CUI^TIVATION OF THE TURBOT. 863 



Before attempting marine pisciculture it is necessary to ask oneself what 

 are the fishes for which such experiments would be practically profitable. It is 

 evident that migratory fishes, or those living in depths the natural conditions 

 of which we can not offer them in captivity, are to be eliminated. Moreover, 

 before attempting the breeding of nonmigratory fishes of commercial value 

 there is a certain number of questions which ought to be answered: (i) Is the 

 fish in question of sufliicient commercial value to render its breeding profitable? 

 (2) Is its growth in captivity sufficiently rapid, and is the cost of bringing it 

 to its commercial size disproportionate to its market price? 



In the last analysis it will appear that among the fishes inhabiting our 

 European waters there are only four species which are profitable objects of 

 marine pisciculture. These are the sole {Solea vulgaris Quensel), the turbot 

 {Rhombus maximus Linnaeus), the umbrina (Labrax lupus Cuvier), the surmul- 

 let {Mullus surmuletus Linnaeus). According to Cunningham, the turbot at the 

 age of two years is from 28 to 38 centimeters long, and reaches 60 centimeters at 

 the age of four years. As to the sole, it reaches only 23 centimeters at the age 

 of two years. 



Of all these various edible fishes, the most profitable from the point of 

 breeding is the turbot, on account of its high price, its particularly rapid growth, 

 its prodigious fecundity (the turbot yields about 9,000,000 eggs per year) and, 

 lastly, its hardiness and the ease with which it may be fed and fattened. Un- 

 fortunately, however, this species is the one the artificial reproduction of which 

 presents the greatest difficulties, as was justly observed in 1905 by Fabre- 

 Domergue and Bietrix, whose researches in this line go as far back as 1896." It 

 must be remembered that no natural hatching of turbot could be accomplished 

 at Dunbar and recourse was had to artificial methods of stripping and fecunda- 

 tion, as for fresh-water fishes. 



The problem of industrial marine pisciculture must necessarily traverse 

 two stages before reaching complete realization — a preliminary and purely 

 scientific stage, and a final and really practical stage. 



The scientific success of the problem seems to consist in hatching a reason- 

 able number of young fishes and keeping them in the laboratory beyond the 

 critical stage. (As defined by Fabre-Domergue, the critical stage begins when 

 the umbilical vesicle is entirely absorbed and the young fish begins to look for 

 food among its surroundings.) Practical success consists in keeping a consider- 

 able number of fishes until they acquire such condition that the operation may 

 be really remunerative. It is evident that before attempting the study of the 

 second feature of this problem the first must be solved. It is only when the 



"Fabre-Domergue and Bietrix: Le developpenient de la sole, 1905. Travail du Laboratoire de 

 Zoologie maritime de Concarueau. 



