Cross-front variations in adult abundance and recruitment of Patagonian scallop (Zygochlamys patagonica) at the SW Atlantic Shelf Break Front

A Cecilia Mauna,E Marcelo Acha,Oscar O Iribarne,Mario L Lasta,Ana Baldoni,Bárbara C Franco

doi:10.1093/icesjms/fsn098

Abstract

Abstract Mauna, A. C., Franco, B. C., Baldoni, A., Acha, E. M., Lasta, M. L., and Iribarne, O. O. 2008. Cross-front variations in adult abundance and recruitment of Patagonian scallop (Zygochlamys patagonica) at the SW Atlantic Shelf Break Front. – ICES Journal of Marine Science, 65: 1184–1190. We studied cross-front variations in adult abundance and recruitment of Patagonian scallop (Zygochlamys patagonica) and their relationship with the Shelf Break Front and satellite-derived chlorophyll a in the Southwest Atlantic between 38°S and 39°30′S. Integrated data from commercial fleets (CF, 1996–2005), research cruises (RC, 1998–2005), sea surface temperature (SST; 1985–1997), and satellite-derived chlorophyll a (CSAT; 1998–2004) were included in the analysis. One-way ANOVA was used to assess differences in recruitment and scallop abundance in a cross-front direction. The abundance of scallops was greatest (RC > 200 kg h−1) closer to the onshore side of the front or beneath it, and the East–West extension of scallop beds (∼40 km) matched the seasonal zonal displacement of the front (∼37 km). The highest CSAT gradients were west of or matched the position of the front. The annual mean position of the front correlated with the spatial variability in recruitment within areas where the species recruited successfully (RC > 2000 h−1). The spatial variability in adult abundance and recruitment of scallops is strongly related to the spatial variability in the position of the front and with the high CSAT concentrations associated with it.

Highlights

Marine fronts are usually associated with high biological primary production promoted by physical mechanisms that affect planktonic organisms, such as vertical fluxes, retention, and convergence (Mann and Lazier, 1991)
Our results have revealed that seasonal variability in the position of the front and the location of the surface CSAT maximum correlates spatially with a zone of high recruitment probability and adult scallop abundance
The highest values of scallop abundance were in central –eastern areas within the scallop bed, matching the highest gradients in sea surface temperature (SST) and CSAT concentration at the surface

Summary

Introduction

Marine fronts are usually associated with high biological primary production promoted by physical mechanisms that affect planktonic organisms, such as vertical fluxes, retention, and convergence (Mann and Lazier, 1991). Frontal variability (i.e. position and extension, which can change within and among years) may have consequences on (i) recruitment (Shanks, 1995; Alexander and Roughgarden, 1996), (ii) the distribution and abundance of benthic species (Nodder et al, 2003), or (iii) all the processes that contribute to a dynamic community (Dewicke et al, 2002). These factors are important in understanding patterns in species abundances and community functions, few studies have aimed to understand those processes better (Josefson and Conley, 1997)

Methods

Results

Conclusion