Estimation and biodiversity of sea cucumbers population Jarzouna south Metline (Bizerte, North of Tunisia)

Abstract

Five species of Holothurian (Holothuria tubulosa; H. polii; H. sanctori; H. forskali and H. mammata) were studied during the months of June-September 2014. Investigations were carried out in four marine areas in Tunisian Northern coasts, three of them between Jarzouna port and Ras Jebel; the fourth one in the North of Bizerte Lagoon. The objective of these surveys was to estimate the density of their populations and to deduce their respective biomasses. Overall densities of sea cucumbers of the areas Jarzouna-Metline; El Hawar and Bizerte lagoon were estimated respectively to 3869; 7121; 5192 and 293823 individuals/1000 m² and global stocks of the 5 species have been respectively around 74 500; 1 513; 4 122 and 464 228 individuals. Biometric variables of the study population seem to be correlated with the depth and the quality of the seabed. Considering the much smaller maximum size, in marine studied areas compared to those of other exploited localities in the Mediterranean Sea and the low density values observed, it seems that Holothurians have faced a heavy fishery pressure. Whereas, at least two species from Bizerte lagoon, in the light of the results of the surveys, may be subjects to a rational exploitation.