Mullet is the most heavily fished species in Tunisia, accounting for one-third of the freshwater fish harvest. To ensure the continuity and development of fisheries in the country, Tunisian reservoirs have been stocked with Mugilidae fry collected from coastal and estuarine areas. The quantities of fry introduced and mullet landings were correlated. To determine the spatial distribution and abundance of mullets in these fisheries, a multi-mesh gillnet was used in 10 reservoirs. The results showed a weak global correlation between the fry introduced and mullet landings, while the correlation of these variables in each reservoir separately revealed a high correlation in all the reservoirs, except for Ghezala reservoir. The fishing survey revealed that the numerical yield varied significantly from one reservoir to another. Sidi Saad reservoir recorded the highest yield of mullet (196.52 fish/1000 m2 of nets), while a lower yield was recorded in Lahjar, Seliana, Mellegue, Laabid, Ghezala, Bezirekh, Bouheurtma, Sidi Salem, and Sidi Barrak reservoirs. The harvested mullets’ sizes ranged from 14 to 65 cm, indicating good growth conditions in the Tunisian reservoirs. Our findings demonstrate a high potential for mullet production in the country; therefore, we recommend the sustainable development of this sector.

This paper analysis of the socio-economic situation of the fishing activity in Sidi Saad reservoir in order to estimate the real production of fishing in this dam, to determine the demographic structure of the fishermen and to provide information on the profitability of this fishing activity. The results of this study indicate that the fishermen operating in this reservoir are young (average 39 years), with an education level reached limited to primary school (64%) associated to a low monthly income (do not reach the minimum wage). Estimated fishing productions from the survey made in 2 successive years are higher than those indicated in the statistics of the fisheries administration (95 tons against a declared production of 62 tons in 2007 and 112 tons against 72 tons in 2008). In addition, the socio-economic investigation showed that the majority of fishermen practice a second activity in addition to fishing (61%). Continuous scientific monitoring of the fishing in this reservoir is necessary for the sustainability of this activity and to fix the populations of fishermen in their village.

Bizerte lagoon is a valuable socio-economic ecosystem which is renowned for its significant biodiversity and its strategic position in the Mediterranean and in northern Tunisia. It is characterized by an important biodiversity and a high biological productivity, which makes of it a nursery for several marine species. It is also a place of brood stock maturation for others and a feeding area for many migratory species. Its shores and maritime space host lots of human activities, such as coastal fishing, shellfish farming, maritime traffic, recreational fishing and nautical sports, besides 277 industries spanning several sectors of activity such as leather and textile as well as the refining of hydrocarbons and the steel industry. These activities cause severe pollution and result in many anthropogenic disturbances. The aim of this work is to study the sanitary state of Bizerte Lagoon using a biological and ecosystem approach that exploits bio-ecological indicators at the scale of specimen, population, community or whole ecosystem. The findings of this study have revealed the following facts: the peri-lagoon part of the Northeast zone is distinguished by an interesting biological diversity. According to statistical descriptors, the most abundant and frequent zoological groups are gastropod mollusks followed by crustaceans. In terms of diversity indexes, the values obtained showed that the Northeast zone has a poor to mediocre ecological status. This research demonstrates that Bizerte Lagoon is undergoing an anthropic pressure that has been jeopardizing the biodiversity of this ecosystem.

In this study, we present the technical characteristics and the methods applied for fashioning different types of cages used in the aquaculture of Nile tilapia. This study was based on experiments made in geothermal water and fresh water reservoirs in Tunisia. The structures showed high efficiency in small-scale freshwater fish farming. The results of the growth of tilapia fry, reared in the two areas, showed a wide variation. However, with regards to cages’ effect on its behavior and growth rate, a negligible influence was noted. In fact, after the pre-growth phase of the fry in cages in geothermal waters during 35 days, we obtained a daily growth rate (DGR) of 0.41g/day and a specific growth rate of 7.11%/day. These changes are superior to those found in freshwater cages whose DGR was around 0.18g/day and specific growth rate (5.98%/day). Besides, the grow-out trials carried out in the SidiSaad, Ghezala and Lahma Reservoirs have given encouraging results with respective densities of 75 P/m3, 77 P/m3 and 61 P/m3. The use of 2m3 and 3m3 cages, which are relatively of low cost, showed high efficiency during their handling, such as good shape retention in water and especially low mesh clogging. According to the results of the present study, it is recommend the use of cages with a volume of 50m3 above the water surface in order to prevent fish jumping out of the cage, also the assembly of the cages for pre-growth and the grow-out must be carried out within the same reservoir in order to minimize the production costs.