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BULLETIN OF THE UNITED STATES FISH COMMISSION 1885.

Page 448

SEGREGATION OF THE SEXES OF TROUT.
By Livingston Stone. [Reply to inquiry of S. M. Crawford.**]

At or about the spawning season, it is customary for the two sexes of trout to segregate, the males collecting in one large body by themselves, the females doing the same, or, more correctly speaking, I think, being left to do the same, as the herding together seems to be more active on the part of the males. This continues for a considerable time, about the period of the spawning season, and is not the exception, but the rule.

The same is true also of salmon, as is well known among salmon fishermen. It frequently happens that a whole run of salmon for several days will be composed almost entirely of males, the effect of which, of course, is to leave the females together by themselves, whether they take an active part or not in bringing about the separation. In fact, in hauling a seine frequently in a salmon river for some time, it is generally very noticeable that the sexes alternate in coming up the river about the spawning season, a large body of males being followed by a large body of females, and these by a run of males again, and so on through the season.

In the case of the trout mentioned in Mr. Crawford's letter, it is my impression that the males, in accordance with the custom just described, had separated from the females, and had retired to some other part of the lake (or stream), where if Mr. Crawford had fished he would have caught nothing but males. I suppose Professor Brooks would say that the preponderance of females was probably, the result of an exceptionally favorable environment, but I am, nevertheless, very strongly of the opinion that there was the usual number of males in the lake (or stream), though Mr. Urawford did not happen to find them, and that no general preponderance, of females actually existed.

Charlestown, N. H., January 12, 1855.

** Mr. Crawford, in a letter from Stark Water, N. H., January 6, 1885, says:
"On December 10 I began to catch the trout through the ice in six or seven feet of water, with a beardless hook. At first I caught males and then females, obtaining about 5 females to 3 males. Soon the male trout became more scarce, and of the 40 or 50 trout I have caught lately, I got but one male. The males I took at first I put in a large box with the females, and I have used the male trout until they are exhausted. Can you explain these singular facts?"

END

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