28 Part III. — Twentieth Anmial Report 



remark applies to " other fishes," which are for the most part inedible, 

 the averages for each of the thi-ee periods being 4*0, 4*4, and 5"8. 



The renewed investigation above detailed concerning the change in 

 abundance of the various species within the closed waters confirms the 

 conclusions reached in 1896 on this subject.* It was then stated that " it 

 appears to be fairly well proved that there has been a diminution of the 

 more important flat-fishes in the closed waters, instead of an increase, as 

 was anticipated," and that, on the other hand, the numbers of common 

 dabs and long rough dabs had increased, and had to a certain extent taken 

 the place of the more valuable kinds. The above figures, while they 

 show that these changes occuired between the first and the second 

 periods of years, also indicate that a balance has not yet been established, 

 but that the decrease in plaice and the increase in long rough dabs still 

 appear to continue within the closed waters. The increase in common 

 dabs, as indicated by the recent hauls, is less marked, while lemon soles 

 appear to have lather increased ; and it may be that in the case of 

 these species a balance has been, or is being, established. It will be 

 seen from the Table on p. 27 that in the first period the number of 

 plaice caught exceeded the number of common dabs by 1286 ; in the 

 second period the number of common dabs exceeded the number of plaice 

 by 48, and in the third period the excess of dabs was 197. In the 

 fii-st period the number of lemon soles was greater than the number of 

 long rough dabs by 378 (1431 and 1053), in the second period the 

 long rough dabs exceeded the lemon soles by 657 (2676 and 2019), 

 and in the third period by 349 (870 as against 521). 



The probable explanation of the falling ofi" in the numbers of plaice 

 and lemon soles in the closed watei'S and the increase of dabs is given in 

 detail in the Report referred to, viz. (1) increased capture of the two 

 former species in the off-shore waters where they spawn, so that a 

 considerable diminution has occurred in the number of floating eggs and 

 fry which form the main source of supply to the watei's inshore ; 

 (2) the relatively greater protection of the spawning dabs, which spawn 

 to a large extent inshore ; (3) the selective influence of the trawl net, 

 which takes a much larger proportion of plaice and lemon soles that 

 enter it than of dabs, which are smaller in size, and escape in large 

 numbers through the meshes of the net. The results of further 

 experiments on the latter subject are described in last year's Reportt 

 in which it is shown, for example, that 91 per cent, of the long rough 

 dabs and 69'8 of the common dabs that entered an ordinary otter 

 trawl, used in commercial fishing, made their way out through tbe 

 meshes and escaped, while the percentage of plaice that escaped in this 

 way was only 0*4. 



With regard to round fishes, as already stated, the averages do not 

 allow a certain conclusion to be drawn. The abundance of these 

 fishes, as tested by experimental fishing, while subject to the same 

 vicissitudes as the flat-fishes, is subject to others in addition, due to 

 their shoaling habits and more erratic movements. The diminution of 

 haddocks, for example, from an average of 74*3 and a percentage of 

 62-0 in the period 1890-95, to an average of 3*9 and a percentage of 

 5-3 in the hauls in 1900-1, is obviously unassociated with the closure. 

 The only round fish which shows a progressive increase in both the 

 average and the percentage from one period to another is the gurnard, 

 which spawns very largely indeed in the Firth of Forth, and enters it 



* Foiaieenih Annual Rejjorl, Part iii. p. 144, et seq. 

 t Nineteenth Anmial Report, Part iii., p. 62, et seq. 



