338
J. Robertson et al.
reported industrial fishery. However, given that illegal landings are also a key element
in some of the industrial fisheries it is clear that some reduction should be undertaken
as soon as possible. Alternatively, methods by which the by-catch species may be
excluded from the trawls should be investigated. There is little effort being made by the
fishing industry to reduce discards in the human consumption fishery (except for
Scottish, English, Irish and Swedish fishermen who use enhanced selective devices in
prawn trawls, Robertson (1993) and by Danish fishermen in cod trawls). The fishing
industry should stop discarding of juvenile fish from the human consumption fishery;
stop the practise of by-catch within the industrial fisheries for pout and sprat; limit the
outtake of sandeels and stop the practise of “blackfish” landings. However, economic
as well as legal sanctions will clearly be needed to achieve this. The result could be an
enhanced fishery for the industry.
Alterations in the ecosystem, which have occurred as a result of the high
levels of exploitation on species in the higher trophic levels, have now given rise to a
situation in which the suitabilities and prey preferences have changed. Given the fact
that many of the human consumption species are also potentially at stock levels where
recruitment and growth overfishing are already occurring, it would seem that the only
rapid way to remediate the situation is to combine the two processes of reduction in the
industrial fishery as well as making steps towards controlling or eliminating the high
levels of illegally landed fish. This is a course already well known to the EU member
states, but what is certainly needed to create the appropriate management structure is a
full accounting of the illegal landings associated with all North Sea fisheries.
Greater emphasis must be placed on fish species interactions by way of who
eats who and under what conditions. The consumption of fish by birds and mammals
must also be taken account of more positively and fully within the ecosystem. We can
no longer afford the luxury of paying no heed to the food needs of the creatures within
the North Sea system. The food requirements are important elements controlling the
life of the stocks or the ability for the stocks to grow. All other stock parameters will
follow naturally if enough food is available. Continuous monitoring of the food
requirements of fish should be undertaken and some form of calibration of future food
availability versus increasing stock size is needed. Immediate action is needed if food
availability reduces to levels that cannot sustain the stocks. This is the correct basis on
which catching levels on the various stocks should be controlled.
Based on recent stomach sampling exercises it appears that sandeel and pout
are the two most important food items for the human consumption fish species of the
North Sea. Greater levels of protection of these stocks should be afforded to ensure
enhanced food supplies within the system to allow the stocks to grow. The calculations
contained in this chapter suggest that a reduction in the sandeel fishery would allow
more food to become available to the predators who rely heavily on the sandeel for
sustenance and allow increased spatial overlap between food and predators.
There is clearly a question as to whether or not enough food exists in the
North Sea ecosystem to feed the fish. As Gislason and Kirkegard (1996) suggest “If the
stock sizes of the fish predators should increase, for example due to an overall decrease
in fishing effort in the human consumption fishery in the North Sea, it may be
J. Robertson et al.
reported industrial fishery. However, given that illegal landings are also a key element
in some of the industrial fisheries it is clear that some reduction should be undertaken
as soon as possible. Alternatively, methods by which the by-catch species may be
excluded from the trawls should be investigated. There is little effort being made by the
fishing industry to reduce discards in the human consumption fishery (except for
Scottish, English, Irish and Swedish fishermen who use enhanced selective devices in
prawn trawls, Robertson (1993) and by Danish fishermen in cod trawls). The fishing
industry should stop discarding of juvenile fish from the human consumption fishery;
stop the practise of by-catch within the industrial fisheries for pout and sprat; limit the
outtake of sandeels and stop the practise of “blackfish” landings. However, economic
as well as legal sanctions will clearly be needed to achieve this. The result could be an
enhanced fishery for the industry.
Alterations in the ecosystem, which have occurred as a result of the high
levels of exploitation on species in the higher trophic levels, have now given rise to a
situation in which the suitabilities and prey preferences have changed. Given the fact
that many of the human consumption species are also potentially at stock levels where
recruitment and growth overfishing are already occurring, it would seem that the only
rapid way to remediate the situation is to combine the two processes of reduction in the
industrial fishery as well as making steps towards controlling or eliminating the high
levels of illegally landed fish. This is a course already well known to the EU member
states, but what is certainly needed to create the appropriate management structure is a
full accounting of the illegal landings associated with all North Sea fisheries.
Greater emphasis must be placed on fish species interactions by way of who
eats who and under what conditions. The consumption of fish by birds and mammals
must also be taken account of more positively and fully within the ecosystem. We can
no longer afford the luxury of paying no heed to the food needs of the creatures within
the North Sea system. The food requirements are important elements controlling the
life of the stocks or the ability for the stocks to grow. All other stock parameters will
follow naturally if enough food is available. Continuous monitoring of the food
requirements of fish should be undertaken and some form of calibration of future food
availability versus increasing stock size is needed. Immediate action is needed if food
availability reduces to levels that cannot sustain the stocks. This is the correct basis on
which catching levels on the various stocks should be controlled.
Based on recent stomach sampling exercises it appears that sandeel and pout
are the two most important food items for the human consumption fish species of the
North Sea. Greater levels of protection of these stocks should be afforded to ensure
enhanced food supplies within the system to allow the stocks to grow. The calculations
contained in this chapter suggest that a reduction in the sandeel fishery would allow
more food to become available to the predators who rely heavily on the sandeel for
sustenance and allow increased spatial overlap between food and predators.
There is clearly a question as to whether or not enough food exists in the
North Sea ecosystem to feed the fish. As Gislason and Kirkegard (1996) suggest “If the
stock sizes of the fish predators should increase, for example due to an overall decrease
in fishing effort in the human consumption fishery in the North Sea, it may be