64 MADRAS FISHERIES BULLETIN VOL. XI, 



likely to set free oxygen in quantity than to absorb it. On the 

 other hand poisoning of the water by the excretions of myriads of 

 individuals and by the decomposition products liberated through 

 the death of the short-lived generations of these organisms is 

 sufficient cause for much of the mortality noted; the third, or 

 mechanical factor, has, I believe, particularly harmful influence 

 upon burrowing and sedentary organisms, as these are unable to 

 escape its blanketing effects. 



Fishermen aver that the phase of mortality which I witnessed 

 last year is by no means the climax ; they hold that with a conti- 

 nuation of favourable weather — calm seas and an abundance of 

 sunshine — the trouble increases, being characterized by a thicken- 

 ing of the water and emission of an intolerable stench, entailing 

 an extension of widespread death among larger fishes and occa- 

 sionally among shoals of sardines. As I have not had an opportu- 

 nity to watch this further progress and enhancement of the trouble, 

 I cannot say definitely how it is caused. I have, however, seen 

 the ultimate result of such an extended death in the case of sar- 

 dine shoals as already mentioned.^ I am inclined to the opinion 

 that these more extensive instances of mortality owe their origin 

 primarily to the same cause as induces the more limited and 

 localized cases described above, that is, to the superabundant 

 multiplication of immense swarms of euglenids. The extension of 

 the area covered and the increase in the numbers of fish involved 

 may be explained by (a) simple increase in the extent of the 

 euglenid swarms, reinforced by (b) a progressive intensification of 

 the evil influence due to the putrefaction of ever-increasing quanti- 

 ties of dead fish. Many of the patches of putrefying sardines seen 

 in November 1908 off Mangalore (loc. cit.) were reduced to mere 

 frothy ochreous yellow bacterial scums. These patches were often 

 as much as half a mile in length by half that in width. The 

 atmosphere was horribly contaminated by an intolerable stench of 

 oily decomposition ; the water contamination must have been 

 intense. Healthy fish wandering into these areas of decomposition 

 quickly became affected, rushing hither and thither aimlessly and 

 in evident distress, coming gasping to the surface and finally 

 turning on their sides and dying. With each accession of material 

 to the putrefying mass, the area of contamination continues to 



llorncU, J., Madras Fisheries Buleltin, No. 4, pp. 101-105. 



