Now showing items 1070-1075 of 1075

    • Article

      Year-round sexual maturation of bighead carp Aristichthys nobilis (Richardson) reared in floating cages in Laguna de Bay (Philippines). 

      AC Fermin - Journal of Applied Ichthyology, 1990 - Blackwell Publishing
      Sexual maturation in bighead carp Aristichthys nobilis reared without supplemental feeding in floating cages in Laguna de Bay was observed year-round. Percent maturation ranged from 3 to 94% in females and 0 to 82% in males from July 1985 to July 1986. High maturation rates in both sexes occurring in March 1986 were positively correlated with high inorganic turbidity in the lake. Low natural food productivity (phyto- and zooplankton) during high turbidity did not negatively affect fish growth. Fish may have depended partly on suspended particles as additional food sources when production of more suitable food (zooplankton) was low. Increased production of natural food as a result of water clearing by seawater intrusion during May to September did not enhance growth and maturation of the fish. There was a low negative correlation between chlorinity and percent maturation of both sexes.
    • Article

      Year-round spawning and seed production of the rabbitfish, Siganus guttatus 

      S Hara, MN Duray, MM Parazo & Y Taki - Aquaculture, 1986 - Elsevier
      A series of experiments on the spawning and larval rearing of Siganus guttatus was conducted during a 14-month period in 1984–1985. Spawning occurred every month throughout the year, without hormonal treatment, between the first quarter and the full moon. Fertilization rates and hatching rates were high, with means of 84.2% (n=38) and 89.6% (n=34), respectively. Females that had been fed diets rich in cod liver oil or in a cod liver oil/soybean oil/soybean lecithin mixture spawned repeatedly for at least 4 consecutive months. Larvae reared in 20, 26, and 32‰ salinities showed no significant differences in survival rates at day 21. Survival was higher for larvae fed during days 2–4 with rotifers strained through an 80-μm-mesh plankton net than for those fed unstrained rotifers. Larvae readily accepted Artemia nauplii and artificial diets when these were first introduced on day 15 and day 23, respectively. Higher larval survival was obtained in large tanks (≥5 m3) than in small tanks (500 l). Survival rates of 3.5–16.6% (x=7.5%) at day 45 were obtained in six trials of mass larval rearing and 5500–50100 (x=27 700) juveniles per female were produced at day 45, ready for stocking in grow-out farms.
    • Article

      The yellow mangrove: its ethnobotany, history of maritime collection, and needed rehabilitation in the central and southern Philippines 

      JH Primavera & L de la Peña - Philippine Quarterly of Culture & Society, 2000 - University of San Carlos Publications
      Most mangrove reforestation program in the Philippines and elsewhere in Asia focus on the genus Rhizophora, hence there is a need to identify and develop planting and harvesting techniques for other mangrove species, especially those in high demand by coastal communities. The yellow mangrove Ceriops tagal is one such species. Its many uses as firewood, poles for fish-corrals and traps, house construction, medicine (wound cleansing, treatment of hemmorhages), in the production of dyes (for dyeing fish nets, ropes, cloth and rice as a festive food) and as a mordant from bark are widely reported from the Philippines and all over Southeast and South Asia. An extensive sea-based industry for collecting C. tagal bark or tungog existed in the Philippines in the 1930s-1950s. It is heretofore described as undocumented industry including the boats used, collecting sites, markets, financing system and profit-sharing. Because C. tagal lacks reserve meristems, cutting of the trunk during bark gathering causes tree mortality. This explains the wholesale disappearance of the species from areas where it has been harvested throughout the Philippines, Southeast and South Asia, and East Africa. Research is needed to refine planting techniques and develop bark harvesting methods that do not kill the tree. Until nondestructive procedures for bark collection are finally perfected, C. tagal stands can be planted and harvested on a rotation basis.
    • Article

      Yield of Penaeus monodon Fabricius in brackishwater ponds given different fertilizer combinations 

      PF Subosa & MN Bautista - Aquaculture, 1991 - Elsevier
      Yields of Penaeus monodon Fabricius in brackishwater earthen ponds were determined using different fertilizer combinations in two sets of experiments. Results indicated that the use of fertilizers was vitally needed to sustain growth of shrimps at a stocking density of 5000 individuals/ha. Application of urea (45-0-0) and diammonium phosphate (18-46-0) fertilizers at nitrogen to phosphorus fertilizer rates (N:P2O5) of 15:15 and 30:15 kg/ha, together with 1 t/ha of chicken manure, was inexpensive and resulted in better yields. In another experiment, increase in the amount of nitrogen and phosphorus fertilizers did not significantly improve prawn yields, but did increase the cost of production. Different salinity levels affected survival in both experiments.
    • Article

      Yolk and oil globule utilization and developmental morphology of the digestive tract epithelium in larval rabbitfish, Siganus guttatus (Bloch) 

      EM Avila & JV Juario - Aquaculture, 1987 - Elsevier
      The purpose of this study was to find out how yolk and oil globule absorption in Siganus guttatus proceed as the digestive tract develops, in order to determine the probable causes of early larval mortality. Yolk and oil globule absorption in the rabbitfish were compared with the same processes in the more sturdy seaperch larvae during the first 10 days of larval life under identical rearing conditions in 32‰ sea water at 27°–30°C. The rapid decline of yolk in both species coincided with the rapid development of the digestive system within 24 h from hatching, indicating that most of the yolk was used for organogenesis. Whereas yolk was depleted in both fish in 3 days, the oil globule persisted in the rabbitfish only for 4 days and in the seaperch for 7 days. Oil globule depletion in the rabbitfish coincided with a negative mean length increment, implying an energy deficit even when the larvae had already started to feed. Ultrastructural observations of the gut epithelia of the rabbitfish revealed pinocytosis in the hindgut cells immediately after ingestion of rotifers, well in advance of complete yolk and oil globule absorption. Therefore, starvation due to exhaustion of the endogenous energy reserves in addition to the physical inability to feed were ruled out as major causes of larval mortality in rabbitfish.
    • Article

      Yolk resorption, onset of feeding and survival potential of larvae of three tropical marine fish species reared in the hatchery 

      T Bagarinao - Marine Biology, 1986 - Springer Verlag
      This paper provides basic early life-history information on milkfish (Chanos chanos), seabass (Lates calcarifer) and rabbitfish (Siganus guttatus) which may explain in part the observed differences in their survival performance in the hatchery. Egg size, larval size, amount of yolk and oil reserves and mouth size are all greater in milkfish than in seabass, and greater in the latter than in rabbitfish. During the first 24 h after hatching, rabbitfish larvae grow much faster than milkfish and seabass larvae at similar ambient temperatures (range 26°–30°C, mean about 28°C). The eyes become fully pigmented and the mouths open earlier in seabass and rabbitfish (32–36 h from hatching) than in milkfish (54 h). Seabass larvae learn to feed the earliest. Yolk is completely resorbed at 120 h from hatching in milkfish, and yolk plus oil at 120 h in seabass and 72 h in rabbitfish at 26° to 30°C. Milkfish and seabass larvae have more time than rabbitfish to initiate external feeding before the endogenous reserves are completely resorbed. Delayed feeding experiments showed that 50% of unfed milkfish larvae die at 78 h and all die at 150 h from hatching. Milkfish larvae fed within 54 to 78 h after hatching had improved survival times: 50% mortality occurred at 96 to 120 h, and 10 to 13% survived beyond 150 h. Unfed seabass larvae all died at 144 h, while 6 to 13% of those fed within 32 to 56 h after hatching survived beyond 144 h and well into the subsequent weeks. Unfed rabbitfish larvae all died at 88 h, while 7 to 12% of those fed within 32 to 56 h after hatching survived beyond 88 h. A delay in initial feeding of more than 24 h after eye pigmentation and opening of the mouth may be fatal for all three species.