ZOOLOGICAL SOCIETY BULLETIN 



1339 



by Prof. Chas. W. Greene of the University 

 of Missouri and published in "Transactions of 

 the American Fisheries Society for December^ 

 1915." 



It treats of changes in the Pacific salmon 

 of the genus Oncorhynchus on the long run to 

 the spawning grounds while at the same time 

 their reproductive organs are undergoing devel- 

 opment. Moreover, while the paper does not 

 even hint at this phase of the topic, it gives 

 one a good picture of the exhausted condition 

 of the salmon at the end of the run and explains 

 why they are unable to survive. 



As has been abundantly proved, these sal- 

 mon take no food after entering the brackish 

 water at the mouths of the rivers. For the long 

 run of hundreds to even a thousand miles or 

 more, often against raging torrents, the fish 

 must thus draw upon its stored supplies of en- 

 ergy. At the beginning of the run the repro- 

 ductive organs are immature and the develop- 

 ment of the abundant supplies of eggs and milt 

 also must depend on the release of food material 

 from other tissues. 



The problenl is well stated by Professor 

 Greene : "The two principal facts, namely ( 1 ) 

 the expenditure of the large amount of energy 

 without external food, and (2) the development 

 of one set of organs at the expense of material 

 derived from other organs, form a unique bio- 

 logical experiment in nutrition. The experiment 

 is unusually favorable also because of the fact 

 that it is carried out in nature under conditions 

 that must be assumed to be normal and natural 

 for the animal." 



The king or chinook salmon (^Oncorhynchus 

 tschawitsha) from the Sacramento Basin of Cali- 

 fornia was the particular form chosen for study. 

 Comparisons were made of the condition of 

 fishes of the same length obtained in the sea 

 before the beginning of the run, from the head 

 of brackish water, and later, from the spawning 

 grounds of the United States Fish Hatchery at 

 Baird, California. 



The work deals especially with the muscle, 

 which is the great storehouse of nutritive mate- 

 rial, both for the fish and for man. The weight 

 of the total mass of muscle substance was com- 

 puted both in the wet and dry conditions for 

 fishes from all three localities. 



One very interesting fact is that the fish in 

 working their way from the sea to the head of 

 brackish water actually gain 11 % in weight 

 without taking any food. This is explained by 

 the absorption of water. A gain in weight of 

 5.6% is shown by the wet muscle, but the study 

 of the dry muscle shows that there is actually 

 a loss of 0.8% in the nutritive matter. 



The most important difference, however, is 

 found on comparing fish from the spawning 

 grounds with those from either of the other lo- 

 calities, and the astonishing loss of nearly three- 

 fourths of the dry muscle substance is observed. 

 The figures given for the three localities, in per- 

 centage of dry muscle, are as follows : sea sal- 

 mon, 25.9%; head of brackish water, 25.9%; 

 spawning grounds, 6.8%. Moreover the fat, 

 which is the important nutritive substance, forms 

 from 15% to 20% in the down river individuals, 

 while at the spawning grounds it has practically 

 disappeared, only 1% to 2% remaining. The 

 material left in the muscle is therefore only the 

 proteid, which represents onlj^ about one-third 

 of the nutritive value of the same amount of 

 fat. 



Professor Greene sums up the results of his 

 work in the following statement: "The food 

 material of the salmon stored in its muscles 

 when it begins its run to the spawning grounds 

 is represented by 25.8% of the total weight of 

 the fish, whereas at the end of the spawning- 

 run it is represented by one-third of 6.8%, or 

 2.3% of the total weight of the fish, a loss of 

 between 84% and 85% of the stored material. 



Similarly the other tissues of the body give 

 up their material. The visceral mass, for ex- 

 ample, is reduced to only one-eighth of its orig- 

 inal weight. It thus appears that all the avail- 

 able material is devoted to the production of 

 the sex cells and to the energy required for the 

 long run to the spawning grounds, and thus 

 the fish is actually used up to such an extent in 

 this great culminating effort of reproduction 

 that even the continuance of life is impossible. 



R. C. OSBURN. 



SOME HABITS OF THE FOUR-EYE FISH 

 (CHAETODON CAPISTRATUS). 



By L. L. Mowbray. 



WHILE one is observing fishes among the 

 coral reefs, it is not an unusual thing 

 to see the busy little chaetodons or 

 "four-eye" fishes, as they are commonly called. 

 The species that is known as the four-eye is 

 so called because of the eye-like spot on either 

 side just below the soft dorsal ra5^s. 



The general color is silvery and lemon yel- 

 low. There are numerous lines of brown run- 

 ning along the rows of scales, and a band of jet 

 beginning at the top of the head and running 

 forward and downward, almost completely hid- 

 ing the eye from view, then downward and 



