Examination of data on the abundance of adult 

 and nauplii stages in the Narragansett Bay and 

 Block Island Sound areas (Deevey 1952; Faber 

 1966) for the time of year samples for this research 

 were collected (July-August) showed that, al- 

 though all seven species were present, only A. 

 tonsa, T. longicornis, andC. hamatus were availa- 

 ble in sufficient quantity to be considered major 

 prey organisms. They represented 24.6, 10.8, and 

 10.4%, respectively, of the total copepods availa- 

 ble, while the other four species were less than 3%. 

 The results of this study in calories per gram ash- 

 free dry weight (Table 1) show that A. tonsa had 

 the second highest value while C. hamatus and T. 

 longicornis had the two lowest values. In fact, the 

 difference between A. tonsa and T. longicornis is 

 680 cal/g. This indicates, assuming equivalent as- 

 similation rates, that predators utilizing the 

 copepods like A. tonsa with higher caloric values 

 may have an advantage in acquiring energy for 

 growth and metabolic processes. Predators feed- 

 ing on copepods with lower values, especially T. 

 longicornis, would have to consume more prey or- 

 ganisms for an equivalent energy intake and, 

 given the same density of plankton, would spend 

 more energy searching for their prey. 



Acknowledgments 



I thank John B. Colton, Jr. for his critical re- 

 view of the manuscript and Stephen Hale for his 

 technical assistance. 



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Geoffrey C. Laurence 



Northeast Fisheries Center Narrangansett Laboratory 

 National Marine Fisheries Service, NOAA 

 Narragansett, RI 02882 



METHOD FOR RESTRAINING 

 LIVING PLANKTONIC CRUSTACEANS* 



Studies of the feeding and swimming mecha- 

 nisms of small, active planktonic crustaceans re- 

 quire restraining the organisms so that water 

 flow and limb movements can be observed under 

 the microscope. The usual technique is to place 

 the organism in a watch glass or cavity slide 

 (Cannon 1928; Gauld 1966) or to secure the dorsal 

 side of the animal to a drop of stopcock grease in 



'Contribution No. 3488 from the Woods Hole Oceanographic 

 Institution. This work was supported by NSF Grant GA-41188. 



220 



