REPRODUCTIVE BIOLOGY OF ELEDONE CIRRHOSA (CEPHALOPODA: OCTOPODIDAE) IN THE NORTHERN AND EASTERN TUNISIAN SEA (WESTERN AND CENTRAL MEDITERRANEAN)

The reproductive biology of Eledone cirrhosa (Lamarck, 1798) was studied for the first time in the northern and eastern region of Tunisia. Monthly samples were provided from surveys carried out on board the Tunisian oceanographic vessel "Hannibal" and from commercial catches of bottom-trawl operating in this area from October 2005 to September 2006. Although specimens have been collected at a wide depth range, E. cirrhosa shows the greatest abundance between 100 and 300 m. The sex ratio was estimated at 0.94 with no significant difference (P > 0.05). Length-weight relationships calculated for each sex and the whole sample showed negative allometric growth (b < 3). The allometric coefficient in immature individuals revealed an allometric growth (b < 3) and isometric growth (b = 3) in maturing and mature individuals. A three-stage maturity scale was intended to distinguish between immature, maturing and fully mature animals. The reproductive season for females extended from April to August, with a spawning peak from June to August, and for males from January to August with a peak from April to August. The dorsal mantle length (DML) at maturity, corresponding to the size class when 50% of individuals were mature, was estimated at 6.88 cm in males, and 8.80 cm in females. The juveniles were mainly found in between 100 and 200 m where a nursery area for the species is probably present, while mature individuals were mostly fished at a depth greater than 200 m, which represents the spawning area of Eledone cirrhosa. Potential fecundity, estimated from 37 mature females, was 4171 +/- 1216 oocytes. The number of spermatophores ranged from 42 to 121, with a mean length of 51.34 +/- 4.86 mm.