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The optomotor reaction of schooling carangid fishes
THE OPTOMOTOR REACTION OF SCHOOLING CARANCID FISHES* BY EVELYN SHAW Department of Animal Behavior, The American Museum of Natural History, AND ARLENE TUCKER Institute of Animal Behavior, Rutgers University . Introduction Many schooling fishes maintain parallel orientation with some set range of distances between them, as has been discussed by many authors beginning with Parr (1927) . A usual feature of fishes in schools is their constant swimming and forward movement . As the entire school moves, the individual fish remain essentially parallel, but change position with relation to one another and also alter their velocities without interrupting the smooth forward movement of the school . The sensory stimuli which maintain consistent parallel orientation of the fish during forward movement and changing velocities are apparently of such nature that the fish are stimulated similarly whether they are at the head, the middle, the rear end or on the sides of the school . In exploring the nature of these stimuli, Parr's original work (1927) and the work of many investigators since (reviewed by Morrow, 1948 ; Atz, 1953 ; Breder, 1959) have shown that vision is the important sensory system . Nevertheless, the specific way in which the visual system mediates this behaviour is not known . In our studies we are investigating the optomotor reflex of fish as a possible mechanism by which the fish can shift positions in the school, change velocity and maintain their parallel orientation, (Shaw, 1965) . This study is concerned only with the behaviour of a school once formed and not with the mechanisms of initial school formation .
given in Fig . 2. The drum could be rotated in either direction at speeds ranging from 3 . 5 to 38 . 5 revolutions per minute . The lucite aquarium had its own inflow-outflow system . Water entered into the bottom of the aquarium through a small hole, 8 mm . in diameter . The water flowed out by spilling over the top of the aquarium . The water did not create currents around the aquarium, but moved upwards from the inflow to the top . Three different stimuli, lining the interior of the drum, from top to bottom, were used . These stimuli consisted of (1) a field of alternating black and white vertical stripes, made by pasting black tape on white styrene sheets ; (2) a panel of alternating black and white vertical stripes, subtending an area of 60 ° with the remaining area white and (3) as a control, a plain white styrene sheet. The following procedure was used in testing . After a fish was permitted a period of adaptation, up to one half hour, tests were started with a one-minute observation of the swimming activity of the fish, while the drum was not moving . The drum was then rotated at the lowest speed for one minute and the speed was gradually increased, in step fashion, from the lowest to the highest speeds . At each speed a minute of observation was made on the qualitative behaviour of the fish, and the total number of complete revolutions made by the subject was recorded . The initial direction of rotation in each series was assigned randomly . The species studied were Caranx ruber (Bloch), the bar jack (6 to 9 inches long), and Selar crumenophthalmus (Bloch), the bigeye scad (6 to 8 inches long) . Both species were very fragile when kept under laboratory conditions . Handling caused lesions on the side of the body which resulted in death of the fish within a few days . Occasionally the transparent cornea became cloudy while the fish were in storage tanks or in the apparatus . The results reported here were obtained on those few recently-caught individuals which showed little or no damage
Method The optomotor apparatus consisted of a cylindrical lucite aquarium surrounded by a concentric motor-driven rotating steel drum . Both the aquarium and the drum rested inside a child's plastic swimming pool . The pool was filled with sea water to the top of the apparatus, as seen in Fig . 1, Plate VII . The dimensions are Research supported, in part, by NSF G-10832 and in part by a contract between The American Museum of Natural History and the Office of Naval Research, Contract No . ONR 552 (09) . This work was carried out at the Lerner Marine Laboratory, Bimini, Bahamas .
330
SHAW & TUCKER : THE OPTOMOTOR REACTION OF SCHOOLING CARANGID FISHES
Stationary aquarium
Rotating drum
Fig . 2 . Dimensions of the optomotor
under our conditions . The number of fish observed is indicated on the graphs . Results and Interpretation Qualitative Observations In the observations, taken while the drum was not moving, two kinds of behavioural activity were noted . Fish remained quiescent with the long axis radial to the aquarium wall or moved in either direction, circling the container . Fish remained near the bottom or centre of the aquarium and rarely moved to the top . When fish were exposed to the fully striped field, the most common behaviour was continuous and regular movement in the same direction as the drum and normal to the radius of the aquarium . This is the typical optomotor response observed by Trinckner (1952) in Carassius, the goldfish, and Hortsmann (1959) in Mugil, the mullet, and Harden Jones (1963) in a number of other species . Other activities, not of this typical form, were occasionally seen in individual fish . Sometimes, at low speeds, the subject remained with the long axis of its body perpendicular to the wall of the aquarium and, maintaining this orientation, it pivoted in the same direction as the drum . While in this position, a right and left lateral movement of the head and anterior part of the body was also seen . Since the speed of head movement in each direction was the same (no
331
fast and slow component could be distinguished) this behaviour was clearly not the Striped stimulus panel head mystagmus which Trinckner (1952) described in goldfish and which we have also observed in Menidia, the silversides . In the situation where only a panel was striped, the orientation of the animal to different areas could be observed . Through direct observation and by analysis of films taken of this behaviour, it was noted that the animal's approach to synchrony with the striped apparatus . panel was closest at intermediate speeds as seen in graph 3, (Fig . 5) . At slow speeds, the fish position was slightly ahead of the panel, at fast speeds, slightly behind . Initial position was rarely maintained for several consecutive drum rotations and the animal swam behind or ahead of the stripes . The fish then accelerated or decelerated and a position near the panel was re-established . At the middle range of speeds, the animals tended to stay opposite the panel, although again, the fish was rarely in exactly the same place relative to any given stripes for many consecutive rotations . However, when the drum stopped the animal stopped circling immediately and remained near the striped portion of the field . Thus it became apparent that the animal oriented to the panel of stripes, was moving because of the movement of the stripes, but swam at a variable speed even when the drum speed was constant . Hortsmann (1959) found that mullet, if placed inside of a drum where a third is covered with stripes, moved sometimes with and sometimes against the movement of the drum . This observation differs from that reported here, but the results cannot be compared because Hortsmann did not present data on the speed of drum rotation . When the entire drum was white the fishes remained still, moved circularly, swam erratically up and down the side wall, or moved alternately in clockwise and counter-clockwise directions in short bursts of speed .
332
ANIMAL BEHAVIOUR, XIII, 2-3
GRAPH I BAR JACKS 3 36 cl, ccl
34 0
32
0
_- l cl,
30
(av3 fish) (ov 4 fish
striped
-
'
partly (av 2 fish) t---- -
/
--
white (av 2 fish)
Cc }
28
26 1 24 I
rn, .E
14
-
12
i
r
I,0 8
WA. . . . .
6
. . . . . .. . . . .
r ~
4 2 0 0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
RPM of drum Fig . 3. Revolutions per minute, at various drum speeds and in various stimuli, are compared in the bar jacks .
32
SHAW & TUCKER : THE OPTOMOTOR REACTION OF SCHOOLING CARANGID FISHES
333
GRAPH 2 BIGEYE SCADS 32 30
a 28
_ ._ C03 CI,
striped (ov 5 fish)
o Cl. , partly -- cc,, }striped
0 0
26 . 24 ,
-""--"'-"
~
(av 3 f i sh)
white (OV 2 fish) cl, cc,,)
t
/
22
NFAd01F .APAP VAMP"7 WAMV~~~~ WAM r ~~~~
H+ 0 16
12 10
4
c
2 0 0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
RPM of drum Fig. 4. ReNolutions per minute, at various drum speeds and in various stimuli, are compared in the bigeye scads .
3'4
334
ANIMAL BEHAVIOUR, XIII, 2-3
Quantitative Observations Graphs 1 and 2 (Fig . 3 & 4) show the relationship between revolutions per minute (r .p .m .) of the drum and that of the fish when exposed to the various stimuli . A comparison of the different conditions for both species reveals this : only a field containing vertical stripes produced a following response which increased regularly in speed with increase in r .p .m . of the field . This response is not obtained with rotation of the entirely white field, and it is clear that movement of the animals is because of the moving striped field and not to artifacts such as the moving overhead struts which held the drum
suspended . In Graph 3 (Fig. 5) when only a small part of the field is striped the r .p .m . of both species is alike and similar to the r.p.m . of the drum. A possible explanation is suggested by the qualitative observations given above. Observations of fish in the panel situation show that the fish maintain the position relative_ to the panel within broad limits . It does so by changes in acceleration and only the average r.p.m . is the same as that of the field ; the animal's orientation to the panel and his swimming velocity, relative to it, vary . In Graph 4, (Fig . 6), where the entire field is striped, there is a uniformity of stimuli and no
GRAPH 3 PARTLY STRIPED 28 26
.'
24
~~A
vti 22
20
18
i
/
I
10
8 Bigeye scads, cl, 6
Biyeye scads, ccl, (av 2 fish) „~
4
Bar jacks, cl, Bar jacks, ccl, lav 2 fish)
ii
0 0
2
4
6
8
10
12
14
16
16
20
22
24
26
28
30
RPM of drum Fig. 5 . Revolutions per minute of bar jacks and bigeye scads are compared in the partly striped (panel) field .
32
335
SHAW & TUCKER : THE OPTOMOTOR REACTION OF SCHOOLING CARANGID FISHES
GRAPH 4 STRIPED 38
I
36
Bigeye
scads,cl, (av 5 fish) Bigeye scads,ccl,
34 32
Bar jacks, ci, (av 3fish) --_- Bar jacks, ccl, (av 4fish)
30 28 26 24
N
22
4-- 20 0
28
30
RPM of drum Fig . 6 . Revolutions per minute of bar jacks and bigeye scads are compared in the uniformly striped field .
32
336
ANIMAL BEHAVIOUR, XIII, 2-3
one pair of stripes or one fixation point should be distinguishable from any other . Therefore, if the fish does not synchronize its speed of movement with that of the initial fixation point it cannot alter its velocity to re-establish the initial fixation point, because that point is indistinguishable from any other . The behaviour of the fish in the uniformly striped field is probably the following : the animal adopts a fixation point, swims with it in view for a period of time, loses it, picks up a new fixation point, remains with it for a period, etc . Thus the moving field is "stopped" in the perception of the animal for successive periods . Precise synchrony of animal with drum is not necessary in order to obtain perceptuality a stationary field for successive short periods of time . To maintain these periods of time as the invariant, however, requires an average increase in r .p.m . which is proportional to the increase in r.p .m . of the drum . The average velocity of the animal for any given velocity of the drum is probably partially determined by drum speed and partially by the natural swimming habits of the animal . Harden Jones (1963) also found species differences in the velocities of various fish . The bar jack circles more times per minute, for any given drum speed, than the bigeye scads . We have observed that bar jacks are much faster swimming than bigeye scads under natural conditions . When many fixation points are possible, rather than a few, the influence of natural swimming speeds can be more pronounced without disrupting the basic perceptual function, that of "stopping" the moving field . Discussion and Application to the Schooling Problem The previous section shows that in the optomotor response : (1) the fish moves in the same direction as the moving field and parallel to it ; (2) the fish changes its speed as the speed of the moving field changes ; (3) the fish alters its position relative to the field, that is, it is not always opposite the same area of the stimulus . The similarity between this behaviour and certain features of schooling is striking . In a school : (1) fish are all moving in the same direction ; (2) a fish changes speed as the fish surrounding it change speed ; (3) a fish changes its position relative to other fish, but nonetheless remains parallel to them and in the school . The entire group moves forward while members of the group may be making changes in their positions . Therefore, by exposing a fish to a stimulus
consisting of a series of moving black and white vertical stripes, important features of schooling behaviour have been reproduced . Fish in the school may be providing for other fish in the school a series of successive contrasts which are greatly enhanced because the fish are moving . Baylor & Shaw (1962) have suggested that the teleost eye is capable of perception of small movements with concommittant enhanced contrast . This may be highly adaptive in schooling and the optomotor reflex may play an important role in the features of schooling mentioned above . Such a possibility is also implied by Protasov & Altukov (1961) in their study of optomotor reactions in schooling fish, young fish and river "rheophilic fish . Summary Carangid fishes were tested in an optomotor apparatus and their orientation to different kinds of stimuli was observed . The fish did not orient to any particular region of the stimulus consisting of uniform black and white vertical stripes . The r .p .m . of the fish was generally greater than the r .p .m . of the drum . On the other hand, the fish oriented to the panel stimulus and tended to remain near it during the entire range of revolutions . The r .p .m . of the fish closely followed the r .p .m . of the drum . Certain features of the behaviour of the fish in an optomotor apparatus are compared with certain features of schooling under natural conditions . REFERENCES Atz, J . W . (1953) . Orientation in schooling fishes . Proc. Conf. Orientation in Animals, ONR, 103-130. Baylor, E. R. & Shaw, E . (1962) . Refractive error and vision in fishes . Science, 136, 157-158 . Breder, C . M . (1959) . Studies of social groupings in fishes . Bull. Amer. Mus . Nat . Hist ., 117, 397-481 . Harden Jones, F. R . (1963) . The reaction of fish to moving backgrounds . J. exp. Biol., 40, 437-446 . Hortsmann, E . (1959) . Schwarmstudienunter Ausnutzung einer Optomotorischen Reaktion bei Mugil cephalus (Cuv .) . Pubbl. Staz. Zool. Napoli, 31, 25-35 . Morrow, J . E . (1948) . Schooling behaviour in fishes . Quart. Rev. Biol., 23, 27-38 . Parr, A . E . (1927) . A contribution to the theoretical analysis of schooling behavior of fishes . Occ . Pap . Bingham Oceanogr . Coll ., No . 1, 1-32 . Protasov, V . R . & Altakov, U. P . (1961). The possibility of using the optomotor reaction for controlling the movement of fishes . Plynoe . Khoz. 2, 29-32. (Referat . Zhur . Biol., 1961, 200412) . Shaw, E . (1965) . The optomotor response and the schooling of fish . ICNAF Spec . Publ. (in press) . Trincker, D . (1952) . Reafferenz-Princip and Anpassung . Die Naturwiss ., 39, 115-116 . (Accepted for publication 19th February, 1965 ; Ms . number : 461).
ANIMAL BEHAVIOUR, XIII, 2-3
PLATE VII
Fig . 1 . The optornotor apparatus . The fish can be seen in the circular aquarium .
Shaw & Tucker, Anim . Behav., 13, 2 -3
given in Fig . 2. The drum could be rotated in either direction at speeds ranging from 3 . 5 to 38 . 5 revolutions per minute . The lucite aquarium had its own inflow-outflow system . Water entered into the bottom of the aquarium through a small hole, 8 mm . in diameter . The water flowed out by spilling over the top of the aquarium . The water did not create currents around the aquarium, but moved upwards from the inflow to the top . Three different stimuli, lining the interior of the drum, from top to bottom, were used . These stimuli consisted of (1) a field of alternating black and white vertical stripes, made by pasting black tape on white styrene sheets ; (2) a panel of alternating black and white vertical stripes, subtending an area of 60 ° with the remaining area white and (3) as a control, a plain white styrene sheet. The following procedure was used in testing . After a fish was permitted a period of adaptation, up to one half hour, tests were started with a one-minute observation of the swimming activity of the fish, while the drum was not moving . The drum was then rotated at the lowest speed for one minute and the speed was gradually increased, in step fashion, from the lowest to the highest speeds . At each speed a minute of observation was made on the qualitative behaviour of the fish, and the total number of complete revolutions made by the subject was recorded . The initial direction of rotation in each series was assigned randomly . The species studied were Caranx ruber (Bloch), the bar jack (6 to 9 inches long), and Selar crumenophthalmus (Bloch), the bigeye scad (6 to 8 inches long) . Both species were very fragile when kept under laboratory conditions . Handling caused lesions on the side of the body which resulted in death of the fish within a few days . Occasionally the transparent cornea became cloudy while the fish were in storage tanks or in the apparatus . The results reported here were obtained on those few recently-caught individuals which showed little or no damage
Method The optomotor apparatus consisted of a cylindrical lucite aquarium surrounded by a concentric motor-driven rotating steel drum . Both the aquarium and the drum rested inside a child's plastic swimming pool . The pool was filled with sea water to the top of the apparatus, as seen in Fig . 1, Plate VII . The dimensions are Research supported, in part, by NSF G-10832 and in part by a contract between The American Museum of Natural History and the Office of Naval Research, Contract No . ONR 552 (09) . This work was carried out at the Lerner Marine Laboratory, Bimini, Bahamas .
330
SHAW & TUCKER : THE OPTOMOTOR REACTION OF SCHOOLING CARANGID FISHES
Stationary aquarium
Rotating drum
Fig . 2 . Dimensions of the optomotor
under our conditions . The number of fish observed is indicated on the graphs . Results and Interpretation Qualitative Observations In the observations, taken while the drum was not moving, two kinds of behavioural activity were noted . Fish remained quiescent with the long axis radial to the aquarium wall or moved in either direction, circling the container . Fish remained near the bottom or centre of the aquarium and rarely moved to the top . When fish were exposed to the fully striped field, the most common behaviour was continuous and regular movement in the same direction as the drum and normal to the radius of the aquarium . This is the typical optomotor response observed by Trinckner (1952) in Carassius, the goldfish, and Hortsmann (1959) in Mugil, the mullet, and Harden Jones (1963) in a number of other species . Other activities, not of this typical form, were occasionally seen in individual fish . Sometimes, at low speeds, the subject remained with the long axis of its body perpendicular to the wall of the aquarium and, maintaining this orientation, it pivoted in the same direction as the drum . While in this position, a right and left lateral movement of the head and anterior part of the body was also seen . Since the speed of head movement in each direction was the same (no
331
fast and slow component could be distinguished) this behaviour was clearly not the Striped stimulus panel head mystagmus which Trinckner (1952) described in goldfish and which we have also observed in Menidia, the silversides . In the situation where only a panel was striped, the orientation of the animal to different areas could be observed . Through direct observation and by analysis of films taken of this behaviour, it was noted that the animal's approach to synchrony with the striped apparatus . panel was closest at intermediate speeds as seen in graph 3, (Fig . 5) . At slow speeds, the fish position was slightly ahead of the panel, at fast speeds, slightly behind . Initial position was rarely maintained for several consecutive drum rotations and the animal swam behind or ahead of the stripes . The fish then accelerated or decelerated and a position near the panel was re-established . At the middle range of speeds, the animals tended to stay opposite the panel, although again, the fish was rarely in exactly the same place relative to any given stripes for many consecutive rotations . However, when the drum stopped the animal stopped circling immediately and remained near the striped portion of the field . Thus it became apparent that the animal oriented to the panel of stripes, was moving because of the movement of the stripes, but swam at a variable speed even when the drum speed was constant . Hortsmann (1959) found that mullet, if placed inside of a drum where a third is covered with stripes, moved sometimes with and sometimes against the movement of the drum . This observation differs from that reported here, but the results cannot be compared because Hortsmann did not present data on the speed of drum rotation . When the entire drum was white the fishes remained still, moved circularly, swam erratically up and down the side wall, or moved alternately in clockwise and counter-clockwise directions in short bursts of speed .
332
ANIMAL BEHAVIOUR, XIII, 2-3
GRAPH I BAR JACKS 3 36 cl, ccl
34 0
32
0
_- l cl,
30
(av3 fish) (ov 4 fish
striped
-
'
partly (av 2 fish) t---- -
/
--
white (av 2 fish)
Cc }
28
26 1 24 I
rn, .E
14
-
12
i
r
I,0 8
WA. . . . .
6
. . . . . .. . . . .
r ~
4 2 0 0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
RPM of drum Fig . 3. Revolutions per minute, at various drum speeds and in various stimuli, are compared in the bar jacks .
32
SHAW & TUCKER : THE OPTOMOTOR REACTION OF SCHOOLING CARANGID FISHES
333
GRAPH 2 BIGEYE SCADS 32 30
a 28
_ ._ C03 CI,
striped (ov 5 fish)
o Cl. , partly -- cc,, }striped
0 0
26 . 24 ,
-""--"'-"
~
(av 3 f i sh)
white (OV 2 fish) cl, cc,,)
t
/
22
NFAd01F .APAP VAMP"7 WAMV~~~~ WAM r ~~~~
H+ 0 16
12 10
4
c
2 0 0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
RPM of drum Fig. 4. ReNolutions per minute, at various drum speeds and in various stimuli, are compared in the bigeye scads .
3'4
334
ANIMAL BEHAVIOUR, XIII, 2-3
Quantitative Observations Graphs 1 and 2 (Fig . 3 & 4) show the relationship between revolutions per minute (r .p .m .) of the drum and that of the fish when exposed to the various stimuli . A comparison of the different conditions for both species reveals this : only a field containing vertical stripes produced a following response which increased regularly in speed with increase in r .p .m . of the field . This response is not obtained with rotation of the entirely white field, and it is clear that movement of the animals is because of the moving striped field and not to artifacts such as the moving overhead struts which held the drum
suspended . In Graph 3 (Fig. 5) when only a small part of the field is striped the r .p .m . of both species is alike and similar to the r.p.m . of the drum. A possible explanation is suggested by the qualitative observations given above. Observations of fish in the panel situation show that the fish maintain the position relative_ to the panel within broad limits . It does so by changes in acceleration and only the average r.p.m . is the same as that of the field ; the animal's orientation to the panel and his swimming velocity, relative to it, vary . In Graph 4, (Fig . 6), where the entire field is striped, there is a uniformity of stimuli and no
GRAPH 3 PARTLY STRIPED 28 26
.'
24
~~A
vti 22
20
18
i
/
I
10
8 Bigeye scads, cl, 6
Biyeye scads, ccl, (av 2 fish) „~
4
Bar jacks, cl, Bar jacks, ccl, lav 2 fish)
ii
0 0
2
4
6
8
10
12
14
16
16
20
22
24
26
28
30
RPM of drum Fig. 5 . Revolutions per minute of bar jacks and bigeye scads are compared in the partly striped (panel) field .
32
335
SHAW & TUCKER : THE OPTOMOTOR REACTION OF SCHOOLING CARANGID FISHES
GRAPH 4 STRIPED 38
I
36
Bigeye
scads,cl, (av 5 fish) Bigeye scads,ccl,
34 32
Bar jacks, ci, (av 3fish) --_- Bar jacks, ccl, (av 4fish)
30 28 26 24
N
22
4-- 20 0
28
30
RPM of drum Fig . 6 . Revolutions per minute of bar jacks and bigeye scads are compared in the uniformly striped field .
32
336
ANIMAL BEHAVIOUR, XIII, 2-3
one pair of stripes or one fixation point should be distinguishable from any other . Therefore, if the fish does not synchronize its speed of movement with that of the initial fixation point it cannot alter its velocity to re-establish the initial fixation point, because that point is indistinguishable from any other . The behaviour of the fish in the uniformly striped field is probably the following : the animal adopts a fixation point, swims with it in view for a period of time, loses it, picks up a new fixation point, remains with it for a period, etc . Thus the moving field is "stopped" in the perception of the animal for successive periods . Precise synchrony of animal with drum is not necessary in order to obtain perceptuality a stationary field for successive short periods of time . To maintain these periods of time as the invariant, however, requires an average increase in r .p.m . which is proportional to the increase in r.p .m . of the drum . The average velocity of the animal for any given velocity of the drum is probably partially determined by drum speed and partially by the natural swimming habits of the animal . Harden Jones (1963) also found species differences in the velocities of various fish . The bar jack circles more times per minute, for any given drum speed, than the bigeye scads . We have observed that bar jacks are much faster swimming than bigeye scads under natural conditions . When many fixation points are possible, rather than a few, the influence of natural swimming speeds can be more pronounced without disrupting the basic perceptual function, that of "stopping" the moving field . Discussion and Application to the Schooling Problem The previous section shows that in the optomotor response : (1) the fish moves in the same direction as the moving field and parallel to it ; (2) the fish changes its speed as the speed of the moving field changes ; (3) the fish alters its position relative to the field, that is, it is not always opposite the same area of the stimulus . The similarity between this behaviour and certain features of schooling is striking . In a school : (1) fish are all moving in the same direction ; (2) a fish changes speed as the fish surrounding it change speed ; (3) a fish changes its position relative to other fish, but nonetheless remains parallel to them and in the school . The entire group moves forward while members of the group may be making changes in their positions . Therefore, by exposing a fish to a stimulus
consisting of a series of moving black and white vertical stripes, important features of schooling behaviour have been reproduced . Fish in the school may be providing for other fish in the school a series of successive contrasts which are greatly enhanced because the fish are moving . Baylor & Shaw (1962) have suggested that the teleost eye is capable of perception of small movements with concommittant enhanced contrast . This may be highly adaptive in schooling and the optomotor reflex may play an important role in the features of schooling mentioned above . Such a possibility is also implied by Protasov & Altukov (1961) in their study of optomotor reactions in schooling fish, young fish and river "rheophilic fish . Summary Carangid fishes were tested in an optomotor apparatus and their orientation to different kinds of stimuli was observed . The fish did not orient to any particular region of the stimulus consisting of uniform black and white vertical stripes . The r .p .m . of the fish was generally greater than the r .p .m . of the drum . On the other hand, the fish oriented to the panel stimulus and tended to remain near it during the entire range of revolutions . The r .p .m . of the fish closely followed the r .p .m . of the drum . Certain features of the behaviour of the fish in an optomotor apparatus are compared with certain features of schooling under natural conditions . REFERENCES Atz, J . W . (1953) . Orientation in schooling fishes . Proc. Conf. Orientation in Animals, ONR, 103-130. Baylor, E. R. & Shaw, E . (1962) . Refractive error and vision in fishes . Science, 136, 157-158 . Breder, C . M . (1959) . Studies of social groupings in fishes . Bull. Amer. Mus . Nat . Hist ., 117, 397-481 . Harden Jones, F. R . (1963) . The reaction of fish to moving backgrounds . J. exp. Biol., 40, 437-446 . Hortsmann, E . (1959) . Schwarmstudienunter Ausnutzung einer Optomotorischen Reaktion bei Mugil cephalus (Cuv .) . Pubbl. Staz. Zool. Napoli, 31, 25-35 . Morrow, J . E . (1948) . Schooling behaviour in fishes . Quart. Rev. Biol., 23, 27-38 . Parr, A . E . (1927) . A contribution to the theoretical analysis of schooling behavior of fishes . Occ . Pap . Bingham Oceanogr . Coll ., No . 1, 1-32 . Protasov, V . R . & Altakov, U. P . (1961). The possibility of using the optomotor reaction for controlling the movement of fishes . Plynoe . Khoz. 2, 29-32. (Referat . Zhur . Biol., 1961, 200412) . Shaw, E . (1965) . The optomotor response and the schooling of fish . ICNAF Spec . Publ. (in press) . Trincker, D . (1952) . Reafferenz-Princip and Anpassung . Die Naturwiss ., 39, 115-116 . (Accepted for publication 19th February, 1965 ; Ms . number : 461).
ANIMAL BEHAVIOUR, XIII, 2-3
PLATE VII
Fig . 1 . The optornotor apparatus . The fish can be seen in the circular aquarium .
Shaw & Tucker, Anim . Behav., 13, 2 -3