240 REPORT OF THE COMMISSIONERS OF 



By the use of hand nets, 1,215 were caught up stream, of which 345 were known to 

 be males, 324 females, and 546 of undetermined sex. There is no doubt that the first 

 Lake Lampreys ran up on the last evening of April. On the morning of the 1st of 

 May there was a pair of this species in the trap. Although they were both large, the 

 male did not yet have the dorsal ridge which characterizes the full sexual maturity, 

 nor did the female yet possess the anal fin. The attendant who spent the night in the 

 cabin by the weir said: "The lampreys got into the trap early in the evening, and 

 did more splashing and jumping than any other kind of fish." The lamprey that was 

 caught on the morning of May 5 was seen in both the forenoon and afternoon of 

 May 4, hanging to a stump in the water about half a mile below the weir. By far 

 the greater number of both lampreys and fishes are recorded in the forenoon catch, 

 because they were the ones that were caught running up during the night-time. 

 Most of them ran between sunset and midnight. The attendant reported that the 

 female recorded on May 21 was the first lamprey that got into the trap after 

 midnight, most of them having arrived at this place (about three miles from the lake) 

 at about nine or ten o'clock at night. 



The first male to possess the dorsal ridge, described elsewhere, which was caught 

 in the weir, was the one recorded on May 27, and the first female thus caught 

 possessing the anal fin, characteristic of the sex at spawning maturity, was caught on 

 May 28. Others showing these features had been taken from the spawning beds for 

 some days, and, after the latter date, nearly all that ran up bore these characters which 

 marked them as being fully adult and mature. On May 30 a ball of about forty 

 lampreys was taken from a gigantic spawning nest on the sandy and stony shallows 

 just below the weir, and on the same date two old females, which had spawned out, 

 drifted down stream and lodged in the upper part of the weir. They were placed in 

 a wire box, in a shady place in the stream, but it was impossible to keep them alive 

 longer than three days. Others, of both sexes, occasionally drifted blindly down 

 stream, but they were nearly dead. On June 5 two females were caught which did 

 not have the anal fin, and one male had the dorsal ridge but very slightly developed. 

 These were the last caught from which these structures were absent. 



It will be observed that in the beginning of the season the number of males caught 

 was greatly in excess of the number of females, while in the latter part of the season 

 the females predominated ; also, with the water becoming muddy, the number of 

 running lampreys decreased. This is doubtless because their gills are even more 

 sensitive than the gills of fishes, and foreign particles lodging in the gill pouches 

 would cause very great annoyance and real suffering. Further, the numbers running 

 increased as the water became warmer, and decreased as it became cold. This is 

 especially noticeable in the records for the 1 ith, 15th, 23d and 24th of May, when the 



