Now showing items 1-7 of 7

    • Article

      Daily amount of rotifers taken by a sea bass Lates calcarifer larvae 

      H Kohno & M Duray - Philippine Journal of Science, 1990 - Science and Technology Information Institute
      The amount of rotifers consumed by a single sea bass Lates calcarifer larva per day (R) was examined by both the direct and by the satiation-digestion methods. In the direct method, R is estimated by the number of rotifers left in the larval tanks and larval density in the tanks, while in the satiation-digestion method R is estimated by the amount of rotifers found in the digestive tract of the larvae. In both methods, the amount of rotifers consumed by the larvae increased exponentially with larval growth. The relationship between the total length (TL) and the log-log plots of the maximum amount of rotifers eaten by a larva can be expressed by the following equations; R=1.799 x TL4.398 (r=0.975) for the direct method and R= 4.861 x TL3.432 (r = 0.907) for the satiation-digestion method. The relationship between TL and body wet weight (BW) can be expressed as: BW = 2.607 x 10-4 x TL3.786 (r=0.960) for larvae smaller than 6.5 mm TL and BW = 15.053 x 10-3 x TL2.855 (r = 0.916) for those larger than 6.5 mm TL.

      The index of satiation was almost the same for day 6(0-6), D-9 and D-12 (8.3-23%), higher range was observed in D-15 larvae. The index of daily feeding amount was comparatively higher in D-12 larvae compared to D-6, D-9 or D-15 larvae.
    • Article

      Development of mouth width and larval growth in three marine fish species 

      MN Duray & H Kohno - Philippine Journal of Science, 1990 - Science and Technology Information Institute
      Hatchery-bred larvae of three marine fish species, milkfish (Chanos chanos), seabass (Lates calcarifer) and rabbitfish (Siganus guttatus) were reared on rotifers and Artemia nauplii. Development of the mouth width and larval growth were monitored in the laboratory. Growth was slow on the first six days in milkfish and rabbitfish and on the first four days in seabass. Mouth width at opening was the smallest in rabbitfish (90-110 μm), followed by seabass (170-220) μm) and milkfish (180-270 μm), and the mouth width at the time when the larvae began to eat rotifers was 219 + 7.4 μm, at 82.5 h after hatching, in rabbitfish, 224 +7.9 μm, at 71 h, in seabass, and 3306 + 38.9 μm, at 125 h, in milkfish. A positive correlation between mouth width and larval growth was shown by three species studied.
    • Article

      The effect of lipid-enriched broodstock diets on spawning and on egg and larval quality of hatchery-bred rabbitfish (Siganus guttatus) 

      M Duray, H Kohno & F Pascual - The Philippine Scientist, 1994 - San Carlos Publications, University of San Carlos
      Three isocaloric and isonitrogenous diets formulated to contain 12 (diet A), 15 (B) and 18% (C) lipids were tested on hatchery-bred rabbitfish Siganus guttatus broodstock to determine their effect on spawning and quality of the eggs and larvae. The results show that fish on diet C has higher fecundity than those on diets B and A. Also, fish on diet C yielded eggs of better quality than either fish on diets B or A. This was indicated by spawns resulting in higher percentage of normal hatchlings, larger newly-hatched larvae and higher survival rates until the 14th day of rearing. Dietary lipid levels, however, have no remarkable effects on fertilization, yolk and oil globule volumes, hatching rate nor larval size at harvest.
    • Article

      Effects of continuous lighting on growth and survival of first-feeding larval rabbitfish, Siganus guttatus 

      M Duray & H Kohno - Aquaculture, 1988 - Elsevier
      The effects of 24-h lighting on feeding, growth and survival of first-feeding larvae of Siganus guttatus were tested. Continuous light gave a higher mean survival (31.69%) with a maximum of 40.50% compared to natural daylight (17.10%). Larval size on day 7 also showed that continuous lighting gave improved results. Although feeding incidence increased with age of the larvae, a higher incident rate was observed for larvae held in continuous light from day 3.
    • Article

      Effects of feeding frequency and amount of feeding on the growth of the grouper, Epinephelus malabaricus 

      H Kohno, A Triño, D Gerochi & M Duray - Philippine Journal of Science, 1989 - Science and Technology Information Institute
      The effects of feeding frequency and amount of food on the growth of juvenile groupers (Epinephelus malabaricus) were investigated for 12 weeks of rearing in net-cages set in an earthen pond. The juveniles (110-130 g in body weight, BW) attained marketable size (500 g) in 12 weeks. Feeding to satiation levels once a day gave the best growth (mean BW = 509.4 ± 56.5 g) and relatively good food conversion ratio (4.78) compared to the other treatments (twice a day, once in two days and once in every three days). Concerning feeding levels, in which feed was given twice a day at 15, 10, 5 and 1% of total fish biomass per day, the best fish growth (426.6 ± 54.0 g) and a reasonable food conversion ratio (4.53) were obtained at 5% fish biomass. There was a positive correlation between the growth of fish and water temperature in both experiments.
    • Article

      Morphological aspects of the development of swimming and feeding functions in the milkfish Chanos chanos 

      Y Taki, H Kohno & S Hara - Japanese Journal of Ichthyology, 1987 - The Ichthyological Society of Japan
      Development of swimming and feeding abilities based on morphological development of larval and early juvenileChanos chanos was investigated. In larvae smaller than about 6.5 mm SL, mechanical supports of fins and branchial arches were in a primordial stage of development. Supports and rays of the vertical fins and branchial arches rapidly developed from 6.5 mm SL, and all components appeared by about 10.5 mm SL. Thereafter body depth proportion changed and the supports and rays of the paired fins and gill-rakers developed. These developmental events were nearly or totally completed by about 17 mm SL, and we concluded that the larvae transformed to juveniles at this size. By this time, the mode of swimming of the fish shifted from undulating locomotion to caudal propulsion and that of feeding from swallowing paniculate food to filtering and concentrating substrate food matters using gill-rakers and the epibranchial organ. One of the most characteristic, and well-known, phenomena in the life history ofChanos chanos is the mass occurrence in the surf zone of postlarvae of a limited size range. In view of the scheme of the development of mechanical supports of the body and fins, they may acquire a swimming ability strong enough to move against the current only upon reaching about 10.5 mm SL, and if active shoreward migration of the larvae occurs, it is only during the late period of their journey from the spawning grounds to the shore. The sudden disappearance from the surf zone of larvae larger than 15–16 mm SL is obviously related to a change in food habit.
    • Article

      Transition from endogenous to exogenous nutrition sources in larval rabbitfish Siganus guttatus 

      H Kohno, S Hara, M Duray & A Gallego - Nippon Suisan Gakkaishi, 1988 - Japanese Society of Fisheries Science
      The early larval development of Siganus guttatus was studied with emphasis on the transition from endogenous to exogenous feeding. Three rearing trials were conducted as follows: 1) rearing in a 5 ton concrete tank at 27.9-29.3oC (T-85 trial); 2) rearing in a 0.5 ton fiberglass tank at 22.2-26.5oC (T-86A trial); 3) rearing in the same manner as in T-86A but without food (T-86B trial). On the basis of the developmental events and energy flow in T-86A trial, the early life history of the species could be divided into the following seven phases: 1) rapid larval growth due to rapid yolk resorption (from hatching to about 15 h after hatching (time after hatching: TAH)); 2) slow growth and organogenesis based mainly on yolk energy (to about 50 h TAH); 3) slow growth based on energy of yolk, oil globule and exogenous food (to about 50 h TAH); 4) slow growth based on two sources of energy, oil globule and exogenous food (to about 90 h TAH); 5) the same mode of development and energy flow as in the preceding phase, but with a certain level of feeding amount (to about 120 h TAH); 6) accelerated larval growth and effective feeding and swimming based only on exogenous food (to about 150 h TAH); and 7) the same mode as in the preceding phase with accelerated increase of feeding amount (beyond 150 h TAH). Differences in developmental mode were observed in T-85 and T-86A trials, but it could not be ascertained in this particular study which of the environment factors played the greatest influence. The results of T-86A and B showed that the larvae, in order to survive, have to get over two obstacles on feeding, that is, to start feeding and to change from endogenous to exogenous feeding suitably.