ROLE OF ETHOLOGY 249 



driving the female upward. They cuhninate in a pseudocoitus or 

 ventral mount during which eggs are discharged and sperm shed. 

 Actual spawning beha\-ior was seen to occur only when the light 

 was so dim as to make observations difficult, and it should also 

 be added that territories were not apparently defended or main- 

 tained during darkness. 



Now it is of the essence of the ethological program that obser- 

 vations made upon animals in captivity are vital adjuncts to those 

 made in the field. There is good reason to assume that the primary 

 behavior patterns of such animals as the fish we ha\'e just described 

 are not different under healthy conditions in a well-run aquarium 

 from what they are in nature. What then can be said of the cod 

 in nature from what we have seen by close observation in the 

 aquarium? 



Dominant males exclude other males and immature and spent 

 females, but 7iot females on the point of spawning, from a territory 

 they have established. Prespawning aggression, leading to territor>- 

 formation, starts 3 to 4 weeks before females are ripe for spawning. 

 This would give time in nature for weaker males to be sorted out. 

 The territorial preser\"e around every dominant male would 

 permit the behavioral sequence leading to spawning to take place 

 without interruption and so help to ensure maximal fertilization. 



Spawning occurs between February and May. The spawning 

 shoals are said to lie at between 40 and 100 m. In captivity the 

 courting behavior of the male drives the ripe female upward, 

 while aggressive beha\'ior drives unripe females and other less 

 \'igorous males downward and away from a defended territory. It 

 is possible then to think of cod gathering in the spawning areas 

 at the bottom in water of, say, 150 to 200 m. The aggressive and 

 courting behavior patterns would lead to horizontal layering of 

 shoals or groups of fish, with ripe females at some comfortable 

 "ceiling" (the surface of the water was of course the "ceiling" in 

 the aquarium), the dominant males slightly below or with them, 

 and unripe and other males in the lowest layers. During all this, 

 much display and grunting would be going on. After spawning is 

 over, aggression, including grunting as part of the display, ceases 

 and they pass each other quietly. 



