Development of captive broodstock of the grey mullet, Mugil cephalus

Indtan J Fish, 4712) : 91-96, A~K-Jun., 2000
Development of captive broodstock of the grey mullet,
Mugil cephalus (L)
MATHEW ABRAHAM, M. KAILASAM, P. KTSHORE CHANDRA, P. SIHRANEE,
K.V. RAJENDRAN AND A.V.K. CKARLES
Central Institute of Brackishwater Aquaculture,
Chennaz-600 008, India
ABSTRACT
A captive broodstock of the grey mullet Mugil cephalus has been successfully
developed at Muttukadu experimental station of the Central Institute of
Brackishwater Aquaculture. A stock of 72 sub-adult and adult fish in the size
range of 290-450 mm/300-1,200 g procured from the commercial catches were
maintained in 100 tonne capacity RCC tanks hom January '96. During 1996, about
20% of the stock, both males and females attained final maturity. In 1997, about
60% of the females and 80% of the males attained final maturity In mature females
ova diameter of the matured oocytes ranged from 525 to 614 pa and the mature
males were in oozing stage.
Introduction
Brackishwater aquaculture sector
in India which is shrimp dependent has
witnessed set backs of late due to
disease outbreaks and environmental
problems and therefore the need of the
hour is to adopt eco-friendly farming
with emphasis on species diversification.
The striped mullet, Mugil
cephalus (L) is one of the most popular
and fast growing brackishwater finfish
being cultured in tropical and subtropical
regions (Thompson, 1963). The
advantages of this species for aquaculture
have been well documented
(Odum, 1970; Pillai et al., 1984 and
Rajyalakshmi and Chandra, 1987). In
India farming of this species is being
done mainly by polyculture method
using seed collected from the wild and
is restricted to traditional system. Seed
availability from the nature is erratic
and undependable. Seed production by
induced breeding in captivity is the
only alternative to promote the farming
of this species. Though breeders are
available from the commercial catches,
induced breeding and seed production
have not been accomplished so far
eventhough several efforts have been
made. This is mainly because of the
problems associated with the procurement,
transport and acclimatization of
the breeders (Mathew, et al., 1998).
Hence it is absolutely necessary to
maintain and develop captive broodstock
to facilitate induced breeding and seed
production of captivity. The paper
presents the details of the development
of a captive broodstock cf M~tgil
cephalus at the field centre of the
Central Institute of Brackishwater
Aquaculture at Muttukadu, for the first
time in the country.

Materials and methods
Adult and sub-adult fishes caught
aiive in the commercial catches at
Muttukadu and Kovaiam which are
devoid of any visible injuries were
proc~red and transported to the hatchery
complex at Muttukadu in plastic
tubs having seawater with aeration
during December 1995. They uTere
trest,d vith 1.0 ppm acr~flavine for an
hmr. They wee then released in 20
tome capacity tanks havzllg water
treats: with calcium hypochlorite
(Mzthew t al., 1998). The fishes were
retained or 3 days and t'he survived
ones were trarderi-ed to the broodstock
holding tanks. ,Among about 130 fishes
procured 72 have survived. These
fishes were in the size range of 290-450
nlm and 300-1:200 g.
7% b~oodstock was maintained in
t\b.o 100 s capacity RCC tanks having
raciiiiy for seawater circulation. Water
exchange was done daily @ 1580%. The
tanks were cleaned every alternate uay
to flush out the faecal matter and
debris. Tne fishes were fed with a
formuiated peileted rnatcration feed @
3% of body weight daily During 1996-
'97 they were %d with a high lipid feed
having the prosimate compositiun of
35.30% crude proLeh, 6.0% crude lipid,
3.318 trude fibre, 8.79% ash, 5.47%
moisture azid 41.138 NPE. Eventhough
the fishes have grown well and were in
goo& health the percentage of maturity
was only 30. When few fishes were
dissected and examined. it was found
that there was an excess accumulation
of fat in the coe:o;rr.ic cavity and aroznd
the intessi~e. It is believed that this
ercw faz accumulaticn xighht have
lnterferad with 'he gonadial maturity.
Considering this, two types of feeds
\.;.cw 1 sc.3 difring 1997-'98. A high lipid
feed having the proximate con~positio::
of 3S.08 crude protein, 8.2% crude lipid,
4.47% crude fibre, 14.58% total ash and
7.35% moisture was fed during the
recouping period (January to August)
and a low lipid feed having the
proximate composition of 34.05% crude
protein, 4.54% crude lipid, 12.22% total
ash and 5.91% moisturc was fed during
the gonadial development period
(September-December). The fishes were
also foznd to be feeding on the tenthic
algal ccimmmlty that were allowed to
grow on the wails of the tanks. Water
quality parameters like salinity, pH,
temperature, dissolved oxygen, turbidity,
ammonia and nitrite were estimated
at weekly
The fishes were
examined once in a month to monitor
their health condition. Maturity of
ft\males was examined by - gonadial -
biopsy using a catheter. In the case of
males, ths abdomen was gently pressed
ro see the presence of milt. Rshes were
anesthetised before handlizlg.
The monthly average values of
salinity, pH, dissolved oxygen, temperature,
turbidity and ammonia are shown
in Fig. 1. Variation in the salinity
during the period was not much 2nd
was limited to 5.2 ppt. Maximum
salinity of 32.2 ppt was noted dluring
May '97 and the lowest salinity of 27.0
ppt was recorded during January, 1998.
The pH of the water also did not vary
much and the water always remained
alkaline. Minimum pH was 7.6 and the
maximum was 8.3. Minimum dissolved
oxygen of 6.8 ppm was during July and
throughout the period there was no sign
of oxygen depletion. Water temperature
ranged between 28.5% during January
'98 and 32.g°C during June '97. Turbidity
vdues indicate that the water

Deuelopment of brood stock of Mugil cephalus 93
SALINITY
36 , .-4
71 . . . . I
M A M J J U A S O N D J F
g 7.2 --
DISSOLVED OXYGEN
64 1, 1
M A M J J U A S O N D J F
TEMPERATURE
161 , , , . . , . . , , , 1
M A M J J U A S O N D J F
01 , , , i
M A M J J U A S O N D J F
AMMONIA
r - P
0 J
M A M J J U A S O N D J F
MONTHS
Fig. 1. Monthly average values of water qua1il;Sparameters
in broodstock tanks during
1996-'97.
remained almost clear throughout the
period because of daily water exchange.
Similarly ammonia content also remained
to be low due to regular water
exchange. It was seen that the water
quality parameters did not vary much
during the broodstock development
period.
The broodstock fishes were examiaed
at regular intervals to monitor
their health condition. The fishes were
examined for ecto-parasites mainly in
the gdls and body surface. Parasitic
organisms were found to cause major
problems in captive broodstock development.
This can be attributed to the
presence of natural parasitic fauna in
the wild caught fish and their f~rthsr
proliferation in captivity. Once thp
fishes were found to be infected with
Lernanthropus sp. it was effectively
treated with Dichlorvos @ 1 ppm for one
hour, On few other occasions the fishes
were found to be infected with Caligus
sp. and treatment with formalin @ 100
ppm for 90 minutes was found to be
verjj effective. Later on to prevent
infections, the broodstock holding tanks
were treated at monthly intervals with
formalin @ 100 ppm for one hour as a
prophylactic measure and infections
were minimised later on. Normallv the
treatments are done after reducing the
water level to 25 cm and also under
close watch. Whenever the fish showed
signs of stress during treatment, the
water was exchanged immediately. It
is very essential that the stock should
be maintained free of parasites for their
survival and gonadial maturation.
Gonadial maturity of the stock was
examined at monthly intervals dcring
September and October and at fortnightly
intervals during November-
February by random sampling. The
state of ovarian maturity was assessed
by the in vivo monitoring method
validated by Shehadeh et al., (1973). A
catheter of 1.5 mm O.D. was used. One

Mathew Abraham et al. 94
Fig. 2. Percentage occurrence of different maturity
stiiges in II.fugil cephalus females during
1997.
end of the catheter was inserted through
the oviduct to 5.8 cm and the other end
of the catheter was held in the mouth
of the operator and aspirated while
slowly withdrawing the catheter. The
oocytes in the catheter was blown out
to a petridish having 2% formalin. The
oocytes were examined under microscope
and the ova diameter measured
using calibrated ocular micrometer. In
the case of males, the presence of milt
was physicaliy examined by pressing
the abdomen. The percentage occurrence
of female and male fishes in
different mon4hs was assessed and is
depicted in Fig. 2&3. All the females
were in immature stage upto September.
Initiation of maturation was observed
during October and about 50%
of the females were in maturing stage
with ova diameter ranging fom 200-300
pm. The remaining 50% were in immature
stage. In the succeeding month,
females showed increasing trend in
ovarian development and about 25% of
the females were in mature stage with
ova diameter ranging from 450-540 pm.
The remaining 30% were immature and
45% were in maturing stage. During
December the percentage occurrence of
mature females increased and was 50%.
Out of the remaining 50%, 25% were
immature and 25% were in maturing
stage. During January, 25% were
immature, 25% in mature and 50% in
resorption stages. During February, all
the females were either immature or in
resorption stages. Mature eggs were
non-adhesive, round with tertiary yolk
globule and measured 525 pm or more
in diameter.
In the case of males, dl were in
immature stage during August. Initiation
of maturation was observed in the
first week of September and almost 75%
of the males were in maturing stage
during this month. In October aboat
25% were in immature stage, 15% in
maturing stage and 60% in mature
stage. Maximum number of oozing
mature males (65%) were observed
during November. The percentage of
mature males drastically declined to
15% in December and about 65% males
lost the condition and were in resorption
stage and in January only 5% were
in mature stage. During February, all
were either immature or in resorption
conditon.
From a scrutiny of the percentage
occurrence of mature females and
males, it is seen that majority of males
attained maturitv durinq November
Fig. 3. Percentage occurrence of different maturity
stages in Mugil cephalus males during
1997.

Derelopment of brood stock of Mugil cephalus 95
and females during December. The
maturation of females and males is not
synchronizing and majority of males
attained maturity almost a month
earlier to females. In the commercial
catches also it is observed that the
mature males start appearing as early
as from October onwards and females
through in few numbers, start appearing
from November onwards.
A prerequisite for propagation of a
fish species is the mature broodstock.
In the past, researchers had to rely
solely on nature for breeders. To
overcome this, efforts have been made
to develop captive broostocks and
success have been reported. Liao et at.
(1971) have developed a captive
broodstock ir, freshwater and succeeded
in breeding them after acclimatising
them to seawater three months ~rior to
breeding. Shehadeh et al. (1973) have
maintained three year old mullet in
pond with seawater and provision for
the growth of benthic diatom and
algae. The fishes have attained
maturity in the following year. By
manipuIating photoperiod and ambient
water temperature, it has been shown
that reproductive cycle can be accelerated
(Kuo et al., 1974). It has been
noted that the onset of vitellogenesis is
regulated by environmental conditions.
A sliortened photoperiod (6L118D) initiates
vitcellogenesis and a lower
temperature (2I0C) ensures its completion.
Fishes that have been matured
through environmental manipulations
have been successfully induced to
spawn outside the normal breeding
season.
and Training Centre, broodstocks are
devleloped in concrete raceways
equipped with constant flow of water.
The fishes were fed with formulated
feed having 36.0% protein and 4.1% fat,
@ 3% of body weight daily (Tarnaru et
al., 1993). Outdoor rectangular rubberlined
ponds and round concrete ponds
are used at the Oceanic Institute,
Hawaii for broodstock development.
Here fishes were fed on the naturally
occurring benthic growth and were also
given Purina Trout Chow as supplementary
feed (Lee et al., 1988; 1992). It
has also been reported that striped
mullet females have matured in outdoor
seawatnr or brackishwater tanks and
indoor seawater tanks (Tamaru et al.,
1991). Salinites ranging from 13-35 ppt
are adequate for ovarian maturation in
captive mullet females
The present study has demonstrated
that majority of the broodstock
can attain maturity provided they are
maintained with regular water exchange
and feeding. Fceding the stock
with a maturation feed of high lipid
content (8.2%) during the recouping
period and feeding with a low lipid
(4.54%) during the gonad maturation
period was found to be more effective
to get more fishes matured. The
salinity of the broodstock tanks ranged
from 27.0-32.2 ppt. Since the salinity
range was not significant, it is difficult
to draw conclusion on the effect of
salinity on maturation. However, it is
observed that the period of maturation
coincides with a shortened day and a
decrease in the water temperature.
Hence it is evident that a shortened
Implantation of hormone pellets for photoperiod may help initiate vitelloaccelerating
maturation was found to be genesis and a lower temperature hdps
effective in milk fish (Lee et al., 1986). its completion as already observed in
At Guam Aquaculture Development earlier reports.

Acknowledgments
The authors are indebted to Dr.
G.R.M. Rao, Director, CIBA and to Dr.
K. Alagarswami, former Director, CIBA
for their encouragements during the
course of this study
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