Anchovy larval distribution in the coastal zone off northern Chile: the effect of low dissolved oxygen concentrations and of a cold-warm sequence (1990-95)

This study analyses the patterns of distribution and abundance of anchovy (Engraulis ringens) larvae off northern Chile (18°-24°S), within the coastal zone (out to 100 nm) and their relationship to the oceanographic conditions in the top layer (0-200 m depth). The data were derived from surveys unde...

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Autores principales: Morales,Carmen E., Braun,Mauricio, Reyes,Hernán, Blanco,José L., Davies,Anthony G.
Lenguaje:English
Publicado: Escuela de Ciencias del Mar. Pontificia Universidad Católica de Valparaíso 1996
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Acceso en línea:http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-71781996002400007
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spelling oai:scielo:S0717-717819960024000072003-11-06Anchovy larval distribution in the coastal zone off northern Chile: the effect of low dissolved oxygen concentrations and of a cold-warm sequence (1990-95)Morales,Carmen E.Braun,MauricioReyes,HernánBlanco,José L.Davies,Anthony G. anchovy larval distribution low oxygen concentrations oceanographic conditions northern Chile This study analyses the patterns of distribution and abundance of anchovy (Engraulis ringens) larvae off northern Chile (18°-24°S), within the coastal zone (out to 100 nm) and their relationship to the oceanographic conditions in the top layer (0-200 m depth). The data were derived from surveys undertaken from 1990 to 1995, during each winter (July-September), the season of the main spawning and higher larval abundance. During the 1995 survey, ichthyoplankton samples were also taken at shallower depths (<100 m), to assess the influence of low dissolved oxygen concentration upon the vertical distribution of the anchovy larvae. Both surface temperature and surface salinity distributions revealed that the period of this study covered a sequence from a relatively cold condition (1990) to warmer weak El Niño condition (1992), and back to cooler conditions (1995) in the area. A deepening of the base of the thermocline (15°C isotherm) occurred during the warmer period along the whole of the coast. During cooler conditions, the upper boundary of the low dissolved oxygen layer (ca. 1.0 ml 1-1) was found at shallower depths (<50 m) in most of the northern part of the area (Arica-Iquique) and also the waters above the thermocline were significantly more oxygenated, though variations with depth were greater, than during the warmer periods. Mean intergrated abundances of anchovy larvae varied significantly between the winter periods of 1990 to 1995 (range: 230-5300 larvae in 10 m²), with the highest mean values observed during 1993 and 1994. The highest abundances occurred at the most nearshore stations (1-5 nm) during all the cruises, though high values were also found at some offshore stations, mainly during the 1993-95 period. The comparison of the mean density of larvae (number m-3) over different depth ranges (0-25, 0-50, and/or 0-100 m), suggested the ocurrence of a barrier to their vertical distribution, located in the vicinity of the 0,75 ml O21-1 concentration. Overall, the warmer conditions initiated during 1992 appeared to have provided a more suitable environment for the survival and feeding of anchovy larvae in the area, whereas changes in the distribution of low oxygen concentrations did not appear to have a direct influence on larval abundance and distribution.info:eu-repo/semantics/openAccessEscuela de Ciencias del Mar. Pontificia Universidad Católica de ValparaísoInvestigaciones marinas v.24 19961996-01-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-71781996002400007en10.4067/S0717-71781996002400007
institution Scielo Chile
collection Scielo Chile
language English
topic anchovy larval distribution
low oxygen concentrations
oceanographic conditions
northern Chile
spellingShingle anchovy larval distribution
low oxygen concentrations
oceanographic conditions
northern Chile
Morales,Carmen E.
Braun,Mauricio
Reyes,Hernán
Blanco,José L.
Davies,Anthony G.
Anchovy larval distribution in the coastal zone off northern Chile: the effect of low dissolved oxygen concentrations and of a cold-warm sequence (1990-95)
description This study analyses the patterns of distribution and abundance of anchovy (Engraulis ringens) larvae off northern Chile (18°-24°S), within the coastal zone (out to 100 nm) and their relationship to the oceanographic conditions in the top layer (0-200 m depth). The data were derived from surveys undertaken from 1990 to 1995, during each winter (July-September), the season of the main spawning and higher larval abundance. During the 1995 survey, ichthyoplankton samples were also taken at shallower depths (<100 m), to assess the influence of low dissolved oxygen concentration upon the vertical distribution of the anchovy larvae. Both surface temperature and surface salinity distributions revealed that the period of this study covered a sequence from a relatively cold condition (1990) to warmer weak El Niño condition (1992), and back to cooler conditions (1995) in the area. A deepening of the base of the thermocline (15°C isotherm) occurred during the warmer period along the whole of the coast. During cooler conditions, the upper boundary of the low dissolved oxygen layer (ca. 1.0 ml 1-1) was found at shallower depths (<50 m) in most of the northern part of the area (Arica-Iquique) and also the waters above the thermocline were significantly more oxygenated, though variations with depth were greater, than during the warmer periods. Mean intergrated abundances of anchovy larvae varied significantly between the winter periods of 1990 to 1995 (range: 230-5300 larvae in 10 m²), with the highest mean values observed during 1993 and 1994. The highest abundances occurred at the most nearshore stations (1-5 nm) during all the cruises, though high values were also found at some offshore stations, mainly during the 1993-95 period. The comparison of the mean density of larvae (number m-3) over different depth ranges (0-25, 0-50, and/or 0-100 m), suggested the ocurrence of a barrier to their vertical distribution, located in the vicinity of the 0,75 ml O21-1 concentration. Overall, the warmer conditions initiated during 1992 appeared to have provided a more suitable environment for the survival and feeding of anchovy larvae in the area, whereas changes in the distribution of low oxygen concentrations did not appear to have a direct influence on larval abundance and distribution.
author Morales,Carmen E.
Braun,Mauricio
Reyes,Hernán
Blanco,José L.
Davies,Anthony G.
author_facet Morales,Carmen E.
Braun,Mauricio
Reyes,Hernán
Blanco,José L.
Davies,Anthony G.
author_sort Morales,Carmen E.
title Anchovy larval distribution in the coastal zone off northern Chile: the effect of low dissolved oxygen concentrations and of a cold-warm sequence (1990-95)
title_short Anchovy larval distribution in the coastal zone off northern Chile: the effect of low dissolved oxygen concentrations and of a cold-warm sequence (1990-95)
title_full Anchovy larval distribution in the coastal zone off northern Chile: the effect of low dissolved oxygen concentrations and of a cold-warm sequence (1990-95)
title_fullStr Anchovy larval distribution in the coastal zone off northern Chile: the effect of low dissolved oxygen concentrations and of a cold-warm sequence (1990-95)
title_full_unstemmed Anchovy larval distribution in the coastal zone off northern Chile: the effect of low dissolved oxygen concentrations and of a cold-warm sequence (1990-95)
title_sort anchovy larval distribution in the coastal zone off northern chile: the effect of low dissolved oxygen concentrations and of a cold-warm sequence (1990-95)
publisher Escuela de Ciencias del Mar. Pontificia Universidad Católica de Valparaíso
publishDate 1996
url http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-71781996002400007
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