|
|
|
|
44. Environmental and servicing considerations and the need to safeguard the interests of other users of coastal waters inevitably impose locational constraints on marine fish farm developments. Factors which require to be taken into account in determining the acceptability of individual development proposals in no order of priority include :
Environmental and infrastructural capacity constraints cannot be determined in isolation. The cumulative effects of development require to be considered.
The Water
45. Unpolluted and well-oxygenated water is essential for the culture of marine fish, salmonids and shellfish and shellfish farms require to be carefully sited to minimise the risk of stock contamination. Aquatic organisms have differing water temperature requirements. Growth rates generally increase with temperature and large seasonal fluctuations in temperature can adversely affect both fin and shellfish species. Water temperatures on Scotland’s Atlantic coast are higher and more stable than at similar latitudes elsewhere because of the effect of the North Atlantic Drift. Sheltered, shallow situations, where water temperatures may become elevated during the summer months, can be particularly attractive locations for shellfish cultivation. However, sites where the tidal flushing is poor enough to permit elevated temperatures may be prone to low oxygen levels, low salinity, low natural food levels and poor dispersion of waste.
46. In shallow inner sea lochs and inlets which receive substantial discharges of freshwater, salinities are liable to drop below the optimum for marine aquaculture. Salmon and shellfish farming both require relatively high and stable salinities. Low salinities result in reduced salmon growth rates and can induce premature maturation or "grilsing". Scallops are particularly sensitive to low salinities and many west coast sites are unsuitable for their cultivation because of low salinities during winter.
47. Intensive fish husbandry, particularly that using an external food source, has the potential to alter the water chemistry in and around production sites. The water can become enriched in nutrients. The ecological consequences of excessive nutrient enrichment can include changes in the composition of aquatic plant and animal communities and production of phytoplankton. In some locations it will be appropriate to consider nutrient loading from aquaculture in the context of external factors such as agricultural run-off.
48. Sustainable marine fish farming requires that the levels of nutrient and chemical inputs are not allowed to exceed the carrying capacity of the surrounding aquatic environment. There is clearly a need to ensure that, within any enclosed body of water, the total nutrient input from fish farming and other sources does not exceed the threshold above which an unacceptable increase in phytoplankton production or undesirable changes in species composition would occur. For a range of potentially toxic chemicals, environmental quality standards (EQS) have been established to ensure that concentrations remain well below the level at which adverse ecological effects are detectable. Advice on these standards and the carrying capacities of marine locations can be obtained from SEPA, FRS Marine Laboratory in Aberdeen and the Dunstaffnage Marine Laboratory. In some cases it may be necessary to limit the size of the farm or the quantities of therapeutant chemicals to prevent these EQS from being exceeded. Under EC Directive 91/492, which lays down stringent health conditions for the production and marketing of bivalve molluscs, shellfish harvesting areas have been classified according to the level of bacterial contamination present in samples of mollusc flesh. Advice on the conditions which apply in the various categories of this classification can be obtained from SERAD.
49. Where organic waste accumulates in bottom sediments beneath fish cages, microbial activity results in depletion of dissolved oxygen in the overlying water. Organic enrichment also results in changes in the bottom-dwelling flora and fauna, though the effects are generally confined to the immediate vicinity of the cages. Excessive enrichment of the sediment can result in "site souring" in which conditions in the sediment interact adversely with the farmed fish. Therefore it may be necessary to limit the biomass of fish to prevent an unsatisfactory build up of solid waste organic matter on the sea bed. Although shellfish cultivation does not rely on food input, the material discarded by filter-feeding molluscs can result in accumulations of organically-rich detritus on bottom sediments beneath shellfish farms.
50. In inshore marine locations it is important to select sites with good water exchange characteristics. Strong currents, for example from tidal flushing, disperse waste material, bring in fresh, well-oxygenated water and, in the case of shellfish cultivation, provide fresh supplies of planktonic food. Sites in deeper water permit higher levels of production per unit surface area, are less susceptible to souring as a result of the accumulation of waste material, and generally have more stable salinities. Seabed survey can assist in marine site selection. Sites with thick, muddy sediments tend to have less vigorous water exchange characteristics. Sand and gravel sediments indicate that the site is well flushed.
Natural Heritage
51. Scotland’s varied coastline provides a wide range of important habitats for wildlife as well as landscapes of the highest scenic quality and recreational value.
52. Some of the potential effects of marine fish farming on flora and fauna have already been outlined previously. Other considerations include interactions with predator species; disturbance to wildlife such as seabirds, herons, seals and otters and interaction with wild stocks of salmon and sea trout (see below) and shellfish populations.
53. Sites of particular value for nature conservation enjoy statutory protection as National Nature Reserves (NNRs) or Sites of Special Scientific Interest (SSSIs) and some of these are also protected under EC legislation or international agreements. A number of sites of particular importance for bird populations have been designated as Special Protection Areas (SPAs) under EC Directive 79/409 on the conservation of wild birds (the Wild Birds Directive), while wetlands of international importance as waterfowl habitats are protected under the Ramsar Convention. Directive 92/43 on the conservation of natural habitats and of wild fauna and flora (the Habitats Directive) requires member states to identify sites for designation as Special Areas of Conservation (SACs). In due course SPAs and SACs will cover both land based and marine nature conservation areas of European importance.
54. The Wildlife and Countryside Act 1981 makes provision for important marine habitats to be designated as Marine Nature Reserves (MNRs). There are no MNRs in Scotland at present. In addition, 29 Marine Consultation Areas (MCAs) have been identified to assist bodies which consult SNH on marine conservation issues. While the latter contain marine habitats of particular quality and sensitivity, they do not have any statutory status.
55. Landscapes of national importance have been designated as National Scenic Areas. In addition to formal designations, many coastal areas are valued for their fine views and their wild and remote qualities. Landscapes of regional and local importance can also be designated by local authorities and are identified in development plans. National Planning Policy Guideline 13: Coastal Planning, identifies three types of coast - developed, undeveloped and isolated - as the basis for policy on coastal development. Advice on the criteria to be used in classifying the coast is set out in Policy Advice Note 53: Classifying the Coast for Planning Purposes.
56. Particular care must be taken to minimise the potential for adverse interactions with predator species. The attentions of predators can result in serious stock losses, and conversely, predatory birds and mammals may be drowned as a result of becoming entangled in anti-predator nets. The industry and nature conservation organisations have agreed codes of practice in relation to the interaction between fish farming and predatory wildlife.
Wild salmon and sea trout
57. Scotland's wild salmon and sea trout stocks are a unique and irreplaceable biological resource of considerable economic and social value. The populations of wild fish in the catchments of many salmon and sea trout rivers are believed to be genetically distinct even to the extent of differentiation to individual tributaries and headwaters. The fisheries which they support make an important contribution to Scotland’s rural economy and are a valued part of the country’s cultural heritage.
58. Salmon and sea trout fishing and conservation interests are concerned about the potential effects of commercial salmon farming on wild stocks. It has been suggested that the successful breeding of escaped farmed fish could reduce the genetic diversity and vigour of wild salmon and sea trout populations. Fears have also been expressed about the transmission of disease and parasites from farmed to wild fish though this is potentially equally applicable in reverse.
59. In the White Paper on Environmental Strategy, "This Common Inheritance" the Government recognised the importance of maintaining biological diversity and committed itself to the application of the precautionary principle "particularly where there are good grounds for judging ... that irreversible effects may follow if action is delayed". In this context, proposals for the establishment of hatcheries, smolt and salmon/seatrout farms in the catchments and coastal waters associated with Scotland’s principal salmon and sea trout rivers may prove to be particularly contentious and difficult to determine.
60. The Atlantic salmon is an Annex ll and V species under the Habitats Directive. In addition, wild salmonids act as hosts for the young larval stages of the freshwater pearl mussel (also protected under Annex ll). In areas where freshwater pearl mussels are found, any activities which threaten wild salmon and sea trout populations may therefore also pose a threat to pearl mussel populations.
Other interests
Fishing
61. Care must be taken to minimise the potential for conflict between marine fish farming and local fishing interests. Inshore fishing is an important source of livelihood in many coastal areas.
62. The effects of development on traditional fishing grounds, salmon netting stations and angling interests require to be carefully considered. Advice on fishing interests can be obtained from SERAD, the Scottish Fishermen’s Federation, District Salmon Fishery Boards and the local fishermen’s organisations. The Salmon Net Fishery Association of Scotland can provide advice in relation to salmon net fishing stations.
Navigation
63. It is essential to ensure that marine fish farm development does not constitute a hazard to navigation. Care must also be taken to safeguard established anchorages and harbours of refuge, this can best be achieved by avoiding areas marked by anchor symbols on Admiralty Charts and by reference to the Clyde Cruising Club Sailing Directions. It is important from a safety perspective that sites being fallowed are clearly marked to protect navigation routes.
Recreation
64. Coastal areas are used by a wide and growing range of recreational interests and water-based recreational activities make an important contribution to the economies of many rural communities. These activities include sailing, canoeing, windsurfing, water-skiing, swimming, sub-aqua diving, surfing, recreational fishing and the general enjoyment of the coast. Due attention must be given to public safety considerations and care should be taken to avoid impeding access to the foreshore for recreational purposes. Where appropriate, consideration should be given to the scope for providing joint access for fish farming and recreational activities. Sport Scotland (formerly the Scottish Sports Council) can provide advice in relation to interactions with recreational activities and is a point of contact for all sports governing bodies.
|
|
|