132 FISHERY BULLETIN OP THE FISH AND WILDLIFE SERVICE 



from the fishery in Zones 1 and 2 only, and also feels the full force of the intensified 

 fishery above Bonneville, while stock G, entering the river at the end of the closed 

 season, is given no protection at all. The closed season undoubtedly does help to 

 increase the escapement to some degree, but it seems very probable that the heavy, 

 concentrated run that enters the river during August and September is actually less 

 intensively fished than is the spring run. This lowered fishing intensity is perhaps 

 due in part to reduced effort by the fishermen, brought about by the lower price 

 received for the fish, and also to the fact that with constant effort the percentage of 

 fisb caught when the run is light is probably greater than when the run is heavy. The 

 actual catch per unit of effort is, of course, greater with the heavier run, but the 

 efficiency of the total effort, as measured by the ratio of catch to escapement, is 

 probably inversely related to the intensity of the run. 



Within the last few years the use of fish wheels has been entirely eliminated, and 

 the use of traps greatly curtailed. Ostensibly these restrictions were imposed in the 

 interest of conservation, but they could only be effective insofar as they increased 

 the escapement of fish to the spawning grounds, and correspondingly decreased the 

 commercial catch. It seems rather doubtful that these restrictions have actually 

 had this result, although the available data are inadequate either to prove or disprove 

 the point. It may well be, however, that the elimination of these two forms of gear 

 has only resulted in increasing the catch of other forms, without materially increasing 

 the breeding stock. 



On the whole it would appear that the chinook salmon runs of the Columbia 

 River are subjected to an exceedingly intensive fishery without any effective protection 

 whatsoever, except such as has been afforded by the elimination of certain forms of 

 gear and by artificial propagation. 



PERCENTAGE OF GRILSE 



Along with the larger fish that form the bulk of the chinook salmon run there are 

 always some smaller fish, from 2 to 10 pounds in weight, that are commonly desig- 

 nated as "grilse," or, among the Columbia River fishermen, "jack salmon," or simply 

 "jacks." These are practically all males that have become sexually mature 1 or 2 

 years younger than the average and have, perforce, joined the spawning migration. 

 It has been shown by Gdbert, Rich, and others that most grdse are in their second 

 and third years, while the larger fish are in their fourth, fifth, or sixth years. In 

 counting the fish past Bonnevdle Dam an effort has been made to record these grilse 

 separately, as shown in table 7, and a study of these records has shown some interest- 

 ing and significant fluctuations in the percentages of these smaller fish (fig. 5). 



It is apparent from this graph that, except for 2 periods during which the per- 

 centage of grilse is consistently low, the average is about 20 percent. The fluctua- 

 tions that involve only individual weeks may be taken as due to "sampling error," 

 but those that extend over several weeks and show consistent change challenge some 

 other explanation. 



The 2 periods that show consistently low percentages are those covering the 

 weeks ending June 25 to July 16, and those ending September 10 to September 24. 

 We have already explained the lower percentages of the first period as probably due 

 to confusion of chinook grilse with blueback salmon during the peak of the run of 

 this last species. The second period is that during which the Bonneville count is 



