308 BRITISH FISHERIES 



Once obtained, they are put into the " spawning 

 pond/' which is a large and somewhat deep pond 

 excavated or built, and kept supplied with a current 

 of pure sea-water pumped into it by means of 

 engines and pumps, or perhaps let into it at 

 intervals, if the pond be situated at a lower level 

 than that of high-water mark. The fish are kept 

 supplied with suitable food, and in the course of 

 time they spawn naturally in the pond ; and as 

 there are generally some males in a ripe condition 

 while spawning is going on, the eggs are fertilised. 

 The latter then rise to the surface of the water 

 in the pond, and this surface layer of water 

 may be constantly running off, passing through a 

 large horse-hair sieve as it does so. The eggs are 

 therefore retained by this sieve. Or perhaps the 

 surface of the pond may be swept daily by a 

 large net made of fine material, so as to gather the 

 eggs. There are other methods of obtaining the 

 eggs. Ripe fishes may be caught, and the eggs 

 and spermatozoa obtained by stripping them, that 

 is, by gentle pressure on the abdomen in the 

 region of the reproductive organs. These stripped 

 fish may then be put back into the sea. Or the 

 commercial trawlers may be visited, and such ripe 

 fish as are taken in the trawl-net may be stripped, 

 and the fertilised eggs then brought back to the 

 hatchery. But when it is desired to obtain a large 

 number of eggs, the method of the spawning pond 

 is always adopted. 



