Growth Rate Variability and Lipofuscin Accumulation Rates in the Blue Crab Callinectes Sapidus

To better understand growth and age-pigment (lipofuscin) accumulation rates of the blue crab Callinectes sapidus under natural conditions, juveniles (33 to 94 mm carapace width) were reared in outdoor ponds for over 1 yr. Growth rates, measured by carapace width, during summer and fall exceeded all those reported in the literature; the initial carapace width of 59 ± 14 mm (mean ± SD) increased to 164 ± 15 mm within a 3 mo period. No growth occurred during winter months (November to April) at low water temperatures. Growth rates of crabs in ponds were substantially higher (von Bertalanffy growth parameter K = 1.09) than those of crabs held in laboratory environments, and than rate estimates for natural populations of mid-Atlantic blue crabs. Model comparisons indicated that seasonalized von Bertalanffy growth models (r2 > 0.9) provide a better fit than the non-seasonalized model (r2 = 0.74) for pond-reared crabs and, by implication, are more appropriate for field populations. Despite growth rates that varied strongly with season, lipofuscin (normalized to protein concentration) accumulation rate was nearly constant throughout the year. Although the lipofuscin level in pond-reared crabs was significantly correlated with size (carapace width), it was more closely correlated with chronological age. Lipofuscin accumulation rates were also similar to those observed for laboratory-reared crabs, despite very large differences in growth rates and temperature regimes. The constancy of normalized-lipofuscin accumulation rates of blue crabs across seasons and environmental conditions suggests that lipofuscin concentration can be a more robust indicator of age than carapace width alone.