INCREMENTS IN OTOLITHS AND SCALES - HOW THEY RELATE TO THE AGE AND EARLY DEVELOPMENT OF REARED AND WILD LARVAL AND JUVENILE PAGRUS-AURATUS (SPARIDAE)

The utility of otoliths and scales for age and growth studies on North ern and Southern Hemisphere forms of Pagrus auratus (< 100 days old) w as investigated. A series of illustrations shows the developmental mor phology of wild southern larvae at ages ranging from 0 to 40 days. Rea red P. auratus (of both forms) deposited daily increments in otoliths from or within 1 day of the time of hatching until the age of 40 days. Age-length relationships of wild P. auratus (2.4-8.5 mm standard leng th, SL) from northern New Zealand (1985-86) were not significantly dif ferent among times and there was little variation in length at age amo ng fish. In contrast, great variation in age-length relationships was found for reared larvae (5-30 days old). The data suggest that slow-gr owing fish may suffer high mortality rates in the wild. On the basis o f age-length relationships of wild P. auratus, recommendations are mad e for appropriate sampling frequency in studies of larval abundance. C tenoid scales formed at 8-9 mm SL in both forms of P. auratus. The num ber of increments in newly settled P. auratus (<60 days old) closely a pproximated the number of days since scale formation (i.e. <25 circuli ). This may provide a new method for estimation of the timing of a con current change in the behaviour of some fish larvae (e.g. a change in vertical distribution). Importantly, the number of circuli was correla ted with the growth of juveniles, just as the spacing of circuli is in other species. Thus, circuli in scales potentially provide a history of individual growth in small fish after the formation of scales (to 1 00 days old) and an indication of the time since scales appeared.