50 



Fortieth Annual Report 



north, and it has been possible to show the existence of a continuous 

 procession of crabs northwards along the coast. But these do not 

 by any means account for the crabs that disappear altogether from 

 any particular fishery. Two-thirds of the labelled crabs are never 

 recovered, which fact points to a very great destruction in the stock 

 through natural agencies. The majority of the crabs that provide 

 the catch in any one year are crabs that have cast their shells dur- 

 ing the previous twelve months. 



7. Fish Surpluses. 



Mention has already been made of the large quantity of small 

 haddocks thrown overboard as not being worth gutting and bringing 

 to market and of the amount of valuable foodstuff which is wasted 

 owing to a variety of causes, such as gluts in the market and lack of 

 transport facilities. Neither the industry nor the country can afford 

 such waste, and a practical method of utilising these surpluses is 

 urgently required, and should prove a profitable channel for com- 

 mercial development. 



Experiments have been carried out in the Board's laboratories 

 with the object of discovering new or improved methods : — 



(1) In the preservation of fresh fish, which cannot be disposed 



of as such, for human food. 



(2) In the manufacture of fish meal from surplus fish, heads, 



guts, skins and other fish wastes for feeding cattle, pigs, 

 poultry, etc., and for use as manure. 



(3) In the manufacture of fish meal from the invertebrate 



debris inseparable from trawling operations. - 



One of the great difficulties to be overcome in dealing with fish 

 surpluses is the extremely offensive nature of the smell arising from 

 processes such as are commonly used in the manufacture of guano or 

 similar products. For this reason the factories engaged are strictly 

 regulated, and the necessary licence is not easily obtained. During 

 the investigations now being conducted considerable progress has 

 been made in the elimination of the offensive odour hitherto 

 associated with this branch of the industry, and it is hoped that 

 further research may result in the discovery of improved methods 

 which will be more generally acceptable and equally if not more 

 efficient. 



The Board is indebted to Dr. J. B. Orr, Director of the Nutrition 

 Eesearch Institute, Bucksburn, for carrying out a series of experi- 

 ments in feeding animals with the products of these investigations. 



8. Drift Bottles. 



The extensive liberation of surface and bottom drift bottles made 

 in co-operation with the Ministry of Agriculture and Fisheries to 

 ascertain the direction of drift of the water masses of the "North Sea 

 was completed in September. During the year 4800 surface and 

 4760 bottom drift bottles were liberated from the following 

 stations — Bell Bock Lighthouse, off Buchanness, off Clyth Ness, off 

 Fair Isle, and off Balta Island Lighthouse, and up to the end of the year 

 38 per cent, of the surface bottles and 22 per cent, of the bottom 

 drifters had been recovered. 



