428 EXAMINATION OF THE PRESENT STATE 
those which are too small to reproduce their species ; or (b) merely 
between marketable and unmarketable fish. Of course the former 
standard is considerably the higher in all flat-fish of any considerable 
value (excepting the lemon-sole in the North Sea), while both 
standards are subject to variation according to locality. 
Of late years I do not know that the enforcement of the bio- 
logical limit has been much insisted on, except in cases where it 
chances to fit in with what may be called the economical oppor- 
tunities of the situation. Its advocates content themselves rather 
with the pious opinion that it is desirable that fish should have a 
chance of reproducing their species at least once before they are 
destroyed. Moreover, at least one authority of the highest 
standing, Dr. C. G. J. Petersen, holds that the deterioration of the 
fishing is, in the case of plaice, certainly not owing to a want of 
spawn, since, with regard to young plaice, he finds “ that it is hard 
to imagine there could be any more individuals than there are.” * 
Petersen’s remarks refer here to the Cattegat, and do not profess to 
say whether the young fish are actually as numerous now as in 
former years. He simply suggests that there are enough to furnish 
a remunerative fishery if they were not destroyed at too small a 
size. On the North Sea grounds our fishermen are emphatic in 
their statements that even the small fish are much less numerous 
than they used to be, and I do not think there is any reason to 
doubt their accuracy in this particular. If it is so, although the 
fry may be numerous enough to supply the existing fishery when 
grown up, there must still be an insufficiency of spawn, since I 
take it that the ideal condition would be that the grounds should 
hold the greatest possible head of fish which they can maintain. 
The fishery is growing, and presumably will grow, and the problem 
which we have to face is not only to try and provide for immediate 
wants, but in so far as lies in our power to maintain the grounds at 
the greatest possible degree of productiveness. 
The objection to the biological limit is, of course, that by cutting 
off a large supply of marketable but immature fish, it bears hardly 
both on the producer and the consumer, and especially the latter ; 
while there is no apparent way in which it can be enforced 
with absolute certainty of benefit tothe supply. In this connection 
it will be remembered that we have seen that the conditions of 
deep-sea trawling are not favourable to the return of undersized 
fish in a healthy condition, and therefore if, as we know to be the 
case, mature and immature fish are caught together on certain 
erounds, the latter have but little chance of surviving the process. 
What we have to strive for is a method which shall combine the 
* On the Decrease of our Flat-fish Fisheries, Rep. Danish Biol. Stat., 1894, p. 62. 
