XX REPORT TO THE SECRETARY OF COMMERCE 



NET PRESERVATION 



As a result of continued research on net preservation and field 

 observation in many varied commercial waters, it has been found that 

 the life of twine used in heavy gear, such as traps and seines, can 

 be materially extended by applying toxic dyes to the cotton before 

 the twine is made, followed by the proper application to the finished 

 net of coal tar, prepared within test limits developed by this bureau. 

 Several concerns are now prepared to furnish special dyed twine and 

 also specification tar as recommended by the bureau. 



For the preservation of light gear, such as gill nets, thorough 

 cleansing of the net is of the most importance in extending its life, 

 while storage by suspension in dry shade is of secondary importance. 

 Chemical preservatives are apparently of minor value. 



BIOLOGICAL FISHERY INVESTIGATIONS 



Although the biological researches of the scientific staff of the divi- 

 sion of inquiry respecting food fishes are often regarded as having 

 primary value to conservation as a basis for the regulation or pre- 

 vention of overfishing by State legislation, they have equal value to 

 the Nation through encouraging the wise use of our aquatic re- 

 sources. They offer direct aid to industry by providing exact in- 

 formation regarding the source of supply for the commercial fisheries 

 and in some cases predict years of unusual abundance or scarcity; 

 they aid the water farmer by devising and demonstrating improved 

 methods of fish and shellfish culture. These investigations are or- 

 ganized under responsible heads in each of the major geographical 

 areas of the United States where local field headquarters or labora- 

 tories are maintained, in many cases in space provided by univer- 

 sities. The problems of the fisheries of the Nation are therefore 

 considered as units. 



FISHERIES OF THE ATLANTIC AND GULF COASTS 



Investigations on the changing abundance of the important food 

 fishes of the Atlantic coast have been expanded during the past year 

 by the development of the studies of the haddock supply initiated 

 during 1930. This fishery has experienced a serious decline in yield 

 per unit of effort during the past few years following a period of 

 exceptional production. On the fishing grounds, principally Georges 

 Bank and South Channel, where the bulk of the United States 

 landings have originated, the abundance of haddock increased mark- 

 edly from 1924 to a maximum in 1927. Since then the supply has 

 fallen off sharply to a level in 1930 far below that in 1924 and has 

 continued to decline during 1931. 



By combining with the statistical analysis of the yield per unit of 

 effort a study of the biology of the haddock stock, primarily size and 

 age composition, growth rate, and distribution, it appears that an 

 extraordinarily successful natural production of haddock occurred 

 between 1920 and 1922. In 1925 the full effect of these abundant 

 year groups was reflected in increased landings of scrod sizes, which 

 in the following two years had grown sufficiently to be included as 

 large haddock resulting in a continuing increase in abundance until 

 the peak was reached in 1927. Since that year the catch statistics do 



