Tor Khudree Research Articles

Use of artificial substrates to enhance production of freshwater herbivorous fish in pond culture

Two trials were conducted in mud-bottomed concrete tanks to assess the potential of using artificial substrates to enhance fish production in ponds. Three substrate types were tested: bamboo poles, PVC pipes and sugarcane bagasse bundles. In one trial, periphyton was grown on the substrates in the absence of fish. In the second trial, masheer (Tor khudree Sykes) fingerlings were stocked at three densities. Results showed a significant effect of substrate type on fish growth (P≤ 0.001) and on net fish production (P≤ 0.05), with best growth in the tanks using the bamboo substrate. In the bagasse treatment, 100% fish mortality occurred. Highest extrapolated periphyton-based gross fish yield (i.e. without feed inputs) was 450 kg ha−1 90 d−1 with PVC and 491 kg ha−1 90 d−1 with bamboo substrate. The best periphyton growth occurred on bamboo, followed by bagasse and PVC. Without fish, mean periphyton biomass during the culture period was 0.56–1.20 mg cm−2 on bamboo [ash-free dry matter (DM)], against 0.09–0.36 mg cm−2 on PVC and 0.20–0.59 mg cm–2 on bagasse. No clear effect of fish density or water depth on periphyton biomass could be seen. Only on bamboo, fish density seemed to have a negative effect on periphyton ash-free dry matter and a positive effect on pigment content (chlorophyll-a and phaeophytin). Periphyton from bamboo had a lower ash content (38–47% of DM) than from PVC (54–55% of DM) or bagasse (51–58% of DM). It is concluded that substrate type has a strong effect on periphyton productivity and composition, and on fish productivity. Good fish production was achieved without feed inputs. More research is needed to study the economic viability of periphyton-based systems in the context of Indian aquaculture.

Assemblage structure of stream fishes in the Western Ghats (India)

Macro and microhabitat analyses were applied to characterise the fish assemblage structure in 10 streams of the Western Ghat mountains of Peninsular India. Macrohabitat features, such as channel gradient, stream depth, stream width, riparian cover, instream cover, habitat types and substrates, were used. Microhabitat requirements of the abundant cyprinids (35 species) were also analysed. Macrohabitat assessment indicated that a high habitat diversity was associated with a high species diversity, and that habitat volume was a major determining factor for species diversity and abundance. In all streams, cyprinids were the dominant group in the assemblage and almost all cyprinids were confined to pools with a varied habitat diversity. Riffle dwelling species included ancient forms such as Glyptothorax madraspatnum, G. trewasae and Homaloptera santhamparaiensis. Suitable microhabitats for dominant cyprinid species were pools and riffle edges. Big-sized barbs and mahseers such as Hypselobarbus dobsoni, H. curmuca, H. dubius, Labeo calbasu, Puntius sarana, Tor khudree and Tor khudree malabaricus were confined to deep pools with a large area. Smaller Puntius species like P. fasciatus, P. melanampyx, P. narayani, P. sophore, P. ticto and P. vittatus lived in shallow backwater pools and pools with low flow. Species like P. arulius tambiraparniei, P. amphibius, P. bimaculatus and P. filamentosus were found towards shallow pools with moderate flow. Surface-dwelling species such as Danio aequipinnatus, Rasbora daniconius, Salmostoma spp. and Barilius spp. preferred deepwater habitats with high flow. Habitat-based multivariate analysis revealed four guilds: surface dwellers, column dwellers, generalized bottom dwellers and specialized bottom dwellers.

Association of Aeromonas hydrophila with epizootic ulcerative syndrome (EUS) of freshwater fish in Sri Lanka

Aeromonas hydrophila was the predominant bacteria isolated from the haemorrhagic lesions and necrotic ulcers in the seven species of fish, Etroplus suratensis, Ophicephalus striatus, Puntius sarana, Rasbora danicornius, Trichogaster pectoralis, Tor khudree lonispinnis and Wallago attu affected by eizootic ulcerative syndrome(EUS), during the 1990 and 1991 disease outbreaks in Sri Lanka. Severely affected fish were truly septicemic, as A. hydrophila was recovered from their internal organs. A. hydrophila isolated from diseased fish and injected intramuscularly into healthy E. suratensis and O. striatus induced dermonecrotic lesions resemblin EUS. The results suggests that A. hydrophila is consistently associated with EUS in Sri Lanka anf may play an important role in the patlogenesis of the disease.

Effect of feeding different levels of sardine oil on growth, muscle composition and digestive enzyme activities of mahseer, Tor khudree

Sardine oil was incorporated at 3, 6, 9 and 12% into a fish-meal-based 40% protein diet and fed to mahseer fingerlings for 126 days at 5% body weight. Treated fish showed significantly higher growth than control, but did not differ among themselves. Muscle composition and RNA/DNA ratios reflected the growth trend. Feed efficiency was superior for fish fed the 6% oil diet. Dietary lipid influenced muscle fat content. Protease activity was found to be higher in the intestinal segments than in liver and pancreas in both control and treated fish. Oil incorporation at the highest level induced not only higher lipase production, but also higher protease secretion. The possible role of lipid in sparing protein for growth in mahseer is discussed.

Air transport of mahseer (Pisces: Cyprinidae) eggs in moist cotton wool

A method of transporting by air live eggs of Tor khudree (Sykes), packed in moist cotton wool, is described. Egg mortality after transport was 8% or less and survival after hatching was 75%.