6 OYSTER BOTTOMS OF MISSISSIPPI EAST OF BILOXI. 



of the location and extent of the oyster beds by means of biological 

 and hydrographic examinations and investigation of the character of 

 the barren bottoms in respect to their suitability for purposes of 

 oyster culture. No previous investigation of this character has been 

 made in the region covered by the survey, and there is therefore 

 nothmg on which to base comparisons with past conditions, and no 

 way in which to determine to what extent changes m the beds have 

 been effected by the oyster fishery or variations in the physical 

 characteristics of the waters and the adjacent land. 



METHODS OF THE SURVEY. 



The methods employed were those pursued in former surveys of like 

 character, and are explained in detail in a description of the beds of the 

 James Kiver,*^ from which some of the following is repeated: 



A "boat sheet" was prepared, on which were accurately platted 

 the positions, as determined by triangulation, of lighthouses, buildmgs, 

 tripods, etc., used as signals. These data were furnished by the 

 United States Coast and Geodetic Survey. 



The oyster beds were discovered by soundings with a lead line, but 

 principally by means of a length of cham dragged over the bottom at 

 the end of a copper wire running from the sounding boat. The wire 

 was wound on a reel and its unwound length was adjusted to the depth 

 of water and the speed of the launch, so that the chain was always on 

 the bottom. Whenever the chain touched a shell or an oyster the 

 shock or vibration was transmitted up the wire to the hand of a man 

 whose sole duty it was to give heed to such signals and report them to 

 the recorder. 



The launches from which the soundings were made were run at a 

 speed of between 3 and 4 miles per hour. At intervals of three 

 minutes — in some cases two mmutes — the position of the boat was 

 determined by two simultaneous sextant observations of the angles 

 between a set of three signals, the middle one of which was common to 

 the two angles, the position being immediately platted on the boat 

 sheet. At regular intervals of 15 seconds, as measured by a clock 

 under the observation of the recorder, the leadsman made a soundmg 

 and reported to the recorder the depth of the water and the character 

 of the bottom, immediately after which the man at the wire reported 

 the character of the chain indications since the last soundmg — that is, 

 whether they showed barren bottom or dense, scattering, or very 

 scattering growths of oysters. 



With the boat runnmg at 3 miles per hour the soundings were be- 

 tween 60 and 70 feet apart, and, as the speed of the boat was uniform, 

 the location of each was determinable within a yard or two by dividing 

 the platted distance between the positions determined by the sextant 

 by the number of soundings. The chain, of course, gave a continuous 



o Moore, H. F.: Condition and extent of the oyster beds of Jamea River, Va. Bureau of Fisheries 

 Document No. 729. 



