298 



CIVIC BIOLOGY 



importance, and from these data we should be able to con- 

 struct a table showing the crop of each kind of fish for the 

 entire district. We may then figure per acre production and 

 percentage of effective utilization of each water unit.^ 



In making the survey, seek to arouse the interest of the coniuiuuity. 

 Ask your fish experts — the fish warden, the one who has charge of 

 the nearest hatchery, or some of the best local anglers — to visit the class 

 and present their views for stocking the district. Study the publications 

 of your state fisheries commission and of the United States Bureau of 



Fig. 139. Topography of a fish (Yellow perch) 



1, spinous portion of dorsal fin ; 2, soft portion of dorsal fin : 3, caudal tin; 4, anal 

 fin ; 5, ventral fin ; 6, pectoral fin ; 7, opercle ; 8, branchiostegal rays ; 9, mandi- 

 ble, or lower jaw; 10, premaxillary ; 10 o, maxillary ; 11, snout; 12, eye ; 13, head ; 

 14, lateral line ; 15, series of scales, counting from front of anal fin upward and 



forward to lateral line 



Fisheries. Ferret out all such bulletins in private collections and induce 

 their owners to loan or donate them to the school or public library ; and 

 write to Washington or to your state department for any others that 

 may be needed. 



1 ''It is difiicult to estimate the capacity of ponds for the various stages 

 in the growth of fish. It depends for the most part upon the amount of ap- 

 propriate food available. ' A 2-acre pond producing 10,000 one-year-old black 

 bass from 4 to 6 inches long would be a remarkably successful enterprise, 

 and 20,000 one and one-half to two inch yearling crappie or sunfish to an 

 acre of water would be likewise notable. These numbers have been realized 

 and in some instances exceeded, but the average results are doubtless much 

 smaller." — Johnson and Stapleton, loc. cit., p. 25. 



