Comparison of otolith growth and somatic growth in two macrourid fishes

Otoliths from a wide size range of two Macrouridae species (Nezumia sclerothynchus and Coelorhynchus coelorhynchus) were collected on a monthly basis (December 1996-November 1997) from experimental bottom trawls in the Ionian Sea, Greece, between 400 and 1000 m. All otoliths showed the ring pattern common to teleost fish, opaque and hyaline rings laid down around an opaque nucleus. To assess the annual nature of otolith rings, the evolution over time of the percentage of opaque rings in the otolith margin was determined. The growth parameters and the growth curves obtained from the interpretation of the growth rings showed a low growth rate for both species. However, C. coelorhynchus grew comparatively faster and attained greater asymptotic size than N. sclerothynchus. Since a considerable variation in size at age was found for both species, the relationship of otolith weight and length to fish length was estimated for each age group. This analysis permits a much greater proportion of fish to be assigned ages than is possible with otolith reading alone. The results suggest that since the otolith growth is not synchronous with the growth of fish, otolith weight can be useful in confirming age distribution of the examined fish species. (C) 2000 Elsevier Science B.V. All rights reserved.