OYSTER BOTTOMS IN MATAGORDA BAY. 63 



already noted, in the destruction of Mad Island Reef by the debris 

 carried upon it by the floods in the drainage basin of Mad Island 

 Lake, which discharged close to the shoreward end of the reef. 

 Localities such as this, therefore, are to be avoided for oyster culture. 

 The term " silting," though in general meaning the deposit of any 

 materials, either coarse or fine, from turbid water, is in this special 

 connection restricted to the more or less constant dribbling of fine 

 material upon the bottom. It has but little effect upon adult oys- 

 ters, operating mainly to cover the cultch, either natural or planted, 

 with a deposit, very thin perhaps, yet sufficient to stifle the small irj 

 at the time when it is settling to fix and become spat. This fine 

 sediment is thrown down in general where the currents are slack, 

 and will therefore, under present conditions, be greatest above Dog 

 Island Reef and in the wake of the larger reefs in the lower bay — 

 that is, on the prairie shore. In other words, the peninsula side of 

 the ba}^ below Tiger Island is liable to be more free from silt de- 

 posits, a fact of considerable importance to oyster growers in search 

 of a location. 



ENEMIES OF THE OYSTER. 



The information gathered concerning the enemies of the oyster 

 in Matagorda Bay is neither as definite nor as copious as it is to be 

 desired. As the investigation was made entirely during the months 

 of winter and early spring, direct observations upon this phase of 

 the subject were comparatively few, excepting in the cases of mus- 

 sels, boring clams, and similar organisms having no particular sea- 

 sons of operation or presence. It is evident, however, that in com- 

 mon with other localities on the gulf coast Matagorda Bay is free, 

 or practically free, from two of the most dangerous and trouble- 

 some enemies of the north Atlantic oyster beds — the starfish, which 

 is the dread of the Long Island Sound oyster planter, and the drill, 

 which annually causes great destruction on the Chesapeake. Besides 

 the enemies enumerated below, it is probable that the large ray, 

 known on the Louisiana coast as the " stone-cracker," may cause 

 occasional damage, and there is also probable the occurrence of an 

 obscure parasitic worm (Bucephalus haimeanus), which has been 

 found in Louisiana. 



Drum-fish. — Of the aggressive enemies of the oyster this is appar- 

 ently the most destructive found in -the waters of Matagorda Bay. 

 The species generally known as the ■" black drum" (Pogonias cro- 

 mis) is found on the o}^ster beds more or less along the entire coast 

 from New Jersey to the Rio Grande, but it varies much in destruc- 

 tiveness from year to year and with the locality. A low density of 

 water tends to exclude some oyster enemies, such as the starfish, and 

 a high density others, such as the drill (Urosalpinx) , but the drum- 

 16354—07 m 5 



