PANAMIC-PACIFIC PELECYPODA 33 



Ecuador with its warm water is here deflected westward into the open 

 Pacific, and the mighty Peruvian or Humboldt Current streaming up 

 from the south is similarly deflected on a more westerly course. As 

 a result, the waters off the coast of northwestern Peru are in a constant 

 tumult or conflict, as the drift of the two streams meet and join, the mixing 

 zone shifting its position continually, sometimes to the south or far to the 

 north. At times, the Equatorial stream is the more powerful and is able 

 to push its way southward bringing waters warmer than usual into the 

 coastal zone. This disturbance is known to the Peruvians as "El Nino" since 

 it commonly appears during the Christmas season or simply as "the Aguaje". 

 Although the El Nino is felt somewhat each year, its duration is usually 

 short but at more or less cyclic intervals, it can be very severe, 

 upsetting the normal climatic conditions of the coastal land and 

 bringing catastrophic destruction to life in the sea. The winds which blow 

 normally from the sea or from the southwest, then become northerly or 

 easterly, bring heavy, torrential rains, converting the dry quebradas into 

 rushing streams and covering the otherwise dry and barren land with a lush 

 growth of vegetation. The most severe of the El Nino distrubances in recent 

 years was in 1925: a lesser one in 1953. 



Although the Peruvian Province extends well into the tropics and with- 

 in a few degrees of the equator, its fauna is essentially one of cool or temper- 

 ate waters, maintained partly by the Peruvian Current and by strong, in- 

 shore upweHings from depths. The Peruvian Current (or Humboldt Current) 

 is one of the most remarkable of oceanic streams if judged by the influence 

 which it exerts on the coastal lands along which it flows and by the pro- 

 fusion of marine life which it supports in its waters. The source of this 

 mighty stream lies in the high southern latitudes of the westerly winds 

 which propel it eastward to impinge upon the coast of southern Chile near 

 the island of Chiloe, south of Concepcion. At this place, the stream divides 

 into two branches, one turns to the south, flows to and around Cape Horn, 

 the other and major branch is diverted to the north and skirts the coast 

 of Chile and Peru. Near the city of Chiclayo (lat 6° 30' S.) the coast bends 

 sharply towards the west, thereby turning and driving the Peruvian 

 Current out into the open Pacific at Punta Aguja. Surface temperatures in 

 the stream off the coast of southern Chile in the month of August average 

 about 45° Fahrenheit and between 60 and 65° in the northern sector. The 

 most significant feature of the Peruvian stream is its lower temperatures 

 inshore and higher ones offshore. The maintenance of the lower temperature 

 along the inner course of the stream is mainly due to strong upwellings 

 rather than a direct transport of identical masses of cold water from far 

 southern latitudes. This phenomenon of upwellings appears to be strongest 

 in the northern part of the stream where it flows over the shallower plat- 

 form areas which prevail there rather than in the south where the shelf 

 zone is narrower and the dip-off into deep water is more abrupt. Research, 

 mainly by the Schott Expedition, has shown that this rise of cold submarine 

 water to the surface comes from relatively shallow depths of 30 to 400 



