14 THE AGE AND GBOWTH OF SALMON AND TEOUT. 



(c.) The Scale after the Salmon's Return to the River and the Formation of 



the Spawning Mark. 



Johnston has clearly and unmistakably shown that the sojourn of the 

 salmon in fresh water and the spawning which afterwards takes place may 

 have a most remarkable effect on its scales. The scales of spawned or 

 spent fish (kelts) which were examined by him were found, in consequence 

 of river life and the act of spawning, to be much frayed or worn away, 

 either because of the terrible emaciation of the fish or through partial 

 re-absorption during the fasting which they undergo in fresh water. This 

 wear and tear or re-absorption mainly affects the posterior and upper and 

 lower portions of the scales. This is well shown in Pig. 17 (Plate VI.). 

 Here we see that large portions of the posterior, as well as the upper and 

 lower portions of the scale, are, as it were, eaten away, and to such an 

 extent that the posterior portions of a number of the growth-rings are 

 broken off. When the fish returns to the sea after spawning and feeding, 

 and growth begins again, the new ring formation does not follow the line 

 of the old rin^ formation, but is formed in the usual manner parallel with 

 the outer edge of the broken scale, and in some cases one may find the new 

 growth-rings running in a direction almost at right angles to the old ones. 

 This is clearly shown in Fig. 18 (Plate VII.). In the gap between the 

 broken edge of the kelt scale and the subsequent new growth, a scar is 

 formed which is retained throughout the rest of the fish's life. If it again 

 returns to the river and spawns for a second time, and again returns to the 

 sea and further feeding takes place, we find a second scar or " spawning 

 mark," as it has been termed by Johnston. A scale with two such spawning 

 marks is shown in Fig. 19 (Plate VII.). 



That this is the case has been fully demonstrated by Johnston from the 

 examination of the scales of fish which were marked after spawning. Some 

 of these marked fish were recaptured as clean fish, and the scales were sent 

 to him for examination. In every instance an undoubted " spawning 

 mark " was found on the scales, and he has thus established beyond all 

 possible doubt the fact that the " spawning mark " is the result of spawning, 

 and that when such a mark is found on the scales of any fish it affords 

 unmistakable proof that the fish had previously spawned. 



The number of fish examined by Johnston was, however, too small 

 to make it absolutely certain that it was impossible for a fish to 

 spawn without a scar or spawning mark being left on its scales, and until 

 such proof had been obtained one could not form sound conclusions by 

 statistical analysis of the proportion of previously spawned fish to the 

 general stock in any river. 



I therefore obtained the scales from a large number of salmon caught 



