Biological Survey — Oswego Watershed 189 



centimeters (15 to 16 inches), and from a weight of 5 grams (l/6th 

 oz.) to 200 grams (7 ozs.). 



Every one who has had experience in feeding growing animals 

 knows that it takes much more than a kilogram, or a pound of food 

 to have the animal increase that amount of weight. This is because 

 it requires so much food just to keep an animal alive and supply 

 the energy needed for the heart to beat and the respiration to be 

 carried on, and many other activities of the living body. So with 

 the lamprey, a great deal of the energy supplied by its food is used 

 to maintain its life processes and to hunt its prey, and once at- 

 tached to rasp away the tough skin and the muscles and thus open 

 the blood vessels and suck out the blood. 



As the lamprey is a cold-blooded animal and does not require 

 any of the energy of its food to maintain a constant temperature 

 it may be fairly assumed that more of its food might be utilized 

 for growth and increase in weight than with a warm-blooded ani- 

 mal. Unfortunately there is not the wealth of nutritional infor- 

 mation for cold-blooded animals as for man and the domestic ani- 

 mals that have a fairly uniform body temperature. 



During the last year, however, at the Connecticut fish hatchery 

 some exact experiments* have been made with known diets, and 

 the amounts utilized for growth have been determined with scien- 

 tific accuracy. Three standard diets of liver, skim-milk, and sup- 

 plementary small amounts of yeast and cod liver oil were fed to 

 groups of fifty trout, An average of 29% in weight of the food 

 was utilized in growth by the trout. Assuming that the lamprey 

 would gain an equal amount as the trout on this liver-skim-milk 



Fig. 7. — Diagram showing the relative weight and length of lampreys at 

 maturity (m) and at transformation (t). The sea lamprey (S) is about 

 five times as long and weighs over one hundred times as much at maturity 

 (m) as at transformation (t). The lake lamprey (L) increases about three 

 times in length and twenty-seven times in weight, while the brook lamprey 

 (B) is practically unchanged in length and weight from transformation 

 (t) to maturity (m). 



* Information and permission to use by Dr. C. M. McCay, 



