Potential zooplankton preys (Copepoda and Appendicularia) for &lt;i&gt;Engraulis anchoita&lt;/i&gt; in relation to early larval and spawning distributions in the Patagonian frontal system (SW Atlantic Ocean)

Mariela L Spinelli,Fabiana L Capitanio,Patricia Martos,Graciela B Esnal,Marcelo Pájaro,Marina Sabatini

doi:10.3989/scimar.2012.76n1039

Abstract

We investigated the spatial distribution of the abundance, biomass and size of zooplankton (nauplii, calanoids, cyclopoids and appendicularians) in relation to the distribution of first-feeding larvae and eggs of Engraulis anchoita across the frontal system of Peninsula Valdes. Twelve samples of zooplankton and ichthyoplankton were taken with small Bongo (67 μm) and Pairovet (200 μm) nets during the spring of 2004 along two transects. The total abundance of zooplankton and the chlorophyll a concentration were higher in homogeneous waters, while total biomasses were higher in stratified waters. Temperature was negatively correlated with biological variables and was the main factor affecting the zooplankton distribution. In both transects, abundance peaks of first-feeding larvae were detected at coastal stations along with the smallest fraction of zooplankton ( < 500 μm), while the largest fraction was dominant at the external stations, coinciding with the highest egg abundance. The physical structure of this front generates different levels of food availability for first-feeding larvae. Calanoids (southern transect) and cyclopoids (northern transect) are predominant followed by nauplii and appendicularians. The biomass of zooplankton preys contributes to the carbon transfer to the upper trophic levels and is probably important for the survival and growth of anchovy larvae in this frontal system.

Highlights

Copepods are considered the most abundant mesozooplankton group in many pelagic environments (Kiørboe 1998), and along with appendicularians, they are the most important secondary producers (Gorsky and Fenaux 1998, Hopcroft and Roff 1998, Sato et al 2008)
SUMMARY: We investigated the spatial distribution of the abundance, biomass and size of zooplankton in relation to the distribution of first-feeding larvae and eggs of Engraulis anchoita across the frontal system of Peninsula Valdés
The total abundance of zooplankton and the chlorophyll a concentration were higher in homogeneous waters, while total biomasses were higher in stratified waters

Summary

Introduction

Copepods are considered the most abundant mesozooplankton group in many pelagic environments (Kiørboe 1998), and along with appendicularians, they are the most important secondary producers (Gorsky and Fenaux 1998, Hopcroft and Roff 1998, Sato et al 2008). B o t h g r o u p s p l a y a n im p o r t a n t r o l e a s c o n s u m ers of both the phytoplankton and microbial components of food webs. They are preyed on by several pelagic ichthyoplankters (Berggreen et al 1988, Deibel and Lee 1992, Flood et al 1992; Stibor et al 2004, Castro et al 2010). The availability of prey for fish larvae will partially depend on the transference rate of primary producers through copepods

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Conclusion