60 MADRAS FISHERIES BULLETIN VOL. XI, 



contained comparatively few Euglenids, was slightly higher, being 

 I026"5 at the same temperature. On 5th October when the water 

 in the bay had begun to clear, a distinct rise in the specific gravity 

 of the inshore-water was noticed, being 1026*5. Off shore-water 

 was undoubtedly coming in and driving out the foul water, for coin- 

 cident with the rise in density, the number of Euglenids were now 

 comparatively few, their place being taken by several species of 

 diatoms common to ordinary sea-water on this coast. 



The Euglenid-infected water noted at Calicut and Quilandj 

 from 9th to l6th October, ranged in density from 1025 to I026'5 at 

 82° F. The Euglenids appear to flourish equally at the higher as 

 at the lower density. 



On the evening of l6th October a break of weather occurred, the 

 fine sunny conditions of the preceding week giving place to heavy 

 rain and cloudy sky. On 17th October sea-water from near the 

 shore showed an almost entire disappearance of Euglenids and a 

 fall in density to I024'5 at 8o° F. No further swarms of Euglenids 

 were noted during the remainder of the month which was charac- 

 terised by a continuance of rainy weather. 



There can now be no question that the prodigious multiplication 

 of Euglenids in shallow water on the Malabar coast causes extensive 

 recurrent local mortality amongst the inshore fauna ; whether 

 other organisms also cause mortality and the precise way in which 

 stupefaction and death are brought about remain uncertain. 



With regard to the former question, it is to be noted that never 

 before has fish mortality been attributed to the superabundance of 

 flagellate infusorians such as the Euglcua above described ; all 

 other observations point either to the group of Peridiniales or Dino- 

 flagellata or to the cysto-flagellate Noctiluca as being the organisms 

 involved in those cases where fish mortality has been traced to the 

 occurrence of the phenomenon termed " Red-water " in other parts 

 of the world. The phenomenon is by no means unique. Nishikawa 

 has recorded interesting cases from Japan ' while Gilchrist has 

 recorded others from South Africa.* 



Nishikawa records that in September IQOO, "streaks and 

 patches of brownish yellow water emitting an unpleasant odour 



^ Nishikawa, T. " Gonyaulax and the discoloured water in the Ba\- of Agu," 

 Aimoialioiu's Zoologicu Japomnses, Vol. IV, part i, pp. 31-34, Tokio, 1901. 



•• Gilchrist, J.D.F. "An enquiry into fluctuations in fish supply on the South African 

 coast," Marine Biological Reports (Union of South Africa), No. 2, Cape Town, 1914. 



