1 1 



are raised and the seaward screen dropped home into its 

 grooves. A skilful operator can so judge and control 

 the strength of the outflowing current as to keep it 

 so weak that it has no power to carry out any of the fry 

 in the ponds — it is for this reason the sluice doors 

 are raised so slightly. The natural instinct of the fry to 

 swim aoainst a current is also counted on, while to 

 prevent larger fish passing out the screen at the pond 

 end of the sluice is kept lowered during deboire. Occa- 

 sionally however the fry do endeavour to pass out in 

 some quantity ; when this is observed the sluice shutters 

 are at once closed. When the operation is finished for 

 the day a considerable quantity of fry and prawns are 

 frequently found congregated in the sluice ; these are 

 caught and put into the ponds in the same manner as 

 when stocking the ponds with fry. It must be noted 

 that this operation of emptying a portion of the pond 

 water is carried out usually during spring tides, whereas 

 the operations for catching fry in quantity are carried 

 out during neaps. This and the greater height to 

 which the sluice shutters are raised durino- the latter 

 operation — involving a stronger current — are the two 

 important differences. 



The converse operation of faire boirc, or actual 

 "freshening", is merely the reversal of the two opera- 

 tions already described. It consists of a regulated inflow 

 of sea water during spring tides equal to the amount 

 expelled during deboire and lost by evaporation. In 

 this operation both the wire-net screens are raised 

 (PI. II, Figs, i and 2) and then before opening one of 

 the sluice shutters the mouth frame of the sleeve-net is 

 dropped into position, the net itself being thrown into 

 the pond. As soon as the rising tide attains a higher 

 level than the surface of the ponds a sluice shutter is 

 raised slowly and with the utmost care in order that 

 the inrushing water may be adjusted with nicety to a 

 strength sufficient to distend the sleeve-net but not 

 violent enough to burst it. Text-figure 3 will make this 

 operation clear. 



The scene in the pond during this process of freshen- 

 ing is extremely interesting (PI. II, Fig. 1). The great 

 24-foot long sleeve-net, distended and appearing taut to 

 the point of rupture, streams straight into the pond, and 



