THE BEHAVIOUR AND PHYSIOLOOY OF HERRINO AND OTHER CLUPEIDS 341
For instance, a t certain times of year spent herring are to be found on
the Fladen ground and off the Belgian coast where the prevailing currents
might have taken them after spawning.
Nothing is known of the ability of marine fish to orientate to the
sun, though this ability is present in Lepmis (Haaler et al., 1968). It
is also known that sunlight may have a directional component to
considerable depths (e.g. to 90 my Sasaki et d., 1958). This would
provide a mechanism for the southerly migration of maturing herring
in the North Sea, but probably not for the migration of Norwegian
herring during the winter darkness, where the herring are a t the surface
a t night and 300-600 m deep by day and moving 0-7 miles in 24 hr
(Devold, personal communication). Devold has shown that the initial
migration of the Norwegian herring towardr, the spawning grounds
might be merely the following of a hydrographioal front a t speeds
of 6-7 miles per day but, in the later stages near the coast, they broke
through the barrier into the Atlantic water towarda the coast, aa if by
some directional urge, attaining sometimes speeds of 20-40 miles per
day. Galkov (1968) reported that small schools of herring migrated
across the Norwegian current by day and night a t depths down to
500 m.
One inevitably turns to the question of lemming in this respect.
Wynne-Edwards (1962) suggested that tradition played an important
part in the movements of fish migrating in a regular manner. If this
were so, a highly deleterious effect would be produced if stocks were
reduced to too low a limit, for a breakdown in the migration pattern
would result. It is well known that in herring the older fish usually
mature and enter the spawning fishery first, aa if they might have been
leading the recruit spawners ; but how is on0 to explain even a learned
ability to orientate?
4. Summary
It may be said, by way of summary, that there is good evidence for
the aggregation of clupeids into defined areas, partly as controlled by
land maases and partly as the result of kineees. These favourable areas
may themselves be moving, giving yearly variations of the migration
pattern. This, and a possible drift with the residual current aftm
spawning to overwintering or feeding areas (depending on the spawning
time), may partly explain migration. A more directed movement,
particularly to the spawning grounds, needs also to be postulated, but
it haa yet to be explained, either aa a result of a contranatant migration,
or a8 a reaction to gradients of temperature or chemical factore by
means of a taxis, or aa a result of an orientation to the sun or other
For instance, a t certain times of year spent herring are to be found on
the Fladen ground and off the Belgian coast where the prevailing currents
might have taken them after spawning.
Nothing is known of the ability of marine fish to orientate to the
sun, though this ability is present in Lepmis (Haaler et al., 1968). It
is also known that sunlight may have a directional component to
considerable depths (e.g. to 90 my Sasaki et d., 1958). This would
provide a mechanism for the southerly migration of maturing herring
in the North Sea, but probably not for the migration of Norwegian
herring during the winter darkness, where the herring are a t the surface
a t night and 300-600 m deep by day and moving 0-7 miles in 24 hr
(Devold, personal communication). Devold has shown that the initial
migration of the Norwegian herring towardr, the spawning grounds
might be merely the following of a hydrographioal front a t speeds
of 6-7 miles per day but, in the later stages near the coast, they broke
through the barrier into the Atlantic water towarda the coast, aa if by
some directional urge, attaining sometimes speeds of 20-40 miles per
day. Galkov (1968) reported that small schools of herring migrated
across the Norwegian current by day and night a t depths down to
500 m.
One inevitably turns to the question of lemming in this respect.
Wynne-Edwards (1962) suggested that tradition played an important
part in the movements of fish migrating in a regular manner. If this
were so, a highly deleterious effect would be produced if stocks were
reduced to too low a limit, for a breakdown in the migration pattern
would result. It is well known that in herring the older fish usually
mature and enter the spawning fishery first, aa if they might have been
leading the recruit spawners ; but how is on0 to explain even a learned
ability to orientate?
4. Summary
It may be said, by way of summary, that there is good evidence for
the aggregation of clupeids into defined areas, partly as controlled by
land maases and partly as the result of kineees. These favourable areas
may themselves be moving, giving yearly variations of the migration
pattern. This, and a possible drift with the residual current aftm
spawning to overwintering or feeding areas (depending on the spawning
time), may partly explain migration. A more directed movement,
particularly to the spawning grounds, needs also to be postulated, but
it haa yet to be explained, either aa a result of a contranatant migration,
or a8 a reaction to gradients of temperature or chemical factore by
means of a taxis, or aa a result of an orientation to the sun or other