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for the various annual series of the fry live generally separated from the 

 older individuals, near land, preferring, particularly, certain shallow coves 

 and seas; but the young fish emigrate to deeper waters as they grow older. 

 The first annual series of plaice (specimens under 2 — 3 inches) is 

 (with few exceptions) missing in the Baltic, and is most numerously repre- 

 sented in the northern parts of the Cattegat. The youngest individuals are 

 also missing in most of the fjords (the cause of this I shall return to after- 

 wards). The fertilized eggs of the plaice, on the other hand, are some- 

 times found in great numbers in the western part of the Baltic Sea. 

 {ITensen*). — 



Note : Cunningham., especially, has lately studied the growth of sea fish (See Jowrn. 

 Marine Biol. Assoc. Plymouth), hut he tries to solve the question in a somewhat 

 different way than I have done here; besides founding his opinion on the growth 

 of the fish in captivity (a very dangerous thing) he calculates the age of the fish 

 which are caught in open nature by estimate, by means of the size only. He 

 writes (loc. cit. N. S. vol. fl, p. 96): But it is difficult in this way to ascertain the 

 maximum growth for one year, since a number of specimens of one species often 

 form a continuous series in size, and it becomes difficult or impossible to say 

 where those of one year old end and those of two years begin* ; ■ — and loc. cit. 

 p. 97 : »It is not difficult to recognise with certainty young fish only a few weeks 

 or months old; but the individuals of a given species brought up in numbers at a 

 single haul of the great beam-trawl form usually a regular series of sizes, so that 

 it is difficult if not impossible to separate definitely those which are one year old 

 from those which are two, and those which are two years from those which are 

 three «. — 



I must grant him, of course, that the extremities of the annual series, especi- 

 ally 2 and 3, are very much alike, and that it is therefore impossible with respect 

 to many individuals to say how old they are, and, indeed, I can hardly under- 

 stand how he has been able by a mere estimate to get so near the truth as he 

 appears to have done in many cases. He has conjectured, for instance, that the 

 plaice can commence spawning in its second year, but that it does not generally 

 do so till it has filled its third ; I should hardly have been able to form this con- 

 jecture if I had not seen the size-groups in open nature, not only those of the 

 plaice but also those of Plenr. flesus; at any rate we must fake these into considera- 

 tion when we discuss this question, as it is one of the very greatest importance 

 to all fishery-legislation — where everything depends on knowing, not the growth 

 and age of the single individual, but the average growth and average age of the 

 fish. With regard to the plaice Cunningham's uncertainty is particularly conspi- 

 cuous pp. 347—350 in a Joum. Marine Biol. Assoc. Plymouth. (N. S.) vol. II. 

 1891 — 92 « when he settles the age of plaice of c. 8 — 12 inches in spring and early 

 summer. He looks upon these as but little more than one year old, but admits 

 that it is possible they are more than two years of age. P. 350 he says of some 

 plaice of 8V 2 — 12 V? inches, which on the 16. May were caught ofEEsbjerg: Hhave 

 accordingly estimated the age of the specimens of May 16th from the Denmark 

 coast at twelve to sixteen months; a conclusion supported by the fact that they 

 were all immature. But some of these specimens may be in their third yearc. 

 Yes, I think they are all in their third year, i. e. over two years old and belonging 

 to the 2-group; but this question can be finally settled only by a new examination 



