188 Conservation Department 



ing substance which is poured out near the rasping tongue where 

 it can bathe the torn surfaces and come in contact with the blood 

 as it emerges from the vessels, and keep it liquid. 



(e) The amount of blood required to fill the intestine of a full- 

 grown lake lamprey was found on measurement to be about 25 

 cubic centimeters (nearly a fluid ounce). The fishermen often 

 speak of the paleness of the fish which they find a lamprey attached 

 to ; is it any wonder if they look pale after losing so much blood ? 



Estimation of Damage Done by Lampreys. — With the above 

 facts in mind, it is possible to give an intelligent discussion of the 

 very practical question of how much injury the lampreys actually 

 do to the food fishes in the waters where the lampreys are found. 

 As shown above, large numbers of fishes are attacked, and of course 

 the greater the number of lampreys the more damage they do. 



One year accurate count was kept of all the lampreys caught on 

 the spawning beds, and the number of nests in the main inlet of 

 Cayuga lake. Over four hundred nests were counted in the extent 

 of about 2% miles, and more than one thousand lampreys were 

 actually caught. That of course did not make the full number that 

 spawned that year. They are not so numerous every year. On 

 May 31, 1920, members of the department of zoology were taken to 

 the inlet of Seneca lake above Montour falls. The water was 

 teeming with lampreys and nearly five hundred were secured in 

 a couple of hours. Great numbers have also been secured at other 

 seasons in that place, so that it is quite intelligible why so many 

 of the fish in Seneca lake are lamprey marked. 



Suppose that Oneida, Seneca or Cayuga lake has one thousand 

 lampreys in its waters at one time. This would represent only a 

 part of those that went down to the lake to begin their predatory 

 life. In nature there is a great mortality. Of the hundreds of 

 thousands of eggs deposited in a stream any one year, only a very 

 few survive to reach maturity and return for laying eggs for 

 another generation. Many of the larvae are caught by fish when 

 they are washed out of the mud, and even the transformed ones 

 at the beginning of life ' ' the blue lampers, ' ' are snapped up on 

 their way to the lake and in hunting for victims. 



"To eat and be eaten" is the law of the water as of the jungle. 

 There are also unknown causes that produce mortality with the 

 lampreys as of other living things. Death may come at any time 

 from the egg to the adult stage of life. One lamprey was found 

 early in the season up one of the spawning streams with its branch- 

 ial region so far digested that the cartilages of the branchial basket 

 were exposed. Dr. Wright told me that on one occasion he was 

 watching the lampreys in the inlet and saw a big water snake go 

 in, grab a lamprey and carry it out on land. In spite of the great 

 mortality there must be a large number preying on the fish of the 

 lake all the time. 



The question then is how much fish food in the form, mostly of 

 blood, is necessary for the young lake lamprey to grow from a 

 length of 13-14 centimeters (about 5 to 6 inches), to a length of 40 



