sidered to give better returns than would be the case if 

 they were drained and put to agricultural or grazing 

 purposes. 



These fish farms, or reservoirs a poissons as they are 

 named at Arcachon, consist of large shallow ponds and 

 broad waterways occupying the site of former salt pans 

 and marshes. There is no regularity or settled usage as 

 to shape or area ; the configuration of the old marshes 

 and the size of the proprietor's farm are the determining 

 factors. The principal ponds in each farm are however 

 as broad as possible and a usual size is from 300 to 600 

 yards long by 80 to 120 yards in width, but as I have said 

 there is no rule and some extend to twice and even three 

 times a greater area. Several ponds are found on each 

 farm connected by canals and separated by stretches of 

 low land which furnish scanty pasturage for cattle. 

 Each fish farm is separated from the basin by a protec- 

 tive dyke or bund of height and strength sufficient to 

 prevent flooding during high tides and storms. One or 

 more sluices in this embankment provide the means of 

 establishing connection at will between the ponds within 

 and the sea water of the basin without. These sluices 

 and their proper management are the pivots upon which 

 the system depends for its success. Through the 

 careful manipulation of the sluice gates at the right 

 season, outflowing currents are set up which attract the 

 shoals of fry required annually to repopulate the ponds. 

 Another important duty devolving upon the sluices is 

 to keep the water of the ponds in a wholesome and well 

 aerated condition during the period the imprisoned 

 fry are growing to the adult stage. This process of 

 freshening consists of two operations called respectively 

 faire boire and faire ddboire. The former allows the 

 entry of the well oxygenated sea-water of the basin, 

 charged too with quantities of minute life welcome to the 

 smaller creatures within the ponds — the younger fry as 

 well as the minute animals on which the fry feed. By 

 the converse operation, faire dcboire, is expelled a 

 proportionate amount of pond water more or less con- 

 taminated with decomposition products arising from the 

 dejecta of the fish and from decaying vegetation; this 

 water is also less well charged with oxygen than the 

 compensation water admitted from the sea. 



