i6 



Age and Rate of Growth. 



Mullet and bass take generally three years to attain 

 marketable size, while Gemzoe * has proved that eels do 

 not seek to pass to the sea till after \\ to 7 J years sojourn 

 in the case of males and an even longer period in the case 

 of females, the great range in the length of the sedentary 

 stage being determined by local conditions and circum- 

 stances. 



Mullet, which enter the Arcachon ponds as tiny fry 

 i| to 2 inches long, are stated to weigh on an average 

 at the end of three years about half a kilogram or 

 about 18 ounces under normal conditions. But this 

 rate of growth is considerably surpassed in the better 

 situated ponds and when a series of warm and sunny 

 seasons occur consecutively. Under such circumstances 

 Millet f has claimed that 1,000 mullet fry reared in the 

 Arcachon pond will yield 1,000 kilos of fish within 

 three years. 



The growth of the eel is considerably greater ; Coste 

 has estimated that these fish when reared in ponds 

 attain a weight of 2\ kilograms (5^ lbs.) within 4 to 5 

 years, but this again varies greatly with locality and the 

 relative amount of food supply available, and the rate 

 of growth must be worked out independently for 

 each separate district. Comparatively little exact re- 

 search has been devoted to this subject of the rate of 

 growth of sea-fishes ; precise information upon it is 

 urgently needed together with an analysis of the relative 

 value of the factors which favour and retard growth. 



Extent and Profits of the Arcachon Industry. 



The total area of the ponds devoted to fish rearing on 

 the borders of Arcachon basin has been estimated at not 

 less than 300 hectares or about 740 acres. A few large 

 properties account for the bulk of this, one farm alone 

 having more than half the total area, others again do not 

 amount to a full hectare. 



* K. J. Gemzoe, Age and Rate of Growth of Eels. (Report of the Danish 

 Biological Station to the Board of Agriculture, xiv, 1906. Copenhagen, 1908.) 

 f La Production animal et vegetale. Paris, 1S67. 



