48 



Fortieth Annual Report 



trawlers which were working on the same grounds and landing at 

 Aberdeen market, except that none of the fish in the experimental 

 hauls was discarded. 



At the end of July, 23,300 haddocks were caught in 21 hours 

 actual trawling, giving an average of 1100 per hour. The sizes 

 ranged from 16 cm. to 56 cm. (6J to 22 in.), the mean length being 

 20 - 6 cm. (8 in.), but what is much more significant is that half the 

 total number of fish caught were between 197 cm. (7f in.) and 

 22*1 cm. (8f in.), and less than a quarter of the number were over 

 23 cm. (9 in.). Early in September similar hauls yielded 23,500 

 haddock in 9 hours, giving an average of 2570 per hour. The mean 

 size had then increased to 216 cm. (8J in.), due to the growth of the 

 fish in a period of less than. 5 weeks. Half the total catch were 

 between 20*7 cm. (8£ in.) and 22*5 cm. (8| in.), and less than a 

 quarter were over 23 cm. (9 in.), and a haddock only 9 inches in 

 length is a very small haddock indeed from the point of view of the 

 market. The very large majority of each total catch was of the same 

 age, belonging to the year-class spawned in the spring of 1920. 



Further hauls by the " Goldseeker " in mid-November showed 

 that there had been a considerable increase of larger and older 

 haddocks on these grounds, and that fish as a whole were scarcer. 

 In 38 hours' trawling 15,989 haddocks were caught, giving an 

 average of only 420 per hour. The mean length was 25*6 cm. 

 (10 in.), and half the fish were between 24 cm. (9 J in.) and 28*4 cm. 

 (11 in.). The increase in size for the fish given here compared with 

 that for those taken earlier in the year is due to the admixture of 

 the larger fish. By an examination of the scales, as in the case of 

 the herring, it is possible to sort out the catch into separate year- 

 classes. An examination of this catch by these methods showed 

 that the 1920 year-class, to which the bulk of the previous catches 

 belonged, had now grown to an average length of 25 cm. (9f in.). 



A very large number of these small haddocks were captured by 

 commercial vessels and thrown overboard as not worth bringing to 

 market. In this connection it appears a matter for consideration 

 whether the size of the mesh of the trawls commonly used is not 

 smaller than is consistent with the true interests of the industry. 



Although it would be premature to make any definite forecast, 

 it may perhaps be remarked that it would be in conformity with 

 previous experience if the catches of haddock in the next 2 or 3 

 years showed an increase in the percentage of the larger sizes. 



5. Plaice. 



The more intensive investigations on the plaice have now come 

 to an end, and definite recommendations have been made by the 

 International Council as to the policy which should be followed for 

 the preservation of this fishery. Work on this species is however 

 being continued on a reduced scale, more particularly with regard to 

 the apparent difference in the rate of growth between the younger 

 year classes in the Moray Firth and on the East Coast of Scotland. 

 It is found that the average length of a four year old plaice from the 

 Moray Firth is 23*5 cm. (9 J in.) and off the Aberdeenshire coast 29 5 

 cm. (11 J in.), and to ascertain whether the difference in growth rate 



