Assessment of 16 months of Paracentrotus lividus (Echinodermata, Echinoidea) exploitation along the northern Tunisia coastline in the SW Mediterranean Sea

Abstract : Exploitation of sea urchins as a food resource has started in the southern and eastern Mediterranean Sea. An evaluation of the scale of fisheries-based exploitation of this resource is essential before establishing any means of limitation. In this study Paracentrotus lividus yield was estimated on the northern Tunisian coast. Eleven tons were harvested over 16 months, of which almost half came from one fishing station. The analysis of the population structure during the main fishing period did not show significant decrease in sea urchin test diameter. Indeed, the fishermen had respected our preliminary recommendations i.e., 80 kg quota per fishing zone per day and a minimum size of 50 mm. The total landings, catch per unit effort, gonad indices, percentage of urchins able to emit gametes and levels of toxic metals (cadmium, lead and mercury) in the gonads were estimated per fishing zone. Several periods were shown to have more intensive fishing activity, the main one being concomitant with the maximal gonad index. These data allow us to recommend the suspension of fishing between June and October. Finally, this study did not find any metal contamination in the gonads, although we suggest that a survey should be made concerning sea urchin health variables. Other recommendations are made for the long-term sustainability of this fishery.