Ontogenetic changes in habitat use by postlarvae and young juveniles of the blue crab

Abstract

Changing habitat requirements are evident during the developmental cycles of many species. In this field investigation, we attempted to distinguish between depth (shallow vs deep), habitat structure (seagrass species), and study site as factors influencing the distribution and abundance of postlarvae and juvenile blue crabs Callinectes sapidusin the Chesapeake Bay. Deep (2 70 cm mean low water [MLW]) and shallow (1 50 cm MLW) suction samples in monospecific Zostera marina and Ruppia maritima beds were taken in the York River, a tributary of the Chesapeake Bay. Our studies revealed ontogenetic changes in habitat use, which suggested that blue crabs are influenced differently by physical and biological factors even during the earliest life stages. Postlarvae through 3rd instar distributions were not related to seagrass species, but their densities increased with distance upriver (regression, p < 0.004, n = 36 to 38, postlarvae: r'= 0.173, 1st instars: r2 = 0.308, 2nd-3rd instars: r2 = 0.231). Thls suggests that the smallest instar distributions are related to larval supply and physical forces, such as currents and winds, which determine water-column transport. In contrast, 4th and greater instars were significantly more abundant in Ruppia than in Zostera (ANOVA, df = 1, p < 0.05), possibly because of the high shoot density of Ruppia beds. Habitat use by 4th and greater instars may be related to seasonal changes in seagrass shoot density. Water depth did not influence the distribution of any crab stage. We suggest that habitat selection and differential mortality among habitats influence larger instar distributions more strongly than they influence the distribution of postlarvae and the earliest instars of C. sapidus.

Exotic macroalga Gracilaria vermiculophylla provides superior nursery habitat for native blue crab in Chesapeake Bay

“…Small and large juveniles of Callinectes sapidus differentially inhabit vegetated primary nurseries and unvegetated secondary nurseries, respectively (Pardieck et al 1999, Lipcius et al 2007). This has been proposed to be due to a size-specific habitat shift during ontogeny, given that crabs < 30 mm carapace width (CW) are abundant within seagrass beds, whereas larger juveniles inhabit sublittoral mudflats, where they may escape density-dependent growth reduction, cannibalism and predation (Pile et al 1996, Hovel & Lipcius 2001, Lipcius et al 2007).…”

Settlement of megalopae and early juveniles of the velvet swimming crab Necora puber (Decapoda: Portunidae) in flow conditions

“…An ontogenetic shift of habitat use by early juvenile instars has been observed for the shore crab Carcinus maenas (Hedvall et al 1998, Moksnes 2002) and the blue crab Callinectes sapidus (Pardieck et al 1999, Etherington & Eggleston 2000. In the latter, active post-settlement dispersal has been shown in early juveniles through planktonic movement (Blackmon & Eggleston 2001).…”

“…High density has been evoked as a strong influence in the distribution of early juveniles of Callinectes sapidus in nature (Pile et al 1996, Moksnes et al 1997, Pardieck et al 1999, Etherington & Eggleston 2000, van Montfrans et al 2003, causing dispersal by density-dependent agonistic interactions and/or cannibalism. In the trials, the high numbers of individuals necessary for the statistical tests meant that the density used was much higher than that encountered in the field, and cannibalistic and agonistic behaviours could have pressured animals for a more even distribution.…”

Ontogenetic changes in the olfactory antennules of the shore crab,Hemigrapsus oregonensis, maintain sniffing function during growth

“…There is evidence that juvenile crabs use chemical cues in order to avoid predation [4] and late-stage larvae use olfaction to detect settlement cues from the environment [53]. Thus, odour capture is an important aspect of crab biology throughout ontogeny.…”

“…For example, malacostracan crustaceans use odours to track and locate food, avoid predation, identify conspecifics and mediate reproduction [1][2][3][4][5][6][7][8][9][10][11].…”