This document discusses the environmental impacts of aquaculture cage farms and how to manage them sustainably through aquaculture parks. Key points: - Less than 30% of nutrients from fish feed are retained by fish, with the remainder released into the environment, impacting sediments and water quality. - Unsustainable nutrient levels can lead to thick organic layers smothering habitats, algal blooms with low oxygen causing fish kills. - Data is presented on two mariculture parks showing higher biomass and impacts at one site. - Environmental monitoring and modeling of impacts is needed to optimize farming practices and prevent cumulative damage within parks and their zones of effect.

1. Planning and management of
aquaculture parks for sustainable
development of cage farms in the
Philippines
Regino R. Regpala
Environmental impact
www.aqua-park.asia

2. Nutrient balance

3. Inputs, uptake and outputs
Less than30 % of inputs are retained by the
fish. The remainder go into the environment

4. Impact on the sediments
• Sustainable levels – slight build up of
organic layer on the seabed
• Unsustainable level - Build up of thick
organic layer on the sea bed
• Smothering of seagrass
• Smothering of corals
AquaPark Mid-term meeting - interim results

5. Phosphorus plume from fish cages

6. Impact on water column
• Increasing nutrient concentration in the
water
• Sustainable levels lead to algae
production – zooplankton production –
increased wild fishery production
• Unsustainable levels leads to high algae
production – algal bloom – algae die off –
low/no oxygen – fish kill
AquaPark Mid-term meeting - interim results

7. Comparison of impacts
Mariculture
Park
Biomass
(mT)
Cage
size
(m3)
Stocking
(pcs)
Survival
rate (%)
Culture
period
(mos.)
Feeding
ratio (%)
Monthly
growth
rate (%)
FCR
Ignition
Loss
550oC
(%)
pH
Dark
layer
(cm)
Panabo
3.28
400
15,000
96.9
4.3
4.09
228.2
2.17
7.82
7.8
10.8
Sual
43.9
2,544
108,000
81.3
9
1.71
77.8
2.3
9.94
7.8
15.09

8. Environmental survey - Sual

9. Natural sediment
Heavily impacted sediment

10. Corer 800 m from cage no black layer

11. Corer 500 m from cage 5 cm black layer

12. Corer 87 m from cage 13 cm black layer

13. Corer at cage 20 cm black layer

14. Modelling environmental impact
3 important aspects:
1.How severe is the impact – what is the maximum impact underneath cages?
2.How far to the boundary of the impact? (Allowable Zone of Effect)
3.How can husbandry practices be optimised to use the zone most
productively?
Objectives
Predict if impact is SEVERE underneath cages
as shown by this deposition footprint
Zone colour
Predict distance to boundary of MODERATE impact
Zone colour
Edge of Park

15. Environmental impact
Limited local Impact
Cumulative impact

16. Cumulative impact
• Increasing disease problems
• Lower survival
• Poor food conversion rate
Often blame
• Poor fry quality
• Poor food quality
But the problem is usually high
environmental impact
WAS Istanbul - Competing Claims

17. Monitoring
Monitoring of the MP is necessary
• To check the level of impact on the
environment
• Check if the impact is getting worse,
staying the same or getting better
• Early warning of future problems
• Oil spill contingency plan
WAS Istanbul - Competing Claims