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Fish Fry Recruiting Devices


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 ectobanthic phase1 - 3 YearsReproductionPelagic Phase1 - 3 monthsAdultsEggsLarvaeEstablishmentMetalarvaeYoung individualsFryDispersionDevelopmentLife Cycle

Numeric Balance

10 1 Adults10 6 Eggs10 5 Larvae10 4 Metalarvae10 2 Young individuals10 3 FryPopulation dynamics( )Actual Survival1 pair/ 10 5 - 10 7 ancestorsReproductive dynamics

Development by weight

10 -1 +110 -6 -710 -6 -510 -5 -410 -2 -110 -4 -3Development(Kg) Multiplier: 10 6 - 10 7 Development of fish (weight) From: 0.1-1 mg it reaches: 0,1-100 kg

Intervention and Regulation FeaturesNectobenthic phaseControl of fishing pressure & Protection Very important role play: Selectivity of fishing gears - Large ability for intervention Sustainable fisheries & protection techniquesPelagic 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

EggsPrelarvaeLarvaeMetalarvaeFryYoung ind.AdultsPreadults


PopulationReproduction( Re-introduction 105 - 107 eggs / kg per pair)



Spatial representation of fish life cycle

0 ReproductionEggsPrelarvaeMetalarvae1 Pelagic dispersion(currents)

Young individualsAdultsLarvae

2 CoastalsettlementFryPre-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 activityZone 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 grassbeds- 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 yearsReproductionPelagic Phase1-3 monthsAdultsEggsLarvaeSettlementMetalarvaeYoung individualsFryDispersionLife cycleCreation of selected fish concentration zones (Massive concentration)Creation of proper equipmentfor fish protectionfor safe installationProtection from fisheriesDevelopment of technologiesfor early life stage(Food, Habitats)

Intervention Period

Recruitment and fry protection


Fry SettlementCoastal zoneArea of device installation


Recruitment and fry protection


Fry SettlementCoastal zoneArea of device installation


Various types of artificial reefs

Other types of artificial reefs

Small concrete artificial reefs


The alternative solutionFish Fry Protecting Devices 3 Dimensional labyrinthsAlgal formationsPermeable cage nets

Prism protection cages

Tree-like 3-dimensional Escape structures

Testing procedure


Epifauna growth

Fish attraction

Advantages- DisadvantagesAdvantages: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 cant be applied to all fish. But they are covering the main commercial fish species.