Summary of a study carried out on exploited sea urchins

A study on Paracentrotus lividus in the Maltese Islands was carried out in 2019, following an agreement between the University of Malta and the Environment and Resources Authority. The study intended to acquire scientific knowledge on the conservation status of P. lividus within the Maltese Fisheries Management Zone (FMZ).

The study included the survey of a 4000m2 area at each of ten (10) selected sites: seven (7) in Malta and three (3) in Gozo. Each site was surveyed twice between May and June 2019, representing the pre-bathing season, and between October and December 2019, representing the post-bathing season.

The conclusions of the study were the following:

  1. Low abundances were recorded for live P. lividus, ranging between 0 – 0.00525 individuals/m2, during the pre-bathing season, and between 0 – 0.00425 individuals/m2, during the post-bathing season. The values also indicate the presence of an inter-seasonal variability despite the spawning season taking place in the end of the autumn season;
  2. Exploitable sizes (> 7cm) of the P. lividus were poorly represented throughout both surveys, constituting only 17% of all live individuals recorded. This size category also experienced a sharp drop, down to 5% representation, during the survey carried out in the post-bathing season;
  3. Despite the relatively low numbers of live P. lividus specimens being recorded throughout the study, the predominance of medium-sized individuals (5-7cm), that heavily influence the spawning season, was encouraging;
  4. The data indicates that the overall density of live P. lividus specimens recorded at the different sampling sites might be partly attributable to human exploitation, although other variables also likely exert influence;
  5. Sites from which the highest abundances of P. lividus were recorded, are also popular diving sites and/or fall within Marine Protected Areas (MPAs);
  6. Sites identified as potentially important recruitment sites should be considered for the introduction of management measures pursuant to improving the conservation status of the species, also noting the protection of specific sites in question; and
  7. The hypothesised decline in P. lividus population numbers is suggested as a real one; hence, management measures are deemed pertinent, including the potential introduction of a temporary ban on exploitation of the species.