Size and age at sexual maturity and sex ratio in ocean quahog, Arctica islandica (linnaeus, 1767), off northwest iceland

摘要

Ocean quahogs, Arctica islandica, were collected in February 1994 from near-shore populations off north-west Iceland for determination of developmental stages relative to size, age, and sex. A microscopic examination of histologically prepared tissue of 206 ocean quahogs showed that s6 specimens (31-70 mm shell length) were immature and could not be sexed. Sexual differentiation was evident in 200 individuals, 17 were in the intermediate stage and 183 were mature. On the basis of annual internal growth bandings in the shells of the specimens, the age ranged between 7 and 32 y in the intermediate stage and the individuals were from 24 to 60 mm in shell length. The smallest and youngest individuals that could be sexed were males. The smallest mature male was 36 mm in length, but the youngest aged individual was 10-year-old (49 mm length), The youngest mature female was 44 mm and 13-year-old. Age and size of maturity showed a wide range and may be dependent on growth rate and environmental conditions. Sex ratio between males dominating in the smallest size classes, which may be related to their earlier development of germinal cells. After 40 mm length was reached, the females dominated in all size classes except 65 to 69 mm (1.3:1) and 70 to 74 mm (1:1).