NO. 2 (1917) FISH MORTALITY 63 



Prior to my Malabar experience last year, my attention had 

 been drawn to this subject by a small occurrence of bright red 

 water at Tuticorin. In this case the colour was due to the presence 

 of immense quantities of a bright pink peridinian of very minute 

 size. A few small fish were seen dead where this water settled, 

 but the swarm passed away quickly and was of too small extent to 

 cause serious harm. This bright red water (not the brownish- 

 yellow of the Japanese " red-water ") emitted an intolerable stench, 

 a blend seemingly of sulphuretted hydrogen with the smell of 

 decomposing fish oil. Accompanying this red water was a dense 

 scum of a sage green tint due to the presence of vast quantities of 

 an extremely large species of a green Paranweciiini, which appeared 

 to be preying upon the peridinians. 



From this experience and remembrance of Mr. Nishikawa's 

 Japanese observations, I began the Malabar investigation on the 

 hypothesis that the cause of fish mortality was to be sought in an 

 undue abundance of some peridinian. As my first samples of 

 water taken at Cannanore, from a place where discoloured water 

 with accompanying fish mortality had been seen a fortnight previ- 

 ously, contained considerable numbers of two species of yellowish 

 green Peridinians ( Gymnodiniiim spp.), my belief was strengthened 

 but, as above detailed, I had to abandon this in face of the repeated 

 conjunction of euglenid-infested water with widespread mortality 

 of fishes, crustaceans and molluscs within the same area. 



The immediate cause of death in the case of fishes, crabs and 

 shell-fish caught in the foul water seen periodically on the Malabar 

 coast is undoubtedly some form of suffocation in the wide sense 

 of a poisoning of the blood of the animals concerned by some 

 asphyxiant present in the surrounding medium — the water of the 

 sea. The symptoms are distinctively those of this form of death — 

 the gills dark and livid and movements sluggish. Especially 

 marked was the comatose condition of affected crustaceans. 

 Exactly how the asphyxiation is brought about is uncertain ; it 

 may either be by exhaustion of oxygen in the sea water or by 

 poisoning due to the excretion of waste products on the part of the 

 euglenids or it may be semi-mechanical in cases where bottom- 

 loving animals have come within an area where vast masses of the 

 euglenids have settled to the bottom and have there passed into 

 the jelly-forming resting stage. The first suggestion is the least 

 likely, as the euglenids are possessed of chloroplasts and are more 

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