tionship. It is our experience, however, that these 

 organisms are abundant only on rare occasions 

 in the MARMAP study area. The predictive 

 equations should assist investigators assessing 

 zooplankton standing stock on the continental 

 shelf of the Northwest Atlantic. 



General conversion factors at best yield only 

 gross estimates, thus investigators should be 

 aware of the limitations imposed by these values. 

 A decision must be made by the investigator as to 

 what level of accuracy is acceptable on the basis 

 of what the data is to be used for. Further break- 

 down of the data into smaller subsets than area 

 and season is possible, but the result would be an 

 unwieldy number of equations sensitive to 

 minute changes in trophic conditions. However, 

 one can conclude from this study that effective 

 displacement volume to dry weight conversion 

 equations must to some extent take into account 

 seasonal and areal variations in community com- 

 position. Given these considerations, the data 

 presented here show no increase in variability in- 

 herent in displacement volume over dry weight 

 biomass measures. Displacement volume pro- 

 vides a simple, easily routinized, rapid and non- 

 destructive method of representing biomass, 

 which is appropriate for processing the large 

 numbers of samples typical of survey sampling 

 programs. 



Acknowledgments 



I am indebted to J. R. Green for his guidance 

 throughout the study and to D. Busch who 

 greatly improved the manuscript. Gail Santoro 

 typed the final manuscript and Lianne Arm- 

 strong drafted the figures. 



Literature Cited 



Ahlstrom, E. H., and J. R. Thrailkill. 



1963. Plankton volume loss with time of preservation. 

 Calif. Coop. Oceanic Fish. Invest. Rep. 9:57-73. 

 Be, A. W. H., J. M. Forns, and 0. A. Roels. 



1971. Plankton abundance in the North Atlantic Ocean. 

 In J. D. Costlow, Jr. (editor), Fertility of the sea 1:17-50. 

 Gordon and Breach Sci. Publ., N.Y. 

 Beers, J. 



1974. Biomass. In H. F. Steedman (editor), Laboratory 

 methods in the study of marine zooplankton, Vol. 35, p. 

 352-354. J. Cons. 

 Bsharah, L. 



1957. Plankton of the Florida Current. V. Environmental 

 conditions, standing crop, seasonal and diurnal changes 

 at a station forty miles east of Miami. Bull. Mar. Sci. 

 Gulf Caribb. 7:201-251. 



Comita, G. W., S. M. Marshall, and A. P. Orr. 



1966. On the biology of Calamus finmarchicus. XIII. Sea- 

 sonal change in weight, calorific value and organic mat- 

 ter. J. Mar. Biol. Assoc. U.K. 46:1-17. 

 Curl, H.. Jr. 



1962. Analyses of carbon in marine plankton organisms. 

 J. Mar. Res. 20:181-188. 

 Frolander, H. F. 



1957. A plankton volume indicator. J. Cons. 22:278- 

 283. 



Le Borgne, R. 



1975. Equivalences entre les mesures de biovolumes, 



poid sees, poids sec sans cendre, carbone, azote et phos- 



phore du mesozooplancton de l'Atlantique tropical. 



[In Fr., Engl, abstr.] Cah. ORSTOM, Ser. Oceanogr., 



13:179-196. 

 Lewontin, R. C. 



1966. On the measurement of relative variability. Syst. 



Zool. 15:141-142. 

 Lovegrove, T. 



1966. The determination of the dry weight of plankton 

 and the effect of various factors on the values obtained. 

 In H. Barnes (editor), Some contemporary studies in ma- 

 rine science, p. 429-467. George Allen and Unwin, 

 Ltd., Lond. 



Marshall, S. M., and A. P. Orr. 



1955. The biology of a marine copepod, Calanus fin- 

 marchicus (Gunnerus). Oliver and Boyd, Edinb., 188 p. 

 Menzel, D. W., and J. H. Ryther. 



1961. Zooplankton in the Sargasso Sea off Bermuda and 

 its relation to organic production. J. Cons. 26:250- 

 258. 



Nakai, Z., and K. Honjo. 



1962. Comparative studies on measurements of the 

 weight and the volume of plankton samples. A prelimi- 

 nary account. Indo-Pac. Fish. Counc. Proc, 9th Sess., 

 Sect. II, p. 9-16. 



Platt, T., V. M. Brawn, and B. Irwin. 



1969. Caloric and carbon equivalents of zooplankton bio- 

 mass. J. Fish. Res. Board Can. 26:2345-2349. 

 RlCKER, W. E. 



1973. Linear regressions in fishery research. J. Fish. 

 Res. Board Can. 30:409-434. 

 Rogers, C. A., D. C. Biggs, and R. A. Cooper. 



1978. Aggregation of the siphonophore Nanomia cava in 

 the Gulf of Maine: observations from a submersible. 

 Fish. Bull, U.S. 76:281-284. 



Sherman, K. 



1980. MARMAP, a fisheries ecosystem study in the 

 Northwest Atlantic: Fluctuations in ichthyoplankton- 

 zooplankton components and their potential for impact 

 on the system. In F. P. Diemer. F. J. Vernberg, and 

 D. Z. Mirkes (editors), Advanced concepts in ocean mea- 

 surements for marine biology, p. 9-37. Belle W. Baruch 

 Institute for Marine Biology and Coastal Research, 

 Univ. S.C. Press. 



Sherman, K., C. Jones, and J. Kane. 



1979. Zooplankton of continental shelf nursery and feed- 

 ing grounds of pelagic and demersal fish in the north- 

 west Atlantic. Int. Counc. Explor. Sea CM. 1979/L:27. 



Sherman, K., L. Sullivan, and R. Byron. 



1978. Pulses in the abundance of zooplankton prey of fish 

 on the continental shelf off New England. Int. Counc. 

 Explor. Sea CM. 1978/L:25. 

 Snedecor, G. W., and W. G. Cochran. 



1967. Statistical methods. 6th ed. Iowa State Univ. 



641 



