356 



OCEANOGRAPHIC INVESTIGATIONS 



was considerably reduced, there was a noticeable diurnal rhjrthm in the movement of fish. 

 During the night the white croaker, Gengonemus lineatus , would typically crowd near the port 

 holes, often occurring in such numbers as to completely obscure the port (Fig. 134). With the 

 approach of dawn the croakers would leave the ports but could be seen swimming in large 

 schools, all generally pointed in the same direction, several feet away. It appeared to the 

 writers that the croakers were attracted to the ports to feed on the small crustaceans ( Eupha - 

 usia sp) which gathered at the port holes during the night in great numbers. One curious note 

 concerning the occurrence of these small organisms at the ports is that after the T. V. camera 

 was placed outside the port window in the laboratory area, many would become trapped in the 

 recessed area between the port window and the camera face plate. By morning this area would 

 typically become completely filled with these organisms. After leaving Sealab the writers men- 

 tioned this to the psychologists, who continually monitored the TV receivers and learned that 

 they were completely unaware of the presence of these organisms; apparently TV reception 

 suffered little. 



Fig. 134. White Croakers, Geneonemus Lineatus , crowd near the viewing 

 port in the Sealab II laboratory area 



The small crustacean forms were also a favorite food of the squid, and quite often these 

 strange animals could be seen actively feeding in the company of many types of fish and would 

 thus themselves become food. Such a situation was witnessed by the writers who observed a 

 calico rockfish (Sebatodes dalli) cautiously stalk a squid feeding outside a port in the labora- 

 tory area. Very slowly and carefully the rockfish approached the squid until it was only about 

 15 cm (6 in) from its prey. With a sudden movement the squid's head and tenacles were inside 

 the fish's mouth. The squid then discharged its black ink, which was seen flowing from the 

 sides of the mouth. Very quickly the fish released his hold on the squid and shaking his head, 

 as if the ink was most distasteful, rapidly left the field of view. The squid, however, seemed 

 to be totally unconcerned by his recent experience and remained near the port for several 

 minutes, continuing his feeding activities. To the writers' knowledge, the ink discharge of 



