Reproductive Cycle and Fecundity of the Date Mussel Lithophaga Lithophaga (Bivalvia: Mytilidae)

The reproductive cycle and fecundity of the date mussel Lithophaga lithophaga, L. a well-known, ediblespecies has been examined. Sexes are separate and the mean number of eggs per each gonad is 1.894 x 106 ± 1.044 x 106 S.D. Reproduction first occurs at an age of 2+years and at a shell length greater than 0.9 cm. Gonad activity is annual and is observed at all ages. The sex ratio for individuals up to 7 cm is 3:1 in favour of the males, whereas it becomes 1:1 for individuals greater than 7 cm. The release of gametes by males and females occurs almost simultaneously and begins immediately after a decline in the highest water temperature (≤ 27°C), an increase in salinity (>31‰) and a decrease in the dissolved oxygen (6.5 ppm). Small percentages of mature individuals appear during the first winter months thus lengthening the reproductive period. This phenomenon is attributed to the temperature difference in deeper waters, the delay in gamete release by young individuals, tide, wave action and changes in salinity. The fecundity of Lithophaga lithophaga is high because its life-cycle is adversely affected by environmental factors such as waves and tides. Fecundity increases with shell length, more so with total wet weight and mainly with the age of the animals. Summer seems to be the suitable season to exploit the date mussel of shell lengths > 5 cm.