Hatchery Management of Major Cultivable Fin-Fishes

What is Hatchery Management?

• Hatchery management is a critical component of aquaculture that focuses on the controlled breeding and rearing of fish in captivity. It encompasses a range of practices designed to optimize fish production, particularly finfish, and is integral to sustainable fisheries and aquaculture operations. As the demand for fish continues to rise, hatchery management serves as a crucial strategy for enhancing fish stock availability.
• The process begins with understanding the natural breeding habitats of finfish, which are typically found in both riverine and brackish water environments. These habitats provide the necessary conditions for spawning and development of fish eggs. Effective hatchery management replicates these natural environments, ensuring that conditions such as water quality, temperature, and light are regulated to support healthy reproduction and growth.
• Key to hatchery management is the understanding of hydrological and hydro-biological factors that influence the breeding behavior of finfish. These factors include water flow, temperature, oxygen levels, and the presence of suitable substrates for spawning. Managers must monitor and manipulate these conditions to promote optimal breeding outcomes. For instance, variations in water temperature can induce different spawning responses in various fish species.
• In hatcheries, the breeding cycles of cultivable finfish species are meticulously observed. Managers pay particular attention to the sexual maturity and breeding seasons of the fish, which are vital for gamete development in both male and female fish. This knowledge allows hatchery operators to time breeding events accurately, maximizing the chances of successful fertilization and subsequent larval development.
• Induced breeding techniques are often employed to enhance the efficiency of hatchery operations. This involves the administration of hormones to stimulate spawning, thereby bypassing the natural breeding triggers that may not align with hatchery schedules. Environmental factors such as light intensity and photoperiod can also be manipulated to synchronize spawning, ensuring that large quantities of eggs are available for collection.
• The management of broodstock is another essential aspect of hatchery management. Broodstock refers to the selected adult fish that are used for breeding purposes. Effective management includes maintaining genetic diversity, optimizing nutrition, and ensuring the health of broodstock. This is crucial because the genetic quality of the broodstock directly impacts the health and viability of the offspring produced in the hatchery.
• Moreover, successful hatchery management requires continuous monitoring of larval development and post-hatch care. The early stages of fish development are critical, and hatchery managers must provide adequate nutrition and environmental conditions to promote survival and growth. This includes proper feeding protocols and water quality management, which are essential for the transition from larval to juvenile stages.

Hatchery Management of Indian Major Carp

Hatchery management plays a pivotal role in the aquaculture of Indian major carps (IMC), which are essential for food security and nutrition in India. This management process involves various systematic practices to ensure successful breeding, rearing, and incubation of carp species such as Catla (Catla catla), Rohu (Labeo rohita), and Mrigal (Cirrhinus mrigala).

1. Reproductive Biology
   • Indian major carps exhibit distinct sexual dimorphism. Males possess rough pectoral fins and a non-swollen genital aperture, while females have smooth fins with a swollen, reddish genital opening.
   • The age of sexual maturity varies by species, typically occurring in the second year.
   • The spawning season for these carps generally spans from June to September during the southwest monsoon.
   • Fecundity rates also differ among species, with Catla yielding approximately 150,000 to 200,000 eggs per kilogram of body weight, Rohu producing 340,000 to 380,000 eggs, and Mrigal yielding around 130,000 to 180,000 eggs.
2. Broodstock Management
   • Effective broodstock management is divided into brood raising and brood rearing.
   • Brood Raising: Healthy yearlings of the desired carp species are collected from natural or farmed sources. These fingerlings are quarantined for 2-3 months to prevent disease. The ideal pond size for raising broodstock is between 0.2 to 0.5 hectares with a water depth of 1.5 meters, stocking at a density of 1,500 kg per hectare.
   • Prior to stocking, ponds are cleared of aquatic weeds and predatory fish using bleaching powder and urea, followed by the addition of organic and inorganic fertilizers to promote plankton growth.
   • Brood Rearing: Two- to three-year-old fish, identified as potential breeders, are transferred to brood-rearing ponds. The ideal stocking density is maintained at 1,000 kg per hectare, ensuring that at least 60% of the broodstock consists of the primary species, with the remaining 40% divided among other species.
3. Induced Breeding
   • Induced breeding typically involves administering pituitary gland extract to females in two doses: an initial dose (4-7 ml/kg) and a final dose (10-12 ml/kg). Males receive a single dose during the final injection.
   • The timing between the two doses is crucial and varies based on species and environmental temperature, generally taking 5-6 hours for Indian major carps.
4. Spawning Techniques
   • Spawning can be conducted in specially designed breeding hapas, where one female is paired with two males. These hapas are constructed from fine mesh materials to allow for water circulation and prevent predation.
   • After the breeding pair is placed in the hapa, fertilized eggs are typically collected the following morning.
5. Incubation
   • Fertilized eggs are incubated in a hatching hapa, which consists of an inner and outer layer to optimize conditions. Essential requirements include an optimal temperature range of 28-30°C, a constant flow of water to remove metabolic waste, and a disturbance-free environment to enhance embryo development.
   • The incubation period lasts between 14 to 20 hours, after which hatchlings can be observed swimming around the sides and bottom of the hapa.

Hatchery Management of Common Carp

The management of hatcheries for common carp (Cyprinus carpio) is a complex yet essential aspect of aquaculture, especially given the species’ widespread cultivation and economic significance. Common carp are particularly valued due to their adaptability to varying environmental conditions, as well as their omnivorous feeding habits. This exposition outlines the fundamental practices involved in the hatchery management of common carp, emphasizing their biological characteristics, breeding protocols, and management strategies.

• Overview of Common Carp
  • Cyprinus carpio is a highly adaptable freshwater fish species, often cultivated in tropical and subtropical regions.
  • The species exhibits resilience to extreme environmental conditions, including low dissolved oxygen levels and a broad range of water temperatures.
  • Common carp are omnivores, consuming both animal-based (aquatic insects, zooplankton) and plant-based (phytoplankton, macrophytes) feed sources.
  • There are three primary varieties based on scale patterns:
    • Scale Carp (Cyprinus carpio Communis): Fully covered with regularly arranged scales.
    • Mirror Carp (Cyprinus carpio specularis): Unevenly covered with a few large scales, leaving large areas bare.
    • Leather Carp (Cyprinus carpio nudus): Completely devoid of scales, with a few degenerate scales along the dorsal fin.
• Reproductive Biology
  • Age and Size at Maturity: Common carp typically reach sexual maturity at approximately six months, regardless of size.
  • Sexual Dimorphism: Males possess rough pectoral fins and a deep, pit-like vent, while females have softer pectoral fins and a bulging belly.
  • Breeding Seasons: The primary breeding seasons occur from January to March and again from July to August.
  • Fecundity: The species has a fecundity rate of about 180,000 eggs per kilogram of body weight.
• Broodstock Management
  • Effective broodstock management involves selecting high-quality, sexually mature fish for breeding.
  • Mature males and females should be maintained separately in ponds, with stocking densities between 1,500 and 2,000 kg/ha.
  • A balanced diet, typically comprising rice bran at 2% of their body weight per day, should be provided.
  • Regular health checks are crucial to ensure the broodstock is disease-free and that egg development is progressing appropriately.
• Induction of Breeding
  • Brooders can be induced to spawn through hormonal injections, utilizing either pituitary extract (PE) or commercial hormones (CH).
  • Recommended dosages include:
    • Females: One dose of PG extract (2-3 mg) or CH (0.1-0.2 ml/kg).
    • Males: PE (2 mg) or CH (0.1 ml/kg).
  • After induction, fish should be placed into spawning pools or hapas in a 1:1 ratio of males to females.
• Spawning Process
  • Select mature individuals for breeding, ideally weighing males at 1 kg and females between 1.0 to 1.5 kg.
  • Breeding hapas, measuring 2 x 1 x 1 meters, should contain one female and two males.
  • Aquatic weeds (e.g., Hydrilla, Najas, Eichhornia) or weighted plastic strands serve as spawning substrates for egg adhesion.
  • The spawning process should commence in the evening, with the induced fish releasing eggs after 6-8 hours, resulting in the presence of small, orange-colored eggs.
• Incubation of Eggs
  • Post-spawning, the eggs should be transferred along with the aquatic weeds to a hatching hapa for incubation.
  • The incubation period for common carp eggs is approximately 15 hours at optimal temperatures between 27-30°C.
  • Upon hatching, the yolk sac remains attached to the hatchlings, which can be observed adhering to the sides and bottom of the hapa.
  • The weeds are removed gently after hatching, and the hatchlings are retained in the hapa for an additional 3-4 days until the yolk sac is fully absorbed.

Hatchery Management of Minor Carp

The hatchery management of minor carps, belonging to the Cyprinidae family, is critical for sustaining aquaculture practices and meeting commercial demands. Species such as Reba (Cirrhinus reba), Bata (Labeo bata), Fringe-lipped carp (Labeo fimbriatus), Calbasu (Labeo calbasu), white carp (Cirrhinus cirrhosus), and Cauvery carp (Labeo kontius) are among the key players in this sector. Understanding their habitat preferences, feeding behaviors, and compatibility within polyculture systems is vital for successful aquaculture.

• Overview of Minor Carps
  • Minor carps are commercially valuable fish that play a significant role in aquaculture systems.
  • Species such as Kuria Labeo and Fringe-lipped Carp exhibit bottom-dwelling behavior, necessitating attention to their competitive interactions with other species, particularly Indian major carps like Mrigal (Cirrhinus mrigala) and Rohu (Labeo rohita).
  • Their integration into polyculture requires careful consideration of their feeding habits and spatial dynamics within the farming environment.
• Reproductive Biology
  • Age and Size at Maturity: Minor carps typically reach sexual maturity at around two years of age.
  • Sexual Dimorphism: Males can be identified by their rough pectoral fins and slender body structure, whereas females have smoother pectoral fins and a noticeably enlarged abdomen.
  • Breeding Season: The breeding season occurs during the rainy season, aligning with environmental conditions favorable for spawning.
• Broodstock Management
  • The optimal management of broodstock involves selecting mature males and females aged two years or older.
  • Fish should be collected at least three months prior to the breeding season and maintained in broodstock ponds at densities of 1.2-1.5 tons per hectare.
  • A supplementary feeding strategy is essential, with a recommended diet comprising a 1:1 ratio of groundnut oil cake (GNOC) and rice bran, or floating feed provided at 2-3% of total biomass.
  • Certain bottom-dwelling species, such as Kalbasu and Kuria Labeo, require a dough feeding approach for optimal broodstock development.
• Induction of Breeding
  • For successful breeding, matured males exhibiting oozing conditions and females with visibly swollen abdomens should be carefully collected and transported to the hatchery in thick canvas bags filled with water to minimize stress.
  • In the hatchery, males and females are separated and housed in individual breeding hapas within a circular breeding pool equipped with a shower system.
  • A single injection of hormonal treatments, such as Ovaprim or Ovatide, is administered at dosages of 0.3 ml/kg for females and 0.15 ml/kg for males, facilitating successful spawning.
• Spawning Process
  • The breeding hapas are prepared in the evening, and the fish are introduced for breeding after hormone administration.
  • Optimal water temperatures of 27-28 °C are maintained during the spawning process, which occurs approximately 8-11 hours post-hormone injection.
  • Fertilized eggs are collected from the breeding hapas and subsequently transferred to circular incubation tanks or pools.
• Incubation of Eggs
  • Following spawning, fertilized eggs are placed in hatching hapas for incubation.
  • The incubation period for minor carp is approximately 15 hours, with an optimal temperature range of 27-30 °C to ensure effective hatching.
  • After this period, hatchlings can be observed clinging to the sides and bottom of the hapa, indicating successful development.
  • The hatchlings are retained in the incubation tank or pool for an additional 60-62 hours to facilitate yolk sac absorption, after which they develop into larvae known as spawns, measuring around 4-5 mm.

Hatchery management of magur

The hatchery management of magur (Clarias batrachus), commonly referred to as the walking catfish, is a pivotal aspect of aquaculture, particularly in regions like Odisha, West Bengal, Bihar, and the northeastern states of India. Recognized for its favorable taste, nutritional profile, and therapeutic values, magur has emerged as a popular food fish in India and Bangladesh. This species thrives in diverse aquatic environments, including swamps, shallow channels, and paddy fields, where it can adapt to conditions with low dissolved oxygen and high concentrations of carbon dioxide and ammonia.

• Overview of Magur
  • Magur is valued for its easily digestible protein, low-fat content, and rich iron levels, contributing to its high consumer preference.
  • Its unique air-breathing adaptations, which include an upper branchial chamber and specialized gill structures, enable it to thrive in oxygen-deprived environments.
• Reproductive Biology
  • Age and Size at Maturity: Magur typically reaches sexual maturity within its first year.
  • Sexual Dimorphism: Males exhibit a long and pointed genital papilla with a slender, whitish vent, while females have a round, oval, button-shaped genital papilla and a bulging reddish vent.
  • Breeding Season: The breeding season extends from June to August, with peak spawning activity observed in July.
  • Fecundity: Females can produce between 15,000 and 20,000 eggs per kilogram of body weight.
  • Parental Care: After laying eggs in pits, females exit the nesting site, leaving males to guard the eggs and young for several days.
• Broodstock Management
  • Maintaining optimal water quality and nutrition is essential for the successful maturation of broodstock.
  • Fish weighing over 150 grams, typically in their first year, are suitable for broodstock. They are kept in small ponds (100-200 m²) or tanks at stocking densities of 3-4 fish per cubic meter.
  • Cement or concrete tanks are recommended, with a substrate of 4-6 cm of soil to support the brooders. Fish should be stocked at least two to three months prior to the breeding season.
  • A diet consisting of trash fish and rice bran in a 9:1 ratio should be provided, with feeding rates of approximately 10% of the body weight.
• Inducing Breeding
  • The breeding process can be initiated using synthetic hormones such as Ovaprim, Ovatide, WOVA-FH, Gonopro, or carp pituitary gland extract. The recommended dosage for synthetic hormones is 1-1.5 ml per kilogram of body weight, while the optimal dosage of carp pituitary gland extract ranges from 30 to 40 mg/kg.
• Preparation of Sperm Suspension
  • For breeding, a male brooder weighing between 100-150 grams is selected. If the male does not respond to stripping, it may be necessary to sacrifice the fish for testis extraction.
  • A viable sperm suspension can be created by macerating the creamy white testis in a saline solution (0.9% sodium chloride).
• Spawning and Artificial Fertilization
  • Following hormone induction, females are ready for artificial fertilization approximately 15-17 hours post-induction. Eggs are stripped into a plastic tray, and water is added to activate sperm for fertilization.
  • The eggs are thoroughly mixed with the sperm suspension using a bird feather for 2-3 minutes, ensuring successful fertilization. The fertilized eggs are then rinsed in running water to remove excess sperm.
• Incubation of Eggs
  • Once fertilized, the eggs should be transferred to a flow-through hatchery for incubation.
  • The incubation period for magur is approximately 25-26 hours, with an optimal temperature range of 27-30 °C for successful hatching.
  • Following this period, the eggs hatch into larvae, which remain in the incubation tank or pool for yolk absorption. After the yolk sac is absorbed, the larvae develop into small fish, known as spawns, measuring around 4-5 mm.

Hatchery Management of Singhi

The hatchery management of singhi (Heteropneustes fossilis), commonly referred to as the stinging catfish, is a crucial component of aquaculture in Southeast Asia, particularly in India. Recognized for its delectable flavor and significant nutritional and medicinal properties, singhi offers high iron content (226 mg/100 g) and relatively high calcium levels compared to many other freshwater fish. It thrives in diverse aquatic environments such as ponds, swamps, and marshes, and can even tolerate slightly brackish water. Its omnivorous diet and lean body make it an excellent choice for health-conscious consumers.

• Overview of Singhi
  • Singhi is characterized by its ability to survive for extended periods out of water due to its accessory respiratory organs, making it a hardy species.
  • Its culinary and nutritional significance has elevated its market value in various regions.
• Reproductive Biology
  • Age and Size at Maturity: Singhi typically reaches sexual maturity within its first year.
  • Sexual Dimorphism: Males exhibit streamlined bodies, while females have swollen abdomens, especially as they approach spawning.
  • Breeding Season: The breeding season occurs from June to August, with peak activity in July.
  • Fecundity: Females can produce between 1,500 and 2,000 eggs per kilogram of body weight.
• Broodstock Management
  • Optimal water quality and proper nutrition are vital for the maturation of broodstock.
  • Fish weighing between 50 and 100 grams are ideal for use as broodstock. They should be maintained in small ponds or tanks at a stocking density of 10-12 fish per cubic meter.
  • A diet comprising molluscan meat or a formulated feed containing rice bran, fish meal, soybean meal, and groundnut oil cake should be provided to ensure healthy growth and reproductive readiness.
• Inducing Breeding
  • To stimulate breeding, synthetic hormones such as Ovaprim, carp pituitary gland extract, 17α-hydroxy-progesterone, and 17α-hydroxy-20β-dihydroprogesterone are administered to females. The recommended doses are:
    • Ovaprim: 0.6-0.9 ml/kg body weight
    • 17α-hydroxy-progesterone: 8 mg/kg body weight
    • 17α-hydroxy-20β-dihydroprogesterone: 2 mg/kg body weight
  • Males receive half the dosage administered to females.
• Preparation of Sperm Suspension
  • If male brooders do not respond to stripping, they may be sacrificed to collect the testis.
  • A viable sperm suspension is created using the creamy white testis, which is macerated in a normal saline solution (0.8% saline).
• Spawning and Artificial Fertilization
  • After hormonal induction, females are ready for artificial fertilization approximately 8-10 hours later. Eggs are stripped into a plastic tray for fertilization.
  • The eggs are mixed with the sperm suspension using a bird feather for 2-3 minutes, ensuring effective fertilization. Subsequently, the fertilized eggs, which are greenish-blue and moderately adhesive, should be washed in running water. Unfertilized eggs typically appear white and float.
• Incubation of Eggs
  • Fertilized eggs should be transferred to a flow-through hatchery for incubation.
  • The incubation period for singhi is approximately 16-19 hours, with an optimal temperature range of 28-30 °C for successful hatching.
  • Once hatched, the fry remain in the incubation tank to absorb their yolk sac. Following yolk absorption, the larvae develop into small fish, known as spawns, measuring around 2.5-2.7 mm in length.

Hatchery Management of Golden Mahseer

Hatchery management of golden mahseer (Tor putitora), a significant cyprinid species, plays an essential role in aquaculture, particularly in the clear, flowing waters of Asia, ranging from Himalayan streams to Southeast Asian rivers. Often referred to as the “King of Indian Aquatic Systems,” this species is distributed widely across various regions in India, including Jammu & Kashmir, Sikkim, and Assam. Golden mahseer thrives in habitats characterized by rapids and fast currents, making it a highly adapted swimmer with an elongated, slightly compressed body covered in large scales.

• Overview of Golden Mahseer
  • This species is omnivorous during its adult phase, primarily feeding on diatoms, filamentous algae, insect larvae, and small mollusks, which contributes to its ecological role in freshwater environments.
• Reproductive Biology
  • Age and Size at Maturity: Males typically reach sexual maturity by the second year, while females do so by the third year.
  • Sexual Dimorphism: Males exhibit smaller, narrower bodies, with a straight ventral profile and pectoral fins reaching up to the sixth lateral line scale, alongside the presence of tubercles and brighter coloration. In contrast, females have bulkier abdomens with an arched ventral profile and pectoral fins reaching only up to the fifth lateral line scale, lacking tubercles.
  • Breeding Season: The breeding season occurs from May to August, during which fecundity ranges from 3,000 to 9,000 eggs per kilogram of body weight.
• Broodstock Management
  • Broodstock should be collected from natural spawning grounds during the breeding season or raised in controlled environments. Females should be at least three years old, weighing over 900 grams, while males should be at least two years old and exhibit milt excretion from the genital aperture, indicating readiness for breeding.
• Inducing Breeding
  • Synthetic hormones such as Ovaprim and carp pituitary gland extract are used to induce breeding in golden mahseer. The hormone dosage required for induced breeding includes:
    • For females:
      • Initial dose of pituitary gland extract (PGE): 6 mg/kg body weight
      • Final dose: 12 mg/kg body weight
      • Ovaprim: 0.6-0.8 ml/kg body weight
    • For males:
      • A single dose of PGE and Ovaprim: 0.2-0.3 ml/kg body weight
• Spawning and Artificial Fertilization
  • Following hormonal induction, females are prepared for artificial fertilization approximately 6-12 hours later. Eggs are stripped into an enamel tray, and milt is collected from male fish. Fertilization occurs by mixing the milt with the freshly collected eggs using a feather, resulting in fertilized eggs that are typically demersal and exhibit a lemon-yellow or brownish-golden hue.
• Incubation of Eggs
  • Fertilized eggs should be transferred to a flow-through hatchery system for incubation. The incubation period for golden mahseer ranges from 76 to 96 hours, averaging about 82 hours, with an optimal temperature of 19-24 °C. After the incubation period, the eggs hatch, and the spent shells are pipetted out of the tray while the larvae are allowed to remain undisturbed for optimal development.

Hatchery Management of Trout

atchery management of trout species, including rainbow trout, brown trout, and brook trout, is critical for optimizing aquaculture practices, particularly in cold-water environments. These species have been introduced into India, particularly in regions such as Jammu-Kashmir and Himachal Pradesh, where the conditions are suitable for their cultivation. Trout has emerged as a valuable fish due to its high market demand, both domestically and for export, thereby creating opportunities for aquaculture expansion in upland areas.

• Overview of Trout Species
  • Cultivable trout thrive in cold waters, making them suitable for specific geographical regions where water quality can be maintained through systems such as raceways, which facilitate a continuous flow of fresh water.
• Reproductive Biology
  • Age and Size at Maturity: Males reach sexual maturity by their second year, while females mature by their third year.
  • Sexual Dimorphism: Males are characterized by smaller, narrower bodies, a straight ventral profile, pectoral fins reaching up to the sixth lateral line scale, and the presence of tubercles. Females, in contrast, possess bulkier bodies with an arched ventral profile, pectoral fins extending only to the fifth lateral line scale, and lack tubercles.
  • Breeding Season: The breeding season extends from May to August, during which females produce between 3,000 and 9,000 eggs per kilogram of body weight.
• Broodstock Management
  • Broodstock can be sourced from natural spawning areas or cultivated on farms. Key considerations for effective broodstock management include:
    • Temperature: Brook trout should be maintained at temperatures between 12-14 °C, while brown and rainbow trout thrive in a range of 10-20 °C.
    • Rainfall: Moderate rainfall is crucial as areas with heavy rainfall may lack essential mineral content.
    • Water Source: Ideal sources include rheocrene and limno springs, whereas heleocrene springs are unsuitable due to the presence of humic acid and organic matter.
    • Water Quality: It is essential that the water used is pure, transparent, and free from pollutants and suspended particles to ensure optimal growth conditions.
• Inducing Breeding
  • Natural spawning occurs without the use of synthetic hormones. The identification of sex in broodfish relies on secondary sexual characteristics. The stripping method is employed to collect eggs and milt from females and males, respectively. Two primary methods are used for egg collection:
    • Wet Method: Eggs are collected in a water-filled pan.
    • Dry Method: Eggs are collected in a dry pan, which is preferred as it prolongs the viability of spermatozoa since they do not mix with water.
• Fertilization Process
  • Fertilization typically requires the milt from two males for the eggs from two to four females. The eggs and milt are mixed gently with a feather 2-3 times before fertilization occurs. Fertilized eggs display a greenish hue, commonly referred to as “green eggs.”
• Incubation
  • After spawning, fertilized eggs are transferred to various incubation systems, including vertical flow incubators, flat troughs, and Vibert jars. The incubation period for trout lasts approximately 21 days, with an optimal temperature range of 14-15 °C. Successful hatching is monitored closely to ensure that conditions remain ideal throughout the incubation phase.

Hatchery Management of Seabass

Hatchery management of seabass, particularly the species Lates calcarifer, is essential for sustainable aquaculture in tropical and subtropical regions, including both the Pacific and Indian Oceans. This species, commonly known as giant sea perch, has garnered attention due to its adaptability to low salinity environments, including freshwater. In India, seabass is predominantly found along the east and west coasts, with a notable concentration in the Bengal region, where it is cultivated in various water bodies such as ponds, canals, and paddy fields.

• Overview of Seabass Species
  • Lates calcarifer is a predatory fish that primarily feeds on small fish, shrimp, snails, and worms. It exhibits cannibalistic behavior under conditions of food scarcity or when stocked with size-unequal groups. As a percoid fish belonging to the family Centropomidae, it demonstrates a unique life cycle, spawning in marine environments while utilizing brackish waters and mangrove areas for juvenile development.
• Reproductive Biology
  • Age and Size at Maturity: Seabass reaches sexual maturity by the third year of life.
  • Sexual Dimorphism: Males are characterized by a slender body and a reddish-pink papilla, while females exhibit a softer, bulging belly.
  • Breeding Season: The primary breeding season occurs from April to August, with fecundity ranging from 2.1 to 17 million eggs per female.
• Broodstock Management
  • Broodstock should be collected from natural environments or wild farms and treated with antibiotics at a dosage of 20 mg/kg. Males and females are then transported to broodstock tanks designed for ample swimming space. The recommended stocking density is approximately 1 kg/m³. Given the carnivorous nature of seabass, they are typically fed frozen trash fish, constituting about 5% of their body weight.
• Inducing Breeding
  • Two primary methods are employed for inducing breeding:
    • Natural Induction: Wild, sexually immature seabass can be reared until gonads mature. This species exhibits protandrous hermaphroditism, initially maturing as males before transitioning to females. To induce natural spawning, water conditions should be adjusted by increasing salinity to 30-32 ppt and raising the temperature to 26-28 °C. Following this, milt and eggs are collected through stripping for fertilization.
    • Hormonal Induction: This method involves administering Carp Pituitary Gland Extract (CPGE) along with hormones such as LHRHa or Ovaprim. The most effective hormone is LHRHa, with recommended dosages of 60-70 IU/kg for females and 30-35 IU/kg for males. CPGE and HCQ require two doses, the first at 50 IU HCG and 0.5-1 mg/kg CPGE, and the second at 100-260 IU HCG and 1.5-2 mg/kg CPGE.
• Spawning Process
  • Fish treated with LHRHa typically spawn 30-36 hours post-administration, primarily during the late evening. At spawning time, vigorous movement occurs, releasing a milky substance that can be detected by odor several meters away. In natural spawning, the optimal timing is between 6 PM and 11 PM during the low tide, specifically following the full moon and new moon phases. After spawning, eggs are collected from females, and milt is collected from males via the stripping method for artificial fertilization.
• Incubation
  • Fertilization in seabass is external, and fertilized eggs measure approximately 0.75 to 0.80 mm in size. These pelagic eggs are transparent, making monitoring essential. The incubation temperature should be maintained between 26-28 °C, with an incubation period of 17-18 hours before hatching occurs.

Hatchery management of milkfish

Hatchery management of milkfish (Chanos chanos) plays a critical role in the sustainable aquaculture of this important species, which is commonly found in the Indian and Pacific Oceans. Known for its rapid growth and wide salinity tolerance, milkfish has been traditionally cultured in brackish water ponds and pens across tropical regions. In India, its fry and fingerlings are prevalent in coastal waters, estuaries, and brackish water bodies, contributing to the local economy and food supply.

• Overview of Milkfish
  • Milkfish is the only extant species in the family Chanidae and is recognized for its substantial size and longevity. It is referred to by various names in different Indian languages, including Paal Meen in Tamil and Poomeen in Malayalam. As a high-quality food fish, milkfish is not only fast-growing but also exhibits remarkable resistance to diseases, making it a prime candidate for aquaculture. Furthermore, it is euryhaline and eurythermal, meaning it can thrive in a variety of salinity and temperature conditions.
• Reproductive Biology
  • Age and Size at Maturity: Milkfish typically reaches sexual maturity between the ages of 3 to 5 years.
  • Sexual Dimorphism: Males can be identified by having two openings in the anal region, whereas females possess three openings.
  • Breeding Seasons: The primary breeding seasons occur from January to April and from October to November, with fecundity ranging up to 1 million eggs per kilogram of body weight. The eggs are spherical, translucent, and pelagic in nature.
• Broodstock Management
  • Broodstock can be reared in various facilities, including floating cages, concrete tanks, and canvas tanks, with floating net-cages being favored for their economic advantages. Once broodstock are established in smaller cages, they are transferred to larger cages to allow for greater movement and growth. Stocking densities should not exceed 1.5 kg/m³. Feeding protocols typically involve commercial feed pellets at a rate of 1.5% to 2% of the fish’s body weight per day.
• Inducing Breeding
  • Two primary methods are employed for inducing spawning in milkfish:
    • Hormonal Induction: Broodfish are treated with partially purified salmon gonadotropin, mullet pituitary gland extract (PGE) with human chorionic gonadotropin (HCG), or combinations thereof. This approach facilitates more controlled breeding outcomes.
    • Non-Hormonal Induction: This method relies on the lunar cycle, specifically targeting the 1st to 7th, 12th to 18th, and 24th to 30th days of the lunar phase for optimal spawning conditions.
• Spawning Process
  • Milkfish spawn when water temperatures range between 29-30 °C and salinity is maintained at approximately 26 ppt. Spawning typically occurs at midnight. Following spawning, eggs are collected from females while milt is gathered from males using the stripping method, after which artificial fertilization is performed.
• Incubation
  • The incubation period for milkfish begins 20-35 hours post-fertilization. Optimal conditions for incubation include temperatures of 26-32 °C and salinity levels of 29-34 ppt. The incubation duration is approximately 17-18 hours before the eggs hatch.

Hatchery Management of Grey Mullet

Hatchery management of grey mullet (Mugil cephalus) is vital for the sustainable aquaculture of this highly adaptable species, which is recognized as the most widespread member of the family Mugilidae. Capable of thriving in diverse aquatic environments—including marine, estuarine, and freshwater settings—grey mullet exhibits significant resilience and growth potential. This fish is traditionally harvested in coastal lagoons, brackish-water lakes, and estuaries, where it contributes to local fisheries and aquaculture.

• Overview of Grey Mullet
  • Grey mullet is a euryhaline species, allowing it to survive in varying conditions of salinity, turbidity, and dissolved oxygen levels. This adaptability, combined with its hardy nature, makes grey mullet a suitable candidate for aquaculture. The fish primarily feeds during the daytime, consuming a diet consisting mainly of zooplankton, detritus, and dead plant matter. Being catadromous, grey mullet migrates between freshwater and estuarine habitats during its lifecycle, often forming schools as adults.
• Reproductive Biology
  • Age and Size at Maturity: Grey mullet typically reaches sexual maturity between the ages of 3 and 4 years.
  • Sexual Dimorphism: Males tend to have smaller bodies with a slender belly, while females exhibit larger bodies with a noticeably swollen belly.
  • Breeding Seasons: The primary breeding season occurs from October to January, with a fecundity rate of approximately 1,320,000 eggs per kilogram of body weight.
• Broodstock Management
  • Broodstock for grey mullet can be collected from the wild or reared in ponds from juvenile stages. These fish are often maintained in reinforced concrete tanks, designed for continuous flow-through seawater. Stocking density should not exceed 1 kg/m³, and optimal salinity for broodstock rearing is between 32 and 35 ppt. As bottom feeders, grey mullet are provided with sinking pellets, fed at a rate of 3% to 5% of their body weight, administered twice daily.
• Inducing Breeding
  • Breeding induction can be achieved through hormonal administration:
    • Hormonal Induction: This includes the injection of Carp Pituitary extracts and LHRHa at doses of 20 mg/kg and 200 µg/kg of body weight, respectively. Additional hormonal treatments may include mullet pituitary gland extract along with 10-60 rabbit units of synahorin hormone. Furthermore, salmon gonadotropin and HCG at a dosage of 60 IU per gram of body weight can be administered in two doses: the first at 20 IU, followed by a second dose of 40 IU after 24 hours. Following hormone administration, the mature oocytes and milt are collected using the stripping method.
• Spawning Process
  • Upon administration of the resolving dose, broodstock should be maintained at a sex ratio of approximately 2-3 males for every female in the spawning tank. Spawning typically occurs within 12 to 14 hours of hormone administration. After spawning, the eggs are collected from females, and milt is gathered from males through the stripping method, followed by artificial fertilization.
• Incubation
  • Once spawning is complete, eggs are transferred to incubation tanks. The incubation period occurs at temperatures ranging from 20 to 26 °C, with adequate oxygen levels maintained. A salinity of 35 ppt is ideal for keeping the eggs suspended. The duration of the incubation period for grey mullet eggs is approximately 28 to 30 hours at a temperature of 26 °C.

Hatchery Management of Cobia

Hatchery management of cobia (Rachycentron canadum), commonly referred to as black kingfish, plays a crucial role in the sustainable aquaculture of this species. As the sole representative of the family Rachycentridae, cobia has garnered significant interest due to its rapid growth rate, adaptability to captive conditions, and high market demand, particularly in the sashimi sector. Found in warm marine waters worldwide, cobia occupies various habitats from coastal areas to continental shelf waters and is known for its excellent meat quality.

• Overview of Cobia
  • Cobia is characterized by its fast growth rate and resilience in aquaculture settings. These attributes, combined with low production costs and a high demand for its flesh, especially in high-end culinary markets, make it an appealing candidate for aquaculture operations.
• Reproductive Biology
  • Age and Size at Maturity: Males reach sexual maturity at approximately 1 to 2 years of age, while females mature between 2 and 3 years.
  • Breeding Season: The breeding season spans from April to September, peaking in July.
  • Fecundity: Cobia females can produce between 1.23 million to 1.80 million eggs per spawning event.
• Broodstock Management
  • Broodstock for cobia are typically harvested from the wild and subsequently conditioned in captivity. For effective broodstock development, individuals weighing between 8 and 15 kg are selected.
  • These fish are then housed in 100-ton reinforced concrete (RCC) tanks for maturation and long-term holding within the hatchery environment.
  • A suitable feeding regimen is crucial, with broodstock fed twice daily on a diet consisting mainly of sardines (Sardinella sp.), as well as other fish species such as Pellona and Ilisha, with occasional supplementation of squid and portunid crabs at approximately 5% of their body weight.
• Inducing Breeding
  • Hormonal induction is a common practice for spawning cobia. Females are injected with LHRH at a dosage of 20 μg/kg, while males receive a dose of 10 μg/kg.
  • Additionally, an intramuscular injection of HCG is administered at a rate of 500 IU/kg for females and 250 IU/kg for males.
  • For optimal results in induced breeding, a sex ratio of two males for every female is recommended, with a stocking density maintained between 1 and 1.9 kg/m³.
• Spawning Process
  • Following hormone injection, spawning occurs approximately 39 hours later, typically between late night and early morning.
  • The number of eggs produced by a single spawning event can range from 0.4 to 4 million.
  • Eggs are collected from females, and milt is harvested from males using the stripping method before proceeding with artificial fertilization. In natural conditions, spawning generally occurs in both nearshore and offshore waters.
• Incubation
  • After collection, the eggs are transferred to incubation tanks, where the incubation process begins.
  • Optimal hatching conditions require a temperature range of 28 to 30 °C, with eggs typically hatching after an incubation period of approximately 22 hours.

Hatchery Management of Pampano

Hatchery management of silver pomfret (Trachinotus blochii), a tropical species from the family Carangidae, is essential for supporting aquaculture operations and sustaining wild populations. Commonly found in the Indo-Pacific region, silver pomfret inhabits coral reef areas and is valued for its culinary qualities. This deep-bodied fish, characterized by its silvery coloration, thrives in warm coastal waters and various habitats, including estuaries and tidal flats.

• Overview of Silver Pomfret
  • Silver pomfret is known for its toothless structure, small scales, narrow tail base, and forked tail. Its wide distribution in tropical and temperate regions highlights its ecological significance and market value.
• Broodstock Management
  • Broodstock is typically sourced from cultured farms utilizing floating net cages or broodstock tanks.
  • Optimal selection criteria include fish weighing around 1 kg, free from physical abnormalities, and exhibiting a balanced body structure.
  • Within the holding tanks, broodstock are fed a diet consisting of 3-5% of their body weight, ensuring proper growth and conditioning prior to breeding.
• Inducing Breeding
  • To initiate spawning, broodfish receive an intramuscular injection of HCG at a dosage of 350 IU/kg of body weight.
  • Breeding tanks should have a minimum capacity of 10 m³ to accommodate the fish comfortably.
  • A balanced sex ratio of 1:1 (one male to one female) is maintained, with the understanding that male pomfret are generally smaller than females.
• Spawning Process
  • Spawning occurs approximately 2 to 3 days after hormone injection, primarily during late night to early morning hours when environmental conditions are optimal.
  • After spawning, eggs are collected from females, while milt is harvested from males through the stripping method. Following this, artificial fertilization is performed.
  • The spawning output of pomfret brooders ranges from 50,000 to 150,000 eggs per event, indicating a significant reproductive capacity.
• Incubation
  • Post-spawning, eggs are transferred to incubation tanks where optimal conditions are maintained for successful hatching.
  • The incubation period lasts between 18 to 24 hours, resulting in viable larvae that can be further cultured for grow-out in aquaculture systems.

Importance of Hatchery Management

The following points highlight the importance of effective hatchery management:

• Sustainability of Fish Stocks
  • Hatchery management aids in the conservation of fish species by facilitating breeding programs that support the replenishment of wild stocks. This is particularly important for species that are overfished or endangered.
• Enhanced Growth Rates and Survival
  • Proper management practices in hatcheries can significantly improve growth rates and survival of fish larvae and juveniles. Controlled environments ensure optimal conditions for temperature, salinity, and oxygen levels, which are vital for healthy development.
• Quality Control of Stock
  • Hatchery management allows for the selection and breeding of high-quality broodstock, ensuring that the resulting offspring exhibit desirable traits such as faster growth, disease resistance, and improved feed conversion ratios.
• Economic Benefits
  • Effective hatchery management contributes to the economic viability of aquaculture operations by providing a steady supply of fingerlings or juveniles. This helps reduce dependency on wild capture, stabilizing market prices and enhancing profitability.
• Research and Development
  • Hatcheries serve as important research facilities where scientists can study fish biology, reproduction, and ecology. This research can lead to advancements in breeding techniques, disease management, and feed formulation.
• Food Security
  • By increasing the availability of farmed fish, hatchery management plays a pivotal role in food security. Aquaculture provides a sustainable source of protein for growing populations, reducing reliance on wild fisheries.
• Ecological Restoration
  • Hatcheries can be integral in restoring degraded aquatic ecosystems by reintroducing native species and maintaining biodiversity. This is essential for the health of marine and freshwater environments.
• Biosecurity Measures
  • Effective hatchery management includes implementing biosecurity protocols to prevent the introduction and spread of diseases. This helps protect both hatchery stock and surrounding wild populations from outbreaks.
• Community Development
  • Local hatchery operations can foster community development by creating jobs and providing training in aquaculture techniques. This supports livelihoods and promotes sustainable practices in local fisheries.