The project ECONET is the result of a joint effort of the Institute of Marine Biological Resources (IMBR), University of Crete (UoC), DIOPAS SA and NAYS Ltd to meet the market demand for innovative products that could help the fishing industry to apply large scale fish protection programs using inexpensive materials.

1. Fish Fry Recruiting Devices
(HCMR)

2. 1 – Massive production & Dispersion (R Strategy)
2 – Survival is dependent on random factors
3 – Facing the jungle of predators
The survival probability of an individual
to reach adulthood is minimal
(± 2 /106)
Development Strategy of Fish

3. Life cycle of fish
Benthic– Νectobanthic phase
1 - 3 Years
Reproduction
Pelagic Phase
1 - 3 months
Adults
Eggs
Larvae
Establishment
Metalarvae
Young individuals
Fry
Dispersion
Development
Life Cycle

4. Numeric Balance
10 1 Adults
10 6 Eggs
10 5 Larvae
10 4 Metalarvae
10 2 Young individuals
10 3 Fry
Population dynamics
(Αριθμός ατόμων)
Actual Survival
1 pair/ 10 5 - 10 7 ancestors
Reproductive dynamics

5. Development by weight
10-1 +1
10-6 -7
10-6 -5
10-5 -4
10-2-1
10-4-3
Development
(Kg)
Multiplier: 106 - 107
Development of fish (weight)
From: 0.1-1 mg it reaches: 0,1-100 kg

6. Intervention and Regulation Features
Nectobenthic phase
-Control of fishing pressure & Protection
- Very important role playν:
- Selectivity of fishing gears
- Large ability for intervention
Sustainable fisheries & protection techniques
Pelagic Phase
- Control of zooplankton feeders
(95-99% loss in the first 2 months
- Very important role play:
- Detection & Size
- Minimal ability for intervention
(Introduction of metalarvae to the habitat)
Settlement
- Control of trophic chain
(80 - 90% loss from predation)
- Very important role play:
- Recruitment zones and environment
- Minimal ability for intervention
Eggs
Prelarvae
Larvae
Metalarvae
Fry
Young ind.
Adults
Preadults
1
103
102
10
105
104
106
Population
Reproduction
( Re-introduction
105 - 107 eggs
/ kg per pair)
0 321 Years

7. Spatial representation of fish life cycle
0 – Reproduction
Eggs
Prelarvae
Metalarvae
1 – Pelagic dispersion
(currents) Young
individuals
Adults
Larvae
2 – Coastal
settlement
Fry
Pre-adults
3 – Nectobenthic
settlement
Depth
0 -100m
=> Period of massive dispersion
(difficult to intervene)
=> Large number of fish with gregarious behavior
(easy to collect them)
=> Area of controlled fishing activity
Zone of intensive fishing activity

8. Environmental characteristics of
Infant fish
- Main areas of infant/larval development (seeking feed)
- Coastal areas: Sandy or muddy depth (plenty of organic material)
- Depth areas up to 50 m (photosynthetic activity)
- Upwelling areas (nutrient recycling -primary production)
Areas of easy access to trawlers if no protection exist
- Other infant growth areas (foraging & protection)
- Posidonia sea grass beds
- Coral reefs
- Small reefs and rocky areas

9. Fish fry protection devices
A novel way to utilize the high fish reproduction potential
Development of the food chain
(Stabilizing the concentration)
Creation of protection zones
and habitats
(Minimization of predation)
Benthic phase
1 - 3 years
Reproduction
Pelagic Phase
1-3 months
Adults
Eggs
Larvae
Settlement
Metalarvae
Young
individuals
Fry
Dispersion
Ανάπτυξη
Life cycle
Creation of selected fish
concentration zones
(Massive concentration)
Creation of proper equipment
for fish protection
for safe installation
Protection from fisheries
Development of technologies
for early life stage
(Food, Habitats)
Intervention
Period

10. Recruitment and fry protection
Eggs
Larvae
Fry
Settlement
Coastal zone
Area of device installation
Adults

11. Recruitment and fry protection
Eggs
Larvae
Fry
Settlement
Coastal zone
Area of device installation
Adults
Intervention with the creation of
habitats for protection from predators

12. Various types of artificial reefs

13. Other types of artificial reefs

14. Small concrete artificial reefs

15. The alternative solution
Fish Fry Protecting Devices
3 Dimensional labyrinthsAlgal formations Permeable cage nets

16. Prism protection cages

17. Tree-like 3-dimensional
Escape structures

18. Testing procedure

19. Installation

20. Epifauna growth

21. Fish attraction

22. Advantages- Disadvantages
Advantages:
-Provision of effective protection against natural predation
- Low installation and maintenance costs
- Possibility of constructing large-scale plants
- Ability to remove the plant
- Equivalent effect compared to more expensive permanent facilities
- They are not fishing gears and do not create conflict
to commercial fisheries
- Contribution to the sustainable management of marine biological
species richness
Disadvantages:
-Require legal actions to protect them from fishing activities (trawlers)
- Require possibly physical protection against unauthorized activity
of towed gears
- Short shelf life compared to fixed permanent installations
- They can’t be applied to all fish. But they are covering the main
commercial fish species.