workshop on environmental licenses for aquaculture ......(integrated multi-trophic aquaculture) a...
TRANSCRIPT
Experiences of compensatory measures
Workshop on environmental licenses for aquaculture
Stockholm, 12.-13.11.2019
Pia Kupka HansenInstitute of Marine Research, Norway
EFFLUENTS FROM AQUACULTURE
The amounts and quality of effluents and the potential environmental impacts of
aquaculture varies with:
• Species
• Production system
• Production intensity
• Management
• Location
• Environmental carrying capacity to absorb impacts
Nutrients and organic waste (feaces and excess feed)
In landbased and closed systems waste streams can be directed and waste collected.
In open net cage systems everything is lead into the surrounding environment.
There are various types of closed systems where the effluents can be
collected and used:
• As feed for other species – collection of the organic waste to be
used to feed f.ex. polychaetes in tanks
• Production of fertilizers
• Biogas production
Compensatory measures for nutrients and organic waste from open net pen fish farming:
• IMTA - no collection of waste, it is used directly as it is released into the water. Very
dependent on location and current system.
• Polyculture/production of other species
• Collection of waste (feaces and excess feed)
Jansen et al. 2018)
Organic waste(feaces and excess feed)
Nutrients(N and P)
Local Intermediate Regional
impact zone impact zone impact zone
Current and impact zones from net pen fish farming
Nutrients
Faeces
Excess feed
Sedimentation of Sedimentation of Dissolved substances
larger particles smaller particles
The importance of current at
different depths:
Supply of oxygen and removal
of soluble waste products
Dispersion of particles
Oxygen to the sediment
Percentage increase in plant plankton production with a fish production of 1,3 mill. tonnes/year, 2 mill. tonnes/year, 3 mill. tonnes/year, 4mill. tonnes/year, 5 mill. tonnes/year and 6 mill. tonnes/year.
RISK ASSESSMENT OF NORWEGIAN FISH FARMING 2016
Outer fjord Inner fjord
6 – 17 times higher deposition of organic carbon at inner-fjord location
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Dispersion current and sedimentation at two sites in a fjord
Greater dispersal: Lower localised benthic impact
Lower dispersal: Greater localised benthic impact
Bannister et al. 2012, Valdemarsen et al. 2014
Bannister et al. 2016.
A.Sinking velocity distribution of faeces from 1.5 kg salmon.B. Dispersion of organic material from a fish farm
RISK ASSESSMENT OF NORWEGIAN FISH FARMING 2016
Farming pressure
Water body types (EU Water Framework Directive)
RISK ASSESSMENT OF NORWEGIAN FISH FARMING 2016
Kart og Plan i Blå sektor - Nordland 9. -11. januar 2018 28
The municipalities makes spacial plans and allocates areas to various activties
IMTA(Integrated Multi-
Trophic Aquaculture)
A concept where different
species are grown
together in such a way
that the invertebrates
and/or plants can recycle
the nutrients and organic
material that are lost from
the culture of the other
species.
DFO Canada
Experiences with IMTA:
• Macroalgae
• Blue mussels
• (Polychaetes)
Consensus that the main focus in
IMTA should be on the larger
particles that settle under the net
pens (Strand et al, 2019)
Benthic organisms are most likely to
benefit (e.g. sea cucumber, sea
urchins, polychaetes)DFO Canada
“Salmonid farming in Norway releases
considerable amounts of carbon, nitrogen
and phosphorus. Maintaining a
sustainable resource economy, reducing
pollution and climate change are good
reasons for efficient reuse of these
emissions, preferably for food production,
with the lowest possible negative impact.
Integrated multi-trophic aquaculture
(IMTA) is regarded as a possible solution,
but it must be biologically, technically and
commercially viable.”
Directorate of Fisheries, Norway, 2019.
Trial with polychaetes
We know from earlier studies that certain polychaetes
(Ophryotroca spp) can be found in large numbers under and
around fish farms overlaying hard bottom where there are
low currents (densities up to 100.000 indiv /m2)
The polychaetes produce mucus which makes it possible for
them to stay on the bedrock
The polychaetes consume large parts of the organic waste
on the bottom
The polychaetes disappear when the organic waste is
consumed (during fallowing)
The polychaetes come back when the fish production starts
up again
(Hansen and Bannister 2011; Eike 2013 (Master thesis))
Fish farm
Reference station
The polychaetes had a higher content (>30%) of PUFA
than the fish feaces (5-9%)
The polychaetes had an amino acid profile that meets
requirements for fish feed
The polychaetes had a 77% uptake efficiency of organic
waste
112 g polychaetes can decompose an input of
1gC/m2/day
Brennan 2018 (Master thesis); Jansen et al. 2019; Nederlof et al. 2019
Results
Polychaetes (Ophryotroca spp) aggregates in large
numbers within a week on trays placed under net
cages where the organic waste accumulates
Polyculture in Sanggou Bay (China)
Longline seaweed and bivalve culture in SG Bay
• Area of SG Bay 133.3km2,
average depth 8m
• Seaweed culture long history,
mainly kelp Laminaria japonica.
• 20+ aquaculture farms in bay,
diverse culture type: longlines,
lantern nets & net cages
• Annual mariculture production:
• Kelp: 80,000 t dry weight
• Abalone Haliotis discus 2,000 t
fresh weight with shell
• Oyster Crassostrea gigas
120,000 t fresh weight+shell
• Scallop Chlamys farreri 10,000 t
fresh weight + shell
• Finfish: 100 t
• Sea cucumber Apostichopus
japonicus 100 t fresh weight
Photo: Erik Røed
Thank you