Broodstock development, captive breeding and seed production of bagrid catfish, Mahanadi rita, Rita chrysea (Day, 1877)
Introduction
Rita chrysea is a freshwater, medium-sized catfish, belongs to the bagridae family and its popularly known as “Mahanadi rita”. It inhabits in freshwater streams, rivers and reservoirs (David, 1953; Menon, 1999; Sarkar and Lakra, 2007). R. chrysea exhibits an elongated body and the lead-grey colour on the dorsal side. It has three pairs of barbel as well as a strong and denticulate dorsal spine (Fig. 1). It is a column and bottom feeder, predominantly feeds on molluscs, insects and plant materials. It attains maximum size of 30 cm and spawns during the monsoon season (Talwar and Jhingran, 1991; Menon, 1999). R. chrysea was commercially fished for human consumption by barrier nets (Talwar and Jhingran, 1991) and the landings of this catfish was registered as high as 20.2 and 15.1 t from the Hirakud reservoir, Odisha, India during 1978 and 1979, respectively (Varghese et al., 1981); However, the rampant fishing and destruction of breeding ground due to anthropogenic activities were the major threat for its abundance in many water bodies and currently this species is listed as “near threatened” on the IUCN (International Union for Conservation of Nature) list (Dahanukar, 2011). Mahanadi rita is an ideal species for aquaculture because of its good market value (US$ 3–4 kg−1), lesser pin bones and delicious taste. There is no literature available on induced breeding, seed production and even basic biology of this commercially important catfish species; therefore, the present study was conducted to standardize the broodstock development, induced breeding and seed production of R. chrysea under captive conditions. These techniques would be useful in standardizing the farming practise of any new species and for the conservation of the species. Broodstock size and age are the vital factors that influences the reproductive performance, egg quality and higher production viable offspring. There are lot of studies reported for the importance of broodstock size on successful breeding and quality larval production in captive condition. The female broodstock size had positive influence on the egg size and quality (Beacham and Murray, 1985; Trippel, 1998). Gall (1974) has reported in his study that bigger sized and heavier female trout produced larger eggs than younger and smaller broodstock fish. Also, Pitman (1979) studied the rainbow trout female broodstock age and size effect on the growth and survival of offspring. In Tilapia, its reported that the female age and size affected the egg size and fecundity (Jalabert and Zohar, 1982; Rana, 1988). Rana (1988) reported that the breeding performance and egg quality of tilapia was more importantly influenced by the female body weight than the age of broodstock. All these reports were defined the importance of broodstock size and its influence on breeding performance, egg quality and viable seed production. Accordingly, our present experiment was designed to study the effect of female broodstock size on the reproductive performance and larval production of Mahanadi rita, Rita chrysea in captive condition. In this study, two experiments were conducted to develop the breeding and seed production techniques of R. chrysea: 1) evaluation of broodstock size on breeding performance and hatchling production and 2) effect of larval stocking density on the growth, survival and fry production in captive conditions.
Section snippets
Broodstock collection and maintenance
One hundred and twenty Rita chrysea juveniles of 30–130 g (13–32 cm) sizes were collected in three attempts from the Mahanadi river at Munduli barrage (Lat: 20°26′50.03“N; Lon: 85°44’44.72”E), Cuttack, Odisha, India (Fig. 2). These fish were transported to the ICAR-Central Institute of Freshwater Aquaculture, Bhubaneswar, India and stocked in indoor tanks with provision of aeration and water flow-through system for acclimatization. After a brief quarantine in the indoor system, fish were
Experiment 1: effect of broodstock size on breeding performance and hatchling production
Ovulation was observed in five and eight females out of 12 females from each group (50–80 g and 90–130 g) indicating positive response to the induced breeding protocol. The latency period was observed 13–15 h in both broodstock groups with the injected hormone dose of 1 ml kg−1 female body weight. Ovulation response was observed to be higher (66.67%) in the bigger sized broodstock group (90–130 g) compared to 41.67% in the smaller group (50–80 g). The ovulated eggs were demersal, non-adhesive
Experiment 1: effect of broodstock size on breeding performance and hatchling production
The higher ovulation response was recorded in the 90–130 g broodstock size group, compared to the smaller 50–80 g size group and it might be due to the better gonadal maturity of the bigger sized broodstock fish. The same trend was also observed in Clarias gariepinus broodstock and reported that bigger sized fish responded better ovulation compared to the lower weight fish (Ataguba et al., 2012). Ayinla and Nwadukwe (1989) reported that C. gariepinus female brooders of 500–800 g considered as
Conclusions
The present study demonstrated a newly developed protocol for the induced breeding of the Mahanadi rita, Rita chrysea. This study indicated the feasibility of raising the Mahanadi rita broodstock in captive condition with diet supplementation and well-maintained water quality. Bigger brood fish with the body weight range of 90–130 g shown higher breeding response and could be recommended as an ideal broodstock size for induced breeding and seed production in captivity. In addition, stocking
Authors' contribution
Conceived and designed the experiment: SF SKS SSG BKD BRP. Performed the experiments: SF SKS. Analysed the data: SF SKS PCD. Contributed reagents/materials/analysis tools: SSG PCD BKD BRP. Wrote the paper: SF SKS.
Conflict of interest
Authors declare they do not have any conflicts of interest.
Acknowledgements
The authors are grateful to the Director, ICAR-Central Institute of Freshwater Aquaculture, Bhubaneswar, Odisha, India for providing necessary facilities to conduct experiment.
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- 1
The first two authors contributed equally to this study.