870 RECENT KEPORTS OF FISHERY AUTHORITIES. 



should liave beeu a fairly continuous decrease in the numbers of plaice 

 and lemon soles in the closed waters throughout the period. Fluctua- 

 tions have undoubtedly occurred from year to year, but, as has been 

 frequently pointed out in previous reports, the statistics show a fairly 

 steady falling off in the abundance of the species ; and of such a 

 character, when compared with the variations of other species, as to 

 preclude the idea that it is due to the operation of natural causes. 

 It was naturally expected that the prohibition of the use of the beam- 

 trawl in the Firth of Forth and !St. Andrews Bay would be followed by 

 an increase and not by a decrease in the numbers of these species 

 within the closed area, because the beam-trawl is the most effective 

 fishing instrument by which they are captured, and its interdiction was 

 equivalent to the removal probably of their greatest enemy.* 



" But such has not been the case. Before dealing with the probable 

 cause of the falling off among plaice and lemon soles attention may be 

 directed to the increase in the numbers of common dabs and long rough 

 dabs, which may be said to have taken the place to some extent in the 

 closed waters of the more valuable flat-lishes. Takimr the figures for 

 the closed area of the Firth of Forth as the result of 574 hauls of the 

 net during the ten years, the decrease in the number of plaice caught 

 per haul of the net is found to have been 8"7, and of lemon soles 8-4, a 

 decrease almost exactly counterbalanced by the increase in common 

 dabs, which was 8 "9, and in long rough dabs, which was 6'2. This 

 clearly indicates a change in the relative proportion of the flat-fishes in 

 the area, from whatever cause arising. Now there are some important 

 differences in this connection between the dabs on the one hand, and 

 the plaice and the lemon soles on the other. The dabs become mature 

 while still comparatively small, and escape in great numbers through 

 the meshes of an ordinary trawl net, and they spawn to a large extent 

 in the closed waters. Plaice and lemon soles, on the contrary, do not 

 spa\vu within the closed waters, and immature individuals are caught in 

 great numbers by the ordinary trawl net. Thus the size at which 

 common dabs and long rough dabs become mature is about 5 inches — 

 the males frequently at a smaller size— while plaice do not become 



* "The in'oportion of the fish lu'csent in a given area that may be captured by fishing 

 apparatus is frei]ueiitly under-estimated. Of several tliousands of plaice, marked for 

 future identification and retuined living to the closed waters, about 12 per cent, were 

 subsequently recaptured and returned to me within 18 months — and mostly within a few 

 montlis — of their liberation. Tliey were nearly all retaken iu the closed waters by hook ; 

 and as tliere is no reason to suppose that the marked fish were more prone to seize the bait 

 than the fish around them wliich hud not previously been captured, it may be assumed tliat 

 at least 1 in 9 or 1 iu 10 of tlie jilaice living on au area fall victims to the hook of the 

 fisherman. With the beam-trawl the jiroportion would have been very much greater. — 

 Vide ' An Kxperinicntjd Investigation on the Migrations and Rate of Growth of the Food 

 Fishes,' Part III., Eleventh Annual JRcjwrl, p. 176." 



