterization of fish assemblages and population structure of freshwater fish in two Tunisian reservoirs: implications for fishery management.
abstract: To monitor and assess the state of Tunisian freshwater fisheries, two surveys were undertaken at Ghezala and Lahjar reservoirs. Samples were taken in April and May 2013, a period when the fish catchability is high. The selected reservoirs have different surface areas and bathymetries. Using multi-mesh gill nets (EN 14575 amended) designed for sampling fish in lakes, standard fishing methods were applied to estimate species composition, abundance, biomass, and size distribution. Four species were caught in the two reservoirs: barbel, mullet, pike-perch, and roach. Fish abundance showed significant change according to sampling sites, depth strata, and the different mesh sizes used. From the reservoir to the tributary, it was concluded that fish biomass distribution was governed by depth and was most abundant in the upper water layers. Species size distribution differed significantly between the two reservoirs, exceeding the length at first maturity. Species composition and abundance were greater in Lahjar reservoir than in Ghezala. Both reservoirs require support actions to improve fish productivity.
authors.affiliation: Unité de recherche: Exploitation des Milieux Aquatiques, Institut Supérieur de Pêche et d'Aquaculture de Bizerte, Errimel, B.P.15, 7080, Bizerte, Tunisia.
authors.forename: Sami
authors.initials: S
authors.lastname: Mili
authors.affiliation: Laboratoire Milieu Marin, Centre la Goulette, Institut National des Sciences et Technologies de la Mer (INSTM), La Goulette, Tunisia.
authors.forename: Rym
authors.initials: R
authors.lastname: Ennouri
authors.affiliation: Laboratoire Milieu Marin, Centre la Goulette, Institut National des Sciences et Technologies de la Mer (INSTM), La Goulette, Tunisia.
authors.forename: Amel
authors.initials: A
authors.lastname: Dhib
authors.affiliation: Centre Technique d'Aquaculture, 5, rue du Sahel Montfleury, 1009, Tunis, Tunisia.
authors.forename: Houcine
authors.initials: H
authors.lastname: Laouar
authors.affiliation: Laboratoire Milieu Marin, Centre la Goulette, Institut National des Sciences et Technologies de la Mer (INSTM), La Goulette, Tunisia.
authors.forename: Hechmi
authors.initials: H
authors.lastname: Missaoui
authors.affiliation: Laboratoire de Chrono-Environnement, UMR CNRS 6249, Université de Bourgogne Franche-Comté, Besançon, France. lotfi.aleya@univ-fcomte.fr.
authors.forename: Lotfi
authors.initials: L
authors.lastname: Aleya
mesh_terms: D000818:Animals; D044822:Biodiversity; D018533:Biomass; D005398:Fisheries / Q000706:statistics & numerical data*; D005399:Fishes; D060106:Lakes; D011157:Population Dynamics; D014416:Tunisia
keywords: Fish assemblage; Fish metrics; Multi-mesh gill nets; Tunisian reservoirs