70 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



are almost entirely responsible for any cleaning of 

 the spawning area before spawning. 



Belying their appearance, the males are not 

 pugnacious. Occasionally one would make threat- 

 ening motions at another male, but no vigorous 

 fighting was observed. Several whitefish (Core- 

 gonus dupeaformis) and a large eel (Anguilla 

 hostoniensis) were seen among the milling lake trout 

 and were unmolested. It was noted, however, 

 that the males were nearly of the same size. Per- 

 haps they had already disposed of any venture- 

 some small males. 



Merriman (1935) and others have observed the 

 spawning lake trout splashing at the surface. In 

 Otsego Lake this was noted only infrequently, 

 possibly because the spawning was on a steep 

 slope in 2 to 15 feet of water — deeper water than 

 that in which Merriman made his observations. 



The males began their courtship upon the ap- 

 pearance of the females on the spawning area. 

 Usually the male nudged the female in the side 

 with his snout (fig. 4) and then attempted the 

 spawning act. Frequently two or more males 

 courted and attempted to spawn with a female at 

 the same time. During courtship the males dis- 

 played the characteristic coloration (fig. 1) and 

 commonly held the dorsal fin erect. These dis- 

 plays were apparently identical to those noted by 

 Merriman (1935). 



The spawning act or attempts at it normally 

 consisted of one or two males approaching a 

 female, pressing against her sides with their vents 

 in close proximity and then quivering all over 

 (fig. 5). Usually the mouths of both sexes were 

 open and the dorsal fin of the male was held erect. 

 This act was seen clearly at close range several 

 times when no eggs or milt were expressed. On 

 two occasions a cloudiness was noted in the vi- 

 cinity of the vents which probably was caused by 

 the emission of sperm. No eggs were seen but 

 this could have been because of the distance of the 

 observer from the fish and the turbidity of the 

 water. No other act or behavior was seen which 

 could be construed to accompany oviposition. 

 Probably the attempt at the spawning act is a 

 part of courtship and is repeated over and over 

 again until fulfillment. 



The spawning act was not limited to two or 

 three trout; as many as seven males tad three 

 females were seen at one time, all pressing to- 

 gether in one large group and quivering in unison. 



No spawning act lasted for more than a few sec- 

 onds, and it seems that a female must accomplish 

 many unions to empty the ovaries completely. 

 The trout are not monogamous and it was impos- 

 sible to follow the movement of any one pair in 

 the milling group. 



No tendency toward oviposition in any definite 

 place on the spawning area was observed. The 

 trout mated at random over the area cleaned off, 

 and there was no attempt by either sex to bury 

 the eggs. This seeming carelessness in regard to 

 the fate of their young was justified when one 

 attempted to find the eggs. A casual examination 

 of the bottom revealed practically no eggs, but 

 they could be picked up by the hundreds when 

 the stones were turned over carefully. Eggs were 

 recovered in water from 3 inches to 14 feet in 

 depth. Those collected in more than 2 feet of 

 water had to be taken in a Petersen dredge and 

 no estimate of their abundance could be obtained. 

 Along shore in less than 2 feet of water, however, 

 where only an occasional trout was seen spawning, 

 from 20 to 50 eggs could be recovered per square 

 foot of bottom. The eggs were difficult to pick 

 up, and the slightest motion of the water sent 

 them rolling further into crevices between the 

 rocks. In their selection of the bottom on which 

 to spawn, the lake trout had chosen an ideal 

 shelter for their eggs and young. 



ENVIRONMENT AND DEVELOPMENT OF 

 EGGS AND LARVAE 



EFFICIENCY OF FERTILIZATION 



It has been a long-cherished belief of fish 

 culturists that the natural spawning of trout is a 

 highly inefficient, hit-or-miss process. Critical 

 investigations have shown this belief to be untrue. 

 White (1930) was able to hatch 79 percent of a 

 sample of naturally fertilized brook-trout eggs 

 removed from their redd and placed in a hatchery, 

 and 66 percent of another lot placed in a screen 

 basket and reburied in the redd. Hobbs (1937), 

 after intensively investigating the redds of brown 

 trout, rainbow trout, and quinnat salmon, found 

 that more than 99 percent of the eggs were 

 fertilized. He also found that subsequent heavy 

 loss in the pre-eyed, eyed, and alevin stages was 

 a result of adverse environmental conditions. 

 Under favorable conditions the natural reproduc- 

 tion was a highly efficient process. 



