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distinguished with certainty were grouped to the next taxonomic level (usu-
ally genus). Linear body dimensions of all individuals collected from the
benthos and identified in gut contents were measured and converted to
dry mass using published regression equations (listed in
Woodward and
Hildrew, 2002
).
The foreguts of the predators collected in the Surber samples were dissect-
ed and examined at 400
magnification. Gut contents were identified from
reference slides and the individual body masses of ingested prey were calcu-
lated using the same methods as for the benthic samples (
Woodward et al.,
2005b
). One dataset was compiled over the six sampling occasions. Each
predator and prey individual involved in a feeding link was measured and
transformed into their respective body masses, which resulted in 2893
individuals.
3. Celtic Sea
The Celtic Sea is an area of continental shelf bordered by Ireland, the UK
and the Bay of Biscay. Precise sampling locations and dates were not given in
the
Barnes et al. (2008)
dataset, from where the data used in this chapter were
extracted, so we pooled data over the whole time period and locations to
capture general patterns. Only locations consistently sampled through the
1987-2001 time series were used (
Blanchard et al., 2005
).
The feeding links of fishes in the Celtic Sea have been described in a
published global dataset of individual predator and prey body sizes and
taxonomy (
Barnes et al., 2008
): in total, 1988 feeding events from 29 predator
species were included in the food web presented here. The original stomach
contents data were collected from dissections carried out on board research
vessels during the annual surveys carried out by the Centre for Environment,
Fisheries and Aquaculture Science (Cefas) (
Pinnegar et al., 2003
). Predator
and prey length were recorded and converted to body mass by
Barnes et al.
(2008)
using published regression equations. Only vertebrate prey were iden-
tified and measured, with the vast majority being identified to species.
4. Coilaco, Guampoe and Trancura Rivers, Chile
Similar studies were conducted in three rivers (Coilaco, Guampoe and Tran-
cura Rivers) within the catchment of the Tolt´n River in south Chile, South
America. The Coilaco River (discharge 2.1-16.8 m
3
/s), Guampoe River (dis-
charge 1.8-7.5 m
3
/s) and Trancura River (discharge 8.8-49.3 m
3
/s) are all
circumneutral (pH 6.7-7.6) (
Figueroa, 2007
).
