FISHERY BULLETIN: VOL. 81, NO. 4 



TABLE 2. — Comparisons of zooplankton volumes (cc/100 m 3 ) by subarea between MARMAP data and the earlier 

 studies on the northeast continental shelf. No significant differences were found between MARMAP data and earlier 

 studies in comparisons of displacement volumes (Kruskal- WallisP > 0.05). Volumes reported by Bigelow( 1926) for 

 late summer on Georges Bank were relatively high compared with those for the same season in MARMAP data 

 However, Bigelow's sampling was heavily biased towards the northeast peak of Georges Bank. The range of mean dis- 

 placement volumes for that region in the MARMAP data is 24.4-191.7 cc/100 m\ 



findings are in contrast with the 30-yr decline in 

 zooplankton including the copepod component 

 reported for large areas of the North Atlantic and 

 North Sea (Colebrook 1978b). It appears that the 

 climatic changes influencing the zooplankton de- 

 creases in the northeast Atlantic are more pronounced 

 in the open ocean areas of the North Atlantic drift 

 which in turn have greater impact on plankton in the 

 North Sea (Colebrook 1978a, b, 1982; Garrod and 

 Colebrook 1978). Based on MARMAP studies of the 

 Northeast Fisheries Center, we have not detected 

 large-scale influences of Gulf Stream eddies on pop- 

 ulations of zooplankton or ichthyoplankton on the 

 northwest Atlantic shelf (Laurence and Burns 1982; 

 Cohen et al. 1982). 



The fish stocks representing the mid-size predator 

 component of the ecosystem of the northeast con- 

 tinental shelf have declined recently. During the 

 period 1968 through 1975, the biomass of principle 

 fish species declined about 50%. The decline was 

 correlated with heavy fishing mortality (Clark and 

 Brown 1977). The relative stability observed in both 

 zooplankton standing stock and species composition 

 when considered in relation to the decline in finfish 

 biomass and subsequent population explosion of 

 fast- growing, short-lived, zooplanktivorous sand eel 

 (Sherman et al. 1981a) suggests that the reductions 

 in fish abundance are not attributable to a lack of 

 food at the lower end of the food chain. It appears that 

 fishing mortality has imposed greater perturbations 

 on fish populations of the northeast shelf than any 



changes in the abundance of zooplankton. 



ACKNOWLEDGMENTS 



We thank Kurt Lambert, Institut fur Hochsee- 

 fischerei, Rostock, GDR; Bohdan Draganik, Morski 

 Instytut Rybacki, Gdynia, Poland; and Vyacheslav 

 Sushin, AtlantNIRO, Kaliningrad, USSR, for their 

 cooperation in implementing the joint MARMAP 

 surveys. We are also grateful to the technicians and 

 crews of the research vessels Goerlitz (GDR); 

 Wieczno (Poland); Albatross IV, Delaware II, Kelez, 

 and Mt. Mitchell (USA); and Argus, Noglicki, 

 Yubileiny, Belogorsk, and Evricka (USSR) for the 

 effort made, often under difficult sea conditions, to 

 expedite the collections of zooplankton. We thank 

 the staff of the Plankton Sorting Center in Szczecin, 

 Poland, for sorting and identifying the zooplankton 

 used in the study, and Thomas Plichta, Northeast 

 Fisheries Center Narragansett Laboratory of the 

 National Marine Fisheries Service for his assistance 

 in the statistical analyses of the zooplankton data. 

 We are indebted to William Dunkle, Archivist at the 

 Woods Hole Oceanographic Institution, for making 

 available original zooplankton data from the Bigelow 

 and Sears study of 1929-32. 



LITERATURE CITED 



Bigelow, H. B. 



1926. Plankton of the offshore waters of the Gulf of 



860 



