74 OYSTER BOTTOMS IN MATAGORDA BAY. 



It will be observed that while certain parts of the upper bay — 

 notably the middle of section I — are prolific in oyster food, the gen- 

 eral average is lower than below Dog Island, where the food value 

 per liter (1J quarts) of water averages 251,327 units, as compared 

 with 189,490 units above that reef, an excess of about 33 per cent. 



In the lower bay the greatest fertility found anywhere during the 

 survey was in Tiger Island Channel, where there were 493,100 units 

 per liter, an extraordinary figure, due mainly to the abundance of 

 one large diatom, Coscinodiscus lineatus, ordinarily found on or close 

 to the bottom, its unusual abundance in the water specimens being 

 doubtless due to its being lifted and carried by the strong currents. 

 This locality would be a valuable one for oyster culture, but its use 

 for private ends is prohibited by the fact that it is now and has been 

 for a long time a natural bed. It is an interesting fact that the sec- 

 tions (E and F) immediately above and below this are practically 

 less productive of oyster food than any in the bay, and so far as sec- 

 tion E is concerned, it is the portions nearest Dog Island Reef and 

 along the north shore which are most deficient, while on the south 

 shore, near Forked Bayou Reef, it is especially rich, a quality reflected 

 in the fatness of the oysters on that bed. 



In sections C and D, lying between Lake signal and Shell Island 

 Reef, the waters of the peninsula shore are more fertile than either 

 the north shore or the middle, the food value being about 27 per cent 

 greater than the former and 17 per cent greater than the latter. Far- 

 ther down the bay, in sections A and B, the middle of the bay is most 

 richly laden with food, exceeding the north side by about 29 per cent 

 and the south side by not less than 60 per cent. The middle of the 

 bay, in section B, about opposite Oyster signal, is the richest water 

 above Half Moon Reef. Above Dog Island Reef the most fertile 

 water lies generally in the middle of the bay, but with the exception 

 of the middle of section I this belt is much inferior in food produc- 

 tion to the best parts below Forked Bayou, the difference being about 

 17 per cent. The poorest water above Dog Island Reef lies, as might 

 have been expected, close to the mouth of the Colorado, and the best 

 is in the middle of section I, between Middle and Boggy lumps, where 

 a really high degree of fertility is reached. The excellence of the 

 food supply in this vicinity is reflected in the fatness of the oysters 

 on Boggy Lump, a condition in which Middle Lump would undoubt- 

 edly participate were the growth there less badly clustered and 

 musseled. 



The method developed in this report of estimating the food value 

 of waters is new, and there are no definite data for comparison ; but it 

 is the opinion of the writer, based upon general experience, that any 

 water containing over 200,000 units of food organisms per liter may be 

 regarded as good, while over 250,000 is very good. In any event there 



