—o: 
PROGRESS IN BIOLOGICAL INQUIRIES, 1926 585 
Even to the nonmathematical eye it should be plain that the trend can not 
be determined until a great many years’ records are available. In such fisheries, 
detection of a decline in abundance or in total yield may require more time 
than has elapsed since the beginning of the real fishery. 
It seems, finally, that the separation of economic effects is difficult and ocea- 
sionally impossible. 
The biological problems involved in the study of the reaction of the species 
to intensive fishing revolve for us very largely around the possibility of greater 
resistance at lower levels of abundance. ‘To illustrate: A highly respected 
English scientist postulates ° that the more intense the fishery, the better con- 
dition it finds itself in. This reasoning is based on the sequence in events 
in the North Sea as a result of its closure and is, very briefly, a theory that 
under natural conditions the competition between adults and young starves the 
latter and vastly reduces their number and their rate of growth. When the 
banks are intensively fished, the removal of the adults allows the young to 
grow faster and survive in greater numbers, so that they replace all that the 
fishery takes. Unfortunately, it is impossible for us to ignore selection by the 
fishermen when both young and adults are available, and facts from other 
sources” indicate that as a result of the North Sea closure both young and 
adults increased in numbers. Furthermore, the young occupy “nursery areas.” 
They do not inevitably compete with the adults, nor are the great ‘mass of 
their competitors for food necessarily members of their own species. But I 
am not criticizing the paper; it is theory I am interested in, and Garstang’s 
theory does at least present the possibility that an intensive fishery leads to 
a greater productivity at lower levels of abundance. He makes use of facts 
of growth, and should make use of facts of migration, to formulate his equation, 
for such it really is. 
Another attempt is equally interesting. A Russian scientist’ postulates that 
the production of a surplus pound of fish requires thrice the nutriment that 
the maintenance of a pound requires. The abundance of fish, under his theory, 
will fall until sufficient food supply is freed for use, so that the rate of repro- 
duction (beyond that to maintain the stock existing each year) exceeds the 
demand by man. It is hard to understand, at least for me, but he does make an 
effort to expresss the preblem of the increased resistance or increased produc- 
tivity of a species, which he assumes exists at a low level of abundance. He 
believes the food supply to be definitely limited in amount and used largely 
by the plaice, as does Garstang, but fails to see that the rule he applies to the 
plaice might well apply equally to the animals it uses as food. The intensive 
use of the food supply by the plaice might lead to greater productivity of the 
said foods and the elimination of useless competitors, so that in the end it 
might not make any difference how many plaice existed—they would never 
run short of food, any more than mankind would run short of plaice. 
However, the battle is fairly joined, as to the productivity of a species under 
various intensities of fishing. To me the only possible method of solution is 
the experimental one. But it is a great problem, indeed, and in its solution 
lies our sole hope of reducing the exploitation of our major marine resources 
to a logical basis. 
In passing, I would like to call your attention to the biological importance of 
such studies. Mankind’s demand on the fisheries is a type of adverse condition 
leading to greater mortality, very similar in many of its effects, perhaps, to 
the adverse conditions met by a species in nature. The power of survival 
exhibited by a species in contact with man seems to me to be that power 
that has enabled it to survive through the ages; and the record of evolution 
may be, in fact, the record of development of these powers. 
Our analysis of the factors important to us may throw light upon the nature 
and methods of evolution. 
Let us consider for a minute the facts brought to light in the study of 
dominant year classes in herring, sardines, and other fish. It might be sup- 
posed that the abundance from year to year would remain level; but our 
experience with sardines, herring, and Mr. Sette’s mackerel, as well as ‘locusts 

4 See Ne Plaice in the North Sea. London Times, Apr. 21, p. 15, and Apr. 
> Dp. : - 
®Heincke and Mielck: Schongebiete fiir die Scholle in der Nordsee. Berichte der 
aah Sees Wissenschaftlichen Kommission fiir Meeresforschung, neue Folge, Band 11, 
e 4 
7Baranov: On the question of the dynamics of the fishing industry. Bulletin of Fishery 
Economics, No. 8, Moscow, 1925. 
