68 



Appendices to Twentij-jirst Annual Report 



APPENDIX IV. 



NOTES ON THE LENGTH MEASUREMENTS OF UNSPAWNED 

 SALMON AND GRILSE "MARKED" IN NOVEMBER 1902. 



By H. W. JOHNSTON. 



Of the salmon and grilse " marked " in the six days during which 

 netting was carried on above Perth, in November, there were 244 in an 

 unspawned condition. It is difficult to state with accuracy the number of 

 salmon, as distinct from grilse, as in the breeding season the characteristic 

 features of each are somewhat modified, and in individual cases doubts 

 arose as to their classification. It may, however, be stated generally 

 that grilse were more numerous in the lower reaches immediately above 

 Perth than in the river higher up, and that both in their number and 

 weight an increase was apparent towards the end of the month. An 

 analysis, based on length, of unspawned salmon and grilse strikingly 

 brings out the preponderance of one or other of the sexes in groups of 

 different measurements. This would not appear to be the result of 

 chance, as it was observed in each day's operations. The following Table 

 shows the number and percentage of each sex in various length-groups : — 



Group. 



Length. 



Number. 



Percentage. 



Remarks. 



M. 



F. 



Total, i 



M. 



F. 



1 



26 inches and under, 



7 



.58 



65 



11- 



89- 



Chiefly Females. 



2 



26i to 27 inches, - 



12 



16 



28 



43- 



67- 



Mixed Sexes. 



3 



27^ to .31| inches, - 



59 



9 



68 



87- 



13- 



Chiefly Males. 







78 



83 



161 



48-5 



51 "5 





4 



32 to 37 inches, 



4 



54 



58 



7* 



93- 



Chiefly Females. 



.5 



37^ inches and over, 



19 



6 



25 



76- 



24- 



Chiefly Males. 







101 



143 



244 



41-4 



58-6 





In comparing the dimensions of fish nearly ready to spawn, some allow- 

 ance must be made for the seasonal increase in the length of males, in 

 consequence of the growth of the snout, which need not be taken into con- 

 sideration in the case of females. The investigations in connection with 

 Tweed fish (given in the Appendices to the Fourteenth Annual Report) pro- 



