DISCUSSION 



The extent of the landings by the combined 

 effort of the summer and winter fisheries has 

 been the cause of concern and has raised the 

 question as to whether or not the stock can 

 withstand indefinitely the present amount of 

 exploitation. Increased fishing effort during 

 the past several years has been due largely 

 to increased development and activity of the 

 summer seine and trawl fisheries and more 

 recently (1930) to the rapid expansion of the 

 winter trawl fishery. 



The major fluctuations in yield prior to 

 1929 were mainly the result of natural changes 

 in abundance, but since that year, changes in 

 yield have been further affected by increased 

 fishing effort. Despite this increase in ex- 

 ploitation, there has been no decline in abun- 

 dance. That the stock is not exposed to ex- 

 cessive fishing is indicated by continued high 

 yields of the summer and winter fisheries 

 and by the relatively small number of returns 

 from summer and winter tagging experiments. 



It does not necessarily follow that the scup 

 fishery is entirely free from conditions and 

 practices that may result in the future dimi- 

 nution of the stock to the point where com- 

 mercial fishing for the species becomes 

 temporarily unprofitable. It has been pointed 

 out that the present year-round fishing may 

 be expected to continue and increase in ac- 

 tivity. The stock may be subject to fluctuations 

 in numbers as the result of changes in avail- 

 ability and in variation of annual increments 

 to the stock as the result of changes in the 

 relative success or failure of reproduction. 

 This may, as in the past, cause a decline 

 in abundance so as to materially reduce the 

 population of scup. When this happens, the 

 decline of commercial-sized fish will be much 

 shari)er than in the past because of the greatly 

 Increased fishing effort. 



To render such inevitable decline less 

 severe and to maintain best possible catches, 

 the available supply should be wisely utilized. 

 The present destruction of undersized and 

 small unmarketable scup by both the summer 

 d'nd winter fisheries is contrary to this end 

 and constitutes an unnecessary obstacle to 



the continuance of the present high-catching 

 rate. This practice, however, is not unpardon- 

 able as many would assume, nor is its con- 

 tinuance reasonably justified. 



Argument in support of its continuance can 

 be based on the ground that as long as scup 

 are abundant and in excess of market demands 

 so much as to constitute a glut, no harm is 

 done in destroying young fish. In fact, it may 

 be argued that if the species is enormously 

 abundant, "thinning out" of the stock by de- 

 struction of the smaller sizes would Improve 

 conditions for the older and larger market 

 fish, because less crowding would allow better 

 development of market sizes and tend to 

 diminish the rate of natural mortality, all of 

 which would tend to compensate for the de- 

 struction of the smaller and less marketable 

 sizes. This, it might be argued, would be 

 comparable in results to the practice of 

 transplanting fish from crowded areas to 

 regions of more ample food supply and less 

 crowding. This is the practice of many years 

 in the plaice fisheries of certain European 

 countries bordering the North Sea (Blegvad, 

 1935). 



However, the opinion that destruction of 

 small fish constitutes a needless waste and 

 obstacle to continued good yields is worthy 

 of careful consideration, especially in light 

 of results of the present study. Since the scup 

 population is subject to very sharp, natural 

 changes in abundance, it is apparent that the 

 stock can reach exceedingly low levels irre- 

 spective of the amount of fishing effort pre- 

 vailing. This has been convincingly demon- 

 strated at various times during the history of 

 the fishery. Hence, in the periods of low 

 abundance, the small fish of marketable size 

 would be extremely valuable, and those below 

 legal limit would be a source of revenue If 

 allowed to grow another year or two. In addi- 

 tion, the survivors among these young and 

 small fish would have to carry the burden of 

 the whole fishery for scup, both in winter and 

 summer, until the next good year class or 

 classes came along. Fishing activity by that 

 time might be so increased that a diminished 

 supply of small fish would be quickly caught 



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