CRUSTACEA AS FOOD FOR YOUNG FISH. 19 



MALACOSTRACA. 



The Aselliis, while fairly common at times and in places, com- 

 pared with some other crustaceans is not abundant. It doubtless 

 enters more or less into all open crustacean culture inclosures fed by 

 surface water. Its habits do not render it ]3articularly desirable, 

 although it is in itself a good fish food for fishes large enough to 

 swallow it. No special effort to cultivate it has been suggested. 



AMPHIPODA. 



Of all the crustaceans, the amphipods, or scuds, inappropriately 

 called shrimp, have been most strongly advocated and most com- 

 monly used as food for young fish, particularly those which have 

 attained the fingerling stage at fish-cultural establishments. The 

 common amphipod of Europe which has been thus employed is 

 GatnTTiarus pulex {pulex meaning flea). 



Eaveret-Watell (1887) stated that at Gremaz arrangements were 

 also made for raising amphipods. Alongside the fish ponds artificial 

 rivulets were filled with water cresses and other aquatic plants and 

 stocked with these crustaceans. However, the fish were not placed 

 in these rivulets or ditches to feed, but the crustaceans were rationed 

 out to the fish in their own inclosures. A sufficient quantity of 

 " shrimp " was gathered in a few minutes to supply the fish with the 

 amount of food required. It was said that when being fed the young 

 trout would come from all directions " in dense masses " and would 

 not allow a single " shrimp " to reach the bottom of the pond, and 

 that no matter how large the quantity of shrimp it quickly van- 

 ished. It was claimed that the young trout thrived admirably upon 

 the diet. 



It was stated, also, that these small " shrimp streams " were so 

 profitable that they would soon give place to a still simpler method, 

 i. e., by proceeding in exactly the same manner as employed with 

 Daphnia (alternately stocking and admitting fish to different in- 

 closures). There were said to be 3 ponds ("basins"), each having 

 a surface of about 120 m. and containing about 70.000 fish of the 

 jT^ear, grouped according to size. It was stated that experiment had 

 determined that one basin 35 m. (114.8 feet) long and 3 m. (9.84 feet) 

 broad, with an average depth of 40 cm. (1.3 feet) of water, may con- 

 tain 20,000 young fish from 8 to 12 months old, or 3,000 two-3^ear- 

 old trout having an average weight of 250 gm. (0.55 pound). Re- 

 garding the amount required, it had been determined that 10 kg. 

 (about 22 pounds) of "shrimp" per diem, or 300 kg. (about 660 

 pounds) a month, would suffice for the fish ; and that inclosures of 

 the above dimensions would produce 300 to 350 kg. (660 to 770 

 pounds) of shrimp without at all interfering with Daphnia, Nais, 

 Limnea, insect larvae, etc., which were incidental or secondary prod- 

 ucts of the shrimp culture. It was said that it was necessary to have 

 only tAvo ponds for each lot of fish and to transfer the fish back 

 and forth once a month. 



Later Consul Frank H. Mason (1887) described the methods at 

 the Gremaz establishment more fully than the preceding writer. He 



