CRUSTACEA AS FOOD FOR YOUNG FISH. 



15 



form has at times caused considerable damage to the Mississippi 

 dikes. The different species vary much in size, many of them being 

 large enough to be actually of considerable commercial importance. 

 The smaller purely aquatic species form an important food for sev- 

 eral species of fishes, and Hankinson (1908) reports that they " form 

 a very important, if not the chief, food of the black bass, rock baSs, 

 and perch," in Walnut Lake, Mich. It is a favorite bait for the small- 

 mouth black bass in Lake Erie, at least locally. The eggs of cray- 

 fishes are carried during incubation attached to the swimmerets of 

 the abdomen, and the young are of the form of the adult, when 

 hatched. They cling for a time after hatching to the hairs of the 

 swimmerets by 

 means of their 

 little upper feet, 

 and are carried 

 about by the 

 mother crayfish. 



POSSIBILITY O F 

 sue CES SFUL 

 C R U S T A C EAN 

 CULTURE. 



Various persons 

 have advocated the 

 culture of crusta- 

 ceans as food for 

 fishes, particularly 

 young fishes, and 

 have regarded it as 

 a practicable pro- 

 cedure. Such pronouncements have been based upon both experi- 

 ment and theory. The reports concerning European practices 

 of years ago indicated that they were to a certain extent successful. 

 Information indicating to what extent the success has been main- 

 tained or the methods improved is not at present available. In those 

 early days American fish-culturists who advocated the same pro- 

 cedure in this country based their confidence in the practice upon the 

 success attained in Europe. Some, claiming to have tried the meth- 

 ods, were enthusiastic in praise of the methods and the results ob- 

 tained. One fish-culturist at least doubted the practicability of rais- 

 ing the crustaceans on a scale to meet the demands in this country. 

 The enthusiasm and special efforts to raise crustaceans seem finally 

 to have died out, thus in a way supporting the contention of fish- 

 culturists of adverse views. In more recent years in this country 

 the question occasionally arises, but principally among those who base 

 their views partly, at least, upon the reproductive capacity of various 

 species. A few observations have been made with feasibility of cul- 

 ture in view. 



Actual observations in this direction are valuable, as they yield 

 scientific data. By correlating other data and known facts regard- 

 ing conditions of environment, life processes, and competition, and 

 considering possible imknown favorable and unfavorable factors, 

 approximately correct conclusions may be reached regarding one 



Fig. 10. — Crayfish ; " crawfish ; " " crab." Cambarus hartonl. 

 Natural size. After Ward and Whipple. 



