72 SALT-WATER FISHES 



reaching a low ebb. It may be that certain inshore grounds, 

 which represent only a very narrow strip of water, contain 

 less fish than they did ; it may be, indeed it must be, that 

 a hundred fishing-boats to-day catch less fish per boat than 

 did ten half a century ago. When we bear in mind that 

 Dr. Hjort and Dr. Knut Dahl have recently discovered the 

 presence in the cold northern surface waters of myriads on 

 myriads of young gadoids, too small for any besides purely 

 scientific tow-nets to interfere with them, we may rest assured 

 that the cod family, at any rate, is in no danger from over- 

 fishing. On the other hand, it must be admitted that no one 

 ever asserted that the round-fish were in danger at all. It is 

 to the flat-fish that the fears of the pessimists are restricted ; 

 and it must be apparent to all that, so far as the inshore waters 

 are concerned, the flat-fish, particularly the plaice, show a 

 serious falling-ofi^ in the matter of both size and numbers. 



We shall presently find a very marked difl^erence in the 

 life-history of the flat and round fish, one that has direct 

 bearing on this question of their exhaustibility by over-fishing. 

 The migratory mackerel and the stationary plaice will serve 

 to illustrate this difference. There are seasons of the year, 

 varying in duration on different parts of our coasts, in which 

 the mackerel vanish completely from our ken. No man 

 knows where they are or whither they journey, and none 

 are during that period taken by any method of fishing with 

 either hook or net. It is true that investigations conducted at 

 Plymouth and elsewhere are yearly throwing fresh light on 

 this mystery of the mackerel, and almost any day we may 

 receive information of the whereabouts of that prolific and 

 capricious fish during the cold months in which it absents 

 itself from our coasts. Whether the publication of that know- 

 ledge will be an unmixed benefit is very doubtful. Even if 

 the trawl or drift-net, as now used, proved impracticable in the 

 deeper ocean water to which these fish are supposed to migrate 

 about Christmas-time, it is conceivable that the ingenuity of 



