ELEVENTH ANNUAL REPORT. IQl 



ROCK BASS. 



without fishes, until the use of a seine in one corner showed 

 that the yeUow perch fry introduced tw^o years before had already 

 attained good size. The presence of snags elsewhere in this lake 

 prevented the use of the net. The management of this pond will 

 always be difficult and unsatisfactory. 



A lake in the Zoological Park, stocked with yellow perch fry in 

 1903, was represented to be \vithout fishes, until the use of a 

 seine, sent from the Aquarium a year later, showed it to be well 

 supplied. The full utilization of this lake is however impossible, 

 since its bottom has many scattered rocks which prevent effective 

 seining. If the rocks had been removed originally, a good sized 

 seine would sweep it from end to end. 



Water Supply. — The water supply of the fish-pond is the most 

 important thing to be considered. It must in fact be taken into 

 consideration before the artificial pond is made. The flow of 

 water should be abundant. About twice as much will usually be 

 required as the beginner thinks is necessary. 



Ponds fed by strong springs are excellent and are not subject to 

 the dangers to which stream-fed ponds are exposed. Their tem- 

 perature is naturally more equable throughout the year and they 

 are less liable to heavy freezing in winter. In warm weather 

 and in the winter time, pond-fishes avoid extreme temperature by 

 frequenting the vicinity of bottom springs. Spring-water, how- 

 ever, contains less life available as fish food, and less air than 



