MIDWATER COMMUNITY STUDIES OFF NEW ENGLAND 

 USING THE JOHNSON SEA-LINK SUBMERSIBLES 



Ronald J. Larson 1 G. Richard Harbison 1 , Phillip R. Pugh 2 , 



John A. Janssen^, Robert H. Gibbs^, James E. Craddock 6 , 

 Claudia E. Mills 6 , Richard L. Miller', and Ronald W. Gilmer 1 



1 - Harbor Branch Oceanographic Institution, Fort Pierce, FL 



2 - Institute of Oceanographic Sciences, Wormley, England 



3 - Biology Department, Loyola University, Chicago, IL 



4 - Fish Division, U.S. National Museum, Washington, D.C. 



5 - Woods Hole Oceanographic Institution, Woods Hole, MA 



6 - Friday Harbor Laboratories, Friday Harbor, WA 



7 - Biology Department, Temple University, Philadelphia, PA 



ABSTRACT 



The midwater community off New England was studied using 

 manned submersibles. Twenty-three dives were made in three 

 submarine canyons SE of Woods Hole in 800 m of water. We found a 

 diverse community present. Gelatinous zooplankton (medusae, 

 siphonophores and ctenophores ) were represented by 38 species, 

 several are undescribed. The vertical distributions of most were 

 determined and it was discovered that they were mostly 

 mesopelagic (occurring below 400 m). Ctenophores were both 

 diverse and numerous in contradiction to the results of studies 

 using nets. The siphonophore Nanomia cara , which showed evidence 

 of a 150 m diel vertical migration, was most abundant. 

 Crustacean micronekton consisted mostly of Meganyctiphanes 

 norveqica , Sergestes sp., and Themisto gaudichaudii . These 

 species all vertically migrated 100 m or more and were sometimes 

 very numerous in midwater strata or near the bottom. Midwater 

 fishes were found in the mesopelagic but some migrated into the 

 upper 100 m at night. It is concluded that predation by visually 

 orienting predators in surface waters may be the primary factor 

 which determines vertical distributions. Nevertheless, the 

 mesopelagic is not a good refuge from predators because there are 

 large numbers of gelatinous predators there. 



INTRODUCTION 



Although a large number of studies have been done on the 

 midwater fauna of the North Atlantic little is known about the 

 species composition and vertical distribution of most taxa in 



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