Hatchery Design and Infrastructure

Hatchery Design and Infrastructure

• Fish hatcheries facilitate artificial breeding, hatching, and rearing of finfish and shellfish during their early life stages.
• They produce larvae and juvenile fish, shellfish, and crustaceans to support the aquaculture industry, where they’re transferred to on-growing systems like fish farms to reach harvest size.
• Fish hatcheries are complex systems including units for seawater intake, water treatment and storage, broodstock holding, algal and rotifer culture, larval rearing, a laboratory, feed/chemical storage, waste water treatment, a workshop, and staff accommodation.
• Annual production target is a key consideration for hatchery size.
• Site selection must include:
• Road access
• Stable water quality and temperature
• Constant electricity
• Being away from waste disposal and flood areas
• Protection from cyclones
• Access to fresh water.
• During the hatchery design, consider:
• Locations for water pumping stations, aeration systems, and packing areas
• Bio-secure areas
• Water storage tank elevation to facilitate water flow throughout the hatchery, and separation of hatchery sections to prevent cross-contamination.
• Quarantine facility is important for broodstock treatment to prevent pathogens entering the hatchery, and should be suitably sized with seawater, freshwater, and aeration access.

Facilities and Tanks

• Broodstock holding facilitates adequate stocks of parent fish for quality fertilized eggs.
• Spawning tanks should be in quiet areas to reduce broodstock disturbance, and made of concrete with smooth surfaces for easy cleaning.
• Live feed culture facilitates phytoplankton and zooplankton stock culture and enrichment.
• Each unit has to be housed as separate bio secured area to avoid cross contamination
• Larval tanks require careful design to protect fish larvae from diseases. They can be made of FRP or concrete materials and should be rectangular with epoxy painting.
• Considerations for larval tanks:
• Larval visibility
• Easy cleaning
• Absence of dead zones
• Optimized aeration, cost-effectiveness, and space utilization
• Simplified support systems (water circulation, air/power supply, illumination)
• Minimal manpower needs
• Smaller tanks to better protect against disease.
• Nursery rearing units hold fish larvae until they are ready to eat inert larval diets

Ancillary Units

• Pumping stations and air blower rooms must have pump sizes and capacities calculated according to water requirements.
• Seawater filtration and water storage requires the sea water to be pumped and filtered before storage to avoid unwanted pathogens.
• Electrical generator rooms must have generators installed in a sound proof area, with the capacity to support the hatchery, pumps and blowers.
• Workshop and storage rooms should be full-fledged for maintenance activities, with dedicated storage for aeration, water pipes, and other utilities.
• Fish feed stores should have air conditioning unit to store larval feeds, inert diets and health management chemicals.
• Laboratory rooms should be close to the relevant units and house necessary equipment
• Office and seed packing areas should be at the entrance to avoid visitors entering production facilities.

Natural Food Production

• Phytoplankton forms the base of marine food chains and are used commercially to rear marine animals.
• Micro-algae produce zooplankton mass quantities which serve as food for crustaceans and fish.
• There are over forty species that are cultured as pure strains under intensive systems.
• Important algal species:
• Skeletonema costatum
• Thalassiosira pseudonana
• Chaetoceros gracilis
• Chaetoceros calcitrans
• Isochrysis galbana
• Tetraselmis suecica
• Monochrysis lutheri
• Chlorella spp

Algal Production

• Key parameters for algal growth include nutrient quantity, quality, light, pH, turbulence, salinity, and temperature.
• Optimal conditions vary by species and may be interdependent.
• Macronutrients like nitrate, phosphate (6:1 ratio), and silicate are critical, as cell concentrations in cultures are generally higher than in nature.
• Light helps converts inorganic carbon for algae to use as organic matter.
• the pH range for most cultured algal species is between 7 and 9, with the optimum range being 8.2-8.7.
• Mixing helps prevent algae sedimentation, ensure nutrient exposure, avoid thermal stratification and improve gas exchange.
• Optimal temperature for phytoplankton cultures is generally between 20-24°C.
• Salinity changes that is slightly lower than the natural habitat is best for algae growth, optimal being 20-24.

Growth Phases

• Algal culture growth includes:
• Lag or induction phase
• Exponential phase
• Declining growth rate phase
• Stationary phase
• Death or "crash" phase.
• Batch culture involves a single inoculation followed by growing and harvesting after several days.
• Continuous culture involves continuous fertilized seawater pumped into a growth chamber, with excess culture washed out to maintain maximum growth.
• A semi-continuous technique prolongs tank cultures by partial harvesting periodically, topping up to the original volume, and nutrients.
• Algal nutritional value is dependent on cell size, digestibility, production of toxic compounds, and biochemical composition; algae can also be a rich source of ascorbic acid.

Microalgae in Fish Hatcheries

• Nannochloropsis, high in essential fatty acids, which is an ideal feed to rotifers and fish larva
• Isochrysis, rich in DHA
• Chaetoceros, with high silica content.
• Tetraselmis, with high chlorophyll and carotenoids that boosts boosts larva immunity.

Rotifers

• Brachionus plicatilis can be live food for fish larva.
• Rotifera are the smallest metazoa, with 90% inhabiting freshwater habitats.
• Rotifer lifespan can be 3.4 to 4.4 days at 25°C.
• Brachionus plicatilis life cycles can be closed two ways: via amictic females that produce amictic (diploid eggs), or under specific environmental conditions, producing mictic and amictic females with different chromosome counts.
• Brachionus rotundiformis (S-type) and Brachionus plicatilis (L-type) are aquaculture morphotypes with different lorica lengths; S-types have pointed spines, while L-types have obtuse angled spines.
• Intensive rotifer production typically occurs in batch culture indoors.

Artemia

• Artemia nauplii are widely used food in larviculture
• Artemia can form dormant embryos called cysts, accounting for its designation as a suitable larval food source.
• Artemia cysts hydrate in seawater to resume metabolism, hatch, and release free-swimming nauplii
• The first larval stage (instar I) has three pairs of appendages for sensorial function, filter-feeding, and food uptake.
• Nauplii concentration can be improved via phototaxis by focusing light on the conical bottom of the hatching tank.

Tilapia

• Worldwide harvest of Tilapia is over 800,000 metric tons
• Nile tilapia was one of the first fish species cultured,
• Most commercially valuable Tilapia is available in brackish water ponds, freshwater tanks, ponds, and cages.
• Common cultured Tilapia species include:
• Nile tilapia (Oreochromis niloticus)
• Mozambique or 'Java' tilapia (Oreochromis mossambicus)
• Red tilapias (Oreochromis spp.)
• Blue tilapia (Oreochromis aureus)
• Black chinned or Blackchin tilapia (Sarotherodon melanotheron)
• Breeding tilapia requires considering physical and genetic characteristics.
• Male tilapia can be distinguished from females through its secondary sex characteristics
• Good water quality should be maintained by changing the rearing water once a week or when deemed necessary.

Open Pond Method - Tilapia

• Breeders are stocked into the ponds and allowed to spawn naturally at controlled interval.
• With fingerling collection method, a pond acts as both spawning and rearing

Fry Collection Method - Tilapia

• Fry collection starts on the 10th day after stocking
• Fry is collected until 21st, before being reared into fingerling size tilapia.
• A hapa (net enclosure) may be used for rearing and can be used for fingerling production.
• A commercial/formulated diet at 3-5% should be provided as the total body weight per day.
• Fish can also be spawned in concrete tanks with dissolved oxygen, while maintaining good water parameters

Milkfish

• Selecting milkfish broodstock requires fish to be strong and healthy to ensure a good harvest.
• Farmers look for mature fish, approximately 5-7 years, weighing around 5-6 kilograms.
• Broodstock live in large seawater ponds (500-1000 m²) or circular concrete tanks (50-100 m³), with water temperature of 26-30°C, salinity between 28-35 ppt, and supplied with enough oxygen.
• Milkfish can be fed high-protein formulated feeds and natural food.
• To trigger spawning, hormone injections are used.
• Female milkfish are bigger and heavier than males, weighing 5-7 kg when mature.
• Males have pointed genital papilla, while females have swollen genital areas.
• Cannulation, ultrasound scanning, or biopsy/dissection can test milkfish to know their sex.

Milkfish Spawning

• Milkfish spawn mostly during April-September in warm tropical waters.
• They tend to spawn during full and new moons, and at night.
• Males become more active and nudge females prior to being external fertilized.
• Each female is able to release 1 to 5 million eggs in one event
• Eggs hatch in 24 hours to transparent larva of up to 3mm long.
• From days 1 to 3 they can be fed rotifers enriched with microalgae, and from day 4 to 10 they can be fed newly hatched brine shrimp and shift to commercial feed.
• In the wild milkfish is carried by ocean currents and migrate back after some months to continue their cycle
• Healthy eggs are round, clear, 1.1-1.2 mm. in diameter and can float, while unhealthy eggs are deformed and sink.
• Using clean water, clean disinfectants help prevent the spread of infections through the hatchery
• The eggs are placed at 28-30 degrees celcius with a salinity of 30-35 ppt for gentle aeration.
• After hatching, the Larvae is stored at a density of 100-150 larvae per liter.
• Regular check ups is performed to check regular health and administer carefull feeding.