The document discusses the culture of cobia (Rachycentron canadum), highlighting its biology, seed collection, and culture techniques suitable for aquaculture, especially in India. Cobia is a highly valued fish for its meat quality and fast growth, making it a promising candidate for marine aquaculture. Key information includes details on spawning, incubation, nursery rearing, and farming conditions, emphasizing the importance of proper water quality management and feeding practices.

1. Faculty of Fishery Sciences
Submitted By
Haladhar Hembram
Reg:- 6408 Of 2018-19
M.F.Sc 1st Year
Dept Of Aquaculture
Submitted To
Prof. T.K Ghosh
&
Dr. S.K Sau
Dept of AQUACULTURE
Topic:- Culture Of Cobia- Its Biology, Seed Collection & Culture Techniques.
Sub:- Coastal Aquaculture And Mariculture Farming System (AQC-502)

2. Content:-
• Introduction
• Biology
• Seed collection
o Quarantine
o Water quality management
o Spawning
o Cannulating brood fish
o Incubation
o Nursery Rearing
o Packing and transportation
• Culture Techniques (Farming In Cage)
o Water Quality Requirement
o Cage Degine
o Stocking
o Feeding
o Growth Pattern
o Harvesting
o Conclusion
o References

3. Introduction:-
Cobia , Rachycentron canadum also known as Lemon fish or Ling is an
oceanodromous , migratory and pelagic fish that lives in brackish and marine
waters.
The fish is popular known by the common names-Black kingfish, Black
salmon, runner or sergeant fish, crab eater and Sea murrel.
It is a highly priced game fish with high market value both in domestic and
international markets.
Cobia known for its excellent meat quality is a famous premium food fish
highly preferred by people in Taiwan and Japan. The white meat of the fish is
served in restaurants as raw fish called Sashimi.
The fast growth rate, adaptability to captive breeding (attains 6-8 kg/year) are
the major attributes which makes cobia as an excellent candidate species for
aquaculture.
Cobia is one of the marine finfish species with high aquaculture potential
particularly for cage culture in India.
Sashimi

4. Biology:-
They are able to tolerate a wide range of temperatures (eurythermal) and salinity (euryhaline) between 1.6 and 32°C
and 5-35 ppt in the environment.
Cobia prefer warm water (>20 °C) and typically have annual migratory patterns.
Breed throughout the year with peak spawning activity from October to February.
Sexual maturity -in males at 1-2 years and in females at 2-3 years
Females grow larger and faster with maximum sizes up to 78 kg.
Spawning occurs in both nearshore and offshore waters where females release thousand to million eggs (1.4 mm
diameter) which are then fertilized by the males.
Cobia:- Rachycentron canadum

5. The viable eggs begin development, are heavily pigmented, buoyant,
and hatch in approximately 24 hours.
Cobia larvae grow rapidly and are large in comparison to most marine
species
Juvenile fish are found in both nearshore and offshore waters, often
among weed lines where they seek shelter from predators and can feed.
Cobia are opportunistic feeders and examinations of stomach contents
have revealed various fish, shrimp, squid, and, in particular, crabs.

6. Production cycle

7. Seed Collection:-
The sub-adult fish is collected from wild or farm for developing into brood
stock.
Wild fish is collected by hook and line, anesthetized with 25 ppm clove oil
solution and is transported by boat in covered FRP tank with aeration.
The biomass of the fish should not exceed 50 kg/m3 in the tank during
transportation.
The fish is given a freshwater dip for 3-5 minutes to remove ectoparasites and
microbes.
The gravid brood fish are selected, anesthetized with 10-20 ppm clove oil and
transferred to quarantine tank after measuring its body weight and length.
The fish is kept under quarantine for 3 weeks.

8. Quarantine
• Following quarantine, fish
weighing at least 5 kg are moved
to maturation tanks (25–100 t
capacity) with recirculation
capabilities.
• For appropriate nutrition, the
brood fish are given designed fish
sausage fortified with vitamins
and minerals twice daily at 1-2%
of the body weight.
This Photo by Unknown author is licensed under CC BY-SA.

9. Water Quality Management
Water is collected directly from the sea or shore well.
A filter net is used to remove debris.
The saltwater is chlorinated at 35 ppm in a settling tank to remove suspended
particles.
The water then goes through a slow sand filter and pressure sand filter after being
dechlorinated through aeration. This removes particles larger than 25 micrometer.
A cartridge filter at 1 micron level is also used.
An ozonizer or UV sterilizer is used to disinfect the water.
EDTA at 5-10 ppm is added to remove heavy metals and reduce pollution.

10. Spawning
A transparent flexible cannula with 1mm inner and 2mm outer
diameter is inserted into the female oviduct and male cloaca of the fish
under anesthesia.
This is done to regularly collect gametes to assess gonadal
development.
The collected sample is examined under a microscope to determine:
 The size and stage of development of the female ovum.
 The density of the male milt
Then the cannula is withdrawn while suction is applied at the other
end.

11. Cannulating brood fish
Male and female fish in 1:1 ratio are selected based on thick
milt and ova diameter of at least 600 μm respectively.
LHRH-a hormone is injected into the females at 20 μg/kg and
males at 10 μg/kg.
Spawning occurs within 36-40 hours of hormone treatment at
temperature of 26-27°C.
The eggs are cream colored, globular, measuring 1.35-1.40
mm in diameter with single oil globule.
External fertilization happens. Fertilized eggs float while
unfertilized eggs sink.
Fecundity ranges from 2-4 lakh eggs per kg of body weight.

12. Incubation
The eggs are harvested using a 1x1x1 meter net with a mesh size of 500–600 μm after
12 hours of spawning.
The fertilized eggs are weighed, treated with betadine for 1 minute, and a sample is
tested to measure the fertilization rate.
The eggs are either stocked directly into indoor rearing tanks (10-30 tons) at a density
of 10-20/liter or incubated in 500 liter tanks at a density of 300-500/liter with gentle
aeration.
The eggs hatch within 21-24hrs at temperatures of 27-30°C. The hatching rate is about
80%.
Newly hatched larvae are around 3.5 mm long including the yolk sac.
The mouth of the hatchlings opens up to around 200 micrometers by the third day after
hatching.

13. Nursery Rearing
• Nursery rearing of cobia fingerlings for one month is essential to reach an ideal
stocking size of 20 grams.
• Nursery rearing can be conducted in either tanks (minimum 10-tonne capacity)
or sea cages (6-meter diameter) with smaller mesh nets.
• Recommended stocking density in indoor nursery tanks is 1 fish/10 liters with
200% water exchange, while in nursery cages, it's 1.8-3.0 kg/m3.
• Suitable-sized artificial feeds (800 – 1800 microns) should be provided during
nursery rearing.
• Floating or slow-sinking pellet feed with 50% crude protein and 10% crude fat
is suitable for successful nursery rearing.
• High protein and fat nursery feeds are available in India at reasonable prices.
• Proper storage of such feeds is essential to maintain their quality during their
shelf life.
Credit:- CMFRI Mandapam

14. Packing and transportation
1-3t tanks with oxygenation or/and aeration facilities
are typically used to transport seeds over long distances.
Using oxygen cylinders, the DO level is kept above 8
ppm; one tonne of tank requires 340 cm3 of cylinder
capacity per hour.
In an open tank with a maximum biomass density of 10
kg/m3 of water, the seed is conveyed.
48 hours of starvation precedes transit.
2 ppm Euginol is used to administer mild sedation.
De-ammonifiers like 5 ppm Ammonil are used to
regulate ammonia.

15. Culture Techniques (Farming in Cage)
• Site Selection
• Selecting a suitable site for sea cage farming is crucial for smooth
operations.
• A healthy sea bed with sandy soil is necessary for maintaining good
water quality.
• Cage farming generates organic waste materials.
• Under normal conditions, these wastes are consumed by wild
organisms or flushed away by water currents.
• Cages should be moored at an appropriate depth (minimum 2 - 3
meters) to allow waste materials to move away.
• Poor planning or mooring in shallow areas can lead to increased
organic load, causing problems like turbidity and bacterial growth.
• Ideal cage farming sites have a minimum depth of 6 meters during low
tide, with cage nets typically at 3.5 meters depth.
• Ensuring fish are not too close to the seabed helps prevent oxygen
depletion (anoxia) issues.

16. Water quality requirement
Temperature : 28- 33°C
Salinity : 25-35ppt
DO : 5-8 mg/l
pH : 7.9-8.3 ppm
Transparency :- 40cm and above

17. Cage Degine
• Cobia can be farmed in sea cages made of High Density Polyethylene
(HDPE) or galvanized iron (GI) pipes.
• HDPE cages last 10-15 years, while GI cages typically last only up to
three years with good maintenance.
• GI cages have a lower initial investment cost.
• Grow-out culture is done in circular floating sea cages with a 6-meter
diameter.
• A handrail is fixed at one meter height from the base of the cage.
• There is a one-meter space between the inner and outer rings of the cage.
• Cage nets are made of HDPE ropes with 2.5 mm thickness.
• Mesh sizes are 20 mm and 40 mm for inner net cages and 60 mm for
outer net cages.
• Net cage depths are maintained at 3.5 - 4.0 meters from the cage frame's
base.
• The net cages maintain a circular shape with the help of circular ballast.

18. Stocking
• Fish require space for movement as they grow.
• Net cages have limited space, so stocking an optimal number of
fingerlings is crucial for maximum growth.
• Overstocking can weaken fish, increasing the risk of infections.
• Higher stocking densities may lead to insufficient dissolved
oxygen levels, especially during low tide and poor water currents.
• Inadequate dissolved oxygen can result in anoxia and fish
mortality.
• A 6-meter diameter cage with a 3.5-meter net depth can
accommodate 900 cobia fingerlings at a rate of 9-10 fingerlings
/m3

19. Feeding
• For juvenile cobia, feed 5-10% of their total biomass
with chopped low-value fish(e.g., sardine, lesser
sardine, rainbow sardine) twice daily for two months.
• Initially, provide feed at 10% of the biomass
production cost, gradually reducing to 8% and then 5%
as fish grow.
• Maintain consistent feeding times, preferably early
morning or late afternoon.
• Adjust feed quantity during fish stress, rough weather,
or low water temperatures.
• Feed slowly to ensure all fish have adequate feeding
opportunities.
• Marine fish typically require high protein (35-40%)
and fat (8-10%) for growth.

20. Growth assessment
• Random sampling can be carried out at
the time of net exchange with the
sample size of at least 30 cobia fishes
per cage. The entire grow-out culture
is carried out for a period of 6-8
months. The growth details of cobia as
recorded in sea cages at a stocking
density of 8 nos./m3.
Credit:- CMFRI Mandapam

21. Harvesting
Cages are usually harvested by moving them
into shallow water, crowding the fish into a
corner of the net. Otherwise, the cage net can
be lifted partially out of the water so that the
fish are crowded into a smaller volume, and
then it can be harvested. This makes it possible
to partially harvest fish from cages as and when
needed for local markets. Weight at harvest: 3 -
5 kg • Production : 2.0 - 4.0 tonnes per cage of
6m diameter

22. Conclusion
• Cobia fish farming is a promising aquaculture venture in India.
• It's attractive due to its fast growth rate and high market demand.
• India's coastal regions with favorable climates are ideal for cobia
culture.
• Both land-based recirculating systems and floating sea cages are used
for cobia farming.
• Government programs, research collaborations, and technological
advancements support the growth of India's cobia aquaculture industry.
• This sector holds great potential for seafood production, income
generation, and the adoption of sustainable aquaculture practices in
India.

23. References
• https://vikaspedia.in/agriculture/fisheries/package-of-aquaculture-
practices-fisheries-1/production-of-cobia#section1
• https://mpeda.gov.in/?page_id=754
• https://www.slideshare.net/RkInhellFishcos/seed-production-of-cobia
• https://courseware.cutm.ac.in/wp-content/uploads/2020/06/cobia-ppt-
converted.pdf
• http://eprints.cmfri.org.in/15045/1/Farming%20of%20Cobia%20%26
%20Silver%20Pompano_Course%20Manual_CAU_Tripura_2020-
5.pdf

24. Thank You