[15] TRANSFORMATION OF SaLT MARSHES INTO FISH-PONDS. 531 
substituted for this grating a bag-shaped ‘sleeve,’ or net, the meshes 
of which, throughout its whole length, shall measure at least 18 milli- 
meters from the Ist of October till the 1st of March, and 25 millimeters 
from the 1st of April till the 30th of November.” (See Article 27 of the 
above-mentioned regulation.) 
This provision might cause the ruin of the ponds. When the fry enter 
the inner basin, they generally measure only 6 centimeters in length and 
8 millimeters in breadth; meshes of 25, and even of 18, millimeters would 
therefore not only allow the fry to escape, but also, as has been observed 
repeatedly and under different circumstances, liberate those fish which 
have been raised in the ponds, and which have reached the size of 20 cen- 
timeters. 
For ordinary fishing, as in those fisheries which are carried on in the 
sea and in the basin of Arcachon, the prohibition of apparatus with 
narrow meshes is perfectly justified. Narrow meshes, in fact, would 
either injure or capture the fry, which would thus perish uselessly in 
the hands of the fishermen; the use of nets with narrow meshes has 
therefore been prohibited. 
The ponds, on the other hand, which are guarded by apparatus with 
narrow meshes, keep the fry, and furnish them with all the conditions 
which are essential for their preservation and development. 
These facts have been taken into serious consideration by the min- 
ister of marine. Article 9 of the decree of May 10, 1862, contains the 
following: ‘ Fish-pits or fish-ponds may, after proper authority has been 
granted, be constructed on private property which receives water from 
the sea. The licenses granted by our minister of marine and the colo- 
nies will determine, according to the character and extent of the ground, 
the conditions upon which these ponds are to be managed.” 
At this day the size of the meshes of the nets (‘‘sleeves”) placed at 
the opening of the sluices is no longer regulated by law, but the owners 
of fish-ponds adopt the size which suits them best. Only one condition 
is imposed on them, viz, not to bring to market fish which do not have 
the regulation size—barbels 0.10 millimeter in length, mullets 0.14, and 
eels 0.25. 
Under these conditions, the transformation of salt marshes into fish- 
ponds has steadily increased; at the end of 1876, there were 1,022.50 
hectares of such ponds; and there is every reason to hope that this 
number will be increased tenfold, 
