THE OYSTER INDUSTRY OF THE WORLD 561 



public grounds has materially declined in spite of the efforts of the state depart- 

 ments of fisheries to prevent the destruction of grounds by planting shells and 

 seed oysters. In many places along the coast the discharge of domestic sewage 

 and industrial wastes destroyed the oyster grounds, or rendered them unsuitable 

 for the production of oysters for food. The production of oysters through cultiva- 

 tion on privately owned or leased grounds, however, remains more or less stable. 

 Although the private grounds comprise only a small fraction of the total acreage 

 of public reefs, 62 per cent of the total catch of oysters in 1945 was derived from 

 them. 



Century-old experience in the state maintenance of public reefs shows that 

 self-rehabilitation of grounds without active assistance from man is incompatible 

 with intensive commercial exploitation. The enactment of conservation laws, 

 such as closed seasons, size limit, restriction of gear, etc., has been ineflFective 

 in stopping depletion. Likewise, costly efforts of several states to rehabilitate the 

 grounds by planting shells and seed produced no appreciable results. In the ab- 

 sence of a carefully planned system of management and without the control of 

 rate of harvesting, partially rehabilitated grounds became depleted almost as 

 soon as they were opened to fishing. Experience in introducing a system of 

 state management of principal public reefs in Maryland, carried out with the co- 

 operation of the United States Fish and Wildlife Service, has shown that at pres- 

 ent 1 acre of depleted oyster ground can be rehabilitated for about $150.00. Thus, 

 the rehabilitation of a substantial portion of some 180,000 acres of public bars in 

 Maryland alone would require an expenditure of several million dollars of tax- 

 payers' money. The obvious alternative is to permit the leasing of depleted public 

 reefs to private growers and to concentrate the state efforts on the maintenance 

 and development of seed-oyster grounds from which young oysters could be sup- 

 plied to planters. 



Harvesting. Oysters are harvested by grabs, tongs, patent tongs, dredges, and 

 mechanical harvesters. Hand-picking by grabs is practiced in some southern states 

 where oysters are taken from tidal flats exposed at low water. Tonging is adapted 

 to shoal waters and is profitable only on grounds where oysters are plentiful. 

 On the good grounds of Chesapeake Bay a tonger averages 20 to 35 bushels a day. 



Dredges vary in their capacity of from 5 to 25 bushels. They are operated from 

 schooners, motor boats, and steamers. Some of the larger steamers in Long Island 

 Sound are equipped with 6 dredges (3 on each side), capable of harvesting at 

 the rate of 1,400 bushels an hour. In several states no power dredges are permitted 

 on public reefs, but dredging with sail boats is allowed and power-driven hoisting 

 engines can be used for hauling up the gear. 



Mechanical harvesters represent the most recent development in the technique 

 of oyster dredging. At present there are two distinct types: the suction dredge, 

 which works on the principle of a vacuum cleaner, and the scooper. In one of the 

 largest harvesters of the first type, which operates in Long Island Sound, suction 

 is produced by a powerful jet of water directed into one leg of a Y-shaped eductor. 

 The other leg of the eductor is actually the outboard suction unit. Oysters taken 

 through this part are delivered by a strong stream of water to a conveyor located 

 on the deck. The largest harvester of this type, in operation since March 1948, 

 is 95 feet long, 30 feet beam, and 8 feet deep. Its hold has a capacity of 10,000 

 bushels. 



