ZOOLOGICAL SOCIETY BULLETIN 



SHARK-SUCKER 



Lifting a pail of water weighin 



C. H. T. photo 

 ' 21 pounds. 



SCIENCE AND THE DOMESTICATION 



OF FISHES. 



By Sergius Morgulis, Ph. D. 



Avery extensive plan has been worked out 

 by the Government for the domestication 

 of food fishes, and the rivers and ponds 

 of the country are stocked with millions of fish 

 reared yearly in liatcheries. Numerous private 

 concerns also derive profits from raisins; fish for 

 the market. The full utilization of the water 

 resources of the country, for propagating and 

 rearing fish by artificial methods is something 

 which must come in the future. There is no 

 reason for doubting that some day each farmer 

 will raise fish just as he raises fowls today. 



The part played by science in the develop- 

 ment of various industries is too obvious to 

 require any comment. Agriculture and pure 

 science have become inseparable as is evidenced 

 bv the large mmiber of research institutions and 

 experiment stations organized to promote its 

 special interests. The a])preciation of the need 

 of applving modern, scientific methods to the 

 study of various aspects of fish life is also 



Sote — .\t the request of the U. S. Biiiean of Fish- 

 eries, laboratory space in the New York Aquarium 

 has been furnished to Dr. Sergius Morgiilis who is 

 engaged in studies of nutrition in fishes, under the 

 auspices of the Bureau. The work has been going 

 on for several months. — Director of the Aquarium. 



awakening. Above all, from the practical stand- 

 point, it is necessary to obtain scientifically 

 qualified knowledge of the dynamics of fish life, 

 of their functions and energy transformation, 

 since the complete success of the future domes- 

 tication of fish will rest upon this. 



The task of investigating physiologically and 

 biochemically aquatic organisms is a particu- 

 larly difiicult one, owing to the nature of tlieir 

 environment. It is not surprising, therefore, 

 that in its first stages this study should be em- 

 barrassed by erroneous observations and faulty 

 deductions. Even very recently some biologists 

 of renown believed that aquatic animals derive 

 all. or at any rate, part of their nourishment 

 from substances dissolved in the water. It would 

 take us far afield to discuss at length this hy- 

 pothesis, but it will suffice to say that much 

 careful analytical work was required to defin- 

 itely dispose of this erroneous conception of the 

 nutrition of fish. 



Considering the organism merely as a ma- 

 chine, it depends upon the consumption of raw- 

 material food for energy to perform work, such 

 as locomotion, search for nourishment, etc., and 

 to maintain its vital functions, such as the pul- 

 sation of the heart, respiration, digestion, secre- 

 tion and so on. Besides, the organism requires 

 energv for its growth and propagation. 



The food materials of which all living organ- 

 isms partake are of three princpal kinds: pro- 

 teins, carbohydrates and fats. In a general 

 way the first are distinguished by the fact that 

 tlieir elementary composition includes nitrogen. 

 Meat and white of egg are typical representa- 

 tives of this group of food stuil's. Carbohy- 

 drates (sugar, starch) and fats contain the ele- 

 ments carbon, hydrogen and oxygen, the former 

 being particularly rich in oxygen and the latter 

 in hvdrogen. As the amount of energy yielded 

 by the combustion of hydrogen, weight for 

 weight, is greater than that of carbon, the en- 

 ergy value of fat is the higher. Food, when it 

 is digested, becomes absorbed and incorporated 

 in the organism where it sooner or later under- 

 goes oxidation or combustion, thereby setting 

 its potential energv free, usually in the form 

 of heat. This is then transferred into other 

 forms of energv or work according to circum- 

 stances. The digestion, absor))tion and oxida- 

 tion of the food are very complex phenomena. 

 Much of these iilienomena is still beyond our 

 ken. 



The final products contained in the urinarv 

 excretions as well as in the gases given off in 

 breathing have been thus far vcrv little investi- 

 gated in the case of fish. tlii>iigh they have been 



