NA TURE 



8i 



THURSDAY, MARCH 29, 1917. 



FISU MIGRATION. 



Alexander 

 Edward 



The Migrations of Fish. By Prof. 

 Meek. Pp. xviii + 427. (London 

 Arnold, 1916.) Price 16s. net.. 



UNDER the stimulus, and largely by the 

 instrumentality, of the International Council 

 for the Investigation of the Sea, enormous pro- 

 gress has been made in marine biological re- 

 search in its bearings upon economic fishery 

 problems since the founding of that body in 1902. 

 The lapse of its active functions pending the settle- 

 ment of the question of the "freedom of the 

 seas " affords a convenient opportunity for con- 

 sidenng the general results achieved, and thus the 

 time is ripe for the appearance of Prof. Meek's 

 volume, the material for which has been gathered 

 from the numerous publications of fishery investi- 

 gators in this and other countries. The book, 

 however, is not merely a compendium or plain 

 digest of other men's work, but possesses an in- 

 dividuality of treatment which is the author's own. 

 While practically all aspects of modern fishery 

 research — or at least their results — are set forth 

 in this treatise, which thus affords far more sub- 

 ject-matter than the title implies, the main theme 

 is the development of a theory of migration at 

 various stages of growth in relation to currents. 

 In this connection Prof. Meek introduces the terms 

 denatant and contranatant. These are useful 

 words, and will doubtless find permanent employ- 

 ment, but the idea tends to be somewhat over- 

 driven, and the referring of migrations to one or 

 other of these two classes, while satisfying a 

 desire for logical completeness and formal syste- 

 matisation, is liable to give rise to misapprehen- 

 sion in omitting consideration of all the factors 

 involved in fish migration. 



The rather self-evident fact that the pelagic ova 

 and larvae of fishes will migrate passively in the 

 same direction as the mass of water which con- 

 stitutes their habitat- — or, in the author's terms, 

 will migrate denatantly — is a fundamental factor 

 in the distribution of fish species and is rightly 

 emphasised. Also, if A represents the locus of a 

 spawning ground, and B the area to which the 

 passive migration of the early planktonic stages 

 is made and where the individuals grow to 

 maturity, then, if the mature fish return for spawn- 

 ing to their natal area A, the spawning migration 

 from B to A will be against the direction of the 

 current which was responsible for their first pas- 

 sive migration. This is described as a contra- 

 natant migration. In our opinion this mechanical 

 and frequently misleadingly simple representation 

 of the movements of the older stages leads one 

 very little towards a scientific understanding of the 

 migrations of fishes. The author apparently 

 belongs to that school of ichthyologists who 

 depreciate the value of hydrographical research in 

 relation to the problems associated with fish life. 

 In the preface he says : " It is obvious that cur- 

 rents are importantly associated with migration, 



but beyond this I have not found it necessary to 

 introduce hydrographical considerations." One 

 may mention the researches of Schmidt and other 

 Scandinavian naturalists upon the migrations of 

 cod, plaice, eels, etc., as demonstrating the funda- 

 mental importance of hydrographical factors in 

 determining the spawning migrations of these 

 species, while English investigations also point to 

 the correlation between hydrographical conditions 

 — i.e. temperature and salinity of water — and the 

 movements of fishes. It may be that the author 

 considers such correlations insufficiently estab- 

 lished as yet; but in ignoring them he would 

 appear, consciously or vmconsciously, to dissociate 

 himself from the trend of present-day fishery 

 research. 



The omission of reference to food and feeding 

 habits also detracts from the value of this work 

 as a treatise on migration, and further deejiens 

 the impression of a too mechanical and pedanti- 

 cally systematised presentation of the phenomena 

 of migration, in terms of which the following is a 

 sample : " The mackerel are denatant migrants 

 in the young condition, and it is evident that the 

 denatant migration is the dominant feature of the 

 migrations when they become mature. It is, as a 

 fact, usually denatant, but in some cases it may 

 be said to be denatant in direction only." 



Since the larval stages of practically all fishes 

 are planktonic, the exposition of the idea of 

 denatant migration is carried laboriously, but 

 without any serious hitch, throughout the chapters 

 on the various species. In suggesting that the 

 landward migration of the leptocephalus larvae of 

 the eel is purely a matter of passive denatant drift, 

 however, the author surely departs from the views 

 of the authorities on the subject. In fact, 

 leptocephali, though doubtless assisted by the drift 

 of Atlantic water towards the European coasts, 

 have quite considerable swimming power. 



The distribution and migratory habits of North 

 Sea plaice have been investigated by the inter- 

 national collaborators with a thoroughness and 

 with conspicuously conclusive results which may 

 be said without bias to constitute a monumental 

 fabric of fishery research. These results being 

 available in reports published between 1904 and 

 1916, it is a drawback that detailed consideration 

 of plaice migrations should have been limited to 

 the relatively insignificant and unrepresentative 

 fraction of the plaice fauna which occurs off the 

 Northumberland coast and in the Firth of Forth. 



After the unfortunate quotation from Izaak 

 Walton in the introduction repeating the old but 

 now quite exploded notion that a salmon returns 

 from the sea to the river which it left as a smolt 

 or samlet "usually about six months after," one 

 naturally approaches the chapter on Salmonidae 

 with shaken confidence. The above erroneous 

 view is repeated on p. 119 in dealing with the 

 definition of a grilse, and the statement that male 

 smolts are present on the spawning beds is a mis- 

 use of terms. Nor is it correct to assume that 

 female salmon must have spent at least two 

 winters in the sea before spawning, since female 

 grilse are quite common, though not propor- 



