MANUAL OF FISH-CULTURE, 57 



into conduits leading to ponds where larger fish are kept; but a stand of 

 300 troughs has lately been set up with the design of using all the 

 water twice; and for many years there has been one system of 52 

 troughs, arranged in four series, which use in succession the same 

 water, the young salmon thriving quite as well in the fourth series as 

 in the first. 



On one occasion a few of them were maintained for several weeks in 

 the warmer water of a neighboring brook, where a trough was set up 

 and stocked with 100 young salmon taken from one of the troughs at 

 the station July 30. The temperatures observed between 1 and 4 p. m. 

 in the fish-trough on vsuccessive days from July 30 to August 14, not 

 including August 1 or 10, were as follows: 79°, 75°, 77°, 79°, 82°, 82°, 

 78°, 76°, 76°, 76°, 74°, 74°, 74°, 74°, F. 



The fish were fed the same as the lot out of which they were taken, 

 except that they received food only once a day instead of twice, and 

 were returned to the station October 7 without a single loss during the 

 experiment. Moreover, they were all weighed October 10 and found 

 to average 100.6 grains, while those of the original lot that had remained 

 at the station, with a temperature between 50° and 71° F., averaged 

 only 56.1 grains. While the greatly increased weight of the fish kept 

 in the stream was owing in part to more space, as the 100 had as large 

 a trough as 1,505 at the station, the higher temperature was undoubt- 

 edly one of the factors that contributed to the gain in weight, and it is 

 at least plainly shown that the warm water was not unhealthful. 



Though small ponds, excavated by the former proprietor, were in 

 existence at the station and used to some extent for rearing young fish 

 in their first summer as far back as 1888, and older fish have been kept 

 in small ponds each season since that, it was not until 1896 that enough 

 pond work was done to furnish data of importance. 



The i)onds for rearing Atlantic salmon are among the series known 

 as the "south ponds," occupying a smooth piece of ground sloping 

 toward Alamoosook Lake at a grade of 1 in 8. Formerly it was mostly a 

 swale, watered by a copious spring at its head. This series comprises 19 

 ponds of rectangular form, about 50 to 90 feet long and 15 feet wide, with 

 a depth of 2 or 3 feet. The water supply of those used for Atlantic sal- 

 mon is derived from Craig Brook by an aqueduct tapping it at a point 

 where two parts of Craig Pond water are mingled with one part spring 

 water, being substantially the same as the water supplying the most 

 of the rearing-troughs. From 5,000 to 10,000 fish that have been fed in 

 troughs during the early pare of the feeding season are placed m each 

 pond, and for the remainder of the season are fed the same food that is 

 given to the fish left in the troughs; and the results indicate that the 

 stock of fish might be safely increased. 



AVhile the greater part of the salmon reared at Craig Brook are 

 liberated in October, when about seven months old, in 1891-92 about 

 16,000 were carried througli the winter, most of them in tanks sunk 

 in the ground, and nearly as many have been wintered some other 



