PROGRESS IN BIOLOGICAL INQUIRIES, 1935 425 



anchor cliains of ships in the Patuxent River and nndisturbed for 

 many years, only 3 percent were infested, pointing to the insignifi- 

 cance of hirval attachment. 



Although heavy infestation wealvens the shell, in some cases render- 

 ing the oysters unfit for market, in the opinion of some of the 

 oyster packers and planters the sponge does not adversely affect the 

 oyster in these waters. This does not prove, however, that the 

 boring sponge is not a menace in other localities, particularly in the 

 ►South Atlantic States where its destructive power may increase 

 with the increase in mean annual temperature. 



The work in the Middle and South Atlantic States carried out 

 under the direction of Dr. H. F. Prytherch by William Hagen, Lloyd 

 Garris, K. E. Johnson, G. R. Lunz, Jr., and assistants, consisted in 

 large scale drill trapping experiments in the region from Chinco- 

 teague, Va., to Cape Charles, Va., where estimated damages caused 

 by the drills amounted to over $150,000 annually. Also, compre- 

 hensive surveys of the distribution of oyster pests were made in the 

 lower Chesapeake Bay and in the waters of North Carolina, South 

 Carolina, and Georgia. 



Through Paul B. Murphy, director of the Fort Eustis Camp for 

 Transients, the services of approximately 100 transient laborers were^ 

 made available for routine operations. A temporary field camp 

 was established at Cliincoteague and the U. S. S. Kittery^ a 10,000 

 ton steamer, was anchored in the Onancock Harbor for use as a sta- 

 tion ship. Six power boats were used to transport the crews from 

 these locations to the oyster beds, where collections of drills were 

 made b}^ the use of traps in the case of deep-water beds or by hand- 

 picking on exposed tidal flats. 



Small wire bags baited w^ith seed oysters, similar to those em- 

 ployed in New Jersey, were used. Traps attached in groups of 25 

 to a heavy rope line at intervals of 10 feet were fished once a week 

 and the drills which had entered to search for food or to deposit their 

 egg cases on the shells of the seed oysters were removed by vigorous 

 shaking into containers aboard the boats. Experiments were car- 

 ried out to determine the most effective arrangement of trap lines; 

 for removing drills from a given area, and to protect planted beds 

 against invasion of these pests from surrounding bottoms. Over an 

 average period of 12 weeks, 3,744 traps of various designs w^ere used. 



Trial of various methods of trap arrangement showed that the 

 most successful and least expensive procedure for removal of drills 

 from a given area is to anchor one end of a 250-foot trap line in 

 approximately the center of a 4-acre unit and shift the position 

 of the line about 45° each week. The second time that this area 

 was trapped by the same method, the collection of drills decreased 

 over 60 percent, indicating that the previous circuit had caused a 

 significant reduction in the number of these pests. 



Drills may likewise be collected by using parallel lines of traps 

 which may be left stationary or moved a few feet after each weekly 

 fishing, but this procedure involves a greater amount of labor, mate- 

 rial, and time than the circular method. The results indicate that 

 the use of 25 traps per acre on cleaned bottoms in Chincoteague Bay 

 wall remove virtually all of the drills in approximately 18 weeks. 



