Now showing items 1-5 of 5

    • Article

      Induction of larval settlement and metamorphosis in the donkey-ear abalone, Haliotis asinina Linnaeus, by chemical cues 

      RSJ Gapasin & BB Polohan - Hydrobiologia, 2004 - Springer Verlag
      The effects of the chemical inducers, gamma-aminobutyric acid (GABA) and potassium chloride (KCl), on the larval settlement and metamorphosis of the donkey-ear abalone, Haliotis asinina, was investigated. H. asinina larvae (5–6 h post-hatch) were exposed to a range of GABA (0.125–2.00 μM) and KCl (1.00–12.00 mM) concentrations for 72 h. Results of the dose response experiments showed that settlement and metamorphosis vary according to the dose levels of the inducer compounds. Under controlled laboratory conditions, 0.45–0.50 μM and 6.0 mM seemed to be the optima for GABA and KCl, respectively, as these concentrations elicited the greatest number of postlarvae that metamorphosed, settled or survived. However, GABA generally promoted better attachment and metamorphic response as well as survival than KCl in H. asinina postlarvae.
    • Article

      An inexpensive tag for short-term studies in milkfish (Chanos chanos Forsskal) and in seabass (Lates calcarifer Bloch) 

      LMB Garcia & RSJ Gapasin - Journal of Applied Ichthyology, 1988 - Blackwell Publishing
      An opercular tag for marking adult milkfish (Chanos chanos Forsskal) and seabass (Lates calcarifer Bloch) is described. High tag retention and relatively low mortality rates were observed in adult fish handled two to ten times during 14-to 60-day tests. The features and advantages of the tag for marking large-sized fish in short-term studies are discussed.
    • Article

      Nursery culture of grouper (Epinephelus fuscoguttatus Forsskal) and sea bass (Lates calcarifer Bloch) in brackish water ponds: Co-feeding of zooplankton and formulated diets containing L-tryptophan 

      RSJ Gapasin, VR Alava & CL Marte - Journal of Applied Aquaculture, 2012 - Taylor & Francis
      This study compared co-feeding zooplankton (ZP, mixed copepods and mysids) and formulated diets (FD) supplemented with L-tryptophan (TRP) on the survival and growth of grouper and sea bass fry nursed in brackish water ponds. Grouper (84 fry m−3) and sea bass (150 fry m−3) were reared for 30 days and 60 days, respectively, in net cages within two separate 743 m2 nursery ponds. Five treatments (with three replicates each) were compared (P < 0.05): FD-1 = ZP + basal FD (no added TRP, but containing 0.29% endogenous TRP); FD-2 = ZP + (FD 0.58% TRP); FD-3 = ZP + (FD 1.22% TRP); FD-4 = ZP + (FD 2.50% TRP); and FD-5 = minced fish (Sardinella sp.) + basal FD (no additional TRP). TRP supplementation in grouper diets produced no significant affect on growth but increased survival at rates of 0.58% and above. TRP supplementation at 2.5% (FD-4) produced significantly better sea bass growth than other diets but had no affect on survival. Zooplankton improved both survival and growth in both grouper and sea bass juveniles compared to the minced fish diet, and may be a practical and lower cost alternative to indoor nursing.
    • Article

      Response of the tropical abalone, Haliotis asinina, larvae on combinations of attachment cues 

      RSJ Gapasin & BB Polohan - Hydrobiologia, 2005 - Springer Verlag
      The effects of different diatom species and types of substrates in combination with 0.45 μM GABA on the metamorphosis of Haliotis asinina larvae were tested. Diatom slurry elicited the best metamorphic response followed by Amphora sp., Amphora + Nitzschia and Nitzschia cf. frustulum in that order. With regards to substrate types, roughened plexiglass seemed to be the most preferred while fibrocement the least preferred surface. Overall, diatom slurry grown on plexiglass surface promoted the greatest number of metamorphosed H. asinina postlarvae. For economic considerations and practical reasons, chemical inducers like gamma-aminobutyric acid (GABA), should be used singly or separately from other settlement-inducing cues, such as the “substrate-diatom” complex.
    • Conference paper

      Spontaneous spawning, fecundity and spawning periodicity in the donkey's ear abalone Haliotis asinina Linnaeus 1758 

      AC Fermin, RSJ Gapasin & MB Teruel - In A Hylleberg (Ed.), Proceedings of the 10th International Congress and Workshop of the Tropical Marine Mollusc Programme (TMMP), 20-30 October 1999, Hanoi and Haiphong, Vietnamen, 2000 - Phuket Marine Biological Center; Phuket Marine Biological Center Special Publication 21(1)
      Spontaneous group spawning was monitored in wild-caught (WC) and hatchery-bred (HB) abalone broodstock (Haliotis asinina) held in duplicate tanks at 1:3 (male: female) ratio from June 1997 to January 1999. Abalone breeders (mean SL, wild = 69-79 mm, HB = 68-71 mm) were kept in perforated plastic baskets and fed red alga, Gracilariopsis bailinae, to excess given at weekly intervals. Abalone spawned spontaneously year-round. Water temperature during the study ranged from 26-29 degree C. A total of 139 and 128 spawning episodes were recorded for WC and HB group respectively. Spawning in WC group (mean: 7 ± 0.8) were more frequent in September (1998) and from February to April. Spawning frequency in the HB group (mean: 6.4 ± 1) was generally high during September (1998) until April. Likewise, egg production was highest during these months. Pooled mean survival from trochophore to veligers stage ranged from 7 to 30% (n=36). Potential fecundity was determined in sacrificed group of HB females (n=21) varied from 6,741-11,902 oocytes g -1 BW. Mean oocyte diameter ranged from 136 to 150 mu m. Bigger females had higher potential fecundity (range: 6.2 to 11 x 105 oocytes individual -1 than smaller females (range: 2.8 to 3.3 x 105 oocytes individual -1). The time interval between successive spawning among animals that spawned more than twice during a 5-month period ranged from 13 to 34 days for the small-size group and from 18 to 37 days for large-size group. In separately stocked HB females (without male), instantaneous fecundity was shown to range between 1,500 and 12,300 eggs g -1 BW (n=16). In contrast to potential fecundity, smaller and younger individuals gave higher 68-71 instantaneous fecundity (range: >3,000 >12,000 oocytes g -1 BW) than the bigger and older individuals (1,500-6,500 oocytes g -1 BW).