[5] TRANSFORMATION OF SALT MARSHES INTO FISH-PONDS 521 
(1.) The mullet (biack mullet, white mullet, and “Jand-jumper”—saut- 
euri du pays); the black mullet is much more frequent than the others. 
(2.) The barbel only comes in small numbers. 
(3.) Occasionally the plaice and the dorado. About fifteen years ago 
the dorado came in great numbers; but it seems now to have almost 
disappeared from these coasts. 
(4.) The sole only comes acvidentally; and the gurnet and turbot, &e., 
never enter the fish-ponds. 
(5.) Hels come in large numbers in spring, when the sluices are first 
opened. 
In April, fry enter the ponds in large quantities; in September they 
come in tolerably large numbers. They never enter the ponds until they 
have reached the thickness of a quill; those which come in April are 
Jarger than those which come in September. 
The draining process.—By the draining process we understand the 
process by which a portion of the water of the fish-pond is caused to flow 
into the basin of Arcachon. 
For this purpose the frame with the “sleeve” is let down when the 
tide is low, and the gate of the sluice is raised about 0.07 centimeter; 
this causes a slight flow of water into the basin of Arcachon not strong 
enough, however, to draw the young fish from the fish-pond. When 
young fish show themselves near the “sleeve,” through the meshes of 
which they could slip, the gate is closed and the draining process is 
stopped. 
The keeping and fattening of young jfish.—When the young fish have 
entered the fish-ponds, they must be kept there under those conditions 
which are most favorable to their preservation, development, and fat- 
tening. . , 
(1.) Preservation.—Atmospheric influences play a very important part 
in the preservation of fish, especially of those species which are kept in 
captivity; cold winds often cause large numbers of mullet to perish. 
Northeast or southeast winds are particularly dangerous; northwest 
wind is harmless, and south and southwest winds are very favorable. 
Any sudden change from high to low temperature, frost or ice is less 
dangerous than unfavorable winds. In constructing a fish-pond, care 
should, therefore, be taken to protect the fish against these hurtful in- 
fluences. 
For this purpose shelters have been provided in the following manner: 
(1.) The basins are dug in such locations as will afford shelter to the 
sheet of water from the northeast or southeast winds. This object is 
attained by having regard to the natural configuration of the ground, 
by artificial shelters or by trees. 
(2.) If these conditions do not exist, the dikes are made as high as 
possible, so as to form ramparts against the northeast and southeast 
winds, and in every case trees are planted on the banks of the fish- 
