300
J. Robertson et al.
the diet requirements of future generations of increased stock sizes. There is little point
in having protracted discussions on effort limitation of fishing power, technical
measures or other measures to protect the stocks if those fish stocks have no, or not
enough, food to sustain them in the long run. In this chapter we investigate the impact
of the North Sea industrial fishery on the food available to human consumption
species, and attempt to answer the question by analysis of existing data sets, recourse to
the literature and by calculation of the weight of fish consumed in the North Sea to
further investigate changes in trophic level transfer efficiencies.
We therefore approach the problem from three angles to examine the
partitioning of direct food consumption levels of the human consumption species
within the North Sea. We use the consumption levels from the 1981 ICES stomach
sampling exercise and base total consumption on total stock biomass estimates from
1983 to 1985. Then, using MSVPA consumption inputs based on the 1981 and 1991
ICES stomach sampling exercises, we analyse various predator-prey interactions using
the ECOPATH model and compare consumption levels between the years 1977 to 1986
and 1987 to 1994, to see whether there are any changes in consumption and whether
they are due to diminishing stocks of human consumption species or alterations in prey
selection.
In terms of explicit controls on fisheries, these are mainly restricted to
regulating fishing mortality via overall catch levels and technical measures such as
mesh size, minimum landing sizes, and area and seasonal closures. The dynamics of
fishing mortality, however, are heavily influenced not only by ecological interactions
and the types of fishing vessels and gears used etc., but also by market forces. In the
North Sea there is widespread evidence that over quota landings, by-catches and
discards represent a significant proportion of the tonnage of human consumption
species extracted from the sea. To help estimate the level of tonnage involved, identify
the reasons behind these practices and estimate their potential role in the future,
interviews with the fisheries sector in the UK were carried out.
The North Sea Industrial Fishery and its Fish
The industrial fisheries target sandeels, Norway pout, sprat and herring using small
mesh trawls. The landings are broken, pulverised and pressed to extract meal and oil
that are principally used to feed terrestrial and aquatic farmed animals. Some oil is
added to human food such as biscuits and margarine.
The main commercial industrial fishery is for sandeel, of the Ammodytidae
family and for Norway pout, Trisopterus esmarki. Other smaller, but no less important,
industrial fisheries exist for sprat, Sprattus sprattus; horse mackerel, Trachurus
trachurus. Smaller amounts of blue whiting, Micromesistius poutassou are also taken.
Sandeel and pout constitute the two largest tonnages of industrial species
taken. Sandeel comprise five species in the North Sea which are the common sandeel
Ammodytes tobianus, Raitts sandeel ammodytes marinus, the smooth sandeel
Gymnammodytes semisquamatus, the greater sandeel Hyperoplus lanceolatus, Corbins
sandeel Hyperoplus immaculatus (Knijn et al., 1993). The lesser sandeels, common
J. Robertson et al.
the diet requirements of future generations of increased stock sizes. There is little point
in having protracted discussions on effort limitation of fishing power, technical
measures or other measures to protect the stocks if those fish stocks have no, or not
enough, food to sustain them in the long run. In this chapter we investigate the impact
of the North Sea industrial fishery on the food available to human consumption
species, and attempt to answer the question by analysis of existing data sets, recourse to
the literature and by calculation of the weight of fish consumed in the North Sea to
further investigate changes in trophic level transfer efficiencies.
We therefore approach the problem from three angles to examine the
partitioning of direct food consumption levels of the human consumption species
within the North Sea. We use the consumption levels from the 1981 ICES stomach
sampling exercise and base total consumption on total stock biomass estimates from
1983 to 1985. Then, using MSVPA consumption inputs based on the 1981 and 1991
ICES stomach sampling exercises, we analyse various predator-prey interactions using
the ECOPATH model and compare consumption levels between the years 1977 to 1986
and 1987 to 1994, to see whether there are any changes in consumption and whether
they are due to diminishing stocks of human consumption species or alterations in prey
selection.
In terms of explicit controls on fisheries, these are mainly restricted to
regulating fishing mortality via overall catch levels and technical measures such as
mesh size, minimum landing sizes, and area and seasonal closures. The dynamics of
fishing mortality, however, are heavily influenced not only by ecological interactions
and the types of fishing vessels and gears used etc., but also by market forces. In the
North Sea there is widespread evidence that over quota landings, by-catches and
discards represent a significant proportion of the tonnage of human consumption
species extracted from the sea. To help estimate the level of tonnage involved, identify
the reasons behind these practices and estimate their potential role in the future,
interviews with the fisheries sector in the UK were carried out.
The North Sea Industrial Fishery and its Fish
The industrial fisheries target sandeels, Norway pout, sprat and herring using small
mesh trawls. The landings are broken, pulverised and pressed to extract meal and oil
that are principally used to feed terrestrial and aquatic farmed animals. Some oil is
added to human food such as biscuits and margarine.
The main commercial industrial fishery is for sandeel, of the Ammodytidae
family and for Norway pout, Trisopterus esmarki. Other smaller, but no less important,
industrial fisheries exist for sprat, Sprattus sprattus; horse mackerel, Trachurus
trachurus. Smaller amounts of blue whiting, Micromesistius poutassou are also taken.
Sandeel and pout constitute the two largest tonnages of industrial species
taken. Sandeel comprise five species in the North Sea which are the common sandeel
Ammodytes tobianus, Raitts sandeel ammodytes marinus, the smooth sandeel
Gymnammodytes semisquamatus, the greater sandeel Hyperoplus lanceolatus, Corbins
sandeel Hyperoplus immaculatus (Knijn et al., 1993). The lesser sandeels, common