ABNORMAL CONDITIONS 233 



Saldanha Bay (South Africa) the conditions had been preceded by a spell of north-west 

 wind which may be presumed to have driven warm water against the coast. In Japan 

 and India, fine calm weather with plenty of sunshine was the rule. 



Warm surface temperatures, then, seem an essential in the production of discoloured 

 water and fish mortality, though the activity of the surface currents mentioned by 

 Stiglich, if this is accurate, does not tally exactly with the quiet conditions described by 

 the others. In the writer's experience, discoloration was found where the water was in- 

 clined to be sluggish, at Pisco, Callao and the Guanape Islands, but it was not found at 

 Arica where a strong inshore current prevented stagnancy. Whether the larger animals 

 are killed by oxygen want which might arise in a variety of ways in such densely in- 

 habited waters as the Peru Current, or whether from direct contact with the swarming 

 nannoplankton, has not been determined. 



Hart's observation that the ciliate Mesodinium swarms and discolours water under 

 calm conditions is very similar to the above; and that it seems to be cosmopolitan 

 (Paulsen, 1934; Clemens, 1935) opens the possibility that this organism too may be a 

 member of the Peru Current plankton. Although it has not been shown a cause of fish 

 mortality, its swarming if not producing a red, might when scattered produce a khaki 

 colour similar to that figured in Plate XVI, fig. 11. As it disintegrates in bright light 

 and in formalin, it would have escaped record in our catches. 



The conclusion may be drawn that the phenomenon of aguaje occurs in either normal 

 or abnormal meteorological or hydrological conditions. When brought about by El Nino, 

 it is obviously contributing to the abnormal conditions then extant. At other times of 

 the year, it is probably induced in normal meteorological conditions as a result of the 

 convergence of a warm wedge with the coast. Aguaje, further, appears to show every 

 degree of intensity: from slight discoloration with relatively little destruction of marine 

 life, to the extremes produced during a severe invasion of El Nino. 



Whereas in normal conditions aguaje may be traced to the convergence of an oceanic 

 counter-current with the coast, the causes underlying this convergence are obscure. 

 The importance of the anticyclonic swirls cannot be doubted: at the same time, the 

 prominence of the virazon not only at Pisco, but at Callao and the Guanape Islands, may 

 be significant (cf. Fig. 63 with Figs. 4 and 35 and Appendix IV, pp. 259-60). 



MORTALITY OF SQUIDS ON THE CHILEAN COAST 



We may consider whether the annual stranding of Dosidicus gigas in enormous num- 

 bers on the Chilean coast can be ascribed to the above phenomena. D'Orbigny (1835- 

 43) writes of it as follows: 



Nous avons vu la mer couverte de debris d'Ommastrephes, surtout aux mois de Fevrier et de Mars, 

 en approchant des cotes du Chili par 33 degres de latitude sud; et, a la meme epoque, nous en avons 

 vu jetes en grand nombre, encore vivans, a la cote de Valparaiso, sur toute celle du Chili, de la Bolivia 

 et du Perou, a Cobija, au 23^ degre de latitude sud, puis au port d'Arica. La il y en avait tant, que la 

 police s'etait vue forcee, dans I'interet sanitaire du pays, ordinairement insalubre, de faire recueillir 

 les cadavres de ces animaux, dont la putrefaction pouvait rendre I'air plus malsain encore. 



