22 U. S. BUREAU OF FISHERIES, 



As previously indicated, the other three species studied were 

 Gammarus limnoeus^ Eucrangom/x gracilis^ and HyaleVa knicker- 

 hocken^ which are here named in the order of relati^'e size from 

 largest to smallest. 



Embody shows that Eucranojonyx and Hyalella have the widest 

 distribution and are adaptable to a wider ran£,^e of temperature and 

 other conditions than the other two species. According to Embody's 

 observations, Eucrangonyx has the longest breeding period and 

 Hyalella tlie shortest. Gatiimdrus limnrpus requires the coldest water 

 for breeding. Eucrangonyx produces the largest average number of 

 eggs, G. limruvus next, and Hyalella the lowest average. The young 

 of Eucrangonyx grows slowdy as compared with the other three spe- 

 cies. Hyalella, next to G. fasciatus, has the greatest reproductive 

 capacity, followed by G. limiuvus and Eucrangonyx. 



A logical deduction from the foregoing would seem to be that, 

 taken all in all, Hyalella would be of the most general practicability 

 and best suited to the most varied conditions and the greatest number 

 of species of fishes. For Salmonidse. hoAvever, particularly the east- 

 ern brook trout, G. litmueus would be the most suitable, for besides 

 the possibility of raising it in waters cold enough for trout, next to 

 Eucrangonyx it produces the largest number of eggs, and next to 

 G. fasciatus has the greatest reproductive capacity. As has been 

 previously stated, G. livwimus is the " Caledonia shrimp " of fish- 

 cultural fame. 



Shira,^ by means of tables, gave the details of the partial repro- 

 ductive capacity of one pair of Hyalellas, carried through 4 months. 

 Assuming that the males and females of each brood were about 

 equally divided, he calculated that the approximate possible number 

 of progeny produced by the pair and succeeding generations was 339 

 in about 4 months' time. In another pen one pair produced S suc- 

 cessive broods of a total of 122 young in 89 days, the shortest period 

 between broods being 10 days. Shira's opinion, based upon his breed- 

 ing experiments with Hyalella. was that it had been conclusively 

 shown that the species could be reared in a practical way in large 

 numbers as fish food. On Ai^ril 29 a pond was supplied with water 

 and aquatic plants, such as Ceratoph^dum, Philotria, and Potamoge- 

 ton. The plants grew rapidly, and by the time the experiment had 

 terminated had produced a very luxuriant growth. Breeding Hyalel- 

 las to the number of 2,583 were placed in this pond at intervals from 

 May 12 to June 11. From June 15 to August 20 a total of 45,900 

 were removed and transferred to another pond. At the termination 

 of the experiment an attempt was made to approximately estimate 

 the number still remaining in the pond. A small lot was volumetri- 

 cally measured and counted, and from the data thus derived it was 

 calculated that the total number was 63,800. Adding to this the 

 45,900 which had been removed gives a total of 109,700 for the period. 

 Shira thus says: "With a larger pond area and improvement of 

 method, the possibilities of rearing this shrimp as fish food would 

 seem unlimited." He states that the transfer of shrimp from one 

 pond to another was the simple process of brushing through the 

 vegetation with a small hand net of cheesecloth, by which means the 

 shrimp were caught in large numbers. 



•■'Unpublished manuscript, 191 S. 



