Transcript Salmon Farming and the Environment: A Scottish perspective

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