SALMON AND TROUT— SCHULTZ 371 



takes up his position over, a little behind, and to one side of the female. 

 The female usually defends the upper portions of the nest, while the 

 male defends the nest from invaders coming in from any dii'ection. 

 Both drive away either a male or female upon their approach unless 

 fish much larger than themselves swim into the nest. When this 

 happens, often a new male takes possession, and breeding activities 

 continue with little interruption. 



Sometimes when an invading male approaches, he is escorted away 

 by the male owner of the nest (fig. 3). In the case of the little red- 

 fish, a landlocked salmon, the defending male may swim out to 

 meet him, often elevating his dorsal fin. If the intruder does not 

 retreat, the defender will swim slowly toward him, and when about a 

 foot or so away, he will turn so that the two fish are nearly parallel, 

 and they then proceed slowly upstream, sometimes as far as 10 feet 

 before the invader either goes his own way, or makes a dash for the 

 nest. Should the latter happen, the escorting act might occur again. 

 In general the male occupies much of his time in driving away other 

 males, and the female drives away invading males or females. Should 

 the invading male be successful in driving away the original owner, the 

 former now takes possession. Several males usually pair off with the 

 female owner of a nest before she has laid all of her eggs. 



Other activity besides the defense of the nest may occur in the 

 immediate vicinity, since unpaired and paired males continually chase 

 each other about both below, among, and above the area occupied by 

 the redds, or nests. 



COURTSHIP ACTIVITIES 



Between many of the nest-building acts of the female redfish as 

 she drifts back into the center of the nest during recovery and assumes 

 a normal position over the center of the nest, the male usually ap- 

 proaches her from behind and a little to one side. He will just 

 touch his head or snout to her body in the region between the adipose 

 fin and the pectorals, gently move his body toward and against hers, 

 at which moment he will vibrate, or quiver, vigorously for a second 

 or two. He will partially erect his dorsal fin near the end of this 

 act (fig. 2). The female usually remains perfectly still, although 

 once in a while she too wiH quiver in unison with the male. No 

 eggs or milt have ever been seen in the water during this courtship 

 act, thus indicating that no actual spawning occurs. Time and time 

 again the male repeats this courtship act, if no intruder interrupts, 

 as often as every 5 to 10 seconds or at longer intervals. Other court- 

 ship acts occur, too. Frequently the male will swim back and forth 

 over the female when she is resting near the bottom of the nest, 

 often touching her dorsal fin with his body and fins. Another recog- 

 nizable courtship behavior is an act of nudging. The male gently 



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