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Salmon Farming in Scotland: the key environmental issues Kenny Black Scottish Association for Marine Science Oban Dunstaffnage Marine Laboratory 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 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 Summary • The contribution of salmon farming to Scotland • The key environmental effects of salmon farming, risks and strategies 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 Atlantic Salmon Production in Scotland, tonnes 180,000 160,000 140,000 120,000 100,000 80,000 60,000 40,000 20,000 60% production from 11% farms > 1000 t 2001 2000 1999 1998 1997 1996 1995 1994 1993 1992 1991 1990 1989 1988 1987 1986 1985 1984 0 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%. 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. Salmon Farming Wild fish 17% protein, 7-10% oil, 75% water 2.8 kg for protein Soluble wastes N 46g P 4.9g C 323g + 0.8 - 2.3 kg extra for oil Fish Feed 40% Protein 30% oil 9% water 1200g: N 96g P 18g C 660g Particulate wastes N 22g P 9.5g C 185g Harvest Fish 1 kg N 26g P 3.2g C 139g Mortalities and escapes N 1.9g P 0.4g C 13g 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 Waste food and faeces settle on the sea bed: distribution depends on current regime and stratification 0 Current Velocity Source Fine Coarse Medium Effects on Sea bed 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. 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. Pseudonitzschia sp. Diatom Amnesiac Shellfish Poisoning Domoic Acid Wide ranging scallop closures 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. 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. 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. • 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. 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. 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. Medicines and chemicals • • • • Antiparasitics (sea lice) Antibiotics Metals (Antifoulants and feed) Disinfectants 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. • 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. Nauplius stage L. salmonis Female C. elongatus Adult male L. salmonis Sea lice life cycle • 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. •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. Lice treatments • Bath – Hydrogen peroxide – Cypermethrin – Azamethiphos • In-feed - Ivermectin - Emamectin benzoate - Teflubenzuron • Cost – all medicines are very expensive 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 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 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. Antibiotics • Oxytetracycline, oxolinic acid, trimethoprim, sulphadiazine and amoxycillin • Aquaculture is one of the least medicated livestock industries: antibiotics are not used prophylactically 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 subpopulations. 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 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. 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 watercolumn but we do not yet have a budget • Ecological effects not well understood Copper 56.164 SEPA Sediment Quality N 56.163 270 mg/ kg Probably Adverse 56.162 108 mg/ kg Potentially Problematic 35 mg/ kg Possibly Adverse 56.161 Longitude (decimal degrees) -5.524 -5.525 -5.526 -5.527 -5.528 56.160 -5.529 16 mg/ kg Background -5.530 Latitude (decimal degrees) Criteria for Copper Dec 2000 Depth Profile Copper Actual AZE Limits SEPA Sediment Quality Criteria for Copper -0.5 -1.5 270 mg/kg Probably Adverse Action level inside AZE -2.5 Depth (cm) -3.5 -4.5 108 mg/kg Potential Problem Action level inside AZE -5.5 -6.5 35 mg/kg Possibly Adverse -7.5 Action level outside AZE -8.5 -9.5 -150 -125 -100 -75 -50 -25 0 25 50 75 100 125 150 16 mg/ kg Background Distance from farm (m) in the residual current direction SEPA AZE (Allowable Zone of Effects) 25 m. Area in which some damage to environment is allowed: a mixing zone approach. Disease and parasite transfer • • • • Gyrodactylus salaris Infectious salmonid anaemia (ISA) Infectious Pancreatic Necrosis (IPN) Sea lice 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 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 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. The decline of wild salmonid populations 80000 75000 (b) 70000 Rod catch 65000 60000 55000 50000 45000 40000 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 35000 YEAR Declared wild salmon rod catch from the East, Moray, North East and North Statistical Regions, 1970-2000. Dashed lines represent average catches for 19701979 and 1991-2000. (Scottish Executive data). 140 (a) 8000 120 Rod catch 7000 100 6000 80 5000 60 4000 40 3000 20 1000 0 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2000 Farm production (x 1000 tonnes) 9000 YEAR 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. 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 COUNT YEAR 2000 1997 1994 1991 1988 1985 1982 1979 1976 1973 1970 1967 5 YEAR AVG. 1964 COUNT Annual Totals of Migratory Fish Counted at the Awe Barrage (1964-2001) Fyne District Salmon Fishery Board Rod Catch Records (1977-99) 1200 Escapees 1000 Salmon/Grilse 800 600 400 200 YEAR 1999 1997 1995 1993 1991 1989 1987 1985 1983 1981 1979 0 1977 ROD CATCH Sea Trout 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 Lice on a sea trout smolt Lousy salmon smolt caught in the open ocean Left untreated, lice can kill farmed and wild fish Mean Lice Burdens (at Life Stage) of Sea Trout Dunstaffnage Bay 2002 16 Ovigerous Females Mean Lice Burden 14 Pre & Adult 12 Chalimus 10 8 6 4 2 0 15th May 23rd May 11th June Sample Date 20th June Sea Lice • Salmon smolts can be infected with large numbers of sea lice on route to the ocean • > 86 % of the wild postsmolts migrating out of the Sognefjord and 48.5 % - 81.5 % from the Nordfjord were killed by sea lice during the spring of 1999 • Many west coast rivers show declining returns of salmon • Absolute proof is lacking but many scientists consider that lice from farms are at least part of the problem facing wild populations River Awe Salmon Strategies • Regular monitoring of lice numbers • Co-ordinated chemical treatments between farms sharing the same water body • Single generation sites • Fallowing of management areas to break lice cycles • Treatment of lice in the spring when lice numbers are low Area Management Agreements • Fish farmers and wild fish interests • The establishment of trusting relationships! • A welcome start • But seriously hampered in many cases by confidentially of information regarding lice numbers on farms etc. Future • Although lice are now easier to control with better medicines, models indicate that continued increases in production will result in a continued threat. • Relocation of farms away from “important” rivers. • How far away? • Vaccine – a long way off. Escapes • Farmed fish escape and can interbreed with wild populations thus diluting local adaptations with potential impact on fitness of progeny • Farmed fish are often found and caught in rivers Farmed escapes can overwhelm wild population • If 1% of the farmed population escapes each year then, for the west coast of Scotland only, that will amount to over 200,000 fish (in 2000) • Total wild catch for the west coast was 8459 in 2000. Probably relates to about 60,000 returning fish • Recorded escapes in 2000, approx 200,000 • Not known how many actually successfully enter rivers and breed Escapes - conclusion • Even though farmed fish may be reproductively inferior, severe genetic dilution is possible especially where escapes are frequent and large, and local populations are small. Solutions? • Better containment • Genetic modification to induce sterility (e.g. triploidy – although there are problems) • Better methods of tagging fish (some good cheap methods are now available) • Better understanding of fitness consequences (recent work by Ferguson) Feed supplies • Salmon feed is largely fish meal and fish oil sourced from small, oily fish caught in the great industrial fisheries of the world, e.g. N. Europe, South America. • World capture fishery production has plateaued (against a background of increasing fishing effort) at around 86 94 Mt of which 23 - 33 Mt are used annually for the production of fish meal and oil . • Are these fisheries sustainable? Few fisheries are! • Discards = 27Mt How do we fill the gap? • Increased substitution of vegetable oils and meals – much research is underway particularly regarding omega-3 fatty acid requirements (EPA, DHA) and also on amino acids in plant meals • More efficient use of processed wastes and discards Key conclusions • The supply of nutrients to the marine environment is unlikely to be the factor that limits the scale of fish farm production in the foreseeable future. • More likely to limit production are the linked issues of medicine usage and sea lice transfer to wild populations. • The rate of escapes of farmed salmon is probably unsustainable and represents a major threat to wild populations. • Changes in fishmeal supply may affect the sustainability of the industry in the shortterm but substitutes for fish meal/oil are actively being developed to fill the medium-term gap in supply. But feed supply will become a crucial issue! Aquaculture Strategy • A crucial need is for the development of truly Integrated Coastal Zone Management where transparent cost-benefit analyses can help to reassure ALL resource users that the best possible use use is made of our invaluable marine resource. • Aquaculture must be nested into such a system at the basin scale level and not treated in isolation. Thanks to Alan Kettle-White, Kate Willis, James Butler and Jens Christian Holst for use of images and data. Thanks to the British Council and Dror Angel And thanks to you for your attention http://www.scotland.gov.uk/cru/kd01/green/reia00.asp