From these studies it appears that transparency is af- 

 fected by plankton only when it is present in relatively great 

 concentrations. In all cases the volumes are certainly mini- 

 mal, since much of the finest material passes through the 

 meshes of the net and the larger, fast-swimming forms 

 escape it. 



Table VII gives the numbers, adjusted to 60-meter hauls, 

 of the important species of plankton taken at each station. 

 Station 32 is omitted from the table since the sample was 

 not complete. From this table it can be seen that copepods 

 are the major constituent of the plankton. The most abundant 

 copepods numerically were the small species Oithona similis 

 (O. helgolandica in the CHELAN report") and Pseudocalanus 

 minutus, both of which occurred at every station, usually 

 in appreciable numbers, and probably constitute a staple 

 element in the diet of larval fishes and other plankton feeders. 

 Important also among the microcalanids was Acartia longi- 

 remis, with centers of abundance off Cape Romanzof and in 

 Kotzebue Sound. 



Calanus finmarchicus was the most abundant and wide- 

 spread of the larger copepods, occurring at all but two stations 

 (N5 and N23). This is in keeping with its well-known extensive 

 distribution in other northern waters, where it is often the 

 major food for many fish and baleen whales. Other large 

 copepods important in the Bering and Chukchi Seas are Calanus 

 tonsus, Calanus crista tus , and Eucalanus bungii bungii. The 

 number of these large species was minimal, since for best 

 results larger coarser nets should have been used. 



Certain other copepods, while not always abundant, are of 

 special interest because of their characteristic distribution 

 (fig. 57). For example, Epilabidocera amphitrites , Centropages 

 mcmurrichi, and Tortanus discaudatus occurred only in the 

 warmer (39 degrees F or above) waters with some neritic 

 influence, suggesting a close affinity to the Alaskan coast; 

 whereas, Metridia lucens was characteristic of the more 

 open cold waters to the west and north where this species 

 entered the plankton community together with the larger 

 calanoids mentioned above. 



In the study of the CHELAN samples 8 it was brought out 

 that only the northern variety of Eucalanus bungii occurred 

 in the Bering Sea area. The present series of samples verify 

 this finding. The extensive area covered by the USS NEREUS 

 makes possible a further comparison of that interesting 

 species. In the series of stations occupied south of the Aleu- 

 tians it was found that only the northern variety, Eucalanus 

 bungii bungii, was present at the station at 43°29' N latitude 



