BUREAU OF FISHEKIES 115 



pounds can be taken at the lowest cost. These studies indicate that 

 elimination of the present widespread practices of destroying fish 

 below market size and of marketing fish that would be more valuable 

 if allowed to grow to a larger size, offers the greatest promise of 

 improving the condition of these fisheries. Sorting of the catches by 

 pound nets, seines, and otter trawls, whenever possible, is urged. 



Causes of the decline in abundance of the Atlantic coast shad, and 

 measures for restoring the fishery, are being sought in an investigation 

 which was initiated during the year. Because the Hudson River shad 

 catch has staged a spectacular recovery under careful regulation from 

 less than 100,000 pounds in 1917 to nearly 3,000,000 pounds in 1936, 

 this area is being carefully studied to determine what conditions are 

 responsible for the recovery. The fundamental question of the num- 

 ber of spawners necessary to maintain the fishery at a given level of 

 abundance is being attacked by tagging spawning migrants and 

 spent fish, studying scales, and deriving indices of abundance from 

 catch data. The effectiveness of present methods of artificial propa- 

 gation and the possibility of rearing fry to a greater size before liber- 

 ation are also being investigated. 



Widespread concern over the decline of the striped bass fishery in 

 certain sections of the Atlantic coast during the years immediately 

 preceding 1936 led the Division to undertake an investigation con- 

 tinuing and complementing work done by several of the States. 

 Tagging experiments indicate that the fishery takes a heavy toll of 

 the small sizes before they mature, and it is believed that restriction 

 of the catch of these younger and smaller fish would increase the 

 total yield and augment the number of spawners. Extensive seasonal 

 migrations were also demonstrated by the tagging. 



Shrimp investigations on the South Atlantic and Gulf coasts. — 

 The problem of maintaining the present yield of the shrimp fishery 

 witliout endangering future supplies was attacked by tagging experi- 

 ments and the collection of catcli records on both coasts and by explora- 

 tory trawling in the Gulf of Mexico to locate new supplies. 



The discovery of large schools of shrimp in the deeper offshore 

 areas of the Gulf, which was made by the vessel Pelican during the 

 year, furnished proof of the theory long held by Bureau investigators 

 that the shrimp congregate in deep water after they disappear from 

 inshore fishing grounds in the fall and winter. Since it has been shown 

 that some, at least, of these offshore aggregations are large enough 

 to warrant commercial operations, it is believed that the strain on the 

 immature shrimp inshore may be relieved by offshore fishing with 

 beneficial results to the fisliery. By taking more of the large shrimp 

 and fewer of the small, immature stages, fishermen may take the same 

 poundage, but fewer shrimp will be removed from the total available. 

 Commercial fishermen began offshore operations in the early spring 

 months as a result of the surveys by the Pelican. 



The year's tagging operations resulted in the discovery that at 

 least a portion of the shrimp from as far northward on the Atlantic 

 coast as North Carolina migrate to Florida during the winter. From 

 this fact it is clear that the South Atlantic shrimp fishery should be 

 considered as a unit. The need of better protection of the young 

 shrimp is strongly indicated by the fact that the total catch in this 

 area remains at about the same level despite considerable increases in 

 the number of boats and amount of gear. 



