Blue Crab (Callinectes sapidus Rathbun, 1896) Settlement at Three Georgia (USA) Estuarine Sites

The blue crab, Callinectes sapidus Rathbun, 1896, represents the second most important fishery for coastal Georgia; yet, little is known about environmental forces that affect planktonic postlarval settlement in the region. Here, we describe a study to examine the physical mechanisms responsible for blue crab settlement in the extensive salt marsh system of coastal Georgia. Bottom and surface samplers were placed at three sites along a salinity gradient from a low-salinity site in the Altamaha River to a high-salinity area of the Duplin River, Sapelo Island, GA, USA during 2005. Megalopae and juvenile monitoring occurred from July through December. The majority of both megalopae (86.8%) and juvenile (89.3%) blue crabs were recovered in bottom samplers at the low-salinity Altamaha River site during August and early September. Few megalopae were collected at the surface of the Altamaha River or at the two higher-salinity sites in the Duplin and North Rivers. Downwelling winds were unable to explain all settlement events; however, winds with an onshore component regularly preceded settlement events. The use of a multiple-regression model revealed a lagged relationship (r = 0.5461, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ lag = 0–2 days $$\end{document}) between wind events, temperature, salinity, maximum tidal height, and settlement.