1 1 34 BULLETIN OF THE BUREAU OF FISHERIES. 



SUMMARY OF OBSERVATIONS OF THE BREEDING HABITS OF THE HORNED DACE. 



1. The homed dace breeds in southern Michigan from late April to early 



July. 



2. Breeding males are distinguished from females by their larger size, 



brighter colors, the presence of pearl organs, and abdomen not distended as in 

 the female. 



3. The breeding takes place in clear streams, which vary in width from i 

 or 2 feet to 4 or 5 rods, on bottom of coarse gravel, and usually at the heads of 

 rapids. 



4. The male fish builds nests without assistance from the females. 



5. The nests are constructed, each chiefly by an individual male, by pick- 

 ing up and carrying stones in the mouth. 



6. Each male thus excavates, parallel to the course of the stream, a long 

 trench, usually a foot wide and 2 or 3 inches deep, but varying in length from 

 I to 16 or 18 feet. 



7. As he excavates this trench he fills it with the gravel removed in making 

 it, so as to form a ridge of gravel which extends 2 or 3 inches above the top of 

 the trench. 



8. The trench and ridge are extended downstream, and the fish always 

 occupies the unfilled portion of the trench at the lower end of the ridge. This 

 I have called the pit. 



9. The sand washed from between the stones in moving them accumulates 

 in a trail below the pit. 



10. In forming the ridge most of the coarser gravel is deposited so as to 

 form its base, while the finer gravel is used chiefly as a top dressing on the sur- 

 face of the ridge. 



11. The male guards the completed nest, and often defends it by giving 

 battle to other males. 



12. Frequently when the nest of one fish is approached by another male 

 dace of equal size there ensues, not a combat but a "ceremonial" which may 

 be interpreted as a deferred combat. 



13. The females may enter the nest and lay their eggs at any time during 

 the process of nest building, and the eggs thus laid are covered in the subse- 

 quent operations of the male. Consequently they are included in the gravel 

 ridge and this ridge is filled with the eggs of many females. 



14. When a female enters the nest to spawn, she is thrown by the male 

 into a vertical position and encircled by his body; in this spawning attitude 

 the head of the female is always up and the opercle and pectoral fin of the male 

 are pressed against one of her sides while his tail behind the dorsal fin is pressed 

 against her other side. 



