Journal Articles, Conference Papers and Book Chapters by SEAFDEC Staff: Recent submissions

641-660 / 1693

    • Tryptophan requirement of juvenile Asian sea bass Lates calcarifer 

      Coloso, R. M.; Murillo-Gurrea, D. P.; Borlongan, I. G.; Catacutan, M. R. (Blackwell Publishing, 2004)
      The dietary requirement of tryptophan for juvenile Asian sea bass (Lates calcarifer Bloch) was studied. The juveniles (mean initial weight, 5.30 ± 0.06 g) were given semi-purified test diets containing fish meal, gelatin, squid meal, and crystalline amino acids, for 12 weeks. Each set of isonitrogenous and isocaloric test diets contained graded levels of tryptophan. Fish (15 per tank) were reared in 250-L fiberglass tanks provided with continuous flow-through sea water at 26°C and salinity of 28 p.p.t. Fish were fed twice daily at a feeding rate of 8% of the body weight day−1 for the first 4 weeks and at 3.5–2.5% of the body weight day−1 from 5 to 12 weeks. The experiment was in a completely randomized design with two replicates per treatment. Mean percentage weight gains and feed efficiency ratios were significantly different in fish fed varying tryptophan levels. Survival was 100% in all treatments. On the basis of break-point analysis of the growth response, the dietary tryptophan requirement of juvenile Asian sea bass is 0.41% of the dietary protein. This information will be useful in further refinement of practical feed formulations for the Asian sea bass.

    • Partial replacement of fishmeal by defatted soybean meal in formulated diets for the mangrove red snapper, Lutjanus argentimaculatus (Forsskal 1775) 

      Catacutan, Mae R.; Pagador, Gregoria E. (Blackwell Publishing, 2004)
      This study was conducted to evaluate the effect on growth and feed efficiencies of the mangrove red snapper (Lutjanus argentimaculatus) when dietary fishmeal is partially replaced by defatted soybean meal (DSM). In the preliminary experiment, snapper (mean weight±SD, 58.22±5.28 g) were fed in triplicate with different dietary amounts of DSM (7.8–42.2%) that were formulated to be isonitrogenous and isocaloric. After 14 weeks, survival, growth and feed efficiencies, and hepatosomatic index (HSI) did not differ. Based on these results, a feeding trial was done using a positive control diet that contained 64% fishmeal, while the other four diets had DSM levels of 12%, 24%, 36%, and 48% that replaced fishmeal protein at 12.5%, 25%, 37.5%, and 50% respectively. All diets were formulated to have about the same protein level (50%), protein to energy ratio (P/E of 25-mg protein kJ−1), and dietary energy (19.8 MJ kg−1). These were fed to triplicate groups of snapper (mean total weight tank−1±SD, 73.19±1.2 g) at 15 fish (average weight, 4.88 g) per 1.5-t tank for 19 weeks. Growth (final average weight and specific growth rate (SGR), feed conversion ratio (FCR), survival, and HSI were not significantly different (P>0.05) while protein efficiency ratios or PERs were similar in treatments with DSM. Among snapper fed DSM, haematocrit value was significantly lower in fish fed 48% DSM and not different with fish fed 36% DSM. Whole-body crude fat of snapper fed 48% DSM was lowest while the crude protein and nitrogen-free extract (NFE) levels were highest. Histopathological analysis showed that lipid vacuoles in livers of snapper were reduced in size as dietary DSM increased. There was slight lipid deposition in the liver of snapper at 36% DSM while at 48% DSM it was excessive and hepatocytes were necrotic. There were no differences in the histology of snapper intestine. Under the experimental condition of this study, DSM can be used in snapper diets at 24% (replacing 25% of fishmeal protein) based on growth, survival and feed efficiencies, and histology of liver and intestine. For a lesser diet cost, an inclusion level higher than 24% DSM is possible with a bioavailable phosphorus supplement.

    • Fishing cooperatives’ participation in managing nearshore resources: the case in Capiz, central Philippines 

      Baticados, Didi B. (Elsevier, 2004)
      This study documents the resource management initiatives undertaken by fishing cooperatives in Capiz, central Philippines and examines the conditions and the socioeconomic determinants that persuade members to assume responsibility for managing nearshore resources. The results show that in the absence of formal resource management schemes, cooperative members adopt self-management strategies to protect their resource base only if the sustainability of their livelihood is seriously threatened. There is no impediment to female cooperative members (62%) participating in resource management. The factors that positively influenced members’ participation were the number of children, perceived fishery conditions, awareness of mangrove conservation and rehabilitation, and assessment of enforcement of the ban on dynamite and cyanide fishing. Fishing cooperatives, however, fail as a source of information on regulation and conservation education of members. But if they were to undertake more education and training programs on nearshore management, cooperatives may become an effective social force in changing the present fisheries management system.

    • Enhancement of innate immunity in rainbow trout (Oncorhynchus mykiss Walbaum) associated with dietary intake of carotenoids from natural products 

      Amar, Edgar C. ORCID; Kiron, V.; Satoh, S.; Watanabe, T. (Elsevier, 2004)
      The effects of orally administered carotenoids from natural sources on the non-specific defense mechanisms of rainbow trout were evaluated in a nine-week feeding trial. Fish were fed four diets containing either β-carotene or astaxanthin at 100 and 200 mg kg−1 from the marine algae Dunaliella salina and red yeast Phaffia rhodozyma, respectively, and a control diet containing no supplemented carotenoids. Specific growth rate and feed:gain ratio were not affected by dietary carotenoid supplementation. Among the humoral factors, serum alternative complement activity increased significantly in all carotenoid supplemented groups when compared to the control. On the other hand, serum lysozyme activity increased in the Dunaliella> group but not in the Phaffia group, whereas plasma total immunoglobulin levels were not altered by the feeding treatments. As for the cellular responses, the superoxide anion production from the head kidney remained unchanged while the phagocytic rate and index in all supplemented groups were significantly higher than those of the control. These findings demonstrate that dietary carotenoids from both D. salina and P. rhodozyma can modulate some of the innate defense mechanisms in rainbow trout.

    • Investigation of some components of the greenwater system which makes it effective in the initial control of luminous bacteria 

      Tendencia, Eleonor ORCID; dela Peña, Milagros (Elsevier, 2003)
      Two components of the greenwater system, the tilapia water and Chlorella, were investigated separately for their effect on the population of luminous bacteria. For the investigation of tilapia water, Tilapia hornorum was stocked at different biomasses 0, 1 and 3 kg/10 m3. Vibrio harveyi was introduced to the tanks at a final concentration of 103 cfu/ml. Luminous bacteria could not be detected in tanks stocked at 3 kg/10 m3 from day 4 to day 6, and on day 6 in tanks stocked at 1 kg/10 m3. The bacteria could still be recovered in tanks without tilapia on day 6. Investigation of the effect of chlorella alone on V. harveyi was undertaken using sterile flasks containing 500-ml autoclaved seawater provided with aeration. In treated flasks Chlorella was added, whereas no Chlorella was added to control flasks. No luminous bacteria were recovered on day 2 and day 3 in flasks with Chlorella, while those without the microalgae still harboured luminous bacteria at day 3.

    • Water quality and holding capacity of intensive and semi-intensive milkfish (Chanos chanos) ponds 

      Sumagaysay-Chavoso, Neila S.; San Diego-McGlone, Ma. Lourdes (Elsevier, 2003)
      This study determined the holding capacity of semi-intensive and intensive milkfish ponds and water quality in relation to fish biomass and feed input. Six units of 1000 m2 brackishwater ponds were used, three ponds for intensive system (20,000 fish ha−1) and three for semi-intensive system (8000 fish ha−1). Average production was significantly higher in intensive pond (3652 kg ha−1) than in semi-intensive pond (1352 kg ha−1) after a desired marketable size of fish was reached. Highest concentrations in effluents (mg l−1) of rearing water measured every 2 weeks were 0.369 and 0.289 for chlorophyll a (chl a), 0.485 and 0.512 for PO4–P, 0.279 and 0.811 for TAN, 0.094 and 0.082 for NO2–N, and 14.040 and 8.649 for NO3–N, 216 and 142 for total suspended solids (TSS), 15.0 and 21.7 for biological oxygen demand (BOD), in intensive and semi-intensive ponds, respectively. Lowest morning dissolved oxygen (DO) in intensive pond was 2.2 mg l−1, and did not decrease further because of aeration. In unaerated, semi-intensive pond, morning DO ranged from 1.3 to 5.0 mg l−1 but occasionally went below 1.0 mg l−1 resulting to fish mortalities at biomass of 835, 1206, and 1489 kg ha−1. Levels of NO3–N and dissolved inorganic N are linear functions of fish biomass or feed input in all systems (P<0.05). The buildup of nutrients is more pronounced at biomass of 1610 kg ha−1 and above while nutrient transformation (conversion of PO4–P or TAN to phytoplankton or vice versa) is apparent at biomass below 1419 kg ha−1. The holding capacity of unaerated, semi-intensive pond is below 1348 kg ha−1 or 54 kg feed ha−1 day−1 based on DO concentration of less than 1.0 mg l−1. However, the holding capacity can be lower than 835 kg ha−1 or 33 kg feed ha−1 day−1 during very calm weather or during rainy days when water column is stratified. Based on the results of regression analysis, the holding capacity of intensive pond should be set below 5107 kg ha−1 or 110 kg feed ha−1 day−1 so as not to exceed the acceptable levels for water quality variables in effluent waters.

    • Nitrogen and phosphorus digestibility and excretion of different-sized groups of milkfish (Chanos chanos Forsskal) fed formulated and natural food-based diets 

      Sumagaysay-Chavoso, Neila S. (Blackwell Publishing, 2003)
      This study determined the digestibility of nitrogen and phosphorus, and the excretion rate of different-sized groups of milkfish fed a commercial diet, a SEAFDEC formulated diet or lab-lab (natural food-based diet). Fish (31.2–263.0 g) were stocked in 12 units of 300-L fibreglass tanks filled with aerated seawater. The postprandial total ammonia-nitrogen (TAN) and phosphate (PO4-P) excretion of fish were estimated from changes in TAN and PO4-P concentrations in water for 24 h. Digestibility was determined from the nitrogen, phosphorus and Cr2O3 content of the diets, and pooled faeces after the fish had been fed diets marked with chromic oxide. TAN excretion rate (mg TAN kg−1 fish day−1) was significantly lowest (P < 0.05) in medium to very big fish fed the lab-lab diet (60.8–124.4) and highest in small and medium fish fed the SEAFDEC diet (333.3–331.6) and small fish fed the commercial diet (280.1). Regardless of size, fish fed lab-lab excreted (mg PO4-P kg−1 fish day−1) significantly lower PO4-P (36.2) but did not differ with fish fed the commercial diet (64.8). Excretion rates decreased exponentially as fish weight increased but positively increased with feed ration. Excretion pattern of milkfish revealed two peaks: the first peak occurred 6 h after feeding and the second peak at 18 h for TAN and 21 h for PO4-P, coinciding with the start of the daylight hours. TAN and PO4-P excretion accounted for 20.5–34.6% of total N consumed and 18.7–42.6% of P consumed respectively. Approximately 27.9–42.5% of N consumed and 47.2–58.5% of P consumed were lost as faeces. Total nutrient losses were lower using the lab-lab diet (0.31 g N and 0.14 g P kg−1 fish) compared with the formulated diets (0.47–0.48 g N and 0.17–0.19 g P kg−1 fish); the losses decreased per kg of fish as fish size increased. Results suggest that the diet and size of fish influence wastage of N and P to the environment with greater losses in small fish and when artificial diets are used. Such measurements will provide valuable information for the preparation of N and P budgets for milkfish in grow-out systems.

    • Change in Aplaya: resource use and responses to changing markets among fisherfolk in Honda Bay, Palawan 

      Siar, Susana V. (University of San Carlos Publications, 2003)

    • Response of bighead carp Aristichthys nobilis and Asian catfish Clarias macrocephalus larvae to free-living nematode Panagrellus redivivus as alternative feed 

      Santiago, C. B.; Gonzal, A. C.; Ricci, M.; Harpaz, S. (Blackwell Publishing, 2003)
      The use of Panagrellus redivivus as live feed for bighead carp and Asian catfish larvae was tested. In experiment 1, carp larvae were given Artemia nauplii (control) or Panagrellus twice daily for 21 days. A third treatment consisted of unfed larvae. The same three treatments were used in experiment 2 plus another with a commercial entomopathogenic nematode (EPN). Bighead carp larvae given Panagrellus in experiment 1 had much lower growth and survival than those fed Artemia nauplii. This could be due to low nematode density (5–30 mL−1 water) during feeding. The unfed larvae had 100% mortality by days 11–13. In experiment 2, growth and survival of carp larvae given Artemia nauplii (5–10 mL−1) and Panagrellus (50 mL−1) did not differ significantly (P > 0.05). All unfed larvae had died by day 13, while larvae fed EPN were all dead by day 8. Two experiments on Asian catfish were likewise conducted. In experiment 1, the catfish larvae were fed Tubifex (ad libitum), Panagrellus (50–100 mL−1 per feeding) orArtemia (5 nauplii mL−1 per feeding) three times daily for 14 days. In experiment 2, larvae were fed Artemia alone (10 nauplii mL−1 per feeding), Panagrellus alone (100 mL−1 per feeding), or their combination with a 38% protein dry diet twice daily. For both experiments, catfish larvae fed Panagrellus had significantly lower growth and survival than those fed Tubifex or Artemia. The combination of Panagrellus and dry diet created little improvement in the growth and survival of catfish larvae.

    • Diet and harvesting regimen for the production of mud crab Scylla olivacea in brackish water ponds 

      Rodriguez, Eduard M.; Triño, Avelino T.; Minagawa, Megumi (Japanese Society of Fisheries Science, 2003)
      The effects of diet (fish bycatch or a mixed diet of 75% brown mussel flesh and 25% cooked cracked corn) and harvesting regimen (bimonthly selective harvesting, or single terminal harvesting) on growth, survival and production of mud crab Scylla olivacea (Herbst) in brackish water ponds were determined in a replicated factorial experiment. The crabs were stocked at 0.6 individuals per m2 for 118 days. There was no significant interaction (P > 0.05) between the diet and harvesting regimen treatments. Regardless of diet, the survival rate and net production of mud crabs were significantly higher (P < 0.05) when crabs were subjected to bimonthly selective harvesting than at single terminal harvest. Comparative cost–return analysis showed that bimonthly selective harvesting and mixed diet treatments attained higher net return and return on investment, and lower cost of production than the other treatments. Partial budgeting analysis showed that bigger profits can be earned by using a bimonthly selective harvesting and a mixed diet of 75% fresh or fresh-frozen brown mussel flesh and 25% cooked cracked corn.

    • Terrestrial leaf meals or freshwater aquatic fern as potential feed ingredients for farmed abalone Haliotis asinina (Linnaeus 1758) 

      Reyes, Ofelia S.; Fermin, Armando C. (Blackwell Publishing, 2003)
      Three terrestrial leaf meals, Carica papaya, Leucaena leucocephala, Moringa oliefera and a freshwater aquatic fern, Azolla pinnata were evaluated as potential ingredients for farmed abalone diet. All diets were formulated to contain 27% crude protein, 13% of which was contributed by the various leaf meals. Fresh seaweed Gracilariopsis bailinae served as the control feed. Juvenile Haliotis asinina (mean body weight=13.4±1.6 g, mean shell length= 38.8±1.4 mm) were fed the diets at 2–3% of the body weight day–1. Seaweed was given at 30% of body weight day–1. After 120 days of feeding, abalone fed M. oliefera, A. pinnata-based diets, and fresh G. bailinae had significantly higher (P<0.01) specific growth rates (SGR%) than abalone fed the L. leucocephala-based diet. Abalone fed the M. oliefera-based diet had a better growth rate in terms of shell length (P<0.05) compared with those fed the L. leucocephala-based diet but not with those in other treatments. Furthermore, protein productive value (PPV) of H. asinina was significantly higher when fed the M. oliefera-based diet compared with all other treatments (P<0.002). Survival was generally high (80–100%) with no significant differences among treatments. Abalone fed the M. oliefera-based diet showed significantly higher carcass protein (70% dry weight) and lipid (5%) than the other treatments. Moringa oliefera leaf meal and freshwater aquatic fern (A. pinnata) are promising alternative feed ingredients for practical diet for farmed abalone as these are locally available year-round in the Philippines.

    • Ontogeny of feeding apparatus and foregut of mud crab Scylla serrata Forsskål larvae 

      Lumasag, Gil J.; Quinitio, Emilia T. ORCID; Aguilar, Riza O.; Baldevarona, Rodolfo B.; Saclauso, Crispino A. (Blackwell Publishing, 2007)
      The development of the feeding apparatus of the mud crab Scylla serrata larvae was studied using electron microscopy for mandibles and light microscopy for other paired mouthparts and the foregut. The six paired mouthparts, which consisted of the mandibles, maxillules, maxillae, first maxillipeds, second maxillipeds and third maxillipeds, were dissected from specimens representing each larval stage. The first five paired appendages were already present in newly hatched larvae while third maxillipeds appeared only at the megalopa stage. Mandibles displayed complex incisor and molar processes at early zoeal stages, which became simple in morphology at megalopa. Mandibular palp buds were observed at the zoea 5 stage and these became fully developed as three-segmented mandibular palps at the megalopa stage. Endopods of other paired mouthparts exhibited increased number of setae and size as the individual metamorphosed from zoeal stages to megalopa and crab instar. The foregut appeared as a continuous cavity at zoea 1 where the cardiopyloric valve was indistinct while the filter gland was clearly identifiable. Zoea 2 and succeeding zoeal stages exhibited a setose foregut; the gastric mill and its lateral and median teeth were prominent at zoea 3 stage. The significance of these morphological changes is discussed in terms of its implication in larval feeding management.

    • Cell growth and nutritive value of the tropical benthic diatom, Amphora sp., at varying levels of nutrients and light intensity, and different culture locations 

      de la Peña, M. R. (Springer Verlag, 2007)
      Two series of experiments were conducted to determine suitable growth factors for the mass propagation of the local algal isolate Amphora sp. A higher growth rate of 0.2 doubling (μ) day-1 was attained at a lower photosynthetic photon flux density (PPFD; 11.4 μmol photon m-2s-1) compared to cultures exposed to higher levels of PPFD (16.1 μmol photon m-2s-1, −0.1 μ day -1; 31.3 μmol photon m-2s-1, 0.0 μ day-1). Cultures located inside the laboratory had a significantly higher cell density (133 × 104 cells cm-2) and growth rate (0.3 μ day−1) compared to those located outdoors (100 × 104 cells cm-2, 0.2 μ day-1). A comparison of nutrient medium across two locations showed that lipid content was significantly higher in cultures enriched with F/2MTM (macronutrients + trace metals) and F/2MV (macronutrients + vitamins). Saturated fatty acids were also present in high concentrations in cultures enriched with F/2M (macronutrients only). Significantly higher amounts of saturated fatty acids were observed in cultures located outdoors (33.1%) compared to those located indoors (26.6%). The protein, carbohydrates and n-6 fatty acid content of Amphora sp. were influenced by the location and enrichment of the cultures. This study has identified growth conditions for mass culture of Amphora sp. and determined biochemical composition under those culture conditions.

    • Larviculture of marine species in Southeast Asia: current research and industry prospects 

      Marte, Clarissa L. (Elsevier, 2003)
      The increased requirement for food fish, the lucrative market for expensive seafood, and the need to conserve marine resources, have motivated the rapid pace of larviculture research in Southeast Asia. Various research and academic institutions in Southeast Asia such as the Southeast Asian Fisheries Development Center Aquaculture Department (SEAFDEC AQD) are carrying out research on commercially important marine species including 10 fish, 6 crustacean, and 7 mollusk species. Since fry availability is a major constraint in the development of culture systems, a major research thrust of SEAFDEC AQD is the development of commercially viable technologies for breeding and seed production of commercially important marine fish and crustaceans such as milkfish, groupers, snappers and mud crabs, in addition to the production of fry and juveniles of endangered and depleted species such as the sea horse and the tropical abalone for stock enhancement and sea ranching. Although hatchery production of milkfish and sea bass are now commercially viable enterprises, research is being pursued to improve fry quality through feed supplementation and to lower production cost by using alternative live or artificial feeds. Larviculture techniques are being developed for technically demanding species such as groupers and snappers. The recent success in larviculture of the mud crab Scylla serrata is expected to stimulate the growth of the mud crab industry in the region. Similarly, encouraging developments in the breeding and larviculture of the sea horse and mollusks such as the tropical abalone will provide the necessary support to carry out future stock enhancement and sea ranching programs for these species.

    • Tank culture of Gracilaria heteroclada (Zhang et Xia) 

      Luhan, M. R. J.; Tanaka, J.; Aruga, Y. (College of Agriculture and Central Experiment Station, University of the Philippines Los Baños, 2003)
      Culture conditions in tanks were manipulated to improve the growth and agar quality of Gracilaria heteroclada Zhang et Xia. Specific growth rates during culture ranged from -0.51% to 1.40% and gel strength of agar from 439 to 2155 g cm-2. G. heteroclada at a stocking density of 2kg ton-1 and fertilized with ammonium chloride at 40 mg L-1 grew best when water was changed once a month and ammonium chloride was replenished at 20 mg L-1 after water change. When water was not changed, good growth was observed in plants supplied with 1 mg L-1 diammonium phosphate on the 3rd wk of culture.

    • Growth and fatty acid production of thraustochytrids from Panay mangroves, Philippines 

      Leaño, Eduardo M.; Gapasin, Rolando S. J.; Polohan, Bernice; Vrijmoed, Lilian L.P. (Mushroom Research Foundation, 2003)
      Optimization of culture conditions with regard to the combined effects of salinity and temperature on biomass and fatty acid production of four thraustochytrid isolates were undertaken. Two strains of Schizochytrium mangrovei (IAo-1 and IXm-6), and one isolate each of Schizochytrium sp. (BSn-1) and Thraustochytrium sp. (IRa-8), isolated from fallen mangrove leaves, were used in this study. Results of the physiological study show that the best growth condition for Schizochytrium isolates was at a salinity range of 15-30 ‰ at 20-30°C, while that for Thraustochytrium sp. was at 22.5-30 ‰ at 25°C. Highest biomass production was 350 mg 50 mL-1 for Schizochytrium spp., and 133 mg 50 mL-1 for Thraustochytrium sp. Total lipid content (% freeze-dried biomass) ranged from 16.0-33.2% for S. mangrovei, 13.0-39.1% for Schizochytrium sp., and 11.4-37.5% for Thraustochytrium sp. Highest lipid production was observed at 15-22.5 ‰ salinity (25°C) for S. mangrovei, and at 15 ‰ (25°C) for Schizochytrium sp. and Thraustochytrium sp. Palmitic acid (16:0) and docosahexaenoic acid (DHA; 22:6n3) were the major components of the total fatty acid (TFA) content, comprising about 39-42% and 24-35%, repectively.

    • The Leiognathus aureus complex (Perciformes: Leiognathidae) with the description of a new species 

      Kimura, Seishi; Dunlap, Paul V.; Peristiwady, Teguh; Lavilla-Pitogo, Celia R. (Ichthyological Society of Japan, 2003)
      Taxonomic analysis of a group of morphologically similar ponyfishes (Perciformes: Leiognathidae) establishes a complex comprising three valid species: Leiognathus aureus Abe and Haneda, 1972, widely distributed in the western Pacific Ocean (Taiwan, Philippines, Thailand, Singapore, Indonesia, and northern Australia); L. hataii Abe and Haneda, 1972, currently known only from Ambon, Indonesia; and L. panayensis sp. nov. Kimura and Dunlap, currently known only from Panay Island, the Philippines. The L. aureus complex can be defined by the following combination of characters: mouth protruding forward, not downward; small but sharp conical teeth uniserially on jaws; a black line between lower margin of eye and lower jaw articulation; and lateral line incomplete, ending below posterior part of dorsal fin base or on anterior caudal peduncle. Leiognathus hataii differs from both L. aureus and L. panayensis in having a large dark blotch below the spinous dorsal fin base and fewer counts of scales (lateral line scales 50–58 vs. 64–85 in the latter two species; scales above lateral line 7–10 vs. 12–18; scales below lateral line 22–26 vs. 30–41). Leiognathus panayensis is distinguished from L. aureus in having a deeper body (41–51% SL vs. 35–45% SL in the latter), long posterior limb of maxilla (21–25% HL vs. 15–23% HL), wholly scaled belly (vs. naked along preanal median keel), and a dark blotch on nape (vs. absent).

    • Distribution of an oxytetracycline resistance determinant tet(34) among marine bacterial isolates of a Vibrio species 

      Kim, Seok-Ryel; Nonaka, Lisa; Oh, Myung-Joo; Lavilla-Pitogo, Celia R.; Suzuki, Satoru (Nakanishi Printing Co, 2003)
      The distribution of tet(34) was examined among oxytetracycline (OTC) resistant Vibrio strains isolated from Japan, Korea and the Philippines. tet(34) was detected in 10 isolates (6 in fish, 4 in seawater) from Japan and Korea, suggesting that it is widely distributed among fish and seawater bacteria in these countries. Ninety-eight percent of the Vibrio strains in the Philippines were sensitive to OTC, but none of the 60 isolates from the Philippines. The minimum inhibitory concentration (MIC) of OTC-resistant isolates increased 2 to 8 fold in the presence of Mg2+, and MICs were higher in the Japanese and Korean isolates than the Philippine isolates. The MIC for furaltadone (FD) was low in Japanese (23.9%) isolates at over 3.1 μg/ml and high in Korean (50%) and Philippine (56.7%) isolates. This was probably due to the different frequency of use of FD in these countries. Sequences of 16S rDNA of tet(34)-positive isolates were 100% identical, suggesting that tet(34) is conveyed in a particular Vibrio species.

    • Tolerance of seahorse Hippocampus kuda (Bleeker) juveniles to various salinities 

      Hilomen-Garcia, G. V.; Delos Reyes, R.; Garcia, C. M. H. (Blackwell Publishing, 2003)
      In line with current conservation efforts, some success in the captive breeding of the seahorse Hippocampus kuda (Teleostei: Syngnathidae) has been achieved. To evaluate the salinity tolerance of these hatchery-bred juveniles, 9-week-old H. kuda were transferred without prior acclimatization from ambient full strength seawater (32–33 ppt) to salinities ranging from freshwater to 85 ppt. Survival, growth, and total body water content were determined after 4 and 18 days of exposure. Juvenile H. kuda are able to survive in dilute seawater (15 ppt) for at least 18 days without any compromise in growth (both wet and dry body weight), survival, and total body water. Fish abruptly transferred to freshwater succumbed within 4–24 h, while survival of 5 ppt-reared fish decreased to ca. 65% in 18 days. Although 10 ppt-reared seahorses had growth and survival comparable with the control (30 ppt seawater), total body water was significantly elevated indicating reduced adaptability. The upper limit of H. kuda salinity tolerance was 50 ppt. Fish reared at salinities ≥55 ppt succumbed within 24 h. Like several other marine teleosts, growth and survival of juvenile H. kuda tended to peak in diluted seawater salinities of 15 and 20 ppt. These results indicate the possibility of growing hatchery-bred H. kuda in brackishwater environments.

    • Shell marking by artificial feeding of the tropical abalone Haliotis asinina Linne juveniles for sea ranching and stock enhancement 

      Gallardo, Wenresti G.; Bautista-Teruel, Myrna N.; Fermin, Armando C.; Marte, Clarissa L. (Blackwell Publishing, 2003)
      A method of marking abalone (Haliotis asinina Linne) for sea ranching and stock enhancement purposes was developed. Three-month-old abalone juveniles (11.8-mm shell length, 0.28 g) were fed artificial diets for 1, 2, or 3 weeks. The width of the bluish-green shell band produced by abalone juveniles was 1.7, 2.6, and 4.2 mm after 1, 2, or 3 weeks of feeding respectively. The growth and survival of juveniles fed artificial diets did not differ from that of juveniles fed the seaweed Gracilariopsis bailinae (control). Feeding the diet-fed juveniles with the seaweed thereafter produced the natural brownish shell, thus forming a sandwiched bluish-green band. An experimental release in outdoor tanks with natural growth of seaweeds and diatoms, and in a marine reserve showed that the shell band remained clear and distinct, indicating the usefulness of this shell marking method in sea ranching and stock enhancement of abalone.