STUDIES OF ESTUARINE DEPENDENCE 

 OF ATLANTIC COASTAL FISHES 



Data Report I: Northern Section, Cape Cod to Cape Lookout. 

 R. V. Dolphin Cruises 1965-66: Zooplankton volumes , mid- 

 water trawl collections , temperatures and salinities . 



By 



John Clark, W. G. Smith, Arthur W. Kendall, Jr., 

 and Michael P. Fahay 

 Sandy Hook Marine Laboratory 

 Highlands , New Jersey 07732 



In 1965, the Sandy Hook Marine Labora- 

 tory began research o'n the extent to which 

 migratory fishes of the Atlantic coast depend on 

 estuaries as essential habitat during the early 

 period of their lives . The final goal is to deter- 

 mine the effects on fishes of the physical dis- 

 ruption and pollution of estuaries that have 

 accompanied accelerated coastal development of 

 the last two decades . 



The young of 60 to 70 percent of the 

 economically important Atlantic species inhabit 

 estuarine environments at some time during 

 their first year of life (McHugh, 1966; Clark, 

 1967). Many species whose young are estuarine 

 dependent spawn offshore, and their progeny,, 

 while still very young, swim shoreward or are 

 transported there by currents to take up life in 

 the estuaries for part of their first year (Clark, 

 1967). 



Although it is widely assumed that 

 estuarine habitat is necessary for survival of 

 those Atlantic species whose young are found in 

 estuaries, the assumption can be verified only 

 with assurance that the young are absent or 

 scarce in the open ocean . The juveniles of any 

 species found in estuaries might be the whole of 

 the population or only a part of a population that 

 occurs largely in the open ocean. We have no 

 estimate of the proportion of the young fishes 

 that enter estuaries . To obtain data on ocean 

 occurrences of larval and juvenile fishes or on 

 offshore spawning areas we began our research 



on estuarine dependence with a systematic sur- 

 vey of the Atlantic continental shelf to locate 

 spawning areas and seasons and to follow the 

 movements of larval and juvenile stages away 

 from the spawning grounds . 



In this report we present the basic data 

 from our first series of surveys , the northern 

 section, which includes eight cruises of the 

 research vessel Dolphin (fig. 1) from Cape Cod, 

 Mass . , to Cape Lookout , N . C . , during the 

 1-year period, December 1965 to December 1966. 

 The data reported here include temperatures, 

 salinities, zooplankton volumes, and the mid- 

 water trawl collections of fishes. Our collection 

 of eggs and larval fishes is under study and will 

 be reported in future publications . 



We acknowledge the assistance of the 

 following biologists from cooperating laboratories 

 whose participation guaranteed the success of the 

 early cruises: John C. Poole, New York Depart- 

 ment of Conservation and Paul E . Hamer , Walter S , 

 Murawski, Jr., and Ronald White, New Jersey 

 Department of Conservation and Economic De- 

 velopment. The following colleagues assisted us 

 in identifying certain species in the midwater 

 trawl collections: C. Richard Robins , University 

 of Miami, Institute of Marine Sciences, Miami, 

 Fla.; and John A . Musick and John McEachran, 

 Virginia Institute of Marine Science, Gloucester 

 Point, Va . We extend our thanks to Gerald 

 Savitz of the Sandy Hook Marine Laboratory for 

 his painstaking preparation of all graphic material. 



