Biological Survey — Oswego Watershed 191 



waters of the lakes communicate through their emptying streams — 

 Seneca river, for example, — it would be necessary to prevent their 

 wandering from one lake to the other. Probably the simplest 

 method would be to rid all the lakes of lampreys; but if that is 

 undertaken it is worth while to know exactly what the effort would 

 involve. A trial (Surface*) was once made in the inlet of Cayuga 

 lake and many early lampreys caught, but a freshet washed away 

 the lamprey traps, and the late lampreys went gaily up the 

 swollen stream to their spawning grounds as usual. 



As a final word, the lampreys can be eliminated but it would 

 be neither a short job nor an inexpensive one. 



Summary of the Economics of Lampreys : 



1. In general, lampreys are both beneficial and injurious. 



2. The brook lamprey does no harm to human food supplies, 

 and its larvae furnish excellent bait for fishing. This lamprey 

 in the New York waters may be put down as wholly beneficial. 



3. The large sea lampreys in the ocean feed upon the blood of 

 fishes and this species is therefore injurious to the sea food-fish. In 

 the rivers on its way to the spawning grounds in the headwaters it 

 takes no food, and is in itself a good food for human consump- 

 tion. Its larvae are excellent for bait. In the inland waters of 

 New York, then, the sea lamprey is beneficial. 



4. The lake lampreys in their larval stage are excellent for bait, 

 and that is their only redeeming feature. The adults live in the 

 waters of the lakes and grow up on the blood sucked from food- 

 fishes, killing some and weakening all they feed upon. 



5. Each lake lamprey lives from 1 1/3 to 3 1/3 years as a 

 parasite on fishes in the lake, and requires for its growth to full 

 maturity, probably at least three pounds of fish blood. 



6. For ridding the lake of lampreys, advantage must be taken 

 of the weak spot in their life cycle, viz. their migration up the 

 small streams to spawn. If they are trapped and killed before 

 laying their eggs, no new generation can be provided for. 



7. As the spawning time extends from the last of May to the 

 first few days of July, the trapping season must correspond, for 

 one pair with their hundred thousand eggs would soon restock 

 the lake. 



8. As the larvae or ammocoetes remain in the mud-banks from 

 four to five years, a new generation would pass down to the lakes 

 for a predatory life each year for that period. 



9. Also as the predatory life is from 1 1/3 to 3 1/3 years it 

 would require from six to eight years continuous effort to rid a 

 lake of lampreys, and every stream in which they spawn would 

 have to be trapped. 



10. And finally provision must be made by which lampreys from 

 neighboring lakes could not reinfest the lake through communi- 

 cating streams: (For example, the Seneca river for Cayuga and 

 Seneca lakes.) 



* Loc. cit. 



