Indian J Fish., 47i2) : 91-96, Apr-Jun., 2000

Development of captiv@broodstock of the grey mullet, Mugil cephalus (L)

MATHEW ABRAHAM, M. KAILASAM, P. KISHORE CHANDRA, P. SIHRANEE, K.V. RAJENDRAN AND A.V.K. CHARLES Central Institute of Brackishwater Aquaculture, Chennai-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 md300-1,200 g procured from the commercial catches were maintained in 100 tonne capacity RCC tanks from January '96. During 1996, about 20% of the stock, both males and females attained final maturitx In 1997, about 60% of the females and 80% of the males attained frnal maturity In mature females ova diameter of the matured oocytes ranged from 525 to 614 pn 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 diversifrca- tion. The striped mullet, Mugil cephalus (L) is one of the most popular and fast growing brackishwater finfish being cultured in tropical and sub- tropical regions (Thompson, 1963). The advantages of this species for aqua- culture have been well documented (Odwn, 1970; Pillai e t al., 1984 and Rajyalakshmi and Chandra, 1987). In India farming of this species is being done mainly by polyculture method i~sinrr send cnllerted frnm the wild and

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 procure- ment, transport and acclimatization of the breeders (Mathew, e t al., 1998). Hence it is absolutely necessary t c maintain and develop captive broodstock to facilitate induced breeding and seec production of captivity. The paper presents the details of the developmen of a captive broodstock d Mugi cephalus a t the field centre of thr Central Institute nf R r a r k i ~ ~ w s t a l

Mathew Abmhnm et al. 92

Materials and methods

Adult and sub-adult fishes caught alive in the commercial catches at Muttukadu and Kovalam which are devoid of any visible injuries were procured and transported to the hatch- ery complex at Muttukadu in plastic tubs having seawater with aeration during December 1995. They were treated with 1.0 ppm acriflavine for an hour. They were then released in 20 tonne capacity tanks having water treated with calcium hypochlorite (Mathew e t al., 1998). The fishes were retained for 3 days and the survived ones were transferred t o the broodstock holding tanks. Among about 130 fishes procured 72 have survived. These fishes were in the size range of 290-450 mm and 300-1,200 g.

The broodstock was maintained in two 100 t capacity RCC tanks having facility for seawater circulation. Water exchange was done daily @ 75430%. The tanks were cleaned every alternate day to flush out the faecal matter and debris. The fishes were fed with a formulated pelleted maturation feed @ 3% of body weight d a i l ~ During 1996- '97 they were fed with a high lipid feed having the proximate composition of 35.30% crude protein, 6.0% crude lipid, 3.37% crude fibre, 8.79% ash, 5.47% moisture and 41.13% W E . Eventhough the fishes have grown well and were in good health the percentage of maturity was only 20. When few fishes were dissected and examined, it was found that there was an excess accumulation of fat in the coelomic cavity and around the intestine. It is believed that this excess fat accumulation might have interfered with the gonadial maturity.

<d.,4..." +I.:" AT.- L.." 2 4--..J-

feed having the proximate composition of 33.0% 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% moisture was fed during the gonadial development period (September-December). The fishes were also found to be feeding on the benthic algal community that were allowed to grow on the walls of the tanks. Water quality parameters like salinity, pH, temperature, dissolved oxygen, turbid- ity, ammonia and nitrite were estimated at weekly intervals. The fishes were examined once in a month to monitor their health condition. Maturity of females was examined by aonadial - - biopsy using a catheter. In the case of males, the abdomen was gently pressed to see the presence of milt. Fishes were anesthetised before handling.

Results and discussion The monthly average values of

salinity, pH, dissolved oxygen, tempera- ture, turbidity and ammonia are shown in Fig. 1. Variation in the salinity during the period was not much and was limited to 5.2 ppt. Maximum salinity of 32.2 ppt was noted during 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 ,no -,-I o n n o 0 a..;, .. T-.- .. mrr rn-.-La

Development of brood stock of Mugil cephalus

SALINITY 36 I

7 1 , , ,

M A M J J U A S O N D J F

DISSOLVED OXYGEN

6 . 4 ' , , , , M A M J J U A S O N D J F

TEMPERATURE

. . : ~ ~ 28

26 M A M J J U A S O N D J F

exchange. It was seen that the water quality parameters did not vary much during the broodstock development period.

0 0 M A M J J U A S O N D J F

0.12 AMMONIA

I

0.08 . h E 11

Y I

0 YP M A M J J U A S O N D J F

MONTHS

Fig. 1. Monthly average values of water qualit: parameters in broodstock tanks durin, 1996-'97.

remained almost clear throughout thc period because of daily water exchange

, I .

The broodstock fishes were exam- ined at regular intervals to monitor their health condition. The fishes were examined for ecto-parasites mainly in the gills and body surface. Parasitic organisms were found to cause major problems in captive broodstock develop- ment. This can be attributed to the presence of natural parasitic fauna in the wild caught fish and their further proliferation in captivity Once the 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 very 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. Normally 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 during September and October and at fort- nightly intervals during November- February by random sampling. The state of ovarian maturity was assessed by the in vivo monitoring method

Mathew A b r h et al. 94

Fig. 2. Percentage occurrence of different matu- rity stages in Mugil cephalus females during 1997.

end of the catheter was inserted through the oviduct t o 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 micro- scope and the ova diameter measured using calibrated ocular micrometer. In the case of males, the presence of milt was physically examined by pressing the abdomen. The percentage occur- rence of female and male fishes in different months was assessed and is depicted in Fig. 2&3. All the females were in immature stage upto Septem- ber. Initiation of maturation was ob- served 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 imma- ture 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 ...-t....,. . F ~ . . . - I A ~ :......----A --.I .---- cnm

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 K r n or more in diameter.

In the case of males, all were in immature stage during August. Initia- tion 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 about 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 resorp- tion 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 during November

Fig. 3. Percentage occurrence of different matu-

Development 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 t o 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 appear- ing 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 overlome this, efforts have been made to develop captive broostocks and success have been reported. Liao et al. (1971) have developed a captive broodstock in freshwater and succeeded in breeding them after acclimatising them to seawater three months prior to breeding. Shehadeh et al. (1973) have maintained three year old mullet in pond with seawater and provision for the growth of benthic diatoms and algae. The fishes have attained maturity in the following year. By manipulating photoperiod and ambient water temperature, it has been shown that reproductive cycle can be acceler- ated (Kuo et al., 1974). It has been noted that the onset of vitellogenesis is regulated by environmental conditions. A sliortened photoperiod (6LI18D) ini- tiates vitcellogenesis and a lower temperature (21%) ensures its comple- tion. Fishes that have been matured through environmental manipulations have been successfully induced to spawn outside the normal breeding season.

Implantation of hormone pellets for accelerating maturation was found to be

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 (Tamaru et al., 1993). Outdoor rectangular rubber- lined 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 supple- mentary feed (Lee et al., 1988; 1992). It has also been reported that striped mullet females have matured in outdoor seawater or brackishwater tanks and indoor seawater tanks (Tamaru e t al., 1991). Salinites ranging from 13-35 ppt are adequate for ovarian maturation in captive mullet females.

The present study has demon- strated that majority of the broodstock can attain maturity provided they are maintained with regular water ex- change and feeding. Feeding 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 t o 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 photoperiod may help initiate vitello- genesis and a lower temperature helps

Mathew Abraham et al. 96

Acknowledgments Marine Food Chains. J.H. Steels, Oliver and Boyd (Eds.), Edinburgh, Scotland.

'Ihe authors are indebted FiUai, S.M.., P.K. Ghosh, T. Rajyalakshmi and G.R.M. Rao, Director, CIBA and to Dr. A.K. Roy 1984. Observation on growth,

K. Alagarswami, former Director, CIBA survival and production of grey mullets, for their encouragements during the Mugil cephalus (L), Liza parsia course of this study. (Hamilton) and Liza tade (Forsskal) in a

coastal low saline polyculture pond. Proc

References Symp. Coastal Aquacult., 3 : 776-781.

Kuo,

Lee,

C.kI., C.E. Nash and Z.H. Shehadeh 1974. The effects of temperature and photope- nod on ovarian development in captive grey mullet (Mugil cephalus L.). Aqua- culture, 3 : 26-43.

C.S., C.S. Tamaru, J.E. Banno and C.D. Kelley 1986. Influence of chronic admin- istration of LIIRII-analogue andlor 17 - methyltestosterone on maturation in milk fish, Chanos chanos. Aquaculture,

Lee, C.S., C.S. Tarnaru and C.D. Kelley 1988. The cost and effectiveness of CPU HCG and LHRH-a on the induced spawning of grey mullet, Mugil cephalus Aquacul- ture, 73 : 341-347.

Lee, C.S., C.S. Tamaru, C.D. Kelley, A. Morinaka and G.T. Miyamoto 1992. The effect of salinity on the induction of spawning and fertilization in the striped mullet, Mugil cephalus. Aquaculture, 102 : 289-296.

Liao, LC., D.L. Lee, M.Y. Lim and M.C. Lo 1971. Preliminary report on induced breeding of pond reared mullet (Mugil cephalus L.). Fish. Sel: Chin-Am. Jt. Comm. Rul: Reconstz, 11 : 30-35.

Mathew Abraham, P.K. Chandra, M. Kailasam and V.K. Charles 1998. Acclimatization cf Mugil cephalus (L) procured from commercial catches. Indian J Fish., 45(2) : 217-219.

Odum, W.E. 1970. Utilization of the direct gazing and plant detritus food chains by the striped mullet, Mugil cephalus. In.

Rajyalakshmi, T. and D.M. Chandra 1987. Recruitment in nature and growth in brackishwater ponds of the striped mullet Mugil cephalus L. in Andhra Pradesh, India. Indian J Anim. Sci., 57(3) : 229-240.

Shehadeh, Z.H., C.M. Kuo and C.E. Nash 1973. Establishing broodstock of grey mullet (Mugil cephalus L.) in small ponds. Aquaculture, 2 : 379-384.

Tamaru, C.S., C.S. Lee and H. Ako 1991. Improving the larval rearing of striped mullet (Mugil cephalus) by manipulating quaIity and quantity of the rotifer, Brachionus plicatilis. In: Rotifer and Microalgae Culture Systems. Proc of a M.S. - Asia Workshop. W. Fulks and K. Main (Eds.), The Oceanic Institute, Honolulu, p. 89-103.

Tamam, C.S., W.J.F. Gerald Jr, and V. Sato 1993. Hatchery Manual for the Artif cia1 Propagation of Striped Mullet (Mugil cephalus). 167 pp. Department of Com- merce, Suite 601, G.I.T.C. Bldg., 590 South Marine Drive, Tamuning, Guam- 96911.

Tamaru, C.S., C.S. Leel, C.D. Xelley, G. Miyamoto and A. moriwake 1994. Oocyte growth in striped mullet, Mugil cephalus (L) maturing at different salinites. J World Aquaculture Society, 25(1) : 109- 115.

Thompson, J.M. 1963. Synopsis of biological data on the grey mullet (Mugil cephalus L). Fish Symp. Div. Oceanogr, C.S.I.R.O., Australia, (1).

Indian J: Fish., 47(2) : 97-101, Apr-Jun., 2000

Larval production by crossbreeding and artificial insemination of freshwater prawns

P. SOUNDARAPANDWV AD4 T. K4NNUPANDI Centre of Advanced Study in Marine Biology, Parangipettai-608 502, India

ABSTRACT

Interspecific crossing has been attempted between Macrobrachium malcolmsonii and M. rosenbergii two cultivable freshwater prawns. The respective females successfully produced viable larvae. The hatching rate and survival percentage increases with increase in size of both the species and it was comparatively higher i n M. rosenbergii females. In intraspecific insemination trials, three M. malcolmsonii females produced viable larvae and another three shed their eggs. However, four M. rosenbergii females produced viable larvae and two shed their eggs. In interspecific insemination trials, females shed their eggs after about 6 to 8 days of incubation.

Introduction

The giant freshwater prawn M. rosenbergii, is an excellent candidate species for aquaculture because of qualities such as rapid growth, good survival, tolerance to wide ranges of temperature and salinity, acceptance of both plant and animal diets, compara- tively tamed behaviour, absence of major disease problems, compatibility with non-predacious species of fish, short larval period and high domestic and export value (Ling and Costello, 1976). However, the Godaveri river prawn, M. malcolmsonii compete prom- isingly with M, rosenbergii in several aspects such as growth rate, feeding habits, lower cannibalistic tendencies, culturability in impounded freshwater, euryhaline adaptability in breeding, fairly good fecundity, larval hardiness in -.+h"+-*a;.." -+ --*- G-- ---I 1 - - - - - - A -...

(Sankolli and Shakuntala Shenoy, 1978). So there is a possibility of transfer of desired traits from one snecies to another species by hybridization.

Uno and Fujita (1972) presented a brief report of success in artificial hybridization of the closely related species, M , formosense and M. nipponense but artificial hybridization with other freshwater prawn species have failed (Dobkinet al., 1973; Sandifer and Smith, 1976, 1979; Sandifer et al., 1977; Shokita, 1978). The crossbreed- ing of male M. malcolrnsonii and female M. rosenbergii was successfully carried out by Sankolli et al. (1982). These two species successfully mated but they shed their eggs after about 10 days of incubation (Soundarapandian e t al., 1995a). The initial attempts involved in mechanical extrusion of spermatophore