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

0

5

10

15

20

25

30

35

40

45

50

8. s

ep.

9. s

ep.

10

. sep

.1

1. s

ep.

12

. sep

.1

3. s

ep.

14

. sep

.1

5. s

ep.

16

. sep

.1

7. s

ep.

18

. sep

.1

9. s

ep.

20

. sep

.2

1. s

ep.

22

. sep

.2

3. s

ep.

24

. sep

.2

5. s

ep.

26

. sep

.2

7. s

ep.

28

. sep

.2

9. s

ep.

30

. sep

.

Cu

rre

nt

velo

city

(cm

s-1

)

0

1

2

3

4

5

6

7

8

9

16

. mar

.

17

. mar

.

18

. mar

.

19

. mar

.

20

. mar

.

21

. mar

.

22

. mar

.

23

. mar

.

24

. mar

.

25

. mar

.

26

. mar

.

27

. mar

.

28

. mar

.

29

. mar

.

30

. mar

.

31

. mar

.

1. a

pr.

2. a

pr.

3. a

pr.

4. a

pr.

5. a

pr.

6. a

pr.

7. a

pr.

Cu

rre

nt

velo

city

(cm

s-1

)

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