Response of bighead carp Aristichthys nobilis and Asian catfish Clarias macrocephalus larvae to free-living nematode Panagrellus redivivus as alternative feed

The use of Panagrellus redivivus as live feed for bighead carp and Asian catfish larvae was tested. In experiment 1, carp larvae were given Artemia nauplii (control) or Panagrellus twice daily for 21 days. A third treatment consisted of unfed larvae. The same three treatments were used in experiment 2 plus another with a commercial entomopathogenic nematode (EPN). Bighead carp larvae given Panagrellus in experiment 1 had much lower growth and survival than those fed Artemia nauplii. This could be due to low nematode density (5-30 mL(-1) water) during feeding. The unfed larvae had 100% mortality by days 11-13. In experiment 2, growth and survival of carp larvae given Artemia nauplii (5-10 mL(-1) ) and Panagrellus (50 mL(-1) ) did not differ significantly (P > 0.05). All unfed larvae had died by day 13, while larvae fed EPN were all dead by day 8. Two experiments on Asian catfish were likewise conducted. In experiment 1, the catfish larvae were fed Tubifex (ad libitum ), Panagrellus (50-100 mL(-1) per feeding) orArtemia (5 nauplii mL(-1) per feeding) three times daily for 14 days. In experiment 2, larvae were fed Artemia alone (10 nauplii mL(-1) per feeding), Panagrellus alone (100 mL(-1) per feeding), or their combination with a 38% protein dry diet twice daily. For both experiments, catfish larvae fed Panagrellus had significantly lower growth and survival than those fed Tubifex or Artemia . The combination of Panagrellus and dry diet created little improvement in the growth and survival of catfish larvae.