282 Memoir Sears Foundation for Marine Research 



of sardine-sized fry may often be seen streaming past some rocky headland, seemingly 

 in an endless procession. What the directive stimulus may be we have yet to learn, for 

 as Huntsman has pointed out, "There is no indication that herring swim against 

 the current unless the water is somewhat turbulent" (65: 83). Whether they make or 

 lose headway over the bottom while doing so depends on their swimming speed relative 

 to the strength of the current. 



No information is available as to how rapidly a school may travel at sea. But Frid- 

 riksson and Aasen have found that specimens held alive in nets swam constantly at a rate 

 of about 0.2—0.25 ^^^ miles per hour (6—8 m/min.) when not disturbed. It is certain 

 that they are capable of long journeys, for individuals tagged on the east coast of 

 Iceland have been recaptured in southern Norway, and vice versa {40: 26, 27). 



How active Atlantic Herring are at any time and place depends primarily on 

 the water temperature. In the Bay of Fundy region, for example, they "move very 

 sluggishly when the water is coldest, in February and March," i. e. when the upper 20 

 fms. or so have cooled to about 32—36°. They become active again when the water has 

 warmed to about 40—43°. 



While the vertical range of this species extends down to an extreme depth of 

 about 100 fms., the vast majority lives at depths shallower than 40-50 fms., living 

 pelagically in the upper water layers for most of the year but close to the bottom during 

 the coldest months. 



Relation to Light. That light is an important factor in controlling their vertical 

 distribution, at least in southern New Brunswick, was discovered by Johnson in 1939 

 {6g: 349-354). He found that at night, in the absence of appreciable light, all sizes 

 were quite near the surface. During weak light, as at dawn and dusk, all sizes still were 

 a foot or so from the surface. However, as the sun rose above the horizon they left 

 the surface, the largest fish, 190-230 mm long, descending to a depth greater than 

 10 feet and those 140—180 mm long to a depth of 10 feet or more; the smaller ones in 

 general were nearer the surface. Also, on cloudy days all sizes were closer to the surface 

 than on clear days. 



Migratory Movements. Because of the economic value of this species, knowledge 

 of the migrational habits, which would make it possible to predict runs in advance of 

 their occurrence, has been and continues to be sought on both continents. In Europe 

 at least, these studies have been complicated by the presence of a large but in- 

 determinate number of local populations or races (p. 287), each with its own mi- 

 gratory pattern, a fact not known until comparatively recently and even now not well 

 understood. As Norman (joi: 263) wrote: 



At some seasons herrings may be found in huge numbers in a given locahty (in Europe), at others they 

 will disappear almost entirely; in other places they may be caught all the year round, but the numbers caught 

 on a given ground may exhibit an immense amount of variation from one season to another. 



To explain these long known and very obvious facts, an older view, widely held 

 until about 1825, was that Atlantic Herring as a whole withdraw in winter to Arctic 



