Now showing items 835-854 of 1064

    • Article

      Rapid rural appraisal and participatory research in the Philippines 

      WG Gallardo, VC Encena II & NC Bayona - Community Development Journal, 1995 - Oxford University Press
      Rapid Rural Appraisal (RRA) was conducted in the fishing village of Lakaran, in the municipality of Dumangas, Iloilo province to identify the resources, livelihood, problems, opportunities, and socioeconomic condition of the villagers prior to the conduct of farmer participatory research on mussel farming. RRA tools such as the construction of the village transect, seasonal calendar and wealth ranking were used.
    • Article

      Rapid wound healing in African catfish, Clarias gariepinus, fed diets supplemented with ascorbic acid 

      G Erazo-Pagador & MS Din - The Israeli Journal of Aquaculture-Bamidgeh, 2001 - Society of Israeli Aquaculture and Marine Biotechnology
      Wound healing in African catfish, Clarias gariepinus, fed diets supplemented with ascorbic acid was studied under laboratory conditions. Fish weighing approximately 80-110 g were stocked in 500 l aquaria in a static water system and fed one of five test diets containing different levels of microencapsulated ascorbic acid (0, 0.06, 0.10, 0.30 and 0.70 g AsA/100 g feed). After two weeks, all experimental fish were wounded by making a 1 x 1 cm dorso-lateral incision above the lateral line of the fish. Wounded tissues were sampled for histopathological analysis 4, 8, 24, 48 and 96 hours, 6, 8, 10, 12 and 14 days after making the incision. There were significant differences in weight gain, specific growth rate (SGR) and feed conversion ratio among the dietary treatments. Weight gain and SGR of fish fed the ascorbic acid free diet were lower than those of fish fed diets supplemented with ascorbic acid. The wound healing response showed a direct correlation to ascorbate level in the diet. Fibroblasts were present at 96 h irrespective of the ascorbic acid level. As 14 days, fish fed no ascorbic acid had some regeneration of muscle tissues, whereas fish fed diets containing supplemental ascorbic acid had a normal epidermis, dermis and muscle structure. There was no mortality during the experimental period, and fish fed ascorbic acid free diets did not exhibit any deficiency signs. Results of this study indicate that about 0.10-0.70 g AsA/100 g feed is needed for wound repair in African catfish.
    • Article

      Rearing of the larval stages of prawn, Penaeus japonicus Bate, using artificial diet. 

      CT Villegas & A Kanazawa - Memoirs of the Kagoshima University Research Center for the South Pacific, 1980 - Kagoshima University Research Center for the South Pacific
      Survival and growth rates of the zoeal and mysis stages of the prwn, Penaeus japonicus Bate, were studied using natural and artificial diets.

      The highest survival rate, 34.2%, was obtained in the larvae fed with the artificial diet, Diet-B. Larvae fed with the diatom, Chaetoceros gracilis, plus Artemia nauplii did not give the best survival; however, growth was the fastest in this group. The larvae metamorphosed into the mysis3 stage in 8 days. The results thus seem to demonstrate tat Diet-B is an effective diet for the early larval stages of the prawn, P. japonicus.
    • Article

      Reducing and managing disaster risk through coastal resource management: A Philippine case 

      JGB Suyo, A Prieto-Carolino & RF Subade - Asian Fisheries Science, 2013 - Asian Fisheries Society
      Recently, disaster risk reduction and management was adopted by the national and local governments in the Philippines to prevent or mitigate the impacts of hazards. As a consequence, the Local Government Units of the coastal municipalities of Guimbal and Tigbauan, Iloilo Province, initiated disaster risk reduction and management activities. It is contended in this article that the condition of coastal and marine resources is fundamental in fostering community resilience to hazards, as exemplified by activities in Guimbal and Tigbauan. However, five major issues that remain to be addressed by the Local Government Units were identified through Key Informant Interviews and Focus Group Discussions. These include the overlapping roles of personnel, poor data management, weak coordination between Local Government Units and communities, lack of comprehensive plans, and a failure to understand the connection between disasters and the management of coastal and marine resources. Policy recommendations are made for amending the disaster risk reduction and management and coastal and marine resources programmes of municipalities.
    • 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

      Replacement of fish meal by animal by-product meals in a practical diet for grow-out culture of grouper Epinephelus coioides 

      OM Millamena - Aquaculture, 2002 - Elsevier
      A feeding trial was conducted to evaluate the potential of replacing fish meal with processed animal by-product meals, meat meal and blood meal (4:1 ratio), in practical diets for juvenile grouper (Epinephelus coioides). Eight isonitrogenous diets were formulated to contain 45% protein and 12% lipid. Fish meal was replaced by 0%, 10%, 20%, 30%, 40%, 60%, 80%, and 100% of meat meal and blood meal (4:1) mixture (diets 1–8). The diet with 100% fish meal (diet 1) or trash fish as feed (diet 9) were used as controls. Grouper juveniles were reared in 250-l circular fiberglass tanks maintained in a flow-through seawater system. Each dietary treatment was tested in quadruplicate groups of 25 fish per tank arranged in a completely randomized design. Fish were fed the diets twice per day at a daily feeding rate of 5–6% of biomass and trash fish at 10–12% of biomass for 60 days. Percentage weight gain, specific growth rate (SGR), survival, feed conversion ratio (FCR) and body composition of grouper juveniles were measured. There were no significant differences (P>0.05) in growth performance among fish fed diets 1–7 (0–80% fish meal replacement) with those fed diet 9 (trash fish as feed). However, fish fed diet 3 had significantly higher (P<0.05) growth than those fed diet 8 (100% fish meal replacement). Survival among fish fed the experimental diets did not significantly differ (96–100%) but was significantly higher (P<0.05) than survival (90%) of fish fed trash fish. These results showed that up to 80% of fish meal protein can be replaced by processed meat meal and blood meal coming from terrestrial animals with no adverse effects on growth, survival, and feed conversion ratio of E. coioides juveniles.
    • Article

      Reproductive development of the threatened giant grouper Epinephelus lanceolatus 

      The giant grouper is presumed to follow the reproductive pattern of most Epinephelus species, characterized by protogynous hermaphroditism wherein male maturation is attained through sex reversal of a functional female. This hypothesis, however, has not been verified due to lack of biological data. The present study addresses this gap by investigating the reproductive development of giant groupers from juvenile stage through sexual maturity. Gonad histological analysis of hatchery-bred juvenile giant grouper from Queensland, Australia (0.8–5.2 kg, n = 43) have shown earliest occurrence of primary oocytes (i.e. ovarian differentiation) in 47.8 cm and 2.5 kg fish. Monitoring of sexual maturity by gonadal biopsy was performed in a stock of wild-caught giant groupers (2–52 kg) held in sea cages in the Philippines and Vietnam from 2015 to 2017. Onset of female sexual maturity was at 96.9 ± 1.6 cm and 23.5 ± 1.5 kg in the Philippines, and 103.0 ± 4.1 cm and 33.5 ± 2.5 kg in Vietnam. In both locations, development of primary males was observed wherein fish produced milt (or spermiated) without passing through a functional female phase. The ratio of primary males to females in both locations was about 1:2. Size at maturity of primary males is 86.5 ± 4.8 cm and 17.1 ± 2.1 kg in the Philippines, and 97.3 ± 1.3 cm and 34.3 ± 0.9 kg in Vietnam. To aid in the monitoring of female maturation, we developed a non-invasive method based on immunoassay of vitellogenin in skin mucus and this was shown to be effective in detecting female maturation 9 ± 2 months prior to first observation of oocytes through gonadal biopsy. Our findings suggest that giant grouper is a diandric protogynous hermaphrodite. This study provides novel information on the reproductive biology of giant grouper, an economically important and vulnerable species.
    • Article

      Reproductive performance and growth of Nile tilapia (Oreochromis niloticus) broodstock fed diets containing Leucaena leucocephala leaf meal 

      CB Santiago, MB Aldaba, MA Laron & OS Reyes - Aquaculture, 1988 - Elsevier
      The effects of dietary leucaena leaf meal on reproductive performance and growth of Nile tilapia were determined. In the preliminary trial, sexually mature Nile tilapia were fed with a control diet or a test diet which had leucaena leaf meal as the only protein source for 24 weeks. Fish fed with the leucaena diet lost some weight and had significantly low (P<0.05) gonadosomatic index and fry production compared to those fed with the control diet. Subsequently, four isonitrogenous diets (20% crude protein) containing varying amounts of leucaena leaf meal (0, 20, 40 and 80%) were fed to Nile tilapia broodstock. Mean weight gain of the female fish decreased as the level of leucaena leaf meal in the diets increased. Females fed with the 80% leucaena diet invariably lost weight. Mean weight gain of males fed with the control diet and the 20 and 40% leucaena diets did not differ significantly (P>0.05). However, growth of males fed with the 80% leucaena diet was remarkably low. Fry production was highest for those fed with the control diet and the 20% leucaena diet. Fry production decreased slightly in fish fed with the 40% leucaena diet and was significantly low (P<0.05) for those fed with the 80% leucaena diet. The low fry production was preceded by a decrease in body weight of the female fish. However, the gonadosomatic indices of the females and the males were not markedly affected by the diets. On the basis of both fry production and growth, leucaena leaf meal should not exceed 40% of the diet of Nile tilapia broodstock.
    • Article

      Reproductive performance and larval quality of pond-raised Scylla serrata females fed various broodstock diets 

      OM Millamena & JB Bangcaya - Asian Fisheries Science, 2001 - Asian Fisheries Society
      Scylla serrata females with initial body weight (BW) of 350 to 400 g were previously raised on a defined diet of 75% brown mussel meat and 25% fish bycatch in grow-out ponds at Molo, Iloilo City, Philippines for 120 days. Crabs were stocked in three units of 4 m diameter concrete indoor tanks at the Crustacean Broodstock Wet Laboratory of SEAFDEC Aquaculture Department in Tigbauan, Iloilo, Philippines. Tanks had sand substrates and were supplied with sand-filtered and chlorinated seawater in a continuous flow-through system with adequate aeration. Each female was provided with individual shelter. Before stocking, crabs were tagged on their carapace and half of the females were ablated while the other half remained intact. Broodstock were fed either T1, natural food consisting of mussel and fish bycatch; T2, a mixed diet of natural food and formulated diet; or T3, a formulated diet. Broodstock reproductive ability was measured as percent spawnings, spawnings with hatching, fecundity or number of eggs per g BW of female, egg fertilization rate and total zoea produced. Larval quality was measured as larval stage index or ability to attain the megalopa stage, the highest larval stage. Females fed on all dietary treatments were capable of maturation and spawnings. However, mixed diet feeding (T2) improved broodstock performance and larval quality over those fed either natural food (T1) or formulated (T3) alone. Eyestalk ablation improved fecundity and produced higher total zoea in T1 and T3 although lower in egg fertilization rate than intact females. All zoea larvae in ablated T2 females were successfully reared to megalops. Overall improvement in larval quality of both ablated and intact females compared with previous studies on wild-caught females was attributed to their dietary history in grow-out ponds. Feeding the females with a suitable diet in ponds enabled them to fortify the reserves of nutrients needed for egg development and improve stability in larval production.
    • Article

      Reproductive performance in induced and spontaneous spawning of the mangrove red snapper, Lutjanus argentimaculatus: a potential candidate species for sustainable aquaculture 

      AC Emata - Aquaculture Research, 2003 - Blackwell Publishing
      A reliable breeding technique was developed for the mangrove red snapper, Lutjanus argentimaculatus (Forsskal 1775), to help sustain the aquaculture of this immensely popular species in Southeast Asia. Using standardized indices of female maturity (based on mean oocyte diameter of ≥0.40 mm), time of injection (1000–1130) and sex ratio (one female to two males), a single injection of 100 μg kg−1 luteinizing hormone-releasing hormone analogue (LHRHa) (n=16 fish), but not 50 μg kg−1 (n=five fish), successfully induced egg (62.5% success rate) and larval (43.8%) production. Human chorionic gonadotropin (hCG) at 500 IU kg−1 (n=five fish) also failed to induce spawning, but doses of 1000 (n=22 fish) and 1500 IU kg−1 (n=15 fish) gave spawning (77.3% and 80.0% respectively) and hatching success rates (72.7% and 60.0% respectively) that were not significantly different from those of 100 μg kg−1 LHRHa. No spawning was observed in saline-injected controls (n=seven fish). While mean spawning latency, egg diameter, egg production per spawn, percent egg viability, hatching rate, percent of normal larvae and cumulative survival of eggs to normal larvae did not differ significantly among the effective hormones and doses, 1000 IU kg−1 hCG had a higher percentage (76.5%) of total spawns with egg production per spawn in excess of one million than those of 1500 IU kg−1 hCG (50.0%) and 100 μg kg−1 LHRHa (40.0%). Mangrove red snapper spontaneously spawned from March–April to November–December with a peak of egg collection and spawning in May–June. Egg collection per spawn ranged from 0.05 to 6.35 million. Spontaneous spawning of mangrove red snapper exhibited lunar periodicity with spawns mostly occurring 3 days before or after the last quarter and new moon phases and occurred consistently between 02:00 and 04:00 hours. High fecundity and good egg quality, coupled with the ability to respond to induce spawning or natural spawning in captivity, provide a sound basis for improving the sustainability of red snapper aquaculture in Southeast Asia.
    • Article

      Reproductive performance of four red tilapia strains in different seed production systems 

      MRR Eguia - The Israeli Journal of Aquaculture-Bamidgeh, 1996 - Society of Israeli Aquaculture and Marine Biotechnology
      The reproductive efficiency of one Thai red tilapia strain (NIFI) and three genetically diverse Philippine red tilapia strains (BFS, FAC, and PF) were compared. Breeders from each strain were stocked separately in land-based concrete tanks and lake-based hapa net cages or fine-meshed net cages at densities of 4 males:12 females per enclosure. Spawning activity, seed (egg and fry) production and hatchability data from the four strains in each hatchery system were monitored once every three weeks for twelve months.

      Results showed that seed production in all strains was lower in cages than in tanks. Daily mean seed production in the land-based hatchery system was highest at 12.41 per spawner for FAC followed by NIFI (11.18), BFS (9.49) and PF (5.56). In the hapa net cages, BFS produced 2.19 eggs and fry per female daily while NIFI, FAC and PF gave daily harvests of 1.40, 1.18 and 1.14 eggs and fry per spawner. Analysis of variance showed that seed production was significantly influenced by the strain, type of hatchery system and the interaction between the two factors.
    • Article

      Reproductive performance of hatchery-bred donkey's ear abalone, Haliotis asinina, Linne, fed natural and artificial diets 

      MN Bautista-Teruel, OM Millamena & AC Fermin - Aquaculture Research, 2001 - Blackwell Publishing
      Hatchery-bred donkey's ear abalone, Haliotis asinina, Linne broodstock were given diets consisting of natural food, seaweed (SW), Gracilariopsis bailinae, D1; combination of SW and artificial diet (AD), D2; and AD alone, D3. Equal numbers of 1 : 1 female and male abalone were stocked in 24 units, 60 L tanks with eight replicate tanks per dietary treatment. Reproductive performance, e.g. number of spawnings, instantaneous fecundity and egg hatching rates, was monitored over 270 days. The mean number of spawnings was not significantly different among treatments. The mean instantaneous fecundity and percent hatching rates were significantly higher in abalone fed D2 or D3 compared to those given D1. Survival of abalone broodstock fed D1 was, however, significantly higher at 88% than those fed either D2 or D3 at 75%. Fatty acid analysis showed that the n-3/n-6 fatty acid ratios of abalone hepatopancreas reflected those of their diets. Mature abalone ovary had n-3/n-6 fatty acid ratio of 1.3. A higher amount of essential nutrients in the artificial diet such as protein, lipid and the highly unsaturated fatty acids, e.g. 20 : 4n-6, 20 : 5n-3, 22 : 6n-3 in abalone fed D2 or D3, may have influenced the increased reproductive performance.
    • Article

      Reproductive performance, lipids and fatty acids of mud crab Scylla serrata (Forsskål) fed dietary lipid levels 

      VR Alava, ET Quinitio, JB de Pedro, ZGA Orosco & M Wille - Aquaculture Research, 2007 - Blackwell Publishing
      Natural food (NF, control), artificial diets (AD) containing total lipid levels of 10%, 12% and 14% (AD10, AD12 and AD14) and their combinations (AD10+NF, AD12+NF and AD14+NF) were fed for 112 days to pond-sourced eyestalk-ablated mud crab Scylla serrata (625±6.4 g) in tanks in order to determine their effects on reproduction and lipid profiles in broodstock tissues and zoeae. Crabs fed NF had the highest number of spawning followed by crabs fed AD10+NF and AD14+NF. Higher offspring production (number of zoeae) was obtained from crabs fed NF and AD+NF than from AD. As dietary total lipid levels increased, total lipid of broodstock ovaries, hepatopancreas, muscle and zoeae correspondingly increased in which AD+NF promoted higher levels than AD. Increased dietary total lipid levels enhanced lipid classes such as triacylglycerols and phosphatidyl choline levels in zoeae, all higher in crabs fed AD+NF than in AD. The major fatty acids in zoeae, particularly 16:0, 18:0, 18:1n-9 and 20:4n-6, 20:5n-3 and 22:6n-3, were higher in crabs fed AD+NF than in AD, the contents corresponding to broodstock dietary total lipid levels. A 10% total lipid in AD in combination with NF was sufficient to provide the essential lipids in crabs in the improvement of larval production and quality.
    • Article

      Reproductive quality of male Penaeus monodon 

      LAO Gomes & J Honculada-Primavera - Aquaculture, 1993 - Elsevier
      The reproductive performance of unilaterally eyestalk-ablated wild male Penaeus monodon was compared with that of unablated prawns (controls). After being stocked for 6 weeks in flow-through tanks, ablated males showed significantly higher sperm count (153.6 × 106 vs.77.5 × 106), less abnormal sperm (45.5% vs 73.3%), larger sperm head diameter (6.682 μm vs. 5.568 μm) and longer spike (5.096 μm vs. 4.360 μm) compared to unablated ones. Gonad index, spermatophore weight and percentage of live sperm were not significantly different between ablated and unablated males. No apparent decline in reproductive capacity was detected when comparing unablated prawns at the start of the study and after 6 weeks.
    • Article

      Requirement for tryptophan by milkfish (Chanos chanos Forsskal) juveniles 

      RM Coloso, LB Tiro & LV Benitez - Fish Physiology and Biochemistry, 1992 - Springer Verlag
      Groups of milkfish juveniles (mean initial weight 7.7 g) were fed semipurified diets containing 0.9, 1.4, 2.1, 3.1, 4.1 and 6.1 g tryptophan/kg dry diet for 12 weeks. The mean crude protein content of the diets (containing white fishmeal, gelatin and free amino acid mixture to simulate the pattern of hydrolysed milkfish protein) was 49%. On the basis of the growth response, the tryptophan requirement of milkfish juveniles was estimated to be 3.1 g/kg diet. Fish fed low levels of tryptophan exhibited low weight gains and poor feed conversion ratios. Survival (92–100%) was consistently high in all treatments. Fish fed diets containing tryptophan levels greater than 3.1 g/kg had slightly lower survival rates. The activity of hepatic tryptophan pyrrolase showed no significant differences with increasing dietary tryptophan levels. No nutritional deficiency signs were observed other than the depression in growth rates in fish given the tryptophan deficient diets.
    • Article

      Requirements of juvenile marine shrimp, Penaeus monodon (Fabricius) for lysine and arginine 

      OM Millamena, MN Bautista-Teruel, OS Reyes & A Kanazawa - Aquaculture, 1998 - Elsevier
      Feeding experiments were conducted using amino acid test diets to determine the dietary requirements of juvenile Penaeus monodon for lysine and arginine. Two sets of the test diets were prepared. The natural protein was supplied by casein and gelatin. Crystalline l-amino acids were added to provide an amino acid profile similar to shrimp muscle protein except for the test amino acid. One set of experimental diets contained graded levels of lysine at 1.18–3.28% of the diet and another set contained arginine at 0.6–3.0% of the diet. The amino acid mixture was pre-coated with carboxymethylcellulose (CMC) and diets were further bound with CMC, cornstarch, and K–carrageenan to prevent leaching losses of amino acids. Shrimp postlarvae, PL20, with mean weight of 21±0.5 mg, were randomly distributed at 10 shrimp per tank in 40-l fiberglass tanks and reared on the diets for 50–56 days. Growth, survival and feed conversion efficiency were determined at termination of feeding trials and signs of nutritional deficiency noted. Lysine and arginine requirements were determined from relationships between weight gains and dietary lysine and arginine levels as analyzed by the broken-line regression method. The requirement of juvenile P. monodon for lysine was estimated to be 2.08% of the diet or 5.2% of dietary protein while the requirement for arginine was 1.85% of the diet or 5.3% of dietary protein. This information is crucial in formulating cost-effective practical diets for juvenile tiger shrimp.
    • Article

      Requirements of juvenile milkfish (Chanos chanos Forsskal) for essential amino acids 

      IG Borlongan & RM Coloso - Journal of Nutrition, 1993 - American Society for Nutrition
      The dietary requirements of juvenile milkfish (Chanos chanos Forsskal) for essential amino acids were determined in a series of experiments. The fish (< or = 8.0 g) were reared in fiber glass tanks provided with flow-through seawater at 28 degrees C and salinity of 32 g/L for 12 wk. In each experiment, a series of amino acid test diets was formulated containing a combination of intact protein sources (casein-gelatin, fish meal-gelatin, fish meal-soybean meal or fish meal-zein) and crystalline amino acids to simulate the levels found in milkfish tissue proteins except for the test amino acid. Each set of isonitrogenous diets contained 40-45% protein and graded levels of the amino acid to be tested. At the end of the feeding experiment, growth, survival and feed efficiency were determined. The requirement level for each essential amino acid was estimated from breakpoint analysis of the growth curve. The dietary essential amino acid requirements (as the percentage of dietary protein) of milkfish juveniles were as follows: arginine, 5.25; histidine, 2.00; isoleucine, 4.00; leucine, 5.11; lysine, 4.00; methionine, 2.50 (cystine, 0.75); phenylalanine, 4.22 (tyrosine, 1.00) or 2.80 (tyrosine, 2.67); threonine, 4.50; tryptophan, 0.60; valine, 3.55. This information is valuable in developing cost-effective practical or commercial feeds and research diets for milkfish juveniles.
    • Article

      Resistance of rainbow trout Oncorhynchus mykiss to infectious hematopoietic necrosis virus (IHNV) experimental infection following ingestion of natural and synthetic carotenoids 

      EC Amar, T Akutsu, S Satoh & T Watanabe - Aquaculture, 2012 - Elsevier
      Further to previous studies showing modulation of innate immune responses by dietary carotenoids, an experiment was conducted to examine the resistance to a viral pathogen in rainbow trout after oral ingestion of synthetic or natural carotenoids. Rainbow trout fry weighing 0.11 g on average (n = 30) were fed casein-based semi-purified diets supplemented with 100 mg carotenoids kg− 1 diet for 6 weeks. The synthetic sources tested were pure β-carotene, astaxanthin, and canthaxanthin, whereas the natural sources were Dunaliella salina, Phaffia rhodozyma, Tagetes erecta, and Capsicum annuum. No significant differences (P > 0.05) in growth and feed performance were found among the groups after 6 weeks of feeding. Subsequently, fish were challenged by immersion in two concentrations (2 × 103 and 2 × 104 TCID50 ml− 1) of a virulent strain of infectious hematopoietic necrosis virus (IHNV) and cumulative mortalities were recorded over a 30-day period. No significant differences in survival (P > 0.05) were found among the groups when challenged with the high viral dose. However, at the lower viral dose, mortality was markedly reduced in fish fed astaxanthin (22%). Consequently, this group exhibited the highest relative percent survival (RPS) of 58%, which was significantly different from the control (P < 0.05). Rainbow trout fed D. salina and T. erecta among the natural sources, had reduced mortality rates and elevated RPS that, nonetheless, did not significantly differ from the control. This study highlights the influence of carotenoids, particularly astaxanthin, in maintaining fish health and disease resistance.
    • Article

      Resistance to a heavy metal mixture in Oreochromis niloticus progenies from parents chronically exposed to the same metals 

      MLA Cuvin-Aralar & EV Aralar - Chemosphere, 1995 - Elsevier
      Adult Oreochromis niloticus were mass spawned in concrete tanks. The one-month old progenies (F1) were exposed for two months to a mixture of 0.01 mg L−1 Hg, 0.1 mg L−1 Cd and 1.0 mg L−1 Zn. The survivors were grown to sexual maturity in a natural environment (lake). The fish were spawned and the progenies (F2) of the exposed F1 (EF1) were exposed to another mixture of the three metals: 3.0 mg L−1 Zn, 0.30 mg L−1 Cd and 0.01 mg L−1 Hg, both in a static and static-renewal system. Another group of F2 from unexposed F1 (UF1) received the same treatment. Results showed that in both exposure systems, survival of the F2 of EF1 was significantly higher (P<0.05) than those from UF1. The medial lethal time (LT50) of the F2's were estimated from the time-response curve following regression analysis: 5.16 days (F2 of UF1) and 9.03 days (F2 of EF1) in the static exposure experiment; 3.34 days (F2 of UF1) and 5.52 days (F2 of EF1) in the static-renewal run. Exposure of the parental stock resulted in the culling out of individuals which were more susceptible to the heavy metals. The more resistant members of the population (survivors) which have the ability to adapt to the toxicants were able to pass on the resistance to their offspring. The results are supported by other studies in the field which demonstrate high resistance in populations of organisms living in contaminated sites.
    • Article

      Resistance to antibiotics of Vibrio spp. and Aeromonas spp. isolated from fish and shrimp tissues and rearing water in Panay island, Philippines 

      EM Leaño, VBM Inglis & IH Macrae - UPV Journal of Natural Science, 1998 - University of the Philippines Visayas
      A survey on the resistance patterns to selected antibiotics of bacterial pathogens of fish and shrimps in Panay Island, Philippines was conducted. One hundred and sixteen (116) bacterial isolates were collected from fish (Chanos chanos, Epinephelus sp. and Lates calcarifer) and shrimp (Penaeus monodon and P. indicus) tissues and rearing water. Among these isolates, only seven were identified as Aeromonas spp., the rest (109 isolates) were Vibrio spp., 42% of which were luminous Vibrio. Results of the sensitivity tests showed that all Aeromonas spp. isolates were resistant to streptomycin, oxytetracycline, and trimethoprim/sulphamethoxazole. Most of the Vibrio spp. isolates (94.5%) were resistant to streptomycin. Multiple resistance to two or more antibiotics was observed in 17 isolates of Vibrio spp. and all isolates of Aeromonas spp.