Résumé:
The edible sea urchin Paracentrotus lividus (Lamarck, 1816) has a geographical
distribution that includes the Atlantic and the entire Mediterranean. It is the subject of many
works that deal with the biology of this species. Samples of specimens were taken at a depth
of between 1m and 3m during the period from February 2019 to April 2019 in two types of
biotopes, namely, Stidia located in an area with high human activity, and Sidi El Majdoube
considered as a reference area. The results were able to show an imbalance of the overall sex
ratio in both sites, the percentage of females is significantly higher than the males with a
percentage of 58% in Sidi El Majdoube and at the site of Stidia the rate of femininity is 48%
and the males correspond to 42% in Sidi El Majdoub against 52% in Stidia. The physiological
indices (IRm and IGm) show significant variations depending on the biotope and the month.
From the cycle of the gonad index, the spawning periods of Paracentrotus lividus were
determined in these two sites which corresponds to the month of March. The study of the
biometric relations shows that the correlation coefficient (r) measuring the degree of
connection between the diameter (D) and the height (H) remains very good for the sea urchins
of Sidi El Majdoub (r = 0.74 in February , r = 0.70 to Mars and 0.73 of correlation for the
month of April) to tell for the Station of Stidia the coefficient of correlation r is less important
(r = 0,73 to February r = 0,60 to Mars and r = 0.79 to April). For the total weight and height of
the sea urchin, the relationship has a minor allometry since b <3 for the two study sites; the
growth is minor between these two variables with the height which grows less quickly than
the weight1The common sea urchin shows a good development, whether it is polluted or
referential environment, it is therefore it is attributed the criterion of good bioindicator and
especially species resistant to the variations of the qualities of the environments which it
frequents.
