STUDYING THE HABITS OF FISHES. II 29 



to be to produce temporary discomfort in the fish that is hooked, and this 

 usually results in the departure of the intruder. 



The attempt of a male to appropriate the nest of another fish of equal size 

 does not always result in an encounter. Frequently it happens that as the 

 strange male approaches the nest the occupant ranges himself alongside and 

 the two fish swim upstream with great deliberation for a distance of 15 or 

 20 feet (text fig. 4). In their course they move slowly and swing their tails 

 from side to side in unison, as though keeping step with them. At the end of 

 their course they settle to the bottom and bring their heads together gently, as 

 though bowing to one another. They then usually separate their heads and 

 bring their tails together, as though about to swim away from one another. 

 They then commonly again bring their heads together and finally separate, the 

 owner to return to his nest, his companion to some near-by shelter. This per- 

 formance, which with some variation is so often seen that it must be regarded 

 as a part of the normal behavior, may be interpreted as a deferred combat. The 

 two fish move along side by side, like two boys threatening each other but each 

 afraid to strike. When they have gone a certain distance they approach each 

 other and make certain threatening movements in unison and then they separate. 

 This mode of behavior, which has the appearance of a ceremonial, is illustrated 

 diagrammatically in text figure 4, where the nest is seen from above with its 

 owner in the pit. The outlines of the stream are represented by the heavy black 

 lines, while the direction of the current is indicated by the large arrows. The 

 nest shows the gravel ridge, the pit at its lower end, and the sand trail below the 

 pit. The movements of the two fish in their upstream course, as well as after 

 they have stopped, and the return of the owner to the nest, are represented 

 by the successive outlines, and their direction is indicated by arrowheads. 



Spawning behavior of male and female. — While the male dace is building 

 his nest the females are waiting in some near-by shelter. At any time during 

 the progress of the nest building they may be seen to approach the nest, usually 

 one at a time, but sometimes in troops of three or four. The females may be 

 distinguished from the males by their smaller size (fig. 10, pi. cxviii), for while 

 they may be as long as the males they are nearly always smaller and frequently 

 not more than one-fourth as long. They are further distinguished by the absence 

 of the bright colors on the body and of the black and orange spots in the dor- 

 sal, as well as by the absence of pearl organs. From larger males they are 

 distinguished by the presence of the lateral stripe. In all these respects they 

 resemble young males, but from these they may be told after a little practice 

 by the fact that their abdomens are distended with eggs (fig. 10). As a female 

 approaches the nest for the first time the male turns toward her and she then 

 usually flees without actually entering the nest. Presently she returns, again 



B. B. F. 190S— Pt 2—29 



