Evaluation of different live food organisms on growth and survival of river catfish, Mystus nemurus (C&V) larvae
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Mystus nemurus is one of the most commercially important freshwater fish in Malaysia. Even though artificial breeding or reproduction of M. nemurus is done in private hatcheries around Peninsular Malaysia, inadequate seed supply coupled with relatively high fingerling prices limits its production. Presently, the supply of fingerlings cannot satisfy the demand for fish farming due to some constraints on the larval rearing, so larval rearing of M. nemurus has yet to be improved in terms of nutrition requirement and suitable size of food for the larvae. At present, the conventional method of fish larviculture using live food such as Artemia nauplii is being practiced by most Malaysian catfish hatchery operators. Using expensive live food like Artemia has made the mass production of catfish fry/fingerlings less profitable. Alternative measures are necessary in order to help minimize importation and use of Artemia. Indigenous species of live food organisms, which are great potential as feed and can easily be cultured and mass-produced at low cost, may be used as substitutes. Studies on those live foods are lacking, hence this study was conducted to determine the effect of different live foods on growth and survival of Mystus nemurus larvae.
Laron, M. A., Kamarudin, M. S., Yusoff, F. M., & Saad, C. R. (2001). Evaluation of different live food organisms on growth and survival of river catfish, Mystus nemurus (C&V) larvae. In C. I. Henry, G. Van Stappen, M. Wille, & P. Sorgeloos (Eds.), Larvi 2001 : 3rd Fish & Shellfish Larviculture Symposium, Gent, Belgium, September 3-6, 2001 (EAS Special Publication No. 30) (pp. 299-302). Oostende, Belgium: European Aquaculture Society.
PublisherEuropean Aquaculture Society
SeriesSpecial Publication No. 30
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Rapid wound healing in African catfish, Clarias gariepinus, fed diets supplemented with ascorbic acid G Erazo-Pagador & MS Din -
The Israeli Journal of Aquaculture-Bamidgeh, 2001 - Society of Israeli Aquaculture and Marine BiotechnologyWound healing in African catfish, Clarias gariepinus, fed diets supplemented with ascorbic acid was studied under laboratory conditions. Fish weighing approximately 80-110 g were stocked in 500 l aquaria in a static water system and fed one of five test diets containing different levels of microencapsulated ascorbic acid (0, 0.06, 0.10, 0.30 and 0.70 g AsA/100 g feed). After two weeks, all experimental fish were wounded by making a 1 x 1 cm dorso-lateral incision above the lateral line of the fish. Wounded tissues were sampled for histopathological analysis 4, 8, 24, 48 and 96 hours, 6, 8, 10, 12 and 14 days after making the incision. There were significant differences in weight gain, specific growth rate (SGR) and feed conversion ratio among the dietary treatments. Weight gain and SGR of fish fed the ascorbic acid free diet were lower than those of fish fed diets supplemented with ascorbic acid. The wound healing response showed a direct correlation to ascorbate level in the diet. Fibroblasts were present at 96 h irrespective of the ascorbic acid level. As 14 days, fish fed no ascorbic acid had some regeneration of muscle tissues, whereas fish fed diets containing supplemental ascorbic acid had a normal epidermis, dermis and muscle structure. There was no mortality during the experimental period, and fish fed ascorbic acid free diets did not exhibit any deficiency signs. Results of this study indicate that about 0.10-0.70 g AsA/100 g feed is needed for wound repair in African catfish.
ArticleMany demersal fish species undergo vertical shifts in habitats during ontogeny especially after larval metamorphosis. The visual spectral sensitivity shifts with the habitat, indicating a change in colour vision. Colour vision depends on sufficient ambient light and becomes ineffective at a particular low light intensity. It is not known how fishes see colour in dim light. By means of a behavioural experiment on larval African catfish Clarias gariepinus in the laboratory, we determined colour vision and colour discrimination in dim light. Light-adapted larvae were subjected to classical conditioning to associate a reward feed with a green or a red stimulus placed among 7 shades of grey. The larvae learned this visual task after 70 and 90 trials. A different batch of larvae were trained to discriminate between green and red and then tested for the ability to discriminate between these colours, as the light intensity was reduced. The larvae learned this visual task after 110 trials in bright light and were able to discriminate colours, as light was dimmed until 0.01 lx, the minimal illuminance measurable in this study, and similar to starlight. The retinae of the larvae were found to be light adapted at 0.01 lx; thus indicating cone-based colour vision at this illuminance. For comparison, three human subjects were tested under similar conditions and showed a colour vision threshold at between 1.5 and 0.1 lx. For the larvae of C. gariepinus, the ability of colour discrimination in dim light is probably due to its retinal tapetum, which could increase the sensitivity of cones.
Conference paperJD Tan-Fermin, RSJ Gapasin, AM Tan, MA Garcia & AC Emata - In CL Marte, GF Quinitio & AC Emata (Eds.), Proceedings of the Seminar-Workshop on Breeding and Seed Production of Cultured Finfishes in the Philippines, Tigbauan, Iloilo, Philippines, 4-5 May 1993, 1996 - SEAFDEC Aquaculture DepartmentClarias macrocephalus is endemic yet dwindling freshwater foodfish in the Philippines. Induced breeding protocol was developed by monitoring the size and maturation of eggs at 0-48 h after a simultaneous injection of luteinizing hormone-releasing hormone analogue (LHRHa; 0.0005 - 0.10 µg/g BW) and pimozide (PIM; 1 µg/g BW). Based on its similar osmotic pressure with catfish plasma, eggs were fixed in 1% phosphate-buffered formalin. Mean egg diameter of fish that were induced to mature increased during ovulation. Oocyte maturation, indicated by oocytes with germinal vesicle breakdown (GVBD), was observed at least 12 h post-injection in fish given 0.01 - 0.10 µg LHRHa + 1 µg PIM/g BW, followed by ovulation 4 h thereafter. Results showed that a simultaneous injection of C. macrocephalus with 0.05 µg LHRHa + 1 µg PIM/g BW at 1800-1900 h followed by stripping at 16-20 h post-injection resulted in high ovulation, fertilization and hatching rates.