16 U.S. BUREAU OF FISHERIES 



the Nutritive Value of Oysters ", published as Fisheries Investigational 

 Report No. 17; and ''The Oyster as a Source of Minerals", a report 

 yet to be published. The above investigation has included other 

 fishery products as well as oysters, but the work has not sufficiently 

 progressed that reports on these commodities can yet be prepared. 



DEVELOPMENTS AND IMPROVEMENTS OF FISHING GEAR 



As stated previously in this report, certain of our technological and 

 marketing investigations are of vital importance in any broad pro- 

 gram of conservation of our fishery resources. There are few other 

 fields of investigation which offer any greater opportunity for con- 

 tributing to real conservation than developments and improvements 

 in the various types of fishing gear which are used in the actual catch of 

 fish. 



MEASUREMENT OF MESH SIZE OF FISHING NETS 



For many years, there have existed in various parts of the country 

 numerous controversies between the conservation authorities of the 

 States involved and interested parties in the fisheries, concerning the 

 mesh size of fishing nets used in the various waters of those States. 

 These disputes are, in themselves, indicative of the great importance 

 of the size and type of fishing nets as an influence on conservation 

 measures. The mesh size of nets determines the kinds and numbers of 

 undersized and immature fish which will be permitted to escape from 

 the commercial fisherman and, in the interests of conservation, con- 

 tributes to the maintenance of the fisheries. Therefore, our technolo- 

 gists, as well as our biologists, have cooperated with the States and 

 with the industry on this great problem. In this connection, during 

 past years, technologists of this Bureau and of the Bureau of Standards 

 have made a study of devices to enable the conservation authorities of 

 the States to establish and apply uniform enforcement of these mesh 

 sizes of nets. However, during 1933, due to limitations of appropria- 

 tions in this Bureau and in the Bureau of Standards, this investigation 

 had to be suspended temporarily. 



NET PRESERVATION 



The development of and tests of commercial preservatives for fishing 

 nets were continued during 1933 by W. T. Conn, a member of the 

 Division's technological staff. The work followed two principal objec- 

 tives, one to confirm previous season's tests and the other to test new 

 formulas developed. Several years ago, our technologists discovered 

 that the greatest menace to fishing nets in fresh water consisted in 

 attacks on the netting by cellulose digesting bacteria. In addition to 

 recommendations for treating these nets with toxic dyes, as described 

 in previous annual reports of this Division, it has been found during 

 the past year that chrome tanning of the cotton netting is superior 

 to these previously developed dye processes and that, where bacterial 

 action is not serious, an improved method of cutching twine produces 

 good service. In all cases, better results are obtained by covering the 

 treated nets with a good grade of tar, properly applied, in addition to 

 one of the above treatments. 



Another serious problem in net deterioration has been the fouling of 

 nets by weeds and other marine growth after the nets have been in 



