Important aspect of this method. This task presents no difficulties, since instruments registering 

 the temperatiire and salinity while the ship is in motion are already available. Ensuring continuity 

 of observations on biomass and composition of plankton is somewhat more difficult. 



The suggested method of observations on the interrelations between organism and environ- 

 ment is an element of the new methodology employed in studying the migrations of fish and can be 

 considered a great achievement. In the past, studying the environmental conditions of fish con- 

 sisted of taking observations at "stations", whereas the method suggested is based on the quanti- 

 tative characterization of the elements of environment and distribution of the species over a large 

 area almost simultaneously. When a large number of fishing boats are fishing herring concentra- 

 tions, It is relatively easy to determine the biological characteristics of the schools, since even 

 now all the captains endeavor to determine the size of the herring concentration on which they fish, 

 while the exploratory ships analyze the catches from the biological viewpoint to establish the size 

 of herring, stomach content, fat content, and stage of sexual maturity. Under these conditions, 

 one or two detailed biological analyses of the herring schools made on board the exploratory boat 

 complete the characterization of the concentration. These analyses become particularly important 

 when the laboratory analyses, including the age determination of the fish, are carried out directly 

 on shipboard. The technique of drift net fishing enables the fishermen to determine the directional 

 movements of schools, a factor which plays an important role in systematizing the observations . 

 Mass tagging of herring from the school on which the fishing is conducted enables the scientist to 

 verify experimentally the movements of schools . 



Tlie work of the commercial fisherman coincides perfectly with that of the scientist en- 

 deavoring to study the migration of fish. This method has great possibilities, as it enables the 

 fleet to remain within the region where the herring concentrate, and this naturally Increases the 

 productivity of its operations. Using this method, we succeeded in following the movement of her- 

 ring concentrations in a number of regions, thougji over rather short distances. The method, based 

 on direct observations on the biological grouping of herring, a method Heincke said could not be 

 applied at the beginning of our century, has now become the technique promising optimum practical 

 possibilities . 



The samples characterizing the biological composition of herring catches were collected 

 througjiout the entire period of research by the same methods . Samples of herring consisting of 

 100-200 specimens, depending on variations in size, were taken from the catches of exploratory, 

 reconnaissance or, though less frequently, fishing boats. In the case of samples obtained from the 

 drift net catches, we always recorded the dimensions of the mesh of the nets in the drifting order, 

 estimated the mean catch per net, the depth of submersion, direction from which the herring enter- 

 ed the net, etc . 



Samples of herring were delivered in sligjitly salted state to the laboratory, where they were 

 subjected to the following thorough biological analysis: Length from the tip of the snout to the end 

 of the median rays of the caudal fin, sex and degree of maturity of the gonads determined by the 

 seven-point system, age, fattlness, etc. In certain samples, we counted the number of vertebrae 

 in all the specimens. Total weight and weight of gonads were determined from fresh material only. 

 During recent Investigations, the complete biological analysis of herring samples, including the 

 determination of the age of herring from the scales, was made on board the exploratory ships . 



In the present article we used a relatively small portion of the data collected by the Polar 

 Institute, which we believed indispensable for solving the problems involved in this research - i.e., 

 the study of biological peculiarities, spawning regions and environment, migrations of young and 

 adult specimens, specific structural details of the spawning stocks and reproductive capacity of 

 the Atlantic-Scandinavian herring. 



