[7] TRANSFORMATION OF SALT MARSHES INTO FISH-PONDS. 523 
especially larve and shells, which certain kinds of fish will eagerly 
devour. 
For raising mullet, and particularly for fattening them, the Ruppia 
spiralis and Ruppia rustellata are the plants which should be particu- 
larly cultivated in fish-ponds ; for by observing the mullet when on the 
pasture-lands and by examining its entrails one will find that this fish 
consumes a large quantity of ruppias and a large number of microscopic 
shells adhering to this plant. This food gives to the mullets from most 
fish-ponds a peculiar flavor, which can be specially noticed when one 
takes care to preserve the detritus of this plant in the body of the fish. 
Another plant has also been noticed, called by the country people 
‘“lége”; it is really an agglomeration of conferve. which makes its ap-— 
pearance in loose threads, forming a sort of green moss on the surface 
of the water. When this plant grows too extensively it has a hurtful 
effect; but otherwise it contributes to the nourishment of several kinds 
of fish, for it nearly always contains a large number of small bivalves 
and diminutive crustaceans. 
For raising and fattening mullet, old fish-ponds are preferable to new 
ones or to those which have been but recently constructed. In these 
last-mentioned ponds the fish grow very little during the first three 
years; after that time they develop in proportion as the pond becomes | 
older. The yield of a pond, which is very small during the first few 
years, increases in proportion as the fish-pond is filled with ooze, plants, 
shells, &c. Careful observations have taught men the method which 
should be adopted to increase the productiveness of a pond during the 
first years and to aid the action of time, which is never very rapid. It 
will be sufficient in most cases to introduce and propagate suitable 
plants which the mullet likes, such as the ruppia, also those marine 
shells which live on these plants, and which are found in great abun- 
dance in old fish-ponds. It might also be advisable to raise only car- 
nivorous kinds of fish during the first year, such as the barbel, the 
dorado, the plaice, the sole, &c., providing them with the food necessary 
for their development by propagating small crustaceans, shells, &c. 
After some years have elapsed, when the time appears to have arrived 
for substituting mullet for carnivorous fish, these latter must all be 
caught, because their presence, at least in large numbers, would cause 
serious ravages among the mullet. 
In order to obtain fish of good size and possess a tolerable degree of 
fatness, the quantity of fry and young fish of different ages should be 
proportioned to the size of the pond and its ability to supply a suitable 
quantity of food. Without observing these precautions it will be diffi- 
cult to obtain fish of the size and quality which are in demand in the 
market. 
THE FISHERIES AND PRODUCTS OF THE FISH-PONDS. 
(1.) Sluice-fishing.—Sluice-fishing is carried on when the level of the 
sea is higher than that of the water in the fish-ponds; at the extreme 
