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vol.30 número1  suppl.SympRevisiting in Situ Chlorophyll-a Data Along the Coast in North-Central Chile Considering Multiscale Environmental VariabilityWarm ENSO Events and their Effects on the Coastal Fish Fauna of Northern Chile índice de autoresíndice de materiabúsqueda de artículos
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Investigaciones marinas

versión On-line ISSN 0717-7178

Investig. mar. v.30 n.1 supl.Symp Valparaíso ago. 2002

http://dx.doi.org/10.4067/S0717-71782002030100032 

Study of the Pelagic Fish
Environmental and Behavioral
Adaptation to Strong Physicochemical
Changes Induced by ENSO in
Peruvian Waters (1997-1998)

Marceliano Segura1,
Arnaud Bertrand2, Luis Vásquez1

1Instituto del Mar del Perú (IMARPE), Gamarra y
General Valle s/n Chucuito, La Punta, Callao - Perú,
E-mail: msegura@imarpe.gob.pe,
lvasquez@imarpe.gob.pe
2Institut de recherche pour le développement (IRD) c/o
Escuela de Ciencias del Mar, UCV, Av. Altamirano
1480, Casilla 1020, Valparaiso, Chile,
E-mail: arnaud.bertrand@ird.fr.

El Niño events are known to have a major impact on the pelagic fish distribution and behaviour. In Peru, the IMARPE (Instituto del mar Del Peru) performs regular accoustic surveys to monitor the distribution and abundance of the main pelagic resources. During the 1997-1998 El Niño event, the sampling rate was increased through cruises on board IMARPE's research vessels Humboldt, Olaya and SNP-2 to study in more detail the evolution of the ecosystem. In the present study we used data from six surveys between September 1997 and June 1999 with the aim of determining the influence of the 1997-1998 El Niño event on the spatial distribution and behaviour of the main pelagic species, the anchovy (Engraulis ringens), sardine (Sardinops sagax sagax), jack mackerel (Trachurus symmetricus murphyi) and mackerel (Scomber Japonicus sp.) in relation to physicochemical factors.

In order to follow the evolution of spatial distribution for each species we applied a new method, i.e. considering the displacement of the centre of gravity of each population and its dispersion in relation to the movement of the water masses. The relations between each specie and temperature, salinity and dissolved oxygen were then modelled using General Additive Models for each survey. The evolution of the model shape during and after the ENSO supplied information about the evolution of the relationships between each specie and its habitat during a strong environmental stress. We therefore discuss the respective behaviour and advantages of each specie. From the results we can see the anchovy is the specie with lower tolerance to oceanographic changes compared to sardine or jack mackerel. The main parameter in its distribution is salinity, and it is usually distributed in areas with values of 35,0 or 35,1psu. In some cases it could be detected in areas with values of 35,2psu which represented the boundary between? subtropical waters and coastal waters. In relation to temperature, it could be detected mostly in areas of 18° to 23°C and, in warm events, up to 26°C. The sardine, horse mackerel and mackerel could be detected in areas where the salinity and temperature were higher than for the anchovy.

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