THE BEHAVIOUR AND PHYSIOLOQY OF HERRINQ AND OTHER CLUPEIDS 365
account for this behaviour. Devold has put forward learning as a poasibility-the fish learning to keep lower in order to avoid the nets after
frequent migrations to the coast during their lifetime. Another
possibility is that the fish with a tendency to swim higher in the water
might have been fished out, or there may be a hydrographical explanation. Polonskij (1961) found an increased warming of surface
layers during this time.
5. Effect of electricity
Groody et al. (1952) and Loukashkin and Grant (1964) studied the
effect of electrical fields on Sardinop caerdea. The fish orientated to
face the anode and were forced to it, when subjected to pulsating direct
current and rectified 60-cycle alternating current of different wave
forms. The current density required to produce galvanotropism waa
critical and varied inversely with the size of fish. Densities below the
optimum produced little response; those above the optimum might
cause temporary paralysis or death.
W . Learning
Clupeids in aquaria do not seem to become tame as do many
other marine species. This may be a characteristic of shoaling species
which are the prey of many other types of animals. There are apparently
no reports of conditioned responses being set up in clupeids, though this
would clearly be of great value in fish behaviour studies, particularly
in relation t o the sensitivity of clupeids to stimuli of differeiit intensity
and quality (e.g. Bull, 1952). Unfortunately the locomotmy behaviour
and general manoeuvrability of clupeids, arid thdr lack of marked
behaviour patterns except shoaling, would mrtko the work more difficult. However some Russian worker8 (mc Section VI, U) conniderorl
that attraction to artificial light W&R the result of a crmditioned rewymrirwt
set up by the association between light and feeding.
Clearly learning and memory could be of the greatest importance irt
capture and avoidance of fishing gear. Both Dcvold and Mohr (see
Section VI, V) have stressed this point, but it is doubtful whether its
importance can ever he assessed, except indirectly by fishing trials on
a population of known size in an enclosed arect, where fish that had been
caught could bo marked and rctleaqed.
Tho role of learning and mcmory in migration has been discussed by
Wynne-Edwards (sce Section VI, R). Possibly the only way of assessing
this would be in plotting the migration pttterns of a stock being
reduced to a very low level and consisting of rocruit fish.
24
account for this behaviour. Devold has put forward learning as a poasibility-the fish learning to keep lower in order to avoid the nets after
frequent migrations to the coast during their lifetime. Another
possibility is that the fish with a tendency to swim higher in the water
might have been fished out, or there may be a hydrographical explanation. Polonskij (1961) found an increased warming of surface
layers during this time.
5. Effect of electricity
Groody et al. (1952) and Loukashkin and Grant (1964) studied the
effect of electrical fields on Sardinop caerdea. The fish orientated to
face the anode and were forced to it, when subjected to pulsating direct
current and rectified 60-cycle alternating current of different wave
forms. The current density required to produce galvanotropism waa
critical and varied inversely with the size of fish. Densities below the
optimum produced little response; those above the optimum might
cause temporary paralysis or death.
W . Learning
Clupeids in aquaria do not seem to become tame as do many
other marine species. This may be a characteristic of shoaling species
which are the prey of many other types of animals. There are apparently
no reports of conditioned responses being set up in clupeids, though this
would clearly be of great value in fish behaviour studies, particularly
in relation t o the sensitivity of clupeids to stimuli of differeiit intensity
and quality (e.g. Bull, 1952). Unfortunately the locomotmy behaviour
and general manoeuvrability of clupeids, arid thdr lack of marked
behaviour patterns except shoaling, would mrtko the work more difficult. However some Russian worker8 (mc Section VI, U) conniderorl
that attraction to artificial light W&R the result of a crmditioned rewymrirwt
set up by the association between light and feeding.
Clearly learning and memory could be of the greatest importance irt
capture and avoidance of fishing gear. Both Dcvold and Mohr (see
Section VI, V) have stressed this point, but it is doubtful whether its
importance can ever he assessed, except indirectly by fishing trials on
a population of known size in an enclosed arect, where fish that had been
caught could bo marked and rctleaqed.
Tho role of learning and mcmory in migration has been discussed by
Wynne-Edwards (sce Section VI, R). Possibly the only way of assessing
this would be in plotting the migration pttterns of a stock being
reduced to a very low level and consisting of rocruit fish.
24