Variability of Biological Features of a Mugilidae Chelon Ramada in Two Tunisian Reservoirs

Abstract

Mullet is the most massively harvested species, representing the third of the total freshwater fish landing in Tunisia. To ensure freshwater fish farming durability and development in the country, reservoirs have been stocked with Mugilidae fry which was collected from coastal and estuaries areas after a short adaptation period. The objective of this paper is to compare and contrast Chelon ramada’’s age, growth, and mortality in two Tunisian freshwater reservoirs (Seliana and Kasseb). The sample species were caught with a multi-mesh gillnets and were classified into five age groups. The study of the age and growth demonstrated variability between Chelon ramada species’ features. The optimal size of the captured mullet (Lopt) was equal to 37.62 cm for M=0.48, L∞=57.05 and K=0.31 in Siliana Reservoir. Whereas, it measured 31.42cm in Kasseb Reservoir, for M=0.795, L∞=48.15 and K=0.31. It has also been found that the fishing mortality rate is very high at Siliana Reservoir when compared to Kasseb Reservoir. This work is a contribution to the identification of the biological features of Chelon ramada that lives in Siliana and Kasseb Reservoirs. It seeks to ensure a rational and sustainable exploitation of fishery resources in these Tunisian freshwater reservoirs and it recommends the development and preservation of mullet fisheries.

Investigating Freshwater Mullet Fisheries in Tunisian Reservoirs: Future Development Prospects

“…These are used to stock freshwater reservoirs [1,13]. Until 2009, several species of Mugilidae were introduced as fry into many Tunisian reservoirs [7,[26][27][28]. The fry of M. cephalus and C. ramada, collected from coastal and estuary areas, were acclimated and introduced into the reservoirs.…”

“…The fry of M. cephalus and C. ramada, collected from coastal and estuary areas, were acclimated and introduced into the reservoirs. These species revealed normal survival conditions, but they were unable to reproduce in freshwater [1,26,29,30]. Previous research on mullet fry exploitation in Tunisian waters revealed that lowland courses had a very high density of fry migrating from the open sea to estuarine waters depending on their intensity and physicochemical water parameters.…”

“…To guarantee optimal growth of mullet, fry must be stored annually at low densities (50 fry/ha) where aquatic vegetation is important and at high densities (100 fry/ha) in reservoirs without aquatic vegetation. The storage must be made in the spring after the migrating fish-eating birds leave the area [26]. The estimation of the stocking's contribution to landing (the stocking vs. landing ratio) must be made after the estimation of the mortality rate [29].…”

“…The estimation of the stocking's contribution to landing (the stocking vs. landing ratio) must be made after the estimation of the mortality rate [29]. The relationships between stocked Mugilidae and catches indicated an increase in landings over 3 years [26].…”

“…As demonstrated by Djemali et al [52] and Mili et al [9,53,54], mullets were heavily abundant below 6 m depth in Ghezla, Sidi Salem, Sidi Barrak, and Lahjar reservoirs, and no individual was caught at a depth greater than 9 m in any reservoir. Mullets are known to display gregarious behavior and live in schools [26,29,52,55]. Fishermen also reported that C. ramada naturally move in schools; therefore, they are easily captured.…”