184 Conservation Department 



Cayuga. In these last, so far as known, only those streams enter- 

 ing the southern end of the lake serve as spawning places. 



In trying to estimate the damage done to the food fishes by 

 lampreys it would be of great help if it were known just how long 

 it takes the lampreys to mature in the lakes. 



During the last 50 years many lampreys preying upon fish have 

 been taken from Cayuga lake at all seasons of the year, even 

 during the spawning season, and from a careful study of the size 

 and stage of development of these direct from the lake it does 

 not seem possible that any of them could reach maturity and 

 lay eggs during their first parasitic year. It is possible that they 

 might be ready to spawn during their second year. As they 

 commence their predatory life mostly in February and March 

 and lay their eggs in May and June, this would make one and 

 one-third years the shortest possible time for their predatory 

 life. From the material studied it seems much more likely, how- 

 ever, that eggs are laid when the lampreys have been from two 

 and one-third or three and one-third years in the lake. Possibly 

 the time may be longer. 



As stated for the time required for their larval growth and 

 development, the only sure way to find out how long a time is 

 required for the growth and maturity of the adults is to secure 

 just transformed lampreys and keep them under as natural con- 

 ditions as possible until they are completely mature. There is 

 no difficulty in keeping them alive in running water in an 

 aquarium, and they are not at all backward in securing a meal of 

 blood from any fish that is available. Unfortunately no such ex- 

 periment has been tried with any parasitic lamprey, therefore at 

 present one must depend on estimates. 



Experiments on the Predatory Habits of Lampreys. — In 



order to see how the lampreys and fish act when in the water 

 together, and how the lamprey attaches itself to a fish, one of the 

 bathtubs in the house was turned into an aquarium. Large and 

 small stones were put in the bottom to make the place as homelike 

 as possible, and running water was supplied all the time. The ex- 

 periment was begun in December 1914 and continued until late 

 in March, 1915, that is, somewhat over three months. At differ- 

 ent times there were one or more bullheads (Ameiurus), suckers 

 (Catostomus) and carp (Cyprinus carpio) with the lampreys. 

 To make the fauna more complete some frogs and a necturus were 

 put in the tub. 



When first brought from the lake the fish and the lampreys 

 were rather restive and tried to get behind or under the stones 

 in the bottom. Then a cover was put over a part of the tub, 

 and they remained most of the time in the shadow. In the eve- 

 ning they swam around anywhere in the tub, but when the light 

 was turned on they mostly retreated to the shaded part. 



The lampreys and the fish seemed wholly indifferent to one 

 another. Often a lamprey would swim alongside a fish or a 



