AGE AND GROWTH OF LITHOPHAGA-LITHOPHAGA (LINNAEUS, 1758) (BIVALVIA, MYTILIDAE), BASED ON ANNUAL GROWTH LINES IN THE SHELL

The life span of Lithophaga lithophaga was found to be > 54 years when the annual growth lines in longitudinal shell sections were counted. The age determination was confirmed by a) length frequency histograms, b) the time taken for the formation of annual and reproduction rings and c) by determining the age in different parts of the shell. The age of individuals of the same length varies, for example, individuals wi th a length of 5.0 +/- 0.2 cm range in age from 18-36 years. The oldes t individuals were found at depths of 1-5 m. Maximum growth (75%) was observed from the end of spring to the beginning of summer. The increa se in length of the borehole, which was 1.5 times greater than the len gth of L. lithophaga, was continuous and occurred at a faster rate in winter. Parameters, such as, shell length, age, axes, the occurrence o f abnormal, white and pearl-containing forms and wetflesh weight varie d significantly with depth. There was no variation in the ratio of bor ehole volume/shell volume. On the basis of the above parameters, and a lso the population density, each depth at which samples were collected , was graded. Depths of 2-4 m were found to be the most suitable for g rowth and habitation. Depths of 0-1 m were most inhospitable due to st rong wave action and the direct effect of the atmosphere.