8 Externalities in Aquaculture
259
here that the negative effects of aquaculture become more conspicuous. It is argued
that growth in demand for fishmeal used in intensive aquaculture increases pressure
on stocks such as anchovy, sandeel, etc., with potentially adverse effects on the
production of edible supplies from marine capture fisheries. The problem, however,
has at least as much to do with the way capture fisheries are managed as with the
growth of aquaculture per se (Hannesson 2003). Where fisheries are effectively
open-access, the over-exploitation of stocks caused by increased demand for fishmeal is likely to be more severe. Nonetheless, the problem of higher fishmeal prices
(and hence increased incentive to over-exploit) will be exacerbated if demand for
fishmeal becomes more inelastic, a situation which seems likely as the global scale
of the industry continues to enlarge and dependence on this source of raw material
increases in the face of limited alternatives (Asche and Tveteras 2004). A quite
separate mechanism by which aquaculture may impose external costs on capture
fisheries is through the spread of disease and infestations, a particularly controversial example being the transmission of sea lice from salmon cages to the wild
salmon stocks. While the evidence for this is still a matter of dispute, if the link
were to be established it would be potentially serious in socio-economic as well as
ecological terms.
Apart from its impact on fish stocks, cage aquaculture may affect the coastal
environment in ways which reduce its amenity value, possibly with implications for
tourism. One way is through reductions in water quality as a result of nutrient enrichment and eutrophication, another is through visual intrusion due to the inappropriate
siting of sea cages. Despite the difficulties of assessing these types of environmental
impact in monetary terms, it is clear that the public has a view about the social
acceptability of aquaculture development in particular circumstances. Katrinidis et al.
(2003) conducted a questionnaire survey of public attitudes towards coastal aquaculture development at two Greek islands and found that a negative attitude to development was more likely where respondents believed that pollution by fish farms
would be high. Further evidence that people are not indifferent to the environmental
effects of aquaculture comes from a survey of public attitudes towards salmon farming in Scotland and the perceived problem of organic pollution. (Whitmarsh and
Wattage 2006). This was conducted through a postal questionnaire sent to a sample
of households across the different Scottish regions. The results showed that respondents placed a relatively high priority on the desirability of minimising pollution from
aquaculture, and this was matched by a Willingness to Pay (WTP) higher prices for
salmon farmed in a more sustainable manner. Aside from this evidence, what we
know about the externalities of pollution from marine aquaculture is very fragmentary. The external cost of eutrophication from coastal cage salmon farming in the
early 1990s has been estimated using Swedish data to be between 50 and 100 SEK
(= US $6.4 and US$12.8) per kg of nitrogen (Folke et al. 1994), figures which it is
claimed would make salmon farming unsustainable if added to the cost of production (i.e., internalised). Though this particular study has been severely criticised for
its methodology (Black et al. 1997), it is worth noting that an economic assessment
of eutrophication in the Baltic based on a Willingness to Pay approach (Gren 2000)
has estimated the external cost of nutrient release (N) from all sources to be 62 SEK
259
here that the negative effects of aquaculture become more conspicuous. It is argued
that growth in demand for fishmeal used in intensive aquaculture increases pressure
on stocks such as anchovy, sandeel, etc., with potentially adverse effects on the
production of edible supplies from marine capture fisheries. The problem, however,
has at least as much to do with the way capture fisheries are managed as with the
growth of aquaculture per se (Hannesson 2003). Where fisheries are effectively
open-access, the over-exploitation of stocks caused by increased demand for fishmeal is likely to be more severe. Nonetheless, the problem of higher fishmeal prices
(and hence increased incentive to over-exploit) will be exacerbated if demand for
fishmeal becomes more inelastic, a situation which seems likely as the global scale
of the industry continues to enlarge and dependence on this source of raw material
increases in the face of limited alternatives (Asche and Tveteras 2004). A quite
separate mechanism by which aquaculture may impose external costs on capture
fisheries is through the spread of disease and infestations, a particularly controversial example being the transmission of sea lice from salmon cages to the wild
salmon stocks. While the evidence for this is still a matter of dispute, if the link
were to be established it would be potentially serious in socio-economic as well as
ecological terms.
Apart from its impact on fish stocks, cage aquaculture may affect the coastal
environment in ways which reduce its amenity value, possibly with implications for
tourism. One way is through reductions in water quality as a result of nutrient enrichment and eutrophication, another is through visual intrusion due to the inappropriate
siting of sea cages. Despite the difficulties of assessing these types of environmental
impact in monetary terms, it is clear that the public has a view about the social
acceptability of aquaculture development in particular circumstances. Katrinidis et al.
(2003) conducted a questionnaire survey of public attitudes towards coastal aquaculture development at two Greek islands and found that a negative attitude to development was more likely where respondents believed that pollution by fish farms
would be high. Further evidence that people are not indifferent to the environmental
effects of aquaculture comes from a survey of public attitudes towards salmon farming in Scotland and the perceived problem of organic pollution. (Whitmarsh and
Wattage 2006). This was conducted through a postal questionnaire sent to a sample
of households across the different Scottish regions. The results showed that respondents placed a relatively high priority on the desirability of minimising pollution from
aquaculture, and this was matched by a Willingness to Pay (WTP) higher prices for
salmon farmed in a more sustainable manner. Aside from this evidence, what we
know about the externalities of pollution from marine aquaculture is very fragmentary. The external cost of eutrophication from coastal cage salmon farming in the
early 1990s has been estimated using Swedish data to be between 50 and 100 SEK
(= US $6.4 and US$12.8) per kg of nitrogen (Folke et al. 1994), figures which it is
claimed would make salmon farming unsustainable if added to the cost of production (i.e., internalised). Though this particular study has been severely criticised for
its methodology (Black et al. 1997), it is worth noting that an economic assessment
of eutrophication in the Baltic based on a Willingness to Pay approach (Gren 2000)
has estimated the external cost of nutrient release (N) from all sources to be 62 SEK