PROGTJKSS IN BIOLOGICAL INQUIRIES, 1933 363 



It was foiiiul that in the case of brook trout (>.l) pounds of food 

 were required to })roduce a pound of fish, while witii the rainbow 

 trout 7.4 pounds were required to i)roduce the same amount. On a 

 dry basis it required approximately l.HG pounds of food to i)roduce 

 1 pound of fish in the case of the brook trout and 2.0.") jjounds in 

 the case of the rainbow. The less efficient use of food by the rain- 

 bow trout may possibly be caused by the greater activity of this 

 species. 



Selective breeding. — Exi)eriments in selective breeding of brook 

 trout were continued at the Pittsford station along much the same 

 lines as in previous years. xVs pointed out in some detail in the re- 

 port for 1932, rigid selection for two generations has resulted in a 

 notable increase in rate of growth and egg production. In fact, 

 the imj^rovement in these resj^ects has been much greater than it was 

 thought could possibly be accomplished in such a brief time. In view 

 of the success of these experiments at Pittsford, the same methods 

 of selective breeding are being extended to rainbow and brown trout 

 at the Leetown station. This is the first season trout have spawned 

 at this station, the oldest fish being only 2 5^ears old. 



In order to obtain a fair comparison of the growth of selected 

 and nonselected fish, three lots of brook trout fingerlings were reared 

 at the Leetown station under as nearly identical conditions as pos- 

 sible with respect to food and water supply. Each lot, 'containing 

 1,200 fingerlings, was placed in a standard hatchery trough on 

 March 1. where the fish remained until the experiment was discon- 

 tinued. Two lots of fish were from eggs taken at the York Pond 

 (N.H.) station. One lot of these eggs w^as from fish which had been 

 reared from wild trout; the second lot from fish still farther removed 

 from the original wild stock. The third lot of eggs was taken from 

 selected stock at the Pittsford station. 



From the beginning of the experiment the fish from the Pittsford 

 station grew more rapidly than those from the York Pond station. 

 There was practically no difference in the growth of these two lots 

 of fish. The experiment was discontinued in August when the fish 

 in each lot were 29.5 weeks old. At this time the average individual 

 w^eight of the Pittsford fish was 11.5 grams. The weight of one lot 

 of York Pond fish was 4.9 grams and the other lot 4.6 grams. There 

 was also a marked difference in mortality, which in one lot of York 

 Pond fish totalled 718 and in the other 54G. The loss among the 

 Pittsford fish was only 1G9 during the same period. The mortality 

 in all tlii'ee lots was abnormal, but no attempt was made to correct it 

 by treatment of any kind. The higher mortality among the York 

 Pond fish should have given them the advantage with respect to 

 growth so the fact that the Pittsford fish grew almost twice as fast 

 is all the more notable. 



Hatchery techinquc. — In an effort to determine the number of 

 young trout which can be handled most economically in hatchery 

 troughs, four troughs at the Leetown station w^ere stocked with rain- 

 bow fingerlings as folh)ws: Trough no. 1 received 500 fish; trough 

 no. 2, 1.000 fish ; trough no. 3, 2.000 fish, and trough no. 4, 3.000 fish. 

 These fish were all from the same lot, with an average weight of 

 approximately 1 gram at the beginning of the experiment. All 4 

 lots of fish grew at about the same rate until April 26 when the 



