16 OYSTER BOTTOMS IN MATAGORDA BAY. 



and eddy and where, therefore, the deposit of mud and silt more speed- 

 ily engulfs the shells and renders them ill adapted to the attachment 

 of spat. 



In other characters, also, the long reefs present general features of 

 resemblance to one another. Each has a crest or backbone, awash 

 or nearly awash at low water, running from end to end. The margin 

 of the bed facing up the bay is comparatively close to this crest, ab- 

 rupt in its rise from the bottom and continuous in its contour, while 

 the opposite margin is farther removed from the crest, merging more 

 gradually with the adjacent barren bottom and broken up into long 

 projecting ridges or spurs separated by narrow, muddy indentations 

 and sloughs. In all of these reefs, also, the upper side is the only one 

 resorted to by the oystermen, as there only are large oysters of good 

 quality to be found in quantities sufficient to make remunerative 

 tonging. On the lower sides of the reefs not only is the density of all 

 sizes of oysters less, but among those that are found there is a prepon- 

 derance of small ones, and all are inferior in fatness to those just 

 across the crest. 



At first thought it might seem* that the proportionately large num- 

 ber of small oysters on the lower sides of these reefs was due to a 

 more abundant set of spat, but this assumption is speedily invali- 

 dated by the fact that the total number of oysters there is undoubt- 

 edly less than on the opposite side, notwithstanding that none are 

 removed by the oystermen. The evidence shows, therefore, that the 

 set of spat is actually less than on the upper side, and the prepon- 

 derance of small oysters is due solely to deficiency of growth. From 

 these facts it is apparent that the conditions on the " up-the-bay " 

 margins are superior as regards both the set of spat and the supply 

 of food, but the exact nature of the difference is difficult to deter- 

 mine from actual observation. On theoretical grounds, however, it 

 would appear to be dependent upon the set of the currents, for it is 

 a general condition of oyster growth that, other things being equal, 

 the set of spat, the rate of growth, and the production of fat are 

 greatest in those parts of reefs where the water flows with great- 

 est velocity. It can be assumed that in the presence of the great 

 bodies of spawning oysters which these reefs furnish the distribution 

 of swimming fry must be so general as to be practically uniform 

 everywhere in their vicinity ; that the food value of the water on the 

 different sides of the reef is essentially uniform was determined by 

 actual observations, as exhibited in the table (p. 73) incorporated in 

 the section of this report treating specifically with that subject. As 

 to the matter of currents, however, what are the actual conditions ? 



In the discussion of the currents of Matagorda Bay subsequently 

 given in this report will be found the statement that the pre- 



