Extensive deep-sea dispersal of postlarval shrimp from a hydrothermal vent

Hydrothermal vent fields on the Mid-Atlantic Ridge (MAR) are small (no more than 0.1-1.0 km(2)) and widely spaced (a reported average of one field per 175 km between 11 degrees N and 40 degrees N). Their faunas are similar an d usually dominated by shrimp of the family Bresiliidae. Little is known ab out the way these animals (and other members of the vent fauna) disperse an d colonize new vents. Vent shrimp juveniles have been taken close to certai n vent sites, and in midwater, but their larvae and postlarvae have not bee n captured. We report here that bresiliid shrimp postlarvae are very widely dispersed around the Broken Spur vent field and extend into the next MAR s egment and the Atlantis Fracture Zone beyond. The populations show density gradients declining both vertically and horizontally from the vent site, in contrast to the overall pelagic biomass. This is the furthest recorded dis persal (> 100 km) of identified larvae from a hydrothermal vent and is suff icient to give them access to adjacent vent fields and thus the scope for c olonising new sites. (C) 1998 Elsevier Science Ltd. All rights reserved.