This document discusses nutrient enrichment from aquaculture and ways to avoid it. It notes that uneaten fish feed and fish waste release nutrients like nitrogen and phosphorus into the environment. This can lead to problems like algal blooms and changes in wildlife populations. To prevent nutrient enrichment, the document recommends site selection away from other pollutant sources, controlling fish feed delivery, modifying fish feed nutrients, optimizing feeding practices, and endocrine manipulations to improve fish growth and feed conversion efficiency.

1. Aquaculture
Environment
k
FEED
NUTRIENT ENRICHMENT
UNEATEN
~5-20%
INGESTED
80-95%
BODY
13-23%
FECAL ~9-19%
URINARY
~40-60%

2. Aquaculture
Environment
k
NUTRIENT ENRICHMENT
0%
50%
100%
organic matter nitrogen phosphorus
Atmosphere/soil
Effluent
Fish

3. Aquaculture
Environment
k
1
10000
100000000
N P
Aquaculture
Agriculture
Industrial
Municipal
Aquaculture
Agriculture
Industrial
Municipal
Scottish
salmon
farms,
2000
Scottish
salmon
farms,
2000
41361
264
840
935
7500
35
14210
3468
908
1240
River
–
87,739
River
-
3040
Contributions of various sources to total N and P loading to Swedish seas, 1990
In 2000, contributions of Scotland’s salmon farms
represented the equivalent of 3.2 million and 9.4
million people for N and P respectively

4. Aquaculture
Environment
k
1
10
100
1000
10000
100000
1000000
beef
shrimp
trout
catfish
tilapia/carp
pork
cotton
steel
alcohol
petroleum
Water use m3/mt production

5. Aquaculture
Environment
k
Nutrient enrichment of the seabed ecosystem
Increased chemical oxygen demand
Increased microbial activity
Increased biological oxygen demand
Changes in macrofaunal populations
Production of H2S and methane
Self fouling and potential for mortalities
40+ meters from cages
NUTRIENT ENRICHMENT
CONSEQUENCES:

6. Aquaculture
Environment
k
NUTRIENT ENRICHMENT
CONSEQUENCES:
Nutrient enrichment of the water column
Hypernutrification
Eutrophication
Increased primary (phytoplankton) production
Changes in phytoplankton populations
(nutrient dependent – Si for diatoms, etc.)
Deoxygenation of water column, changes to fisheries
Increase in algal blooms, some toxic
Decreased primary production near shellfish beds

7. Aquaculture
Environment
k
AVOIDING NUTRIENT ENRICHMENT
Site selection
Examine other users of water source
Check for industrial/municipal outfalls
Evaluate agricultural run-off
Determine annual flow rates and flushing (sea)
Excavate appropriate water control systems
Employ natural (ecosystem) biofilters – wetlands, mangroves, etc.
Check natural occurrence of algal blooms

8. Aquaculture
Environment
k
AVOIDING NUTRIENT ENRICHMENT
tank
controller
assembly
transducer
assembly
effluent
feed
hopper
Control over feed delivery – tank-based system

9. Aquaculture
Environment
k
AVOIDING NUTRIENT ENRICHMENT
net pen
feeder
control unit
video or
acoustic detector
Control unit
feed
hopper
Control over feed delivery – net pen-based system

10. Aquaculture
Environment
k
AVOIDING NUTRIENT ENRICHMENT
Nutrient modifications
Mono-, di-, tri-, tetra- and
penta- myo-inositol phosphates
and inorganic phosphate
+ H2O
Phytase
(E.C. 3.1.3.8)
myo-inositol phosphate

11. Aquaculture
Environment
k
AVOIDING NUTRIENT ENRICHMENT
Feeding behavior and management
Feed farmed inventory following natural rhythmicity
Optimize feed pellet size
Ensure feed shape, color, contrast, texture, taste, etc. is optimal
Distribution of feed should be maximized to ensure total use
Sustained exercise
Compensatory growth

12. Aquaculture
Environment
k
AVOIDING NUTRIENT ENRICHMENT
Endocrine manipulations
hypothalamus
pituitary
Liver and other tissues
thyroid
Tissue growth
gonads
pancreas
Steroids (+)
T3/T4 (+)
Insulin (+)
SRIF (-)/GRF(+)
GH (+)
IGF-1 (+)
Increased appetite
Enhanced FCE
Improved seawater survival
Reduced lipid content
Accelerated growth