RECENT KEPOKTS OF FISHERY AUTHORITIES. 217 



take in the main the same sort of food as the older plaice," and after the 

 end of their first year there is no change in the character of the food of 

 the plaice. 



We may now pass on to our author's discussion of the economic 

 question : how may the plaice fishery be prevented from further 

 deterioration? We may say at once that Petersen is in favour of 

 the imposition of a size limit, but for reasons somewhat different 

 from these commonly given in support of this proposition. He points 

 out that the object to be kept in view is to make the fishery yield 

 as large a profit as possible. It is necessary, therefore, to allow the fish 

 to grow to such a size, that the largest possible weight of fish involving 

 the highest selling price can be obtained. 



Now, a plaice of 10 iu. weighs less than Mb., and one of 14 in. more than 

 twice as much: it follows that, unless in the time that it takes 10 in. 

 plaice to grow to 14 in., the mortality is such as to reduce the population 

 of these plaice to less than half its original number, the total weight 

 of the plaice at 14 in. will be greater than at 10 in. It is not likely 

 that the death-rate is as high as this, because the plaice does in fact 

 grow to a much larger size than 14in. ; further, it would seem that 

 disease is almost unknown among these fish : and their enemies are 

 apparently few. Hence, by allowing the 10 in. plaice to grow to a larger 

 size before capturing them a greater profit will be obtained. There will 

 of course be a limit of size beyond which it will not be profitable to 

 allow the fish to grow, and this limit will depend on the death-rate 

 at each size. 



Our author contrasts his view, which he calls the "growth theory," 

 with the " propagation theory " of other writers. Those who hold this 

 latter view insist on the necessity of increasing the 7mmher of in- 

 dividuals, and, in recommending a size limit, are happy if they can 

 secure that the fish shall be allowed a chance of spawning. Petersen, 

 on the other hand, thinks it of more importance to allow the fish to 

 grow to the size at which they will yield a maximum profit, and holds 

 that ample provision is made in nature for keeping up the numbers. 

 As his point of view is an important one, and as it is stated with great 

 clearness, I do not hesitate to quote him on this point in extcnso. " It 

 has always been hard for me to believe that there should be any want 

 of eggs of plaice in our seas, partly because Hensen's excellent investi- 

 gations have shown what immense quantities there are of them, partly 

 because 1 myself see our seas filled with such eggs. Nor have I 

 ever been able to believe in any want of young plaice. . . . Nay, 

 everything seems to me to indicate that it is not in the heginniny, 

 but in the middle and end of the life of the plaice that wo must 

 look for the injury ; for it is here that man interferes as a troublesume 



