CCAMLR

Age was determined on the basis of growth microincrements in otoltihs. A calibration subsample of 49 specimens (total length range: 3.9 - 59.0 cm) was aged using optical sagittal and transverse otolith sections and/or acetate replicas. Age ranged from 138 to 2116 days. A multiple regression was applied to find a model for the age estimation from measurable fish and otolith parameters. The following formula was obtained:
Age (days) = 131.24 + 27416.4*Otolith weight (mg)
Using this equation the age of 237 fish was predicted. The age data from calibration subsample and predicted from otolith weight were used to fit the von Bertalanffy’s growth curve. The following growth parameters were estimated for P.georgianus: K = 0.39; L∞ = 63.2 cm and t0 = 0.42.

Age determination was carried out on Notothenia gibberifrons specimens collected at two localities of the South Shetland Islands (Low I. and Potter Cove, 25 De Mayo I./King George). Samples were composed by small and medium size fishes (14.8-38 cm of total length). Otolith and scale readings have been compared in 19 Potter specimens. In some of them scale readings resulted one year greater. This could arise from the difficulty to differentiate false from annual checks in scales. Age determination by otolith cross sections proved to be the most reliable method. Mean length data at age presented here for Low I. specimens were compared with previous published values. This confirmed that fishes from the Antarctic Peninsula Subarea smaller than those around South Georgia at the same age group. Likewise, our values are lower than the ones reported previously for specimens of South Bay, Palmer Archipelago. Possible reasons for these differences are discussed. It is expected that the Otoliths/Scales/Bones Exchange System established by CCAMLR will contribute to eliminate discrepancies on age and growth studies of Antarctic Fish.