3* 



system ; in both the aim is to utilize the natural instincts 

 of certain species of fish in such manner as both to stock 

 enclosed ponds automatically with an ample supply of 

 fry at one season of the year and at another season to 

 trap in quantity such fishes as have attained maturity 

 and whom instinct leads to attempt to pass to the sea for 

 spawning purposes. 



The differences and modifications which we shall now 

 describe are clue in the main to the larger field of opera- 

 tions which is involved ; the one deals with ponds of 

 restricted area, the other with sections of an inland sea. 



Apart from the matter of relative size, one of the 

 most important divergences seen at Comacchio is the 

 provision of separate openings in the encircling embank- 

 ments of each pond or valle for the entry of the fry during 

 ascent (monte'e or montatd) and for the construction of 

 pounds or labyrinth traps for the capture of the adult 

 fish. This separation of function is rendered necessary 

 owing to the great extent of the principal ponds and in 

 order to gain full advantage from the freshening influence 

 of the non-saline water of the rivers flowing along two 

 sides of the lagoon. 



All the chief ponds communicate on the one hand 

 with these two rivers by means of massive sluices, and 

 on the other with the sea by one or other of the branch 

 canals arising from the sea-channels which traverse the 

 lido at Maenavacca or Bocca del Bianco. It is the aim 



o ... 



of this dual communication between the ponds and the 

 sea on the one side and the ponds and the rivers on the 

 other, to render possible the mechanical stocking and 

 fishing of the various fish-farms and at the same time to 

 introduce fresh supplies both of river and of sea- water to 

 moderate the high salinity which otherwise would be 

 caused by evaporation and generally to assist in main- 

 taining healthy conditions within the lagoon. 



(a) The stocking of the Lagoon. 



To give entry to the fry of those fishes whose instinct 

 leads them to enter river estuaries when very young, on 

 2nd February in each year, the sluices leading to the 

 Reno and the Volano are opened, together with all those 

 in the sea-canals leading to Magnavacca or the Bocca 

 del Bianco. A temporary third channel, the Taglio del 



