Given the difficulties of cleaning up oil at sea, spilled oil will often threaten coastal resources. It may be possible to protect some of these resources by the strategic deployment of booms. Other measures may also be appropriate, such as closing water intakes to industrial plants or coastal lagoons.
Highest priority should be given to protecting coastal resources which are particularly sensitive to oil pollution and which can be boomed effectively. These can include fish and shellfish farms, industrial water intakes, leisure facilities such as marinas, and environmentally-sensitive areas, such as bird colonies. Whilst some sites will be relatively easy to protect, others such as marshes, mangroves and amenity beaches, are often too extensive for booming to be practical.
Where conditions permit, alternatives to traditional protective strategies may prove effective. In particular, a variety of strategies are available that may help protect mariculture facilities, including:
Relocation of Sea Cages, Pens or Long-lines
Towing floating or submerged facilities and the stock they contain out of the path of an approaching slick may be feasible, if sufficient warning is given and if the facilities are readily moveable. In many cases, this is a complicated and delicate operation that can cause stress and damage to stock and it is therefore unlikely to be a viable option unless it has been well planned and practised.
Transfer of Stock
Where facilities are fixed, it may be possible to move the stock. Primary requirements are sufficient warning of the threat and a suitable reception facility for the stock. Transfer will inevitably be labour intensive, costly, dependent on weather conditions and carry an attendant risk of stress or mortality to the stock. There may also be legal restrictions on the movement of cultured marine organisms.
Harvesting a proportion or all of the stock before it becomes impacted by the spill may be possible if the stock is at a marketable size. Like other strategies, there are likely to be practical and logistical difficulties as well as attendant price and market considerations.
Land-based facilities with water intakes may be able to close intakes or sluice gates and re-circulate water for short periods throughout part or whole of the facility. Care must be taken to ensure that the deteriorating water quality during re-circulation does not cause greater harm to the stock than the potential oil contamination.
Suspension of Feeding
By suspending the feeding of stock it may be possible to reduce the risk of animals coming into physical contact with oil at the water surface or becoming tainted through contamination of the feed by oil. Suspension of feeding prior to closing off water intakes or commencing a re-circulation water management strategy may help maintain water quality. Care should be taken to ensure that suspension of feeding will not cause more harm than the impacts of the potential oil contamination.
Alternative protective strategies should also be considered for coastal resources other than mariculture facilities:
Removal of Mobile Marine Assets
In incidents where there is sufficient warning, it may be possible to move mobile marine assets eg recreational and commercial vessels, floating pontoons and mooring tackle. Although there may be cost considerations in moving assets, they are likely to be less than the cleaning costs of oiled assets and in addition, moving assets may also aid the clean-up of coastal structures eg moving fishing vessels from harbour walls and so improving access.
An oil spill may threaten important coastal habitats for birds eg sand flats and salt marshes. In order to reduce the risk of birds becoming oiled, it may be considered appropriate to use bird hazing (‘bird scaring’) techniques. These include auditory (eg horns and cannons), visual (eg scare tape and flashing buoys), and exclusion (eg netting) techniques with the most effective dependent on the area to be protected, the nature of the habitat and the birdlife at risk. Overflights by small fixed-wing aircraft or helicopters have also been used effectively but care should be taken over seabird colonies where there is a great risk of scaring birds into surface oil slicks. In all cases, consideration should be given to national and local regulations regarding bird hazing.
In most cases, it is important to implement protective strategies quickly and, with limited resources available, decisions must be taken as to which sites should be given priority. This should be pre-determined in contingency plans.