Growth Performance Assessment of the Gilthead Sea Bream Fingerlings (Sparus aurata, Linnaeus, 1758) in Fish Cage Practice in Dakhla Bay (Morocco)

The aim of the present investigation is to assess the growth performance of gilthead seabream fingerlings (Sparus aurata) farmed in marine cages at Boutalha site in Dakhla Bay in Morocco for a period of fifteen months (March 2018 - July 2019). Fingerlings were imported from a European hatchery (50.000 individuals), with an average initial weight of 3.68 ± 0.16g and an average initial length of 6.23 ± 0.53cm. Specimens were placed in fish nurseries and treatments were duplicated in two batches, with 25.000 individuals/ batch. The physicochemical parameters, recorded during the study period, were within the optimal ranges for obtaining the appropriate growth and the survival of gilthead sea bream. In terms of growth performance, average weight (AW), daily growth rate (DGR), and the specific growth rate (SGR) were estimated to fall within the range of 512 ± 19.71g, 1.13 ± 0.08 g/day, and 1.09 ± 0.12 %/day, respectively for the first batch, and 520.29 ± 22.40g, 1.15 ± 0.06 g/day and 1.10 ± 0.15 %/day for the second batch. The relationship between the total body weight (TBW) of gilthead sea bream and total body length (TBL) could be expressed as: TBW₁ = 0.039 TBL^2.892 (n =315, R² = 0.91) for batch 1 and TBW₂ = 0.0035 TBL^2.935 (n =318, R² = 0.90) for batch 2. The final equation of the length-weight relationship of the two gilthead sea bream batches has an allometry coefficient close to 3, which represents isometric growth. Concurrently, the recorded final biomass values, as well as the feed conversion rate, amounted to 11.58 T and 1.18 ± 0.31, respectively for batch 1 and 11.65 T and 1.19 ± 0.34 for batch 2. These trials also demonstrate, for the first time, that the growth of gilthead sea bream is technically feasible, and indicates a potential for improvement through the implementation of a model project which is technically feasible at Dakhla bay.