48 



NATURE 



[September i8, 1919 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can be undertake to return, or to correspond with 

 the writeirs of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous communications. "i 



Sea-fishery Investigations and the Salance of Life. 



The impression that Prof. Mcintosh's address, pub- 

 lished in Nature of July 3 and 10, must leave upon 

 the minds of readers unfamiliar with the history and 

 progress of sea-fishery research must be that there 

 has been a great deal of misdirected energy during 

 the past fifteen or twenty years in the attempt to gain 

 control of the output of the sea by the application of 

 science to sea-fishery problems. If, as Prof. Mcintosh 

 still maintains, the prodigality and bounty of Nature 

 mock all human efforts to modify the natural course 

 of events in the sea for good or ill, it becomes surely 

 a national duty to oppose all further applications for 

 national expenditure upon sea-fishery investigations. 

 As this, judging from his concluding paragraph, is not 

 the aim which Prof. Mcintosh has in view, it seems 

 desirable to inquire a little more closely into the basis 

 for his views, and to give at least the broad outlines of 

 the superstructure of knowledge which has been reared 

 above the basis of that fundamental work of his own, 

 which has been a source of legitimate pride to himself 

 as of appreciation by his successors and colleagues. 



I think it will be conceded that the leading features 

 of Prof. Mcintosh's expressed views are, broadly 

 speaking, as follows : — (i) The fecundity of sea-fishes 

 is so great, and the ultimate food-supply for the fishes 

 themselves is so completely independent of human 

 influence that the idea of exterminating any species 

 of food-fish— or even of seriously diminishing its total 

 numbers — by intensive fishing is chimerical ; (2) so 

 long as man fails to make any serious impression 

 upon the multitudes of young fishes, there is no need 

 for anxiety ; (3) no serious inroad upon the numbers 

 of young fishes has hitherto been made ; (4) therefore 

 all is well, the fears of the pessimists are pointless, 

 the claims of the optimists are established. 



.% Prof. Mcintosh and "J. J." have been good 

 enough to assign me the r6le of arch-pessimist, I may 

 as well clear the ground by the remark that, when I 

 approached the study of sea-fishery problems twenty 

 years ago, the dominating question was : Is the prac- 

 tice of sea-fishing affecting the yield of the fishing 

 grounds, or is it not? It was a case of absolute 

 stability versus depletion or impoverishment. When, 

 therefore, I find a tendency to re-define the question 

 as being one of slight deterioration versus extinction, 

 I demur. If I am to be dubbed a pessimist, that word 

 must be understood to mean a person who, twenty 

 years ago, urged that the " bottom fisheries " were 

 not in a stable condition, not "holding thoir own, "but 

 showing clear signs of progressive impoverishment ; 

 and this was explained as meaning that " the rate at 

 which sea (food) fishes multiply and grow, even in 

 favourable seasons, is exceeded by the rate of cap- 

 ture " (" Impoverishment of the Sea," p. 8). 



Passing on to points (2), (3) and (4), and restricting 

 myself to plaice, as a test-case, the following quota- 

 tions from Prof. Mcintosh's recent articles are rele- 

 vant : — " Plaice have been taken from the North Sea 

 from time immemorial, and yet are distributed to-day 

 over its entire area, while their tiny young swarm on 

 every suitable sandy or muddy beach" (i., p. 356); 

 " the removal of the larger fishes by intensive fishing 

 is the rule, but the gaps thus made are filled later bv 

 the Swarms of the smaller" (p. 3.:;7); "The idea that 

 NO. 2603, VOL. 104] 



the North Sea can be fished oet is chimerical, for even 

 if all were gone over thrice or more frequently a year, 

 such could not produce depletion or exhaustion of its 

 fisheries — plaice included" (ii., p. 377); and, d propos 

 of the International Council's findings with regard to 

 the plaice question : " In other words, all that can be 

 said is that the plaice are not less numerous, but . . . 

 they are smaller — a finding which leaves the plaice 

 in safety " (I.e.). 



Putting these ideas together, it is plain that Prof. 

 Mcintosh regards the progressive diminution in the 

 available numbers of the larger fish as negligible, and 

 the continuous lowering of the average size as of no 

 significance, so long as there are plenty of little fishes 

 on the beaches. He ignores the evidence that the rate 

 of growth of these little fishes and their rate of emi- 

 gration to the offshore grounds no longer keep pace 

 with the rate of capture. He treats the over-fishing 

 problem as one of reproduction and numbers to the 

 exclusion of rate of capture, rate of growth, and actual 

 size attainable. 



Apply this principle to agriculture, and consider 

 what our meat-supply would be if the farmers killed 

 all their cattle as calves except the minimum breeding 

 stock necessary to keep up the number of — calves ; or 

 if, when thinning their turnips, they had regard, not 

 to the production of the greatest possible weight, but 

 merely to the production of that minim-jm number of 

 mature plants which should give them seed sufficient 

 for the next sowing ! 



Prof. Mcintosh asks : " Where have the melancholy 

 anticipations of the pessimists been demonstrated; 

 where has the serious diminution of any food-fish oc- 

 curred ;• where have the principles enunciated in 'The 

 Resources of the Sea ' been traversed by the Inter- 

 national Fisheries Council? " (i., p. 355). The answer 

 to the open mind is " on everv page." 



And what are the practical conclusions of " vigorous 

 optimism "? " Let the authorities and the public plaoi 

 implicit confidence in the resources of the ocean and 

 the ways of Nature therein " (ii., p. 378); " Be vigilant 

 in guarding the national trust! " (I.e.). One may 

 well ask of what comfort is the " marvellous plenitude 

 and endurance of the sea-fishes " if they becomj 

 measurably smaller year by year, or the " prodigality 

 of Nature in their vast abundance and variety " if 

 codlings are to represent cod, and plaice and lemon 

 soles be replaced by dabs and long-roughs. And does 

 " vigilance " consist in ignoring the plainest evidence 

 accumulated by other people, while we sing hymns of 

 praise to Pan or Poseidon? Let us turn now to the 

 superstructure. 



The qualitative basis of sea-fishery science, to which 

 no one contributed more effectively than the veteran 

 professor at St. -Andrews, already shows the outlines 

 of a quantitative structure upon it. Some of these out- 

 lines are still mere scaffolding, but the broad features 

 of the building are discernible. 



The idea of boundless prodigality, with its " chains 

 of life " from diatoms to fishes, is not the end but the 

 beginning. It is being steadily replaced by the concep- 

 tion of a balance or equilibrium of life, the two sides 

 of which are the world of plant-life and small inverte- 

 brates on the one hand, and the world of fish-life on 

 the other. The former has hitherto been beyond the' 

 influence of man, though subject to fluctuations in its 

 total quantity in consequence of annual fluctuations 

 of temperature, sunshine, and similar factors known 

 to influence plant production, and, indirectly, the in- 

 vertebrate and small vertebrate forms immediately 

 dependent for subsistence upon the former. The fish- 

 world, on the other hand, while undergoing annual and 

 cyclical fluctuations in quantity depending on those of 



