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ZOOLOGICAL SOCIETY BULLETIN 



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LARGE-MOUTHED BLACK BASS, 



DO FISHES SLEEP? 



ANY years ago, while at the Government 

 biological laboratory as Woods Hole, 

 Mass., Professor Verrill, of Yale University, 

 made some observations of the nocturnal habits 

 of fishes and came to the conclusion that they 

 often sleep. 



He examined the aquaria after midnight, with the 

 gas turned very low. He found that the fishes took 

 unusual positions and were quickly awakened by the 

 turning up of the light. Their colors when asleep 

 were darker and different from their daytime colors. 

 When awakened they took on at once a brighter 

 coloration. 



It is possible that fishes sleep in the da}'time also. 

 It is no uncommon thing in the New York Aquarium 

 to see the file-fishes (Monacanthus hispidus), black- 

 fish {Tatitoga on!tis),tiLUtog{Taiitogolabrus adsper- 

 siis), hinds {Epinephelus guUatus), and groupers 

 {Epinephelus morio), lying quietly in a corner. 

 Sometimes the hinds assume a vertical position 

 in the rockwork. The trigger-fishes {Balisles 

 carolinensis) often lean against the walls or lie flat 

 on one side. Their colors at such times vary from 

 those exhibited when active. 



In these positions, which may be maintained for 

 hours, the fishes are supported by the rocks so that 

 fin movements are unnecessary and they seem to be 

 perfectly at rest. 



In the black-fish at rest upon the bottom, motion 



may cease entirely, except for 

 the rhythmic movements of 

 the tips of the gill covers and 

 an occasional slight turn of 

 the eyeball. With some fishes 

 in this position "dozing" 

 seems certain, as the leaning 

 body may settle over farther 

 and farther until the fish re- 

 covers itself with a start and 

 assumes the original upright 

 position. 



A lazy black-fish may roll 

 over on its side and lie quietly 

 until disturbed by its fellows. 

 There is generally enough 

 movement of some kind in 

 an Aquarium tank to keep 

 the fish somewhat wakeful, 

 the eyeballs occasionally rolling from mere habit 

 of alertness. Inside the half-open mouth of the 

 black-fish at rest a rhythmic tongue motion is 

 visible. The pectoral fins in a resting fish are 

 thrown out as props against adjacent objects, 

 either a stone or another fish at rest. 



A fish resting partly on its side may use the 

 under pectoral as a prop, the upper one being folded 

 flat. 



A red grouper stowed comfortably in a narrow 

 crevice in the rocks comes about as near to a con- 

 dition of actual rest as it is possible for a breathing 

 fish to effect. It may remain practically without 

 mo^'ement for a long time except for the slow action 

 of the tips of the gill covers. The body appears to 

 cling closely to the rocks. 



A red hind at rest turns very pale, the red color 

 disappearing almost entirely; body and fins are 

 pressed closely to the rockwork, the pectoral fins 

 being thrown out at any angle as a prop. 



The coney {Bodiannus juhnts), in a resting posi- 

 tion has the dorsal fins lowered and the ra3's of the 

 tail fin slightly folded together. The pectoral fins, 

 as in some other fishes at rest, are sometimes used 

 as a prop against the tank, the fish bemg without 

 motion except the tip of the gill cover. 



A vertical position is often assumed by the red 

 hinds. The color of the fish at rest is nearly 

 always different from that when in motion. The 

 fish may stand in the corner of the tank resting 

 directly on the tail, the tip of which is sharply bent. 



