122 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



Neither iu the Kiiddow nor in the Kheda could any law be shown 

 governiug the migrations of these two kinds of fish; while in the Ehine 

 and iu the ri\'ers of Great Britain very easily distinguishable schools 

 of fish of different ages ascend the rivers at different times; and the 

 numerical proportion of the sexes varies greatly in the schools ascend- 

 ing at diflerent times. Observations made during one year in two rivers 

 are of course not sufficient to draw therefrom any general conclusions. 

 The evident differences of the conditions of migration in the different 

 rivers makes it, however, exceedingly desirable that accurate and sys- 

 tematic observations should be taken in as many places as i)ossible, 

 especially in rivers which contain many salmon, such as the Weser, 

 where thus far nothing is done but to count the salmon that are caught, 

 so that all we learn is at best how many fish were caught every day. 

 According to the observations of Miescher-Euesch, the largest number 

 of salmon ascends the Ehine, both in the Netherlands n^id near Basel, 

 in July; while iu the Weser, according to a communication by Dr. Lin- 

 deman in the Weser Zeitung, the largest catches were made during the 

 first half of May. 



This is not the place to give a detailed review of the carefully ascer- 

 tained measurements and weights of the fish, especially as the number 

 of fish observed in the two rivers — 344 — is too small ; but I will simply 

 give a few results of my observations on the measurement and weight 

 of the fish. Thus, taking the height of the body as the unit, the length of 

 the salmon varied between 3.6 and 6.2, while that of the sea-trout varied 

 between 3.5 and 5; and these variations occur with tolerable regularity 

 in fish of eveiy size, from 12 to 54 inches. The proportion b.etweeu the 

 length and the weight of the body, of course, varies just as much. The 

 following are some of the results of my observations : 



A salmon measuring 45.7 inches in length can therefore weigh, in the 

 same water, 16 or even 30 pounds, which ought certainly to involve 

 some diifereuce in the shape of the body. 



