no. 6 (1917) a note on treatment of swamps, etc. 17i 



For paddy fields, wells and small ponds, etc.— 



All species of Chcljs, Hut^lochilus and Polyncanthus. 



For salt or brackish water ponds, etc.— 



Ge n us- Therapon . 



Description a/ ^^<v///5.— Branchiostegals six. Eyes of moderate 

 size. Opercle with spines. Preopercle and sometimes preorbital 

 serrated. Teeth villiform in both jaws, the outer row being some- 

 times the larger : deciduous ones on the vomer and palatines. 

 Dorsal fin single but more or less notched, having from eleven to 

 thirteen spines : anal with three. Scales of moderate or small size. 

 Air vessel divided by a constriction. 



Geographical distribution. — From the Red Sea and East Coast of 

 Africa through the seas and estuaries of India to the Malay Archi- 

 pelago and north coast of Australia. 



" Therapon jarbna " is a most useful species andean be found 

 in all backwaters and will live and thrive in brackish and fresh 

 water ponds. 



Gen\.\%-Polyaca)ithus. 



Description of genus. — Body oblong, compressed. Mouth small 

 and but little protractile. Opercles spineless. Teeth small and 

 fixed in the jaws, palate edentulous. Dorsal fin single, the spinous 

 portion of much greater extent than the soft : the anal of a similar 

 description : ventral with one spine and five well developed rays, 

 some of which are usually elongated. Scales rather large, ctenoid. 

 Lateral line interrupted and may be partially or even entirely 

 absent. 



Geographical distribution. — Fresh waters and estuaries along the 

 coast of India and Ceylon. 



" Polyacanthus cupanus " is a most valuable larvag destroyer 

 for both fresh and brackish water, and can be carried any distance 

 with the greatest of ease without change of water, as it obtains 

 oxygen direct from the atmosphere. 



DESTRUCTION OF IMMATURE FRY AND USEFUL LARVICIDES. 



The practice of trapping streams by inserting fixed engines 

 (basket traps Plates 7-9) from bank to bank and the use of fine 

 mesh nets the strands or meshes of which would not allow the 

 smallest fish to pass through, is a most destructive method of fishing. 



