98 BULLETTN OF THE BUREAU OF FISHERIES. 



DISTRIBUTION OF THE FATS AT AN EARLY INTERMEDIATE STAGE OF THE SPAWNING 



MIGRATION. 



The first station above Ilwaco where salmon were collected was at Warrendale, 

 Oreg. This station is about 6 miles below Cascade Locks and is in the midst of an exten- 

 sive fishing field. Salmon taken here have not yet passed the swifter runs of the river, 

 but have already made a run of about 135 miles above the mouth of the river. The- 

 station was located at the cannery of P. J. McGowan & Sons, and I am particularly 

 indebted to the superintendent, Mr. Charles A. McGowan, for many special favors. 

 This company has a seining ground on the sand bar on the Washington side about i>^ 

 miles below Warrendale. Our specimens were chiefly taken from this point, as the 

 fish captured there were fine conditioned channel fish. 



Fish nos. 120, 121, 122, 125, and 126 were taken at this station during the month 

 of August. In August one secures salmon which clearly show stages of the removal 

 of fat from storage localities. There is at this time of the year considerable variation 

 in the grade of fish at this point. The fatter salmon, for example, no. 120, have their 

 tissues well loaded with a reserve of fat. The poorer salmon, no. 126, show marked 

 stages indicative of retrogression as regards the loading of fat. 



Trunk pink niusc/c. — There is wide variation in the microscopic appearance of the 

 fats in the trunk pink muscle of the fishes at this station. The fattest observ^ed was 

 no. 120 and the poorest no. 126. 



The intermuscular fat is disposed in the muscle according to the same general plan 

 as in salmon from Ilwaco. However, there is a very great diminution in the amount 

 of this fat. This is indicated by the decrease in the size of the larger droplets, and to a 

 less degree in a decrease in the number of droplets. A striking fact in comparison is 

 that in these Warrendale fish the fat is very much less uniformly distributed among 

 the fibers than in either the Ilwaco or in the normal tissue. The comparison between 

 two stations is difficult to make. One can not microscopically measure the number 

 of fat droplets and compute their diameters and thus the volume of material from the two 

 stations. Rather he is limited to impressions made by placing the slides side by side. 

 It is largelv on this type of evidence that the above comparisons are made. However, 

 as regards the intermuscular fat drops, a comparison of the diameters of the largest 

 drops is illuminating. At Warrendale these largest drops seldom measure over 50 fi 

 in diameter (see the protocol for salmon no. 121), whereas at Ilwaco they often measure 

 100 n and more in diameter. In observations made at the time the material was col- 

 lected and sectioned on the grounds at Warrendale it was judged that the amount of 

 intermuscular fat in fish no. 120 was about one-half to two-thirds as great as in fish 

 no. 118 from Ilwaco. Each of these fishes is among the best represented at its station. 

 In those fishes which were relatively poor in fat, as no. 126, the amount of intermuscular 

 fat is very greatly reduced. The amount of this reduction is best shown by comparing 

 figures 8 and 10 of plates vi and vii. Judging from the comparison of a large number 

 of preparations, I would say that the intermuscular fat of this poorest salmon could not 

 be above 25 to 30 per cent of that of the normal type. 



The intramuscular fat is abundant in all of the fibers of the pink muscle from the 

 trimk region. The smaller fibers as usual are more heavily loaded with fat than are the 

 larger. This is shown chiefly by the larger size of the liposomes in these small fibers. 



