5th International Otolith Symposium

Workshop on age validation (whole day)

Organizing committee:
Ole Thomas Albert (Chair), Alf Harbitz,
Richard McBride, Allen Hia Andrews,
and Iñaki Quincoces

Description

To ensure that age determination becomes a reliable element of the assessments underlying the scientific management advice on fisheries and environmental resources, it is of paramount importance to have validation techniques that ascertain that an age determination method is sufficiently accurate. The age validation operates on two different levels; in a narrower sense the term is used to confirm the identification of annual zones in parts of the otolith, and in a wider sense, the term is used to prove that the whole age determination procedure is accurate. Validation of an age procedure indicates that the method is unbiased based on objective validation criteria.

Age validation studies usually provide information of accuracy for only part of the age-span, geographic distribution area, and ambient climatic conditions of a fish population. Such studies must therefore be seen as part of a long-term process of establishing and refining methodologies that provide accurate age information for all ages and all parts of the species range. Further, studies may be considered as truly validation, securing that the method on average provides accurate age estimates, or as corroboration, providing support but not conclusive evidence for one particular method.

Although the term validation, in relation to calcified structures, usually refers to the age estimates, it may also be used with reference to other information captured in the structure. This includes e.g. validation that a given method of shape analysis provides accurate splitting of unit stocks, and that a given trace element analyses provide accurate information of the individuals association with specific water masses.

This workshop aims to update participants on available tools in validation of age, as well as other interpretations made from calcified structures of marine organisms. The WS will also provide examples of their use for selected species. In particular, the WS will examine closer some of the main challenges identified below:

Age validation of long-lived fishes using radiochemical methods, like e.g. red snapper and orange roughy.
Possible biases in validation studies, like e.g. persistent reduced growth rate of tagged fish.
Precision of independent ageing methodologies used for validation of total age estimates from calcified structures, like amino acid racemization, radiochemical analyses and bomb radiocarbon analyses.
Web based resources to help implement validated methods (WebGR, ICES Sharepoint, etc.)
Comparisons of validating techniques such as chemical vs. daily increments
Statistical methodology for evaluation of readings relative to validated sets.
Validation of stock separation by comparing shape analyses and genetics.

The WS invites contributions, both orally and poster presentations, on all of the above topics. The time frame is to focus on age validation before lunch and validation of other interpretations (stock identity, distribution history) after lunch.