Reighard. — Knotuledge of Breeding Habits 99 



The features of interest to us in our present discussion 

 of the breeding habits of fishes may be summarized as 

 follows : 



1. At the breeding season fishes migrate from their ordinary haunts 

 to the breeding grounds. 



2. Each species selects a breeding ground characteristic of it. It 

 shows a preference with respect to the character of the water (warmer 

 or colder, clear or turbid, quiet or running), with respect to the nature 

 of the bottom (sand, gravel, marl, muck, mud) and with respect to 

 the presence or absence of plants. 



3. Both sexes are present at the same time on the breeding ground. 

 Their bodies are in intimate contact at the moment of laying of the 

 eggs and practically all eggs are fertilized. 



4. Some species construct nests for the protection of the eggs. 

 Others construct nests and guard the eggs. Others continue the 

 guardianship for a longer or shorter time after the eggs have hatched. 

 Most species do not construct nests and do not guard the eggs or young. 



In order that fishes may thrive in any natural water it 

 is necessary that there be sufficient food and that there 

 be available breeding grounds suited to each species. 

 Most fishes are not narrowly limited in their choice of 

 food. They are capable, with few exceptions, of utilizing 

 the available animal food. Their choice of breeding 

 grounds is more limited. Yet in attempting to deter- 

 mine the suitability of a particular water for a given 

 fish, far more attention has been paid to food than to 

 breeding grounds. Of the two factors the latter is prob- 

 ably the more important. 



UTILIZATION OF OUR KNOWLEDGE OF THE BREEDING 

 HABITS OF FISHES. 



1. Selection of Waters in Which to Plant Fish. In the 

 earlier days of fish culture in Michigan whitefish and 

 wall-eyed pike were planted in many inland lakes. In a 

 few of these the adult fish were afterward found, but in 

 most of them the water remained as barren of the 

 planted fish as before the planting. Conditions were evi- 

 dently unsuitable, but in what respect? In most of the 

 lakes thus planted it is probable that there was sufficient 

 food for the adults of either of these species. But if suit- 

 able breeding grounds were lacking it is likely that con- 

 ditions were in some way unsuited to the planted fry. 

 In the case of the whitefish we have an imperfect knowl- 



