OTOLITH MICROSTRUCTURE, AGE AND GROWTH OF 2 SPECIES OF CERATOSCOPELUS(OSTEICHTHYES, MYCTOPHIDAE) FROM THE EASTERN NORTH-ATLANTIC

The otolith microstructure of Ceratoscopelus maderensis (Lowe) and C. warmingii (Luetken) was studied with light and scanning electron micro scopy. The two species have a similar otolith structure consisting of a central core with outward radiating aragonite crystals forming incre ments. Growth increments were well defined over most of the sagittal s ections of otoliths except in the transitional area around the core an d outermost parts of the largest C maderensis otoliths. The ages of 39 C. maderensis and 37 C. warmingii were estimated by enumeration of ot olith increments that were postulated to be daily. The ages of an addi tional 40 C. maderensis were estimated from otolith weight through the use of a regression model. No differences in size of males and female s were observed in C. maderensis while in C. warmingii females were la rger than males. Ceratoscopelus maderensis was characterized by linear growth during the first 6 months of fife, attaining over 40 mm SL at that age. A reduction in growth rate occurred at an calculated age of about 10 months and a size of 50 mm. This coincided with the winter se ason and sexual maturation. Only a few specimens over 2 years of age w ere observed, an indication of a high mortality during the second year of life, although sampling bias may have contributed to the lack of a bundance of older fish. With this consideration, the growth parameters of the von Bertalanffy equation estimated for C. maderensis were K = 1.3 and L(infinity) = 79.0 mm. For the C. warmingii samples analyzed, males attained lengths of 46-47 mm at 9-10 months of age, while female s lived over 1 year and reached 64-68 mm. A noticeable decrease in gro wth in males was prominent at the larger lengths, whereas, the growth of females was linear to the maximum size captured.