A Study of Infraspecific Groups of the Baltic East Coast Autumn Herring by Two New Methods Based on Cluster Analysis

In the Baltic Sea the autumn spawning herring forms a smaller number of groups than the spring herring does. This is probably connected with the different location of their spawning grounds. Spawning grounds of the spring herring are concentrated in favorable sites near the coast (in gulf, estuaries, etc.) while between such spawning centers gaps occur usually. Contrary to it, in most parts of the Baltic spawning places of the autumn herring form a continuous chain situated in the open sea. Therefore, differences in environment conditions between the autumn spawning grounds of neighboring areas are small and in large districts the characters of the autumn herring do not reveal essential differences. For instance, there is no significant difference between the autumn herrings caught on various grounds off the Polish coasts (2,5). The autumn herring of the Swedish Baltic coasts can be divided into four groups (that of the Gulf of Bothnia, that of the Bothnia Sea, the herring of the Swedish east coast and that of the Swedish south coast), between which a gradual transition occurs [1].