Sandeel as a link between primary production and higher trophic levels on the Faroe shelf

Abstract

A good correlation has previously been established between primary production and production in higher trophic levels in the marine ecosystem on the Faroe shelf, but identification of potential intermediate species has been missing. Sandeel Ammodytes spp. is known to be of great ecological importance in other areas; thus, we investigated the relationship between primary and sandeel production on the Faroe shelf. Juvenile sandeels have been sampled on the annual Faroese 0-group survey in late June to early July with a standardized procedure since 1982. Measurements on primary production, i.e. estimates of accumulated new primary production and chlorophyll a concentration, have been carried out during spring and summer on the Faroe shelf since 1990 and 1997, respectively. We found positive correlations between the primary production and the mean length and abundance of juvenile sandeels on the Faroe shelf in the period investigated. There was also a highly significant relationship between primary production and an index of juvenile sandeel biomass. Two simple models based on starvation mortality and length-dependent predation mortality, respectively, fitted the data well. These findings verify a clear, almost instantaneous, and rather unique link from primary producers to top predators.