370 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



gressively excavates one or more new nests upstream, some of the 

 excavated material of the new locations covers the eggs in the older 

 nests deeper and deeper — a real conservation of energy. Several 

 batches of eggs may be deposited before the female has completely 

 deposited all of her ova; sometimes, however, a female may select an 

 entirely new location for her next nest. 



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FiGUKE 3.— A diafiram illustrating the escorting act of the male redQsh, Oncorhynchus nerka. Note that 

 the female, 9 (dotted) remains over the nest while the male, cf, drives the invader (solid black) away. 

 The male and female are shown in their positions over the nest. Drawn by Dan Merriman. Courtesy 

 Mid-Pacifle Magazine. 



DEFENSE OF THE NEST 



Both male and female defend their nest against invading fishes by 

 rushing at them or by the male escorting the intruding male upstream 

 or to one side. Sometimes the defender in his rush at an invading fish 

 catches his teeth in the abdomen near the pelvic fins of the invader, 

 and before he can loosen himself the two drift downstream some 

 distance. The defender usually returns to his nest and immediately 



