24 THE ROYAL SOCIETY OF CANADA 



fish varying in length from 55 cm. to 83 cm., six of the ten being over 

 79 cm., their measurements being 74 cm., 75 cm., 78 cm., 79 cm,, and 

 83 cm. There seems to be no room for suspicion that fish of these 

 sizes were not fully grown, and in every one of them the scale mark- 

 ings told exactly the same story (Fig. 1). There was only one winter 

 or check band on the portion of the scale formed during the life in the 

 sea, just as was the case with scales from the 44, 55, and 64.5 cm. 

 fish, and the conclusion is unavoidable that all full-grown Coho 

 are two-year old fish, that the life-cycle of the Coho is a two-year 

 cycle. 



In my earlier paper I also described markings on the scales of a 

 Dog Salmon that seemed to indicate that the fish had spawned as a 

 grilse, had again returned to the sea and had been captured in its fourth 

 summer, apparently on its way to the spawning grounds for the second 

 time. Such a life-history was so markedly at variance with what 

 seems to be the rule for all the species of Oncorhynchus, namely that 

 they spawn but once in their lives, that it seemed worth while to ex- 

 amine the scales of a greater number of Dog Salmon, to determine, 

 if possible, whether the behaviour of this particular fish was an indi- 

 vidual peculiarity, or an example of what was of relatively frequent 

 occurrence in this species. Unfortunately I was able to obtain for 

 examination only eighteen fish, which with those previously examined 

 made a total of twenty-two, but of these only the one individual showed 

 the peculiarity under consideration; the remaining twenty-on3, ranging 

 in length from 61.5 cm. to 83 cm., were all four-year fish when 

 captured and showed no indications of having spawned previous to 

 their capture. 



The number of fish examined is perhaps hardly sufficient for a 

 final determination of the question, but as far as my observations go 

 they indicate that the Dog Salmon, like the other species, spawn as a 

 rule but once. The single individual that showed a spawning scar in 

 the summer of its grilse year was probably a rare exception, and merely 

 serves to emphasize the probability of the general belief that the im- 

 mense majority of individuals of all species of Oncorhynchus die on 

 the spawning grounds. It has already been pointed out that the chances 

 for returning to the sea after spawning are greater in the case of the 

 Dog Salmon than in that of any of the other forms, since this species 

 runs relatively later in the year and finds its spawning grounds in the 

 smaller rivers and streams, frequently at no great distance from the 

 ocean. But, nevertheless, every fish examined was apparently four 

 years old and only four. If it be true that the life-cycle of the Dog 

 Salmon is completed in four years the probability that this is also the 

 case for the Sockeye and Spring Salmon, whose spawning grounds are 



