A comparison of molt states of blue crab megalopae, Callinectes sapidus (Rathbun), sampled with artificial collectors and plankton nets

Abstract

Molt stages of the megalopae of Callinectes sapidus in a northern Gulf of Mexico estuary were compared for those sampled with artificial collectors versus plankton tows. In contrast to other studies from the US east coast, the proportions of molt stages collected did not differ between the two sampling methods; nor did the proportions of molt stages sampled change between months. The time to metamorphosis was inversely related to molt stage; megalopae in less developed molt stages metamorphosed later than those in the more developed stages of the molt cycle. A previously unreported aspect of the relationship between molt stage and time to metamorphosis was discovered. In megalopae settling during pulse periods of greater megalopal abundance, the mean time to metamorphosis was shortened by 43% in both megalopae sampled with artificial collectors and plankton nets. The results of this study indicate that megalopae in more advanced stages of the molt cycle are not more likely to settle than megalopae in less advanced stages of the molt cycle. Furthermore, molt stage may not be a good predictor of the likelihood of settlement in the northern Gulf of Mexico.