TEMPORAL CLARIFICATION OF THE TRANSITION FROM BLUE PHASE FINGERLING TO EARLY JUVENILE BROWN PHASE IN NOTOTHENIA ROSSII FROM THE SOUTH SHETLAND ISLANDS

BARRERA ORO, ESTEBAN; MOREIRA EUGENIA; ALESCIO, NADIA S.; MARSCHOFF, ENRIQUE RICARDO

Hobart, Australia

Congreso; CCAMLR; 2009

Scales and whole otoliths were read for age determination of early stages of Notothenia rossii caught in Potter Cove, South Shetland Islands, in summer of years 2003-2006 and 2008. The sample was composed by blue phase fingerlings of 7-7.6 cm (TL) and age group 0 year and demersal young brown phase juveniles of 8.5-20.9 cm and predominant age groups 1-2 years. Counting of sclerites facilitated the interpretation of the rings, particularly in the central area of the scale. To clarify two issues of controversy in the literature: 1) we believe that the duration of the pelagic fingerling stage at sea is less than one year before migration to the demersal nearshore habitat; 2) the first well defined ring in scales corresponds to the first annulus, while a contiguous nearby ring is a secondary ring deposited after the first winter during the second year, attributable to a shift of habitat from pelagic to demersal. Our inferences, based on interpretation of the distinct sclerite structures that constitute the rings, are illustrated/supported by photographs. A von Bertalanffy growth curve was computed by combining age/length data of the juvenile phase of N. rossii from this and a previous study at Potter Cove, with literature data from the offshore adult population, resulting in the equation: Lt = 86.9 (1-e