SOURCES OF VARIATION IN GROWTH OF THE EUROPEAN EEL (ANGUILLA-ANGUILLA) ESTIMATED FROM OTOLITHS

Tetracycline labelling of otoliths was used for studying the growth of the European eel (Anguilla anguilla), which has strong individual var iability. Two groups of eels were injected with tetracycline and relea sed into a natural pond (Camargue, south of France) in spring 1989 and in autumn 1989. The marginal growth of otoliths between marking (tetr acycline mark) and capture (otolith margin) was measured for all fish sampled until spring 1990. Comparisons of otolith growth rates were ma de according to fish size, age, sex, and growth period (ANCOVA). The r esults showed a great variability. After 15 mo of growth, the mean gro wth in length (back-calculated) was 6.6 cm. The three main factors tes ted, age, sex, and seasonal growth period, had a significant effect on otolith growth and therefore on somatic growth, since the relation be tween fish length and that of the otolith is highly significant (r2 = 0.802). There was also a very significant effect of size at marking on otolith growth. It is difficult to rank qualitative importance of the se various factors, even though there are no interactions among them. The best absolute growth in Mediterranean lagoons could be attained by 2-yr-old female fish growing in the summer months.