DR. Petersen's report of the Danish biological station. 85 



It was found by the fishermen, and is proved by Petersen's observa- 

 tions, that plaice grow much more quickly in these inner waters than in 

 the western expansions of the fjord, and, moreover, reach a larger ultimate 

 size, which increases their value, apart from mere question of weight, 

 since very large fish command, from their rarity and excellent condition, 

 an unusual price. It appears, in fact, from the examination of the few 

 sexually mature females available, that the transported fish are similar, in 

 their relations of size and maturity, to the larger of the North Sea races, 

 from which, of course, they are annually bred.* 



On the other hand, the plaice in the outer broads show a tendency to 

 become mature at a somewhat smaller size. There is, perhaps, to 

 the biologist nothing in the whole Eeport of greater interest than this 

 last observation, since we seem to have before us the possibility of the 

 establishment of two aipimrcnt size-races, derived from common 

 parentage, operating under comparatively slight differences of environ- 

 ment. There is, of course, nothing to show that the differences would 

 be transmitted, even if (1) the fishermen spared any fish to reproduce 

 their race within the fjord, and (2) if reproduction, as seems to be 

 doubted, is possible there at all. 



In any case, the study of biological problems is pretty generally 

 known to bring no grist to the mill, and as Petersen's duties are to the 

 fishermen and not to the ichthyologist, he clearly regards the annual 

 fishing-out of the possible breeders with absolute complacency. In his 

 opinion, undoubtedly a sound one, the preservation of breeders might 

 yield unexpected results ; and I would venture to go further and predict 

 that, if any result in the way of reproduction were achieved, it would 

 inevitably be in the ultimate peopling of the fjord with one or 

 more stunted races of little commercial value. 



Granted that the fish grow more quickly and larger in the inner 

 broads, the question arises, Why is this the case ? The fisherman's 

 answer, that the bottom is more suitable than in the outer part, does not 

 appear to be based on a profound study of the benthos, since Petersen 

 is unable to detect any particular difference in this respect. On the 

 other hand, he produces figures to show that there is a very marked 

 difference in the number of fish which are found per acre in the 

 different parts ; and as the number is infinitely the greater in the outer 

 broads, he concludes that in the latter the fish are stunted in their 

 growth by "over-population." I have quoted the word used, which 

 is not qualified by any explanation, but is surely intended to be under- 

 stood as over-competition for a limited available food-supply. Otherwise, 



• Since Dr. Peteiscu is good enough to refer to me in this connection, I must reniiml 

 him that I proposed 17 inches as tiie biological linut between mature and immature lish, 

 and not as a size-limit for legislative purposes. 



