of the Fishery Board for Scotland. 



13 



or May that the lengthening of the jaws of the male makes it possible 

 to distinguish the sex of the fish. He made a number of observations 

 on the growth of the snout of fish of both sexes. The average length 

 of the snout of the female he found remained the same throughout, but, 

 that of the snout of the male, which among the earliest fish is about 4'5 

 per cent, the length of the body (measured from the nasal opening to the 

 root of the tail), increases in length two-fold during the season. For this 

 reason, in measuring male salmon, he took his measurements from the 

 nasal opening to the root of the tail as being the most reliable points. 

 The salmon which he examined were chosen without reference to sex. 

 He considers, therefore, that they may be taken to represent the propor- 

 tion of the sex of the salmon caught near Basle. The actual number of 

 fish examined were 1029 females and 609 males. He found that females 

 were more numerous than males to the end of August ; during September 

 the excess in the number of females diminished ; in October the number 

 of either sex was nearly equal ; and in November females were again more 

 numerous than males. With regard to the relatively large proportion of 

 males taken in September and October it should be mentioned that it is 

 in these months, more particularly in the latter, that the few ' St^'Jakob's 

 ' Zalm,' presumably grilse, which reach the neighbourhood of Basle are 

 principally taken, and that among these fish it was found that males are 

 relatively much more numerous than among salmon. Dr Hoek also kept 

 records on this point. His observations were made on fish taken between 

 the 1st October and the 30th August during five years, and included 1217 

 females and 605 males. He does not claim, however, that these figures 

 can be taken as an altogether fair representation of the proportion of 

 males and females caught in Holland. The fish he examined had been 

 selected for their size, and might possibly, therefore, include an undue 

 proportion of females, as he found that, on an average, females are larger 

 than males. With regard to the proportion of the sexes among nearly 

 ripe salmon ascending the river in October, November, and December, he 

 mentions that, out of 959 taken in those months in 1884, 493 were males 

 and 466 females ; of the males 450 were ' St Jakob's Zalm,' while among 

 the females the latter numbered only 86. 



The result of the investigations made in Norway with regard to the Migration, 

 migration, growth, &c. of salmon by means of marking was given in Note Qf°g^ 0 u C '' 

 II. of the Eleventh Annual Keport of the Fishery Board for Scotland. ° a mon ' 

 On the Rhine it has been considered, however, that more valuable results 

 are likely to be arrived at by means of statistical records of the length 

 of the fish caught. Such a method, it is contended, will eliminate the 

 numberless variations and exceptions which must always appear in the 

 life-history of these fish, and enable the principal laws which govern 

 their migration, growth, &c. to be ascertained. For this purpose Professor 

 Meischer Ruesch drew up a table showing the relative frequency of the 

 occurrence of the different sizes. In this table the salmon which 

 were taken in the upper Rhine in 1878 and 1879 were divided into 

 groups according to length, the length of the fish in each group not 

 varying more than 20 mm. Dr Hoek collated similar information 

 regarding 4653 salmon taken in Holland in 1893 from March to 

 December inclusive. The most striking fact with regard to these 

 statistics is that certain sizes, occurring at three regular intervals, are 

 represented relatively by a very small number of fish, while midway 

 between these sizes those of the greatest frequency occur ; further, that 

 from the sizes which occur with the least frequency to those which are 

 most numerous the numbers gradually increase until the maximum 

 is reached and decrease again at a similar ratio. A diagram 



