econet project
TRANSCRIPT
Fish Fry Recruiting Devices(HCMR)
1 – Massive production & Dispersion (R Strategy) 2 – Survival is dependent on random factors
3 – Facing the jungle of predators
The survival probability of an individualto reach adulthood is minimal
(± 2 /106)
Development Strategy of Fish
Life cycle of fish
Benthic– Νectobanthic phase1 - 3 Years
Reproduction
Pelagic Phase1 - 3 months
Adults
EggsLarvae
Establishment
Metalarvae
Young individualsFry
Dispersion
Development
Life Cycle
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 Survival1 pair/ 10 5 - 10 7 ancestors
Reproductive dynamics
Development by weight
10 -1 +1
10 -6 -7
10 -6 -5
10 -5 -4
10 -2 -1
10 -4 -3
Development(Kg)
Multiplier: 10 6 - 10
7
Development of fish (weight) From: 0.1-1 mg it reaches: 0,1-100 kg
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.
AdultsPreadults
1
103
102
10
105
104
106
Population
Reproduction( Re-introduction
105 - 107 eggs / kg per pair)
0 321 Years
Spatial representation of fish life cycle
0 – Reproduction
Eggs
PrelarvaeMetalarvae
1 – Pelagic dispersion(currents) Young
individuals
Adults
Larvae
2 – Coastalsettlement
Fry
Pre-adults 3 – Nectobenthicsettlement
Depth0 -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
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
Fish fry protection devicesA novel way to utilize the high fish reproduction potential
Development of the food chain(Stabilizing the concentration)
Creation of protection zonesand habitats
(Minimization of predation)
Benthic phase1 - 3 years
Reproduction
Pelagic Phase1-3 months
Adults
EggsLarvae
Settlement
Metalarvae
Young individuals
Fry
Dispersion
Ανάπτυξη
Life cycle
Creation of selected fish concentration zones
(Massive concentration)
Creation of proper equipmentfor fish protection
for safe installation
Protection from fisheries
Development of technologiesfor early life stage(Food, Habitats)
Intervention Period
Recruitment and fry protectionEggs
Larvae
Fry Settlement
Coastal zoneArea of device installation
Adults
Recruitment and fry protectionEggs
Larvae
Fry Settlement
Coastal zoneArea of device installation
Adults
Intervention with the creation of habitats for protection from predators
Various types of artificial reefs
Other types of artificial reefs
Small concrete artificial reefs
The alternative solutionFish Fry Protecting Devices
3 Dimensional labyrinthsAlgal formations Permeable cage nets
Prism protection cages
Tree-like 3-dimensional Escape structures
Testing procedure
Installation
Epifauna growth
Fish attraction
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.