Use of extractable lipofuscin for age determination of blue crab Callinectes sapidus

The blue crab Callinectes sapidus is an economically and ecologically important species in many temperate estuaries, yet stock assessments have been limited to length-based methods for demographic analyses. We evaluated the potential of age pigments (lipofuscins) sequestered in neural tissue of eye-stalks and brains to estimate the age of blue crabs collected from Chesapeake Bay and Chincoteague Bay. The rate of lipofuscin accumulation was determined using crabs of known age reared in the laboratory. Age pigments were extracted from neural tissues (eye-stalk or brain), quantified, and normalized to protein content to allow comparisons across tissue types and crab sizes. Field-collected blue crabs (35 to 185 mm carapace width) contained highly variable levels of age pigments (coefficient of variation = 58%). Lipofuscin level was significantly related to carapace width, but not significantly different between gender or sampling location. In juveniles (40 to 70 mm carapace width) reared for 6 mo, the age pigments showed no significant change during the rapid summer growth period, but significantly increased during fall (after 3 mo). Lipofuscin contents in known-age reared crabs were positively related to chronological age. Modal analysis of lipofuscin for field-collected adult males provided separation of multiple modes, whereas carapace width showed only a single broad mode. These results confirm the potential use of lipofuscin for age estimation of blue crabs.