PROGRESS IN BIOLOGICAL INQUIRIES, 1935 431 



StyJochus can survive in water which contains little oxygen. The 

 effects of 23 chemicals on StylocJuos in sea water were studied in an 

 attempt to discover some substance which might kill the polyclads 

 on oyster beds, but none of these has given promise of success. The 

 larvae were less resistant than adults, but such high concentrations 

 of poison were required to kill either that there seems little hope 

 of controlling these pests by chemical means. 



Texas. — During the summer of 1935 the oyster bottoms of the 

 Texas coast were surveyed to discover the kinds and numbers of oyster 

 pests present, and wherever possible to devise methods and make 

 recommendations for their control. This investigation was carried 

 out by Dr. Henry Federighi and A. Collier, with the cooperation of 

 the Texas Game, Fish and Oyster Commission, who supplied the 

 boat Vivian, which was converted into a laboratory and houseboat, 

 and also the patrol boat Eugene and other floating equipment 

 stationed along the Texas coast. 



The survey, begun at Corpus Christi Bay and completed at Gal- 

 veston Bay, followed very closely the Bureau's previous surveys in 

 1926 and 1931. Approximately 800 miles were covered during July 

 and August, examinations being made of commercial reefs to deter- 

 mine the condition of the 03"st'ers, the salinity, temperature, character 

 of the bottom, and the kinds and numbers of oyster pests present. 



The most common oyster enemy in Texas, distributed from the 

 Corpus Christi to Galveston Bays, is the common boring clam, 

 Martesia caribaca^ whose habit is to get a hold in an oyster shell 

 and use it as a protective covering. In many cases it was found 

 that a single oyster may harbor several hundred boring clams within 

 its shell. Although it is probable this infestation has some effect 

 on the growth and fattening of the oyster, it is impossible at present 

 to state exactly what the effect is. Little is known concerning the 

 life history of this pest. 



Other pests found during the survey were the borer, Thais haema- 

 stoma, which does considerable damage in Louisiana and Florida; 

 the common conch, Fulgur 'perversa., whose method of attack on 

 oysters is still incompletely known; the boring sponge, Ch.ona sp., 

 found only infrequently on the Texas coast, and probably of little 

 significance; and the mussel, Mytilus sp., scattered here and there 

 along the coast, and varying greatly not only from year to year but 

 from season to season. 



It was found that the tremendous destruction of the oyster beds in 

 this section was due to the extraordinary increase in fresh water 

 flowing from the flooded rivers of the Coastal Plain during May and 

 June. In some areas there was a lack of live oysters due to the 

 influx of the fresh water and its persistence over a period of time. 

 In the northeastern part of Matagorda Bay, in past years the best 

 source of 03^sters on the Texas coast, oysters have either been killed 

 by the fresh water or covered with mud from the Colorado River, 

 carried down into the bay since the removal of the dam. 



IN^TiSTIGATIONS ON OYSTER CULTURE 



Long Island Sound. — Because of increased activities in connection 

 with the oyster pest control investigations, the regular studies on 

 oyster culture were greatly curtailed. A study of seasonal varia- 



