Abstract:

Electrona carlsbergi is a species of pelagic fish that inhabits the Southern Ocean and has important ecological function. However, to date there have been only a few reports regarding the age of such fish. To determine the age of E. carlsbergi and confirm the method of age determination, the diazone numbers obtained under direct light of 73 sagittal otolith samples from 59 fish samples collected from the South Shetland Islands on January, 2010 are used as evidence of age identification. Because of the accessory and false rings of the sagittal plane, a longitudinal section is more suitable than a transverse one for determining the age of E.carlsbergi.Of the fish whose ages are identified, 67.80% are three or four years old. The Total Concordance (TC), Coefficient of Variation (CV) and Average Percentage Error (APE) are calculated to quantify the accuracy of the age determination. The average of each index is 50.23%, 3.67% and 8.60%, respectively. These three indexes are also used to test the accuracy of different age groups. The results show a negative relationship between CV and TC, whereas APE increases firstly and then decreases. The von Bertalanffy growth function for E.carlsbergi is L_t=7.7154(1-e^{–0.5373(t+2.7807)}).

Key words: Electrona carlsbergi, otolith, age determination, age validation, growth