DIETARY INCLUSION OF 10 SEAWEEDS IN SENEGALESE SOLE (SOLEA

a promising flatfish species for Mediterranean aquaculture. Low energy diets seem to be suitable for Senegalese sole production (Borges et al., 2009, Valente et al., 2011) and fishmeal could be replaced up to 75% by a mixture of plant protein diets (Cabral et al., 2011, 2013). Seaweeds are regarded as important nutritional sources in aquafeeds due to its content in proteins, lipids, pigments, vitamins and minerals, but they were never tested in sole. The present work evaluated the inclusion of 10% Undaria pinnatífida and 10% Ulva rigida Senegalese sole juveniles.

Material and Methods

The experiment was conducted in a closed circuit system at the experimental facilities of IGAFA (seawater: 19±1ºC; 35 ‰). Triplicate groups of 77 fish, born in captivity, with an average weight of 22.8±0.1g were distributed by 9 tanks of 1m² and fed three isonitrogeneous (55% of proteins) and isoenergetic (8% of lipids) diets (CTRL, Undaria and Ulva) during 5 months. By the end of the trial, growth performance and chemical composition of fish and tissues were evaluated. The results were compared by a one-way ANOVA followed by the Student´s t-test.

Results and Discussion

By the end of the feeding trial the growth performance of the fish did not differ significantly among dietary treatments (Fig.1).

Fig.1. Growth of Senegalese sole fed with different diets

The final body weight of fish fed with Ulva and Undaria (61-62g) was similar to that obtained in fish fed the control diet (60g) (Fig.1). Feed conversion ratios were also similar among the three tested diets varying between 1.4 and 1.6.

Whole body composition of Senegalese sole fed the different seaweeds did not differ significantly from those fed the control diet. Similarly, muscle protein (18-20%) and lipid (2%) content did not differ among the three diets (Table I). However, in the liver the inclusion of 10% seaweeds led to a significant reduction of both protein (9-10% vs 13%) and lipid content (6-7% vs 8%).

Table I.

Whole body and tissue composition (% wet weight) of Senegalese sole (mean±sd).

This study demonstrate for the first time that Senegalese sole can be fed with diets containing 10% seaweeds (Ulva and Undaria) without affecting the growth performance or the flesh quality. Further studies should be carried out to evaluate the long term effects of these seaweeds on fish well being.

References

Borges, P., Oliveira, B., Casal, S., Dias, J., Conceição, L., Valente, L.M.P., 2009. Dietary lipid level affects growth performance and nutrient utilisation of Senegalese sole (Solea senegalensis) juveniles. Br. J. Nutr. 102, 1007–1014.

Cabral, E.M.; Bacelar, M. ; Batista, S., Castro-Cunha, M. ; Ozório, R.O.A.; Valente. L.M.P.2011. Replacement of fishmeal by increasing levels of plant protein blends in diets for Senegalese sole (Solea senegalensis) juveniles. Aquaculture 322, 74-81

Cabral, E.M; Fernandes, TJR ^] ; Campos, SD ; Castro-Cunha, M ; Oliveira, MBPP; Cunha, LM ; Valente, LMP. 2013. Replacement of fish meal by plant protein sources up to 75% induces good growth performance without affecting flesh quality in ongrowing Senegalese sole. Aquaculture 380, 130-138

Valente, L.M.P., Linares, F., Villanueva, J.L.R., Silva, J.M.G., Espe, M., Escórcio, C., Pires,M.A., Saavedra, M.J., Borges, P., Medale, F., Alvárez-Blázquez, B., Peleteiro, J.B.2011. Dietary protein source or energy levels have no major impact on growth performance, nutrient utilisation or flesh fatty acids composition of market-sized Senegalese sole. Aquaculture 318, 128–137.