Natural abundance of stable nitrogen isotopes reflect changes in pelagic food webs and mobility of size classes of the north Iberian sardine (Sardina pilchardus)
Authors
Bode, A. (Antonio); Carrera, P. (Pablo); Lorenzo-Salamanca, J. (Jorge); Porteiro-Lago, C. (Carmen); Santos, M.B. (María Begoña); Cabanas-López, J.M. (José Manuel)Date
2004Type
working paperKeywords
SardinePlankton
Feeding
Stable isotopes
Migration
NW Iberian Peninsula
Abstract
The natural abundance of stable nitrogen isotopes (δ15N) in sardine (Sardina
pilchardus) and plankton was determined from samples collected between 1998 and
2003 in the northwestern shelf of the Iberian Peninsula with the purpose of studying the
variability in the trophic position of sardine. Sardines were grouped in three size-length
classes (small: < 16 cm; medium: 16-20 cm; large: > 20 cm). Plankton samples were
size-fractionated between ca. 0.7 and 2000 μm of individual length. The plankton at the
base of the pelagic food web in the western shelf region (Galicia) was more enriched in
δ15N than plankton in the northern and eastern region (Mar Cantábrico), likely because
of upwelling. Variability in δ15N in sardine was related both to changes in feeding
strategies during growth and to the mobility of size classes between adjacent shelf
regions. Large sardines showed regional differences in δ15N similar to those of small
plankton, suggesting that old specimens remained for ...
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