OYSTER BOTTOMS IN MATAGORDA BAY. 23 



margin, not shown in all its detail on the chart. The oysters are 

 smaller than on the eastern side and their density is less, the differ- 

 ence being especially noticeable in the larger stock. Of oysters under 

 3 inches in length there are about 36 per square yard, while those 3 

 inches or over number but 16 and most of these barely exceed the 

 size limit set, while on the eastern side the adults average over 4 

 inches. To the westward of the crest the oysters are not only poor 

 in size and shape, but inferior in quality. As it is to be assumed that 

 the entire reef was reseeded at about the same time, the diversity 

 between the two sides must be due to diversity in conditions, more 

 especially as regards the food supply. It is estimated that the west 

 side of Mad Island Reef contained in April, 1905, a total of about 

 •2.500 barrels of oysters about 3 inches in length, and practically all 

 of these w T ere w-orthless for the market. 



There are several small patches or lumps near Mad Island and 

 Shell Island reefs, but they w 7 ere too small to plot satisfactorily. 



SHELL ISLAND REEF. 



i 



This is a long, narrow reef extending from about one-fourth mile 

 outside of Shell Island nearly to the north shore at Mad Island sig- 

 nal. It has a length of about 1^ miles, an average width of about 

 250 yards, and an area of about 145 acres. In its general features it 

 is but a smaller copy of Dog Island Reef, and in the course of time 

 it will eventually form a barrier extending practically across the bay, 

 there being evidence that it has increased about 500 yards in length 

 during the past fifty years or less. A crest exposed during low winter 

 tides runs the entire length of the reef, interrupted at a point about 

 100 yards north of Shell Island, where there is a channel about 20 feet 

 wide carrying about 2J feet of water at low tide, and again near the 

 shore end, w T here there is a wider channel with about the same depth. 

 The crest has an average width of 40 yards and bears a scattered 

 grow 7 th of oysters of raccoon type. 



The tw 7 o sides of the reef present the same diversity observed in 

 the other long reefs of the vicinity, the eastern side being productive, 

 while the western side is commercially almost worthless. The east- 

 ern margin of the reef is regular in contour and lies close to the 

 crest, the w^ater therefore shoaling abruptly. On Shell Island Reef 

 the productive area includes the entire southern part outside of 

 Shell Island Channel and extends well up the eastern side, becoming 

 less important as the water shoals toward the shore. This eastern strip 

 is very narrow and the total area of dense growth as shown on the 

 chart is only about 25 acres. Examinations indicated a density over 

 this area of about 106 adult and 70 young per square yard, and the 

 total of adult oysters is estimated at 35,000 barrels, an average den- 

 sity of about 1,400 per acre. It is possible that this estimate is some- 



