Download FAR 2024/43 Rock lobster (Jasus edwardsii) gastric ossicle direct ageing feasibility

Gnanalingam, G.; Alexander, L. (2024). Rock lobster (Jasus edwardsii) gastric ossicle direct ageing feasibility. New Zealand Fisheries Assessment Report 2024/43. 18 p.

Size at age is an integral component of fisheries stock assessment but there are no established methods to directly estimate age in crustaceans. As crustaceans grow via moulting this was thought to prevent the use of methods that rely on records of growth on calcified structures. To fill the gap, indirect methods of age estimation have been used such as those based on tag release recapture studies but these have their limitations. Over the last decade there has been considerable interest in the use of banding on the gastric ossicles of the crustacean foregut as means of estimating age. Here, the objective was to determine whether there was banding in the gastric ossicles of red rock lobster that could be used in direct age estimates. Banding was identified in two of the three gastric ossicles assessed but the relationship between size and age estimated from the bands was not clear. More work is required to determine the periodicity of banding and whether the range of ages that can be estimated from this method are plausible.