Oxygen Depletion and Associated Benthic Mortalities 

 in New York Bight, 1976 



Chapter 11. Impact on Clams and Scallops 



Part 1. Field Survey Assessments 



J. W. Ropes, A. S. Merrill. S. A. Murawski/ 

 S. Chang, unci C. L. MacKenzie. Jr.- 



' Woods Hole Laboratory, Northeast Fisheries Cen- 

 ter, National Marine Fisheries Service, NOAA, Woods 

 Hole, MA 02543 



^ Sandy Hook Laboratory, Northeast Fisheries Cen- 

 ter, National Marine Fisheries Service, NOAA, High- 

 lands, NJ 07732 



INTRODUCTION 



The large mass of bottom water — deficient in oxygen, 

 and containing above normal quantities of hydrogen sul- 

 fide — caused stress and mortalities in bivalve moliusks off 

 the New Jersey coast beginning in June and July 1976. 

 Reports of surf clams (Spisula solidissirna) showing stress 

 reactions and mortalities were received from divers, otter 

 trawl fishermen, and clammers in early July. From July 

 through September, commercial fishing vessels from Mas- 

 sachusetts and New Jersey ports reported catches of dead 

 and dying sea scallops (Placopecten magellaniciis) off New 

 Jersey. In early August, dead and dying ocean quahogs 

 {Arctica islandica) were found off New Jersey. The general 

 distribution of surf clams and ocean quahogs in the Bight 

 were reported by Merrill and Ropes (1976); sea scallops 

 were reported by Merrill (1962). 



During August through early October. NOAA's Na- 

 tional Marine Fisheries Service (NMFS) used commercial 

 hydraulic dredges to survey surf clams in and beyond the 

 area of suspected oxygen deficiency. The surveys assessed 

 the effects of the adverse environmental conditions on the 

 surf clam resource, and observed mortalities of other in- 

 vertebrates and bivalves, including the commercially im- 

 portant ocean quahog and sea scallop, although the full 

 range of the latter two was not covered. Assessment sur- 

 veys on sea scallops were made in October and November. 



This chapter summarizes the observations and data 

 gathered during the oxygen depletion event. Detailed data 

 from specific survey cruises are included in a workshop 

 publication (Northeast Fisheries Center 1977b). Clam 

 asessnient surveys in April-May 1976 and January-March 

 1977 provided data on clam stock sizes before and after 

 the event and made it possible to estimate the stock loss 

 (Northeast Fisheries Center 1976a, 1977a). 



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