The Food and Agriculture O rganization (FAO) of the United N ations estimates that by 2030, fish farming will have to provide two-thirds of world fish production to meet demand. However, fish farming cannot be presented as a blameless solution. The current characteristics of fish farming, like the farming of mainly carnivorous fish, have significant impacts on the environment. One of the solutions now being advocated is to diversify the species reared to move towards omnivorous fish.
This study was carried out within the framework of a project that aims to experiment a new fish farming field. It consists in experimenting the breeding of mullets in an integrated system, a local omnivorous species, less demanding in terms of protein intake and providing all the qualities required for human consumption.
We have experimented the Effect of Ulva meal, a green algae, as a replacement of soybean meal in the diet on growth p erformance of the thin-lipped grey mullet liza ramada. Experimental diets were prepared with fishmeal, soybean meal , cornflour , wheat gluten, yeast beer, lupin, stale bread and Ulva meal ( Ulva rigida). R aw materials were obtained from commercial suppliers, except Ulva used (32.4% crude protein) . The feeding experiment was carried out in a closed circulation system. Each diet treatment was applied to replicate four times. G roups of 18 fish individually tagged (53.8 ± 2g average wet weight) per tank (60 l ) were arranged in a completely randomized design. The fish were hand-fed to satiation two times daily between 08.00 h and 18.00 h for 37 days. An industrial control diet (Ui ) (EFICO Cromis 832F) and two experimental formulated diets were used: an algae-free diet (U0) and a 20% level of raw Ulva meal (U20) . The formulated diets contain 37% crude protein and 9% lipid . The 20% Ulva meal replace 20% Soybean meal.
The results showed that weight gain, final body weight (FBW) and Specific Growth Rate (SGR) did not differ significantly among groups fed on experimental diets. They had a similar average performance in specific growth rate (SGR = 1.03%/day) and feed conversion index (FCR = 1.85 and 1.92 with U0 and U20, respectively). T he SGR was significantly higher in fish fed with industrial feed than with the two (2) experimental diets.
T his preliminary study indicates that a 20% level of raw Ulva meal could be used in ju venile L. Ramada without causing any adverse effects on growth and feed utilization.