Now showing items 1-16 of 16

    • Article

      Biological evaluation of frozen zooplankton as food for milkfish (Chanos chanos) fry 

      CT Villegas & GL Lumasag - Journal of Applied Ichthyology, 1991 - Verlag Paul Parey
      Milkfish fry with an average standard length and weight of 13.88 mm and 3.95 mg, respectively, were reared for 30 days using live and frozen Moina macrocopa and Brachionus plicatilis at feeding densities of 10–20 individuals per ml. Growth, survival and yield were used as indicators of the overall performances of the various treatment groups. Fry fed live M. macrocopa showed gains (both length and weight), growth and survival rates and yields significantly higher than fry fed with other treatment groups (P < 0.05). However, significant reductions in growth and survival rates resulted when fry were fed frozen M. macrocopa. On the other hand, there were no significant differences in growth and survival rates (P < 0.05) in fry fed live or frozen B. plicatilis.

      The results of the current study showed that although milkfish fry could be grown successfully using B. plicatilis, feeding with live Moina significantly improved growth, survival rate and yield (P < 0.05). Frozen Moina was found to be unsuitable as a feed for rearing milkfish fry because it reduced growth rates and increased mortality. Comparisons between live and frozen rotifers have proven the suitability of frozen rotifers as feed for rearing milkfish fry. By freezing surplus rotifers this would permit short term storage in anticipation of high hatchery demand and overcome any unpredictable failures with live cultures.
    • Article

      Cell growth, effect of filtrate and nutritive value of the tropical Prasinophyte Tetraselmis tetrathele (Butcher) at different phases of culture 

      MR de la Peña & CT Villegas - Aquaculture Research, 2005 - Blackwell Publishing
      A local algal isolate Tetraselmis tetrathele was studied to determine the suitable levels of three growth factors (nutrient medium, light intensity and photoperiod) for mass culture. Significantly higher population cell count (141.92 × 104) were found in 4-day-old cultures (exponential phase) enriched with Conwy medium and exposed continuously to 93.31–103.5 μmole photon m−2 s−1 light intensity compared with two other media (F, SEAFDEC/AQD) under the same light conditions. Cultures exposed to higher levels of photosynthetic photon flux density and continuous photoperiod had a significantly higher cell count regardless of nutrient media used. The chemical composition of T. tetrathele varied as the culture aged. Significantly higher crude protein (49.6%) and crude ash (15.9%) were found in cultures harvested at exponential than at stationary phase of growth. In contrast, significantly higher carbohydrate (55.2%) was noted as the culture aged. There was an increase in the percentage of saturated, monoenoic and n-3 highly unsaturated fatty acids at the stationary phase of growth. Addition of filtrate from various phases of growth and from 10-day-old cultures at various concentrations stimulated cell growth of T. tetrathele. This study identified the optimum growth conditions for mass culture of T. tetrathele and demonstrated its change in the chemical composition as the culture aged.
    • Conference paper

      Culture and screening of food organisms as potential larval food for finfish and shellfish 

      CT Villegas - In Report of the Training Course on Growing Food Organisms for Fish Hatcheries: Tigbauan, Iloilo, Philippines, 3-22 August 1981, 1982 - South China Sea Fisheries Development and Coordinating Programme
      The culture of food organisms for fin and shellfish larvae is discussed in detail. Some of the artificial and enriched media that have been developed and tested for microalgae culture are enumerated and some isolation methods are given. Culture methods for phytoplankton and zooplankton are described. The screening, evaluation, nutritive value and suitability of food organisms are considered and some criteria for the selection of food organisms and best food conditions for larvae are presented.
    • Article

      Duration of feeding and indirect selection for growth of tilapia 

      CT Villegas & RW Doyle - Aquaculture, 1986 - Elsevier
      Duration of spontaneous feeding was observed at three times each day in a laboratory population of nine juvenile tilapia (Oreochromis mossambicus). Growth of the fish was measured as change in length and weight, and also as uptake of 14C-labelled glycine by isolated scales. Duration of the first morning feeding was highly correlated with all measures of growth and was independent of initial size. Later feedings were not correlated with growth. Selection on feeding duration could be used to select indirectly for growth rate; this might be a valuable procedure where individuals in the population are not exactly the same age (i.e., where size-at-age is an inaccurate measure of growth).
    • Article

      Effects of increased stocking density and supplemental feeding on the production of milkfish fingerlings 

      CT Villegas & I Bombeo - Fisheries Research Journal of the Philippines, 1982 - Fisheries Research Society of the Philippines
      Experiments were conducted in twelve 144 sq. m. brackishwater ponds at Leganes Research Station, SEAFDEC, to determine the effect of increased stocking density and supplemental feeding on milkfish fingerling production. Two stocking densities (50 and 75 fry/sq. m.) with and without supplemental feeding with rice bran and a formulated diet were tested in a completely randomized design with three replicates.

      Results showed that increased stocking density from 50 fry/ sq. m. to 75 fry/sq. m. fed with rice bran gave a mean survival rate of 71.50%. Growth, measured in terms of weight and length, was not significantly different between treatments. Profitability of increased stocking density and supplemental feeding are discussed.
    • Article

      The effects on growth and survival of feeding water fleas (Moina macrocopa Straus) and rotifers (Brachionus plicatilis ) to milkfish (Chanos chanos Forsskal) fry 

      CT Villegas - The Israeli Journal of Aquaculture-Bamidgeh, 1990 - Society of Israeli Aquaculture and Marine Biotechnology
      The effects of feeding water fleas, Moina macrocopa Straus, and rotifers, Brachionus plicatilis, to milkfish, Chanos chanos Forsskal, fry at different feeding rates and frequencies were investigated. Fry (4.66 mg average weight and 13.45 mm standard length) were stocked in 20 l round plexiglass tanks at 100 per tank in a completely randomized design with four replicates per treatment.

      Results indicated beneficial effects of feeding M. macrocopa to milkfish fry. Fry fed M. macrocopa reached a mean individual final weight, daily gain in weight and yields which were significantly higher (P<0.05) than fry fed B. plicatilis. Feeding the fry with M. macrocopa at the rate of 60 individuals per ml resulted in fish that were 3. to 4 times bigger than fry fed B. plicatilis. Feeding M. macrocopa to fry did not significantly increase survival rates.
    • Article

      Evaluation of the salinity tolerance of Oreochromis mossambicus, O. niloticus and their F1 hybrids 

      CT Villegas - Aquaculture, 1990 - Elsevier
      The salinity tolerance of freshwater-spawned and reared Oreochromis mossambicus, O. niloticus and their F1 hybrids of various ages was studied. Several tests were conducted using three indices as practical measures of salinity tolerance: (1) mean survival time (MST); (2) median survival time (ST50); and (3) median lethal salinity-96 hours (MLS-96).

      Interspecific and age-specific differences (P<0.01) in salinity tolerance were observed in these species and their F1 hybrids on the basis of MST and ST50 indices, with salinity tolerance generally increasing with age of brood. No significant age-specific differences (P > 0.05) in salinity tolerance were observed in all four groups on the basis of MLS-96 index. At the same salinity O. niloticus fry at ages from 15 to 90 days post-hatch exhibited significantly lower (P<0.05) salinity tolerance than O. mossambicus and F1 hybrids. Changes in salinity tolerance were determined to be more closely related to body size than age.
    • Article

      Food value of Brachionus plicatilis fed three selected algal species as live food for milkfish, Chanos chanos Forsskal, fry production 

      CT Villegas, O Millamena & F Escritor - Aquaculture and Fisheries Management, 1990 - Blackwell Publishing
      The effects of three selected algal species, Tetraselmis tetrahele, Isochrysis galbana and marine Chlorella sp. on the population growth of Brachionus plicatilis was evaluated after 3, 5 and 7 days of culture. The rotifers fed on T. tetrahele showed superior growth with mean peak density of 92.5 individuals per ml to those fed on I. galbana (48.2 individuals per ml) and Chlorella sp. (47.2 individuals per ml) in 5 days.

      In another experiment, milkfish. Chanos chanos Forsskal, fry with initial mean body weight and standard length of 6.26 ± 1.07mg and 13.04 ± 1.40mm, respectively, were fed B. plicatilis reared on the three algal species for 30 days. Results showed that growth, measured in terms of gain in weight and length, was significantly different (P > 0.05) among treatments. Fastest growth was obtained in fry fed B. plicatilis cultured on T. tetrahele with mean gains in weight and length of 61.48 ± 8.40mg and 9.37 ± 1.68 mm, respectively, followed by fry fed B. plicatilis reared on I. galbana (43.56 ± 8.35mg and 6.25 ± 0.48mm). Milkfish fry fed B. plicatilis cultured on Chlorella sp. gave the poorest growth with mean gains in weight and length of 11.05 ± 1.82mg and 2.33 ± 0.29mm, respectively. Percentage survival ranged from 93.1 to 95.3 percent and was not significantly different between treatments (P < 0.05).

      The differences in population growth of B. plicatilis and consequently growth of milkfish fry was almost certainly attributed to the differences observed in the biological values of their algal diet, and in particular their protein and lipid contents. T. tetrahele and I. galbana improved the food value of B. plicatilis as live food for the milkfish fry. Their high dietary value was related to the higher algal protein and fat levels and contents of n-3 HUFA particularly 20:5n-3 and 22:6n-3 compared to B. plicatilis cultured on Chlorella sp. The results of the present study point to T. tetrahele as the most suitable food for the mass culture of the rotifer, B. plicatilis.
    • Conference paper

      Growth and survival of Oreochromis niloticus, O. mossambicus and their F1 hybrids at various salinities 

      CT Villegas - In R Hirano & I Hanyu (Eds.), The Second Asian Fisheries Forum: Proceedings of the Second Asian Fisheries Forum, Tokyo, Japan, 17 - 22 April 1989, 1990 - Asian Fisheries Society
      Growth and survival of Oreochromis niloticus, O. mossambicus, and their F1 hybrids were studied at various salinities (0-32 ppt) in net cages inside 12-tonne concrete tanks after acclimation. Growth, measured as weight gain, and survival were assessed after three months of culture. Results showed that although O. niloticus, O. mossambicus, and their F1 hybrids can be acclimated and grown at varying salinities, optimum salinity ranges for good growth varied greatly. The salinity ranges for good growth of O. mossambicus and F1 hybrids were wider than O. niloticus. O. mossambicus had the highest growth rates at 15 and 32 ppt. The optimum salinity range for growth of F1 hybrids was 15-32 ppt, while for O. niloticus it was 0-10 ppt. Salinity up to 20 ppt had no significant effect (P>0.05) on survival of all test strains. However, at 25-32 ppt survival of O. niloticus was significantly lower (P<0.05) than that of O. mossambicus and the F1 hybrids.
    • Article

      Growth, survival and macronutrient composition of Penaeus monodon Fabricius larvae fed with Chaetoceros calcitrans and Tetraselmis chuii 

      E Tobias-Quinitio & CT Villegas - Aquaculture, 1982 - Elsevier
      Penaeus monodon larvae were reared from zoea1 (Z1) to mysis3 (M3) using two different algal feeds, Chaetocero calcitrans and Tetraselmis chuii. Artemia nauplii were added to both treatments at mysis2. Mean survival and growth rates in both treatments were different at 5% level of significance on the second and third day of culture, but did not differ during the mysis stage and the end of the 8-day culture period.

      Z3 and M3 larvae fed with C. calcitrans had a lower crude protein but a higher lipid content than T. chuii-fed larvae. Differences in carbohydrate content were noticed in M3 larvae. The implication of the findings are discussed.
    • Article

      Preliminary studies on growth and survival of Penaeus japonicus postlarvae fed with Tapes and commercial formula feeds 

      CT Villegas - SEAFDEC Aquaculture Department Quarterly Research Report, 1978 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Growth and survival of P. japonicus postlarvae was studied using Tapes philippinarum and commercial formula feeds. After a 28-day feeding period, the highest survival rate of 100% was obtained in prawns receiving Diet-B, followed by those on Tapes Kyowa Hakko shrimp meal with survival rates of 80 and 76.7%, respectively. The lowest survival rate of 48.3% was obtained among postlarvae fed with squid meal. In this batch cannibalism was observed which resulted in low survival. Growth was highest in the postlarvae fed with Kyowa Hakko and mysid feeds. Diet-B gave a slightly lower weight increase but gave similar gain in length. The composition of the artificial diet, Diet-B, and growth and survival rates are tabulated.
    • Article

      Relationship between diet composition and growth rate of the zoeal and mysis stages of Penaeus japonicus Bate 

      CT Villegas & A Kanazawa - Fisheries Research Journal of the Philippines, 1979 - Fisheries Research Society of the Philippines
      Feeding experiments were conducted on Penaeus japonicus larvae using Chaetoceros gracilis plus Artemia nauplii, an artificially prepared diet (Diet-B), and two commercial feeds (Tapes and mysid meals) in a randomized complete block design with two replicates per diet. The artificially prepared diets were dried and ground to size 10 to 50 microns and fed to the larvae. The larvae were reared in round plastic aquaria each containing 5 liters of filtered seawater. Each aquarium was stocked with 250 larvae and provided with aeration. The larvae were reared from zoea (Z1) to mysis (M3) stage and growth was measured daily.

      The highest survival rate of 34.2% was obtained when the larvae were fed with Diet-B. C. gracilis plus Artemia nauplii feeding gave a survival rate of 21.6%. On the other hand, growth measured in terms of development, was fastest using C. gracilis plus Artemia nauplii. Larvae metamorphosed into stage in 7 days with an average gain in length of 0.46 mm/day. Diet-B feeding resulted in a comparable growth, the larvae reaching M3 stage in 8 days with an average gain in length of 0.30 mm/day. Analyses of the chemical composition of the diets showed no definite relationship between diet composition and growth and survival rates of the early larval stages of P. japonicus.

      Results obtained in this study demonstrate that the early larval stages of P. japonicus can be reared with feeding of Diet-B. Since the chemical composition of the diet is known, it can be used as supplemental data for larval feed development and nutritional requirements studies for the early larval stages of P. japonicus and/ or other penaeids.
    • Article

      Survival rate of Penaeus monodon Fabricius larvae fed Chaetoceros sp. and bread yeast 

      CT Villegas & T Loon Ti - SEAFDEC Aquaculture Department Quarterly Research Report, 1978 - Aquaculture Department, Southeast Asian Fisheries Development Center
      An evaluation was made of the effects of Chaetoceros species, bread yeast and their combination on the survival of Penaeus monodon larvae. In general it was found that feeding with a combination of the 2 resulted in higher larval survival rates.
    • Conference paper

      Technology transfer and information dissemination at SEAFDEC/AQD. 

      CT Villegas - In Aypa S. (Ed.), ASEAN-EEC Aquaculture Development and Coordination Programme (AADCP) Workshop Proceedings on Strategy for Technology Transfer in Aquaculture; 14-18 November 1994; Puerto Azul Beach Hotel, Cavite. AADCP Proc. 6, 1995 - ASEAN-EEC Aquaculture Development and Coordination Programme
    • Conference paper

      Training and information dissemination at SEAFDEC AQD 

      CT Villegas - In TU Bagarinao & EEC Flores (Eds.), Towards sustainable aquaculture in Southeast Asia and Japan: Proceedings of the Seminar-Workshop on Aquaculture Development in Southeast Asia, Iloilo City, Philippines, 26-28 July, 1994, 1995 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The SEAFDEC Aquaculture Department (AQD) is mandated to develop human resources and to disseminate and exchange information for aquaculture development in the region. In 1991-1994, a total of 294 participants attended 23 sessions of nine training courses. Many others participated in AQD's student practicum, internships, and summer work programs. AQD conducted seminarworkshops on aquaculture development in southeast Asia, fish breeding, feeds and feeding, and training needs. Information materials (newsletters, a monograph, two extension manuals, leaflets, and videos) were produced based on research at AQD. To assist fishfarmers and other sectors of the local aquaculture industry, AQD conducted on-site or outreach seminars, and provided resource persons during fairs and exhibits, seminars, and consultative meetings. The AQD Library is open to all users; in addition to the collection of printed materials, a CD-ROM reader is now available for fast retrieval of bibliographic information from computerized databases like ASFA.
    • Conference paper

      Yeasts as food organisms in aquaculture 

      CT Villegas - In Report of the Training Course on Growing Food Organisms for Fish Hatcheries: Tigbauan, Iloilo, Philippines, 3-22 August 1981, 1982 - South China Sea Fisheries Development and Coordinating Programme
      The use of yeast as feed in aquaculture is discussed. It has been successfully used as feed for Penaeus japonicus larvae, for Brachionus plicatilis mass culture, and for the improvement of nutritional quality of Tigriopus japonicus. It has been found most effective as supplemental food when enough phytoplankton cannot be supplied.