Salmon Farming in Scotland: the key environmental issues

1. Salmon Farming in Scotland: the key environmental issues Kenny Black Scottish Association for Marine Science Oban

2. Dunstaffnage Marine Laboratory

3. Scottish Association for Marine Science Established 1884 • Aims to: • develop, promote and support research in marine science • facilitate communication through conferences and seminars • support the teaching of marine science throughout Scotland • become the authoritative voice of marine science in Scotland • www.sams.ac.uk

4. Political background • Petition • Parliamentary Inquiry • Review and Synthesis for Scottish Exec and Parliament, SAMS/Napier Univ. • http://www.scotland.gov.uk/cru/kd01/green/reia-00.asp • Ministerial Working Group on Aquaculture Strategy

5. Summary • The contribution of salmon farming to Scotland • The key environmental effects of salmon farming, risks and strategies

6. Global Aquaculture Trends • 19,244,000 tonnes all fish species 2000 • 46,153,000 tonnes predicted for 2010 • 876,000 tonnes salmon in 2000 • 1,569,000 tonnes predicted for 2010

7. 60% production from 11% farms > 1000 t

9. Economic value to Scotland • The Scottish salmon farming industry employs 6500 people, 70% of which live in rural areas contributing about £2M per week to remote economies in wages alone. • The farm-gate value is around £300M p.a. – greater than Highland beef and lamb combined. • Of a total Scottish food export of £400M, salmon contributes 40%.

10. Salmon Farming • Smolts put to sea in March at 60g and continuously harvested from December (>1kg) for one year (up to 7 kg). • Salmon have very high growth rates. • Salmon feed high in protein and oil. • A 1000 t biomass farm produces about 1750 t of fish per cycle.

11. Wild fish 17% protein, 7-10% oil, 75% water Salmon Farming Budget for the flow of nutrients from oceanic wild caught fish to the coastal environment for a harvest of 1 kg of farmed salmon assuming no substitution with vegetable protein or oil and a ratio of fish feed to product of 1.2:1 2.8 kg for protein + 0.8 - 2.3 kg extra for oil Harvest Fish 1 kg N 26g P 3.2g C 139g Fish Feed 40% Protein 30% oil 9% water 1200g: N 96g P 18g C 660g Soluble wastes N 46g P 4.9g C 323g Mortalities and escapes N 1.9g P 0.4g C 13g Particulate wastes N 22g P 9.5g C 185g

12. Waste food and faeces settle on the sea bed: distribution depends on current regime and stratification

13. Effects on Sea bed

14. Effects on sea bed • Effects dependent on size of farm, quality of management and hydrographic conditions • All severe effects are constrained to the area near the cages • Effects generally undetectable outwith 100m • Farm size is determined by effects on sea bed to keep these within ecological quality standards • Pollution of the sea bed is not a major constraint on expansion of farming.

15. Effects on Water Column • Three main concerns: • nutrients from fin-fish farms have led to an increased occurrence of algal blooms; • nutrients from fin-fish farms have disturbed the natural ratios of nutrient elements so favouring the occurrence of toxic species • nutrients from fin-fish farms have made potentially toxic algae more poisonous.

16. Pseudonitzschia sp.DiatomAmnesiac Shellfish PoisoningDomoic AcidWide ranging scallop closures

17. 1. Increased blooms • Lack of long term data preclude direct comparison with nutrient and phytoplankton levels from pre-fish farm times. • Modelling studies show that only a few sea loch sites are strongly enriched: enrichments are generally low. • In addition, algal production attributable to fish farm nutrients in Scottish coastal areas is small relative to that generated by marine and terrestrial inputs.

18. 2. Altered nutrient ratios favour toxic algae • Despite many lab studies, we are still a long way from understanding what controls the balance of organisms within the plankton. • For those algae associated with eutrophication (Gymnodinium mikimtoi, Phaeocystis pouchetii and toxic flagellates) blooms do seem to be stimulated by nutrient enrichment and increases in the ratio of N and P to Si. • That the abundances of the toxic species of Alexandrium, Dinophysis and Pseudo–nitzschia are related to changes in nutrient ratio in the field remains speculative.

19. 3. Altered ratios increase toxicity of toxic algae • The effect of fish farm waste on nutrient element ratios in most Scottish cases can be shown to be small. • Farm waste has a ratio of nitrogen to phosphorus which is close to natural ratios. • Because of the absence of silicate in fish foods there may be a danger of exceeding the “safe” N:Si limit of 2.5 locally at heavily enriched sites in summer when background nutrient levels are low and silicate has been drawn down by the Spring Bloom.

20. However, modelling studies suggest that broad area effects should be small. Similarly there is no convincing evidence to suggest that changes in nutrients as a result of fish farm inputs ratios is likely to stress potentially toxic species to cause them to increase their toxicity.

21. Water Column Conclusions • Except perhaps in a few enclosed waters, enrichment by fish farm nutrients is too little, relative to natural levels, to have the alleged effects. • BUT we cannot often support this conclusion with data from series of measurements made at key sites over the several decades that span the development of the industry.

22. Aside: Shellfish culture • The cultivation of non-finfish species has few and only local negative environmental impacts. As this type of culture extracts nutrients from the marine system, it is likely that the cultivation of non-fish species can, to some extent, help reduce nutrient inputs from other activities including fish culture.

23. Medicines and chemicals • Antiparasitics (sea lice) • Antibiotics • Metals (Antifoulants and feed) • Disinfectants

24. Sea lice • Sea lice are mobile ectoparasitic copepods, which live on the gills and other body surfaces of fish. They feed on mucus, skin and blood, causing open wounds that expose fish to osmotic and respiratory stress as well as providing a route for secondary infections by bacteria or viruses.

25. In the sea-cage rearing of salmon, two sea lice species can cause severe infestations, heavy mortality and reduced marketability. • Lepeophtheirus salmonis is specific to salmonids and Caligus elongatus is found on over 70 fish species.

26. Nauplius stage L. salmonis Female C. elongatus Adult male L. salmonis

27. Sea lice life cycle

28. The generation time of L. salmonis from egg to ovigerous adult is 6 to 8 weeks at 10oC. Shorter at higher temps and depends of species of salmon host. • C. elongatus has no preadult stage. Generation time is about 6 weeks at 10oC.

29. Sea lice infestations present a major commercial and ecological problem. • But we do not typically see fish like this anymore as medicines are much improved.

30. Lice treatments • Bath • Hydrogen peroxide • Cypermethrin • Azamethiphos • In-feed • Ivermectin • Emamectin benzoate • Teflubenzuron • Cost – all medicines are very expensive

31. Lice treatments • In-feed treatments should represent lower risk to the ecosystem as they are used systemically, hence in lower doses than the topically administered bath treatments, most of which will be released directly and immediately to the environment after treatment

32. Risks • Hydrogen peroxide – low environmental risk but not a good product, little used! • Azamethiphos – relatively low risk to the environment - concentrations quickly fall below EQS • Cypermethrin – generally low risk except during multiple simultaneous treatments • Emamectin – generally low risk • Teflubenzuron – relatively persistent – moderate risk

33. BUT • All of these products are highly toxic to crustaceans and the stated risks are only for authorised product formulations administered according to best practice.

34. Antibiotics • Oxytetracycline, oxolinic acid, trimethoprim, sulphadiazine and amoxycillin • Aquaculture is one of the least medicated livestock industries: antibiotics are not used prophylactically

35. Concerns relating specifically to antibiotic usage by the aquaculture industry are: • Development of drug resistance in fish pathogens • Spread of drug resistant plasmids to human pathogens • Transfer of resistant pathogens from fish farming to humans • Presence of antibiotics in wild fish • Impact of antibiotics in sediments on: rates of microbial processes; composition of bacterial populations; relative size of resistant sub-populations.

36. Risks • We do not know the whole story • Antibiotic usage has reduced considerably over the past decade owing to the advent of effective vaccines, especially for Furunculosis • Sensibly used, antibiotics are probably not a major risk to the environment

37. Metals from feeds • Concentrations in feeds range from 3.5 to 25 mg Cu kg-1 and 68 to 240 mg Zn kg-1. • The estimated dietary requirements of Atlantic salmon for these elements are 5 to 10 mg Cu kg-1, and 37 to 67 mg Zn kg-1. Therefore, it would appear that the metal concentrations in some feeds are unnecessarily high as they exceed salmon dietary requirements.

38. Metals in antifoulants • Formerly tributyl tin was used, very toxic to invertebrates, now banned. • Most antifoulants are now copper based. • Copper can accumulate in very high concentrations in sediments below cages • Copper is probably released into the water-column but we do not yet have a budget • Ecological effects not well understood

39. Copper mg/ kg Probably Adverse mg/ kg Potentially Problematic mg/ kg Possibly Adverse mg/ kg Background SEPA Sediment Quality Criteria for Copper Dec 2000

40. Depth Profile Copper Actual AZE Limits mg/kg Probably Adverse Action level inside AZE mg/kg Potential Problem Action level inside AZE mg/kg Possibly Adverse Action level outside AZE mg/ kg Background SEPA AZE (Allowable Zone of Effects) 25 m. Area in which some damage to environment is allowed: a mixing zone approach.

41. Disease and parasite transfer • Gyrodactylus salaris • Infectious salmonid anaemia (ISA) • Infectious Pancreatic Necrosis (IPN) • Sea lice

42. Gyrodactylus salaris • Parasite transferred from resistant Baltic salmon populations to Norwegian populations lacking resistance as a result of movements of farmed fish in the mid-1970s. Extinction of many wild populations. • Aquaculture and anglers may be possible vectors

43. Infectious salmonid anaemia (ISA) • Major outbreak in 1998-9 on west coast • Many farms compulsory slaughter • Transfer to wild populations has been reported • No real indications of effects on wild populations • New codes of practice to minimise future impact

44. Infectious Pancreatic Necrosis (IPN) • IPN is widespread in many farming areas and it appears that it can be passed to wild stocks. However, very few samples have been analysed from wild populations and further monitoring is required to determine the degree to which transfer is occurring and whether it has significance for wild populations.

45. The decline of wild salmonid populations Declared wild salmon rod catch from the East, Moray, North East and North Statistical Regions, 1970-2000. Dashed lines represent average catches for 1970-1979 and 1991-2000. (Scottish Executive data).

46. Scottish marine salmon farm production and the combined declared wild salmon rod catch for the North West and West Coast Statistical Regions, 1970-2000 Butler, J.R.A. & Watt, J. (in press). Assessing and Managing the impacts of marine salmon farms on wild salmon in western Scotland: identifying priority rivers for conservation. Proc. 6th Int. Atlantic Salmon Symp., 'Salmon at the Edge', Edinburgh, UK, July 2002.

49. Sea lice • Sea lice can be transferred from farmed to wild stocks. • Sea trout smolts can be infected with very large numbers (<10 fatal?) • Sea trout most at risk because of their coastal lifestyle • Sea trout extinct or under threat in many west coast systems

50. Lice on a sea trout smolt