may produce serious indirect effects as well. Biggs 

 (1976) has shown that siphonophores like N. cara 

 can eat prey ranging in size from zooplankton 

 nauplii to small fish. As Fraser (1962) and Zelik- 

 man (1969) have proposed for aggregations of 

 other gelatinous carnivores capable of eating zoo- 

 plankton and larval fish, areas or seasons in which 

 siphonophores are locally abundant could conceiv- 

 ably suffer dramatic reductions of ichthyoplank- 

 ton. Lough^ cited indirect evidence of possible 

 heavy predation by siphonophores upon Atlantic 

 herring larvae based on changes in population 

 densities and distributions of the two species dur- 

 ing winter 1975-76 in the Nantucket Shoals- 

 Georges Bank area. Since the Gulf of Maine his- 

 torically has been an important commercial 

 fishing ground, future research on interaction be- 

 tween siphonophores and ichthyoplankton could 

 lead to a better understanding of the regional food 

 chain and the factors which influence year class 

 success of ichthyoplankton. 



Summary 



Aggregations of the physonect siphonophore 

 Nanomia cara were observed at several dive sites 

 in the Gulf of Maine from Nekton Gama. This 

 siphonophore occurs throughout the Gulf of Maine 

 although the vertical and horizontal distribution 

 is patchy. Densities as high as 1 to 7 colonies/m^ 

 were observed. Colony length ranged in size from 

 0.2 to 3.7 m and most aggregations included sev- 

 eral different sizes. Nanomia cara was negatively 

 photoactic and initiated escape swimming re- 

 sponse at speeds which exceeded 20 to 30 cm/s. All 

 siphonophores were observed below the thermo- 

 cline and generally occurred only where water 

 depth was >128 m. 



Euphausiids, mysids, and hyperiid amphipods 

 were observed among populations of siphono- 

 phores, but we observed only one colony which had 

 eaten prey of this size. In seasons and areas of 

 maximum abundance, siphonophores could con- 

 ceivably influence the success of a year class of 

 ichthyoplankton by heavy predation as well as 

 cause losses of time and money to commercial 

 fishermen by clogging trawl gear. 



Acknowledgments 



We are indebted to H. Wes Pratt of the North- 

 east Fisheries Center Narragansett Laboratory, 

 National Marine Fisheries Service, NO A A for his 

 many observations and to Fred Lux of the North- 

 east Fisheries Center Woods Hole Laboratory for 

 his helpful information. Lianne Armstrong pre- 

 pared the illustrations. 



Literature Cited 



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^x Carolyn A. Rogers 



Northeast Fisheries Center Narragansett Laboratory 

 National Marine Fisheries Service, NOAA 

 R.R. 7 A, Box 522A, Narragansett, RI 02882 



Douglas C. Biggs 



Marine Sciences Research Center 

 State University of New York 

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*Lough, R. G. 1976. The distribution and abundance, growth 

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Richard a. Cooper 



Northeast Fisheries Center Woods Hole Laboratory 

 National Marine Fisheries Service, NOAA 

 Woods Hole, MA 02543 



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