Abstract

Robust fisheries management of crustaceans has been hampered in part by our inability to directly age individuals. Like other crustaceans, lobsters grow through a process of ecdysis long believed to result in the loss and replacement of all calcified structures. As such, conventional ageing methods were thought to be inapplicable. However, Kilada et al. 2012 demonstrated that age could be accurately estimated in four temperate decapods by counting bands deposited in the eyestalk and ossicles of the gastric mill. The technique has since been applied to a few other crustaceans. In the Caribbean, the spiny lobster Panulirus argus supports one of the region’s largest and most economically valuable fisheries whose management would benefit if the age and size of individuals could be differentiated. Here we present the results of an ongoing study to verify use of bands deposited in the gastric mill to directly age P. argus. We have discovered clearly distinguishable bands in the ptero-, and zygo- cardiac ossicles of the gastric mill that differ logically between animals of different sizes from the Florida Keys. Validation of the method with captive reared lobsters of known age (1.5 - 10 years) confirms that bands form annually and are not associated with molting. Counts between independent readers were reproducible with coefficients of variation ranging from 11-26% depending on reader experience and the structure observed. We are currently conducting a laboratory experiment with Barium-tagged lobsters to identify settlement cohorts, and field sampling of populations in the Caribbean to examine patterns of age-size structure in the region. Our results demonstrate for the first time that direct age determination of P. argus is possible.

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