Identification individuelle du mérou brun, Epinephelus marginatus (Lowe, 1834) par les taches céphaliques Individual identification of dusky grouper, Epinephelus marginatus (Lowe, 1834) by cephalic blotches

Lelong P, 1999 – [Individual identification of dusky grouper, Epinephelus marginatus (Lowe, 1834) by cephalic blotches]. Mar. Life, 9 (2) : 29-35. Studies on animal behavior often require the possibility of recognizing each individual. The proposed method for dusky grouper is non-traumatic, durable and does not necessitate preliminary capture, in contrast to usual tagging techniques. This identification is based on the pattern and shape of two groups of blotches close to the eye. These blotches are characteristic for each individual and do not change significantly with time. Left and right sides are nearly symmetrical but not exactly identical. Two applications of this method of visual identification are given: (i) The progress of ten grouper released near the island of Les Embiez in 1994. Five of them were regulary sighted: three stayed in the same place where they had been released, two others moved on to another place, one kilometer further away; (ii) The progress of a small population of dusky grouper in a small territory: from 1989 to 1998 the number of grouper increased from one to four. From 1995, the identification by blotches has enabled us to study the succession of individuals in this territory. The site fidelity of these grouper is of least two to three years duration. For application to exhaustive studies of denser populations or on larger sites, this method will require video and computer assistance.