The magur, Clarias magur is the most promising catfish species for freshwater aquaculture in India, next to carp. It fetches high market value (US $ 5-6 kg-1), has therapeutic benefit and delicious taste and due to these attributes, the species is in high demand for culture in India. The major bottleneck in the expansion of magur farming is the non-availability of quality seeds. The quality of seed primarily depends on the genetic merit of the broodstock and nutrient composition of broodstock diet. Earlier studies on other species has shown that the broodstock size and age has significant effect on the breeding performance and production of viable eggs and larvae. Therefore, the present study was conducted to evaluate the female broodstock size on the reproductive performance and larval quality of magur and determine ideal broodstock size for the quality seed production.
The pond raised matured male and female magur broodstock were selected and grouped into four size groups based on the body weight as follows, 65 ± 5g (F65); 130 ± 7.9g (F130); 180 ± 3.5 g(F180) and 253 ± 9.7g (F250). Each group had five male and five female broodstock for induced breeding operation. The induced breeding was carried out as per the standard protocol developed at ICAR-Central Institute of Freshwater Aquaculture (ICAR-CIFA), Odisha, India. The reproductive performance parameters such as stripping response, total and relative fecundity, fertilization, hatching rate, egg size, hatchling size, larval growth and survival of each broodstock group were evaluated to ascertain the ideal broodstock size.
Results revealed a positive linear relationship of broodstock size with total fecundity and egg size, yolk size, and hatchling size, whereas the relative fecundity showed a negative relationship. Total fecundity (11471±524) was observed significantly higher in F250 broodstock group, but the same group had significantly lower relative fecundity (4624±345). The stripping response (73.22±0.76 %) and hatching rate (87.81±1.87 %) were significantly (P<0.05) higher in F130 and F180 broodstock size whereas F250 broodfish showed significantly lower stripping response (57.68±8.56 %) and hatching rate (65.22±3.10 %). The fertilization rate was more than 95% for all the broodstock group and no significant (P>0.05) difference could be observed among treatments. The egg diameter, egg weight, hatchling length and weight were significantly (P<0.05) higher in bigger sized broodstock F250 group but egg quality of this body weight broodstock group shown significantly lower level. The larval weight gain (32.37 ± 0.94 mg) and survival rate (94.73 ± 0.24 %) were significantly (P<0.05) higher for F130 to F180 broodstock group whereas, F250 broodstock group exhibited significantly (P<0.05) lower weight gain (9.87 ± 0.18 mg) and survival rate (85.73 ± 0.52 %). Present study clearly indicate that the maternal size has greatly influenced the reproductive performance of magur catfish. In conclusion, the female broodstock of 130-180g body weight range could be the ideal size for successful captive breeding of magur to produce quality seeds for grow-out culture.