110 Reproduction, Competition, and Predation 



forces and counter-forces that are active for promoting the well-being of 

 a fish population in a primitive environment are absent from a man-made 

 and man-dominated lake. 



Changes in Fishing 



There are many records of lakes and ponds that once produced ex- 

 cellent fishing but which lost their productiveness after a few years be- 

 cause of the introduction and expansion of undesirable fish or the over- 

 population and stunting of desirable ones. 



Krumholz ^^ working on hybrid sunfish in ponds in Indiana found that 

 39 of 78 ponds stocked originally with hybrids and largemouth bass 

 contained, after two years, other species of fish than were originally 

 stocked. After questioning the owners of 29 of these ponds, 26 admitted 

 that they had introduced other kinds of fish. Among the fish that were 

 introduced were largemouth bass, bluegills, black and white crappies, 

 green sunfish, orange-spotted sunfish, longear sunfish, and warmouth, and 

 in two instances, smallmouth bufiFalo. Most of the pond owners explained 

 their actions with the statement that they wanted to catch a greater 

 variey of fish. 



Ball and Tait^ state: "The knowledge and effort necessary to maintain, 

 over a period of time, a pond producting fast-growing bass and bluegills 

 are beyond the scope of the average pond owner. Consequently, it is 

 recommended that ( 1 ) small ponds be stocked in such a way as to pro- 

 duce the species desired in the greatest edible weight in the shortest 

 time, (2) these fish to be harvested, and (3) restocking be done instead of 

 attempting to maintain a 'balanced' pond over a period of years." This 

 may be a practical solution if ponds are supplied with a drain outlet 

 and fish for restocking are readily available. 



In recording the history of Fork Lake, a farm pond in central Illinois,^ 

 it was discovered that fishing had been considered good from 1926 to 

 1930 but had become poor through the development of large populations 

 of black bullheads, carp, and buffalo fishes. At the time that Fork Lake 

 was censused in 1938, it contained 5350 fish weighing 774 pounds (539 

 pounds per acre) and consisting of 16 species. Only 145 fish of the 5350 

 were of such species and sizes as to interest anglers. 



Stocking for Improvement of a Population 



Biologists are not in complete agreement on the value of adding fish 

 stocks for the improvement of a population that, from the standpoint of 

 fishing, is somewhat less than optimum. Viosca,'^^ after censusing ponds 

 in Louisiana, concluded that the stocking of ponds which already contain 

 fish may cause almost no change in a population of fish. He cited an ex- 

 ample of a pond stocked with 1500 largemouth bass fingerlings which 



