No. 2 (1917) FISH MORTALITY 55 



many) where Karafiir and Kedunir were indicated to me, the 

 specific gravity of such water was found to be fully as high as that 

 of ordinary sea-water in the vicinity. The density of the water in 

 which the dying fish were found on several occasions was also 

 that of normal sea-water. As to mud being a cause, that was 

 early seen to be out of court as no mud was in suspension in any 

 Kedunir pointed out by fishermen nor in that in which fish were 

 found dead and dying. On the contrary this mortality takes place 

 not in rough weather when mud banks are disturbed, but in calm 

 sunny weather when the sea is usually free from sediment. The 

 fish most commonly found dying at the beginning of the phenom- 

 enon are bottom fish such as soles and cat-fish, and these I have 

 found by direct experiment can live and thrive in water in which 

 such mud is kept artificially in suspension. There remains the 

 theory of foul water from rivers ; this is negatived id) by the lack 

 of foul odour in the water when it first occurs, {h) by its density 

 being that of nearly normal sea-water, {c) by the absence of vege- 

 table debris in suspension in the water called Kedunir or Sennir, 

 and lastly, {d) by the fact that it is as frequent in bays into which 

 no great river empties as in those where one does. 



After this short review of facts and theories, I shall now state 

 my own observations and conclusions. 



My first experience of poison water was in November 1908 when 

 on a fishery cruise along the west coast of the Madras Presidency. 

 On that occasion I was so fortunate as to witness one of those 

 specially widespread cases of mortality which affect whole shoals 

 of fish and cover comparatively great areas, but which are said by 

 fishermen to be infrequent and not of annual occurrence. 



In this instance great stretches of water off the Mangalore coast 

 were thick with dead sardines in various stages of putrefaction. 

 The area affected was over fifteen miles in length and lay gen- 

 erally from one to two miles off shore. No organisms except 

 bacteria were present in quantity in the water. The stench was 

 intolerable. Details are recorded in Fisheries Bulletin No. 4.' 



The next occasion when I met with poison water was on 8th 

 November 1912, when my attention was drawn to a dirty and 

 malodorous condition of the water lapping the beach at Calicut. 

 The colour of the water was distinctly brownish, a clear yellowish 



2 Hornell, J. " Report on the Results of a Fishery Cruise along the Malabar 

 Coast," Madras Fisheries liiiileti/i. No. 4, p. loi : Madras, 1910. 



