198
J. A. 0. NICOL
artificial light exerts upon fish. This response, shown by many fishes,
haa been exploited by fishermen all over the world in various kinds of
" light fishing ", and a large literature has accumulated about the
phenomenon (see Kristjonsson, 1959; von Brandt, 1959; Isa, 1961;
Imamura, 1961; Sara, 1962). Herring, pilchards, sardine, cod and
mackerei are some of the commercial fishes attracted by lamps at
night. The behaviour is obviously peculiar and is not to be attributed
to normal phototaxis. It is comparable to the attraction of moths to
a lamp and involves some sort of visual disorientation connected with
the darkness of the surrounding environment in contrast to the brightness of the lamp. Verheyen (19694, analysing this behaviour, believes
that it is an abnormal telotaxis in which the fish exchanges normal
random movements for directed drift towards the light-source. Normal
movements, in so far aa they are affected by photic stimuli, are guidod
by differences in the light-intensitius falling upon the two eyes and on
different parts of tho same retina. An artificial light is most offective
in clear water at night when there i
R no reflexion from a background
that would reduce contrast. Under these conditions the light is coming
mostly from the source and usually affects only one eye at a time,
producing grossly abnormal stimulation. In the absence of any other
modifying stimuli, that from the lamp seizes control of the lower visual
centres and directs muscular activity. When there is much scattering
of the light, natural moonlight, or reflexion from the bottom, mmpetitive photic stimulation of a more normal character intervenea and
the effectiveness of the artificial light is reduced or nullified (Verheyen,
1956, 1958, 1959a, b).
There is accumulating evidence that behaviour is affected to aomo
extent by wavelength as well as intensity. Pacific sardinot3 (8ardinopa
mermlea) in an aquarium prefer blue or green light to white, and red
light produces confusion and alarm in schools ; in these experiments the
fish were responding to the colour of the lights (Loukashkin and Grant,
1959). 'l'eRtR nrudo with colourecl lighta on various RpooicR of marine
finli in tnnkH rcrvcvrlod that tho,y woro attracted by gram and blue anti
woro idifTorcrnt to rod-flyhwoid~a, Monochantus, Pegu, ctc. A n p i &
wtu exccptionnl in that it was indifferent to bluo and green and w&8
attracted by red light. These experiments took into account both
relative radiant energy and radiant visual perceptibility (or spectral
sensitivity) (Kawamoto, 1969; Sara, 1902). Mention has been made
previously of how colour influences the effectiveness of nets. Most
colours, of course, are soon eliminated by differential absorption with
increasing depth, leaving monochromatic blue ur green light (@
Section V). The distinct retinal responses to lights of different wave-
J. A. 0. NICOL
artificial light exerts upon fish. This response, shown by many fishes,
haa been exploited by fishermen all over the world in various kinds of
" light fishing ", and a large literature has accumulated about the
phenomenon (see Kristjonsson, 1959; von Brandt, 1959; Isa, 1961;
Imamura, 1961; Sara, 1962). Herring, pilchards, sardine, cod and
mackerei are some of the commercial fishes attracted by lamps at
night. The behaviour is obviously peculiar and is not to be attributed
to normal phototaxis. It is comparable to the attraction of moths to
a lamp and involves some sort of visual disorientation connected with
the darkness of the surrounding environment in contrast to the brightness of the lamp. Verheyen (19694, analysing this behaviour, believes
that it is an abnormal telotaxis in which the fish exchanges normal
random movements for directed drift towards the light-source. Normal
movements, in so far aa they are affected by photic stimuli, are guidod
by differences in the light-intensitius falling upon the two eyes and on
different parts of tho same retina. An artificial light is most offective
in clear water at night when there i
R no reflexion from a background
that would reduce contrast. Under these conditions the light is coming
mostly from the source and usually affects only one eye at a time,
producing grossly abnormal stimulation. In the absence of any other
modifying stimuli, that from the lamp seizes control of the lower visual
centres and directs muscular activity. When there is much scattering
of the light, natural moonlight, or reflexion from the bottom, mmpetitive photic stimulation of a more normal character intervenea and
the effectiveness of the artificial light is reduced or nullified (Verheyen,
1956, 1958, 1959a, b).
There is accumulating evidence that behaviour is affected to aomo
extent by wavelength as well as intensity. Pacific sardinot3 (8ardinopa
mermlea) in an aquarium prefer blue or green light to white, and red
light produces confusion and alarm in schools ; in these experiments the
fish were responding to the colour of the lights (Loukashkin and Grant,
1959). 'l'eRtR nrudo with colourecl lighta on various RpooicR of marine
finli in tnnkH rcrvcvrlod that tho,y woro attracted by gram and blue anti
woro idifTorcrnt to rod-flyhwoid~a, Monochantus, Pegu, ctc. A n p i &
wtu exccptionnl in that it was indifferent to bluo and green and w&8
attracted by red light. These experiments took into account both
relative radiant energy and radiant visual perceptibility (or spectral
sensitivity) (Kawamoto, 1969; Sara, 1902). Mention has been made
previously of how colour influences the effectiveness of nets. Most
colours, of course, are soon eliminated by differential absorption with
increasing depth, leaving monochromatic blue ur green light (@
Section V). The distinct retinal responses to lights of different wave-