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J. Robertson et al.
Whiting diet: Some 60% of whiting diet comes from the pelagic plaktivores (and most
of this consists of sandeel). Benthic material and demersal piscivores each account for
about 14% of diet. Plankton accounts for 8% of diet with about 3% of demersal
benthivores comprising the remainder. Sandeel are a major component of whiting diet
with equal amounts eaten across all four quarters.
Saithe diet: Plankton and pelagic planktivores account for 79% of total saithe diet.
Demersal piscivores account for 19% of diet and the remainder of insignificant
amounts of benthos and demersal benthivores.
Mackerel diet: Half of mackerel diet consists of plankton whilst pelagic planktivores
(mainly sandeel) account for 37%. Benthic material is also taken (12%).
CONSUMPTION OF FISH PREY SPECIES BY FISH PREDATORS
Fig. 4 sets out the daily tonnages of fish prey eaten by the fish predators. The data are
displayed by quarter. Table 2 illustrates the consumption per day of each prey species
by each predator expressed as a percentage of the total weight consumed per quarter
and year. Fig. 5 sets out the percentage consumption of prey species by quarter.
Predator cod: There is no single fish prey which dominates the diet of cod. It is a
generalised feeder and there is no dominant species taken at any particular period of
the year (except for sandeel during the second quarter which amounts to 40% of diet).
However, cannibalism in cod is 8.5% of its yearly fish diet. Cod also eat extensive
quantities of whiting (20.7%) and haddock (21.2%). Sandeels account for 16.4% over
the year and pout for 17.2% of cod yearly diet. Incidental amounts of herring (9%),
sprat (4.7%) and mackerel (2.2%) are taken.
Predator haddock: Norway pout (49.7%) and sandeel (45.9%) dominate the diet of
haddock. No cod or mackerel appear in the diet of haddock whilst very small quantities
of haddock (0.6%) whiting (0.2%) herring (0.8%) and sprat (2.8%) are taken. The
Norway pout component of the diet is mainly devoured during the first two quarters
although haddock do consume significant amounts of pout during the second two
quarters. The main prey species during the second half of the year is sandeel with
small amounts taken during the first quarter and none during second.
Predator whiting: Sandeel (44.9%), sprat (15.7%), pout (14.9%) and herring (11.1%)
dominate the diet of whiting. Haddock (8.3%) and whiting (4.9% cannibalism) are
lesser targets for the whiting. An insignificant proportion of cod and mackerel are
taken (<1%). The dominance of sandeel in the diet reaches its peak during the second
quarter. This may be associated with post spawning heavy feeding to build body
weight.
J. Robertson et al.
Whiting diet: Some 60% of whiting diet comes from the pelagic plaktivores (and most
of this consists of sandeel). Benthic material and demersal piscivores each account for
about 14% of diet. Plankton accounts for 8% of diet with about 3% of demersal
benthivores comprising the remainder. Sandeel are a major component of whiting diet
with equal amounts eaten across all four quarters.
Saithe diet: Plankton and pelagic planktivores account for 79% of total saithe diet.
Demersal piscivores account for 19% of diet and the remainder of insignificant
amounts of benthos and demersal benthivores.
Mackerel diet: Half of mackerel diet consists of plankton whilst pelagic planktivores
(mainly sandeel) account for 37%. Benthic material is also taken (12%).
CONSUMPTION OF FISH PREY SPECIES BY FISH PREDATORS
Fig. 4 sets out the daily tonnages of fish prey eaten by the fish predators. The data are
displayed by quarter. Table 2 illustrates the consumption per day of each prey species
by each predator expressed as a percentage of the total weight consumed per quarter
and year. Fig. 5 sets out the percentage consumption of prey species by quarter.
Predator cod: There is no single fish prey which dominates the diet of cod. It is a
generalised feeder and there is no dominant species taken at any particular period of
the year (except for sandeel during the second quarter which amounts to 40% of diet).
However, cannibalism in cod is 8.5% of its yearly fish diet. Cod also eat extensive
quantities of whiting (20.7%) and haddock (21.2%). Sandeels account for 16.4% over
the year and pout for 17.2% of cod yearly diet. Incidental amounts of herring (9%),
sprat (4.7%) and mackerel (2.2%) are taken.
Predator haddock: Norway pout (49.7%) and sandeel (45.9%) dominate the diet of
haddock. No cod or mackerel appear in the diet of haddock whilst very small quantities
of haddock (0.6%) whiting (0.2%) herring (0.8%) and sprat (2.8%) are taken. The
Norway pout component of the diet is mainly devoured during the first two quarters
although haddock do consume significant amounts of pout during the second two
quarters. The main prey species during the second half of the year is sandeel with
small amounts taken during the first quarter and none during second.
Predator whiting: Sandeel (44.9%), sprat (15.7%), pout (14.9%) and herring (11.1%)
dominate the diet of whiting. Haddock (8.3%) and whiting (4.9% cannibalism) are
lesser targets for the whiting. An insignificant proportion of cod and mackerel are
taken (<1%). The dominance of sandeel in the diet reaches its peak during the second
quarter. This may be associated with post spawning heavy feeding to build body
weight.