First Annual Report of the CCAMLR Otolith Network, 2002

This report presents results from the first exchange of otoliths under the auspices of the CCAMLR Otolith Network (CON), following the Workshop on Estimating Age in Patagonian Toothfish held at the Centre for Quantitative Fisheries Ecology (CQFE), Old Dominion University, United States, from 23 to 27 July 2001. The National Institute of Water and Atmospheric Research, Nelson, New Zealand; Central Ageing Facility, Victoria Australia; and CQFE, each provided a sample of otoliths, processing and reading one randomly chosen otolith from each pair. Half of the remaining otoliths were sent to each of the other laboratories to process and read using their methodologies. Overall there was reasonable agreement in age estimations between all three readers, with no evidence of biases >2 years that would indicate major differences in the criteria used by the readers. Similarly, there was little evidence that the differences in preparation technique led to major biases or increases in variation in the ages estimated. Instead, there appears from these data to be a broad consensus on the otolith micro-features that need to be exposed during preparation, and the way to interpret them. Small biases and variance in several cases may be explained by apparent differences in the timing of formation of translucent zones between management areas, and readers’ interpretation of the first few translucent zones. Future CON exchanges should 1) define better how these differences in interpretation may affect age estimates, and 2) achieve consensus on their interpretation.