Cage Culture of Grouper and Cobia

Introduction
 Groupers belongs to the family Serranidae.
 Groupers are classified in 14 genera of the subfamily
Epinephelinae, which comprises at least half the approximately
449 species in the family Serranidae.
 Several grouper species have been raised on a commercial
scale, but mostly by growing out captured wild juveniles.

Major farmed species
 Giant grouper (E. lanceolatus)
 Malabar grouper (E. malabaricus)
 Red spotted grouper (E. akaara),
 Orange-spotted grouper (E. coioides)
 Brown marbled grouper (E.fuscoguttatus)
 Camouflage grouper (E. polyphekadion)
 Greasy grouper (E. tauvina)
 King grouper, polka dot grouper (Cromileptis altivelis)

E. lanceolatus
E. fuscoguttatus

• `` E. coioides
• E. malabaricus

• E. tauvina
• C. altivelis

Important species farmed by hatchery produced seed
 Orange-spotted grouper (E. coioides)
 King grouper, polka dot grouper (Cromileptis altivelis)
 Malabar grouper (E. malabaricus)
 Giant grouper (E. lanceolatus)
 brown-marbled grouper (E. fuscoguttatus)

Distribution
 Groupers are widely distributed in the coastal waters of
tropical and subtropical regions.
 Juveniles and adults of some grouper species live in coastal
waters and estuaries, but others prefer the cleaner waters of
off shore reefs.
 They are mainly seen in rocky bottoms or coral reefs.

Biology
 Most groupers that have been studied will mature within 2 to 6
years.
 Most species are solitary and all are predators on fishes and
invertebrates.
 Many serranids are protogynous hermaphrodites and spawn
throughout the year probably with a peak in monsoon seasons.
 In nature, many groupers spawn in large aggregations with a
sex ratio often near 1 male:10 females.

 Eggs are single, non- adhesive, and buoyant.
 Larvae of most species spend at least their first few weeks
drifting with the oceanic plankton.
 As they become juveniles, groupers settle in shallow water
where they can find hiding places.
 larvae at first eat copepods and other small zooplankton, then
larger crustaceans.
 Wild juveniles and adults eat mainly fish, crabs, shrimp, mantis
shrimp, lobsters and molluscs.

Seed collection
 Grouper fry and fingerlings are usually found near river mouths
or in muddy estuaries and bays.
 Different types of seed collecting devices are used like gangos,
lift nets, bamboo shelter, scissor nets, etc.
 Mortality and wastage are the most problems related to seed
collection.
 Destruction of other larvae caught along with the catch.

Seed production
 Kakdwip Research Centre, CIBA has carried out a successful
breeding and sex reversal programme of Grouper.
 Sex conversion:
 11 fishes selected(2.5-9.0kg)
 17α methyl testosterone supplied @ 2mg/kg BW. on alternate
days.
 Milt volume varied from trace to 0.3ml/fish.
 Sperm motility recorded above 90%.
 Sperm cell density estimated 5.5 million/ml.

Induced breeding:
 7 kg female injected 4000 IU HCG maintained with three
males.
 After 24 hrs. 2000IU HCG administered.
 After 48 hrs. 2000IU HCG administered.
 After 72 hrs. LHRHa administered @ 40µg/kg.
 Stripped 1 million eggs after 96 hrs.
 Hatching time 22-24 hrs.
 Mean size of fertilized eggs 0.8mm.
 Mean length of newly hatched larvae is 1.78 mm.

 The site should be in calm water, e.g. sheltered lagoons, inlets,
bay, behind an island or a river mouth to avoid damage caused
by strong winds, waves and currents.
 Have salinity ranging between 20-30 ppt for juveniles and 25-35
ppt for adults.
 Temperature should be between 26-32 0C and dissolved oxygen
(DO) above 4 ppm.
 Have a pH of 7-9 or slightly alkaline and water transparency
higher than 3 m.
Site selection

 Have water depth not less than 3 m during lowest low tide.
 Have good water exchange to maintain good water quality and
ensure effective removal of wastes and adequate supply of
dissolved oxygen.
 Allow at least 1-2 meter distance between the bottom net
cage and the sea bed during the lowest tide water level.

Layout and design of cage
 Net cages used for grouper culture can be either floating or fixed
type.
 A floating cage module is usually composed of 4-12
compartments supported by a framework.
 The net cages vary in sizes depending on the financial capability
of the fish farmer.
 Most manageable and economical sizes are 2m x 2m x1 m, 3m x
3m x 1.5m and 5m x 5m x 2m.

Inshore cages in Xe Cuan Bay, Hainan, China.

Cage Shape
 The square or rectangular shape is mostly preferred than the
circular shape because its easier to assemble and manage.
Cage Frame
 Made of bamboo or wooden planks.
 They must be durable enough to withstand stress caused by
wave action and increased weight during culture operation.
Catwalks
 Attach lumber measuring 6 m in length to the framework.

Nursery rearing
 Sort healthy and conditioned grouper juveniles and stock in
nursery net cages at a stocking rate of 60-100 fish per cu.m.
 The nursery net cages should have 2-5mm mesh size and
measure 2m x 2m x 1m, submerged about 80 cm below the
waterline.
 Feed the juvenile groupers to satiation three times daily at 0600,
1200 and 1800 h respectively.
 During the first month, the fish are fed with live small fish,
crustaceans and insect larvae.

 In the second month, the fish are weaned with finely chopped
trash fish and small shrimp.
 To prevent cannibalism, the fish are sorted every 2 weeks by
manually separating the smaller ones in another net cage.
 Install a 50-watt incandescent lamp inside the cages, at night to
attract live food such as mysids, copepods and other smaller
fishes.
 After 2 months in the nursery net cages, the fingerlings (8-10 cm
body length) are transferred into the grow-out net cages.

Grow out systems
Pond culture
 Ponds vary from 0.2 to 0.3 ha in area and have vertical concrete
dikes to hold a height of about 1.5 m, of water and about 0.5 m
of free board.
 For every hectare of water surface; eight aerators are provided.
 Clear water supply is maintained, with a salinity of 33ppt and
temperature 16-32 °C.
 The ponds are stocked with 9-12 cm long fingerlings at a density
of up to 40,000/ha.

 Feeding with fresh trash fish is done twice a day at 8% of the
body weight.
 The fingerlings grow to 30 cm in length and 600-800gm in
weight in 8 months.
 Survival of about 90% and yield more than 20 t/ha.
Culture in net cages
 The grow-out can be undertaken in net cages measuring 2mx
2m x 1m, 3m x 3m x 1.5 m and 5m x 5m x 2m.
 Feeding is done once or twice a day at a rate of 3-5% of the
body weight.

 The groupers grow fast at a rate of 80-100 g/month and attain a
market size of 600-800 g in about 6-8 months.
 Based on this a net cage of 5 mLx5mWx3mH has been yielding
600 kg in about 6-7months of culture.
Recommended Stocking rate of grouper in grow-out net cages

Off shore cage
 Offshore typhoon resistant cages are being developed to solve
the above problems.
 large floating and submersible circular cages made of high-
density polyethylene (HDPE) are introduced.
 Circular cages generally withstand the rough sea conditions
better because the HDPE frame is more flexible than wooden
or metal frames.
 It can be submerged up to 4-10 m below the sea surface within
8-15 minutes if typhoon conditions prevail.

Comparison of parameters between inshore and
offshore cages

Problems
 The expansion of offshore cage culture is limited by the
availability of hatchery bred seed for stocking.
 The feed cost is still high because suitable pellet specific for
different fish species has not yet been developed.
 There is also likely occurrence of high feed loss through the
net in strong current conditions of deep sea for slow feeding
species like grouper.
 There have been many locally produced formulated feeds for
common marine fish but the results for grouper culture show
that they are not as efficient or economic as trash fish.

Advances
 The on-going FAO/NACA project on “Reducing the dependence
on the utilisation of trash fish/ low value fish as feed for
aquaculture of marine finfish in the Asian region”.
 Local production of polyethylene (HDPE) circular cages which
can withstand the rough conditions.
 Research on seed production technique of many commercial
species is going on.

Cage culture of cobia
Introduction
 Classification
 Order – Perciformes
 Family – Rachycentridae
 Cobia is the only species in the family Rachycentridae.
 Often referred as ‘Asian Salmon
 Cobia are found in shallow areas of the open ocean, often
associated with buoys, reefs, wrecks, and harbours.

Distribution
 Distributed worldwide in
warm marine waters.
 They can be found
throughout the water
column.
 Generally considered
incidental catch.

Biology
 Cobia prefer warm water (>20 ºC) and typically have annual
migratory patterns.
 Sexual maturity is reported in males at 1-2 years and in females
at 2-3 years.
 Spawning occurs in both near shore and offshore waters where
females release several hundred thousand to several million
eggs (1.4 mm diameter).
 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 at 3.5 mm TL at hatching.
 Juvenile fish are found in both near shore and offshore waters,
often among Sargassum patches or weed lines where they seek
shelter from predators and can feed.
 Cobia are opportunistic feeders, feeds on various fish, shrimp,
squid, and, in particular, crabs.

Aquaculture suitability
Characteristics make cobia suitable for commercial culture –
 Fast growth, high survival rates
 low feed-conversion ratio
 Good meat quality
 Fillet yield is better

Broodstock development
 Successful breeding of cobia was achieved by CMFRI at
Mandapam regional centre.
 The broodstock at Mandapam was developed in sea cages of 6
m diameter and 3.5 m depth.
 Total of 37 cobia brooders of size ranging from 12 to 35 kg
weight were maintained in five cages.
 At stocking density of 1.5 kg per m3.
 Fish were fed daily with 70% of fresh sardines and 30%
portunid crabs/ squid at 5 % of their body weight.

 The brood fishes were cannulated at specific intervals to assess
the gonad maturity.
PIT tagging of cobia broodstock
 Passive Integrated Transponder (PIT) was employed for tagging
the cobia broodstock at Mandapam.

 The maturation characteristics of female include egg with size
above 0.7 mm, non-adhesive, white colour and round shape.

Induced breeding
 Selected brooders were introduced in a 100 t roofed cement
tank holding about 60 t of seawater.
 One female and two males were introduced.
 Induced spawning with HCG at doses of 500 IU per kg body
weight for female and 250 IU per kg body weight for males.
 15kg female will produce 2-3 million eggs(1.4 mm diameter).
 The eggs were collected by a 500μm mesh.

Incubation
 The eggs hatched after 22 h of incubation at a temperature
range of 28-30 ºC.
 The percentage of hatching was 80%.
 The newly hatched larvae measured 2.2-2.7 mm in total
length.
 The mouth opening was formed on (on 3rd day post-hatch) at
a length of around 200μm.

Larval rearing
 Greenwater technique was adopted for larviculture.
 The larvae were stocked in FRP tanks of 5 ton capacity for
larviculture.
 Stocking density :30-40 larvae/lit.
 Green water at a density of about 1 x 10 cells/ml (Tetraselmis
/Isochrysis) and rotifers enriched with DHA SELCO at a density of
6-8 nos./ml from 3 to 9 dph.
5

 Critical stage for the larvae was 5 to 7 dph when they entirely
resorted to exogenous feeding.
 Mortality rates are high at this stage, more than 80% mortality is
seen.
 From 9 to 21 dph, the larvae were fed four times daily with
enriched Artemia nauplii by maintaining a nauplii concentration
of 2-3 nos/ml.

 After 25 dph size grading is done to remove the shooters.
 size groups of juveniles with mean sizes of 10 cm (10%), 6 cm
(25%) and 4 cm (65%).
 Fingerlings of 10 cm length and above were stocked for
nursery rearing.

Nursery rearing
 Nursery rearing of cobia generally comprises two phases.
 The first phase was done in 5 tonne capacity FRP tanks with 250
numbers of fingerlings filled at two-third level with sea water.
 100% water exchange is done in the morning and evening.
 Fed both by formulated feeds as well as with chopped sardines.
 Hatchery phase of nursery rearing was continued for a month
till they reached 17-22 cm and weight range of 27-59 gms.

Second phase
 Fingerlings were transferred to nursery cages which were
installed in the nearshore area.
 Second phase of nursery rearing in cages was done for about 20
days.
 Feeding with chopped trash fish and pellets.
 At the end of phase, the length range of fingerlings was 22-26
cm and weight range 35-70 g.

Grow out
 Cage farming of cobia was experimented for the first time in
India in the Gulf of Mannar from the hatchery produced
fingerlings.
 Length range of fingerlings stocked was from 22- 26 cm and
weight ranged from 35-70 g.
 The fish were fed with trash fish adlibitum once in a day.
 After 7 months of stocking in grow out cages, the length range
of the fish was 60-70 cm and weight range 2.8 to 3.5 kg.

Summary of cage culture in china

Summary of cage culture in Vietnam

Prospects
 It has been noted that rapid growth rate and good flesh quality
of cobia make it one of the best species for future expansion of
production.
 The present success in the captive breeding of cobia can be
considered as a milestone for farming of cobia.
 Standardisation of technologies for seed production and
farming of cobia to suit our environmental conditions have to
be further pursued

Problems
 pond management, culture density, feed rate, and water
exchange rates, the aquaculture production of cobia in ponds
may result in water quality issues.
 Diseases affecting the fish in culture are a major issue.
 Intensification of nearshore production has been reported to
result in increased disease outbreaks.
 Use of trash fish and high protien feed.
 Seed production techniques should be more efficient.

References
 Kongkeo, H., Wayne, C., Murdjani, M., Bunliptanon, P., Chien,
T. Current practices of marine finfish cage culture in China,
Indonesia, Thailand and Viet Nam.
 Department of Agriculture, BUREAU OF FISHERIES AND
AQUATIC RESOURCES RFO 8, CRM Center Brgy, Tacloban City,
Tacloban City.
 PROSPECTS OF GROUPER CULTURE IN INDIA, P. NAMMALWAR,
R. MARICHAMY, A.REGUNATHANI AND K. KANDASAMY, Central
Marine Fisheries Research Institute, Kochi - 682014

 Successful seed production of cobia Rachycentron canadum
and its prospects for farming in India. G. Gopakumar, G. Syda
Rao, A. K. Abdul Nazar.
 www.fao.org, fisheries and aquaculture department.
 CMFRI annual report 2010 – 2011.
 Capture based aquaculture by FAO.

Cage Culture of Grouper and Cobia

More Related Content

What's hot

Similar to Cage Culture of Grouper and Cobia

More from SHUBHAM PATIDAR FISHERIES ADDAA

Recently uploaded

In this document

Cage Culture of Grouper and Cobia