Now showing items 1-20 of 30

    • Article

      Agar production from Gracilariopsis heteroclada (Gracilariales, Rhodophyta) grown at different salinity levels 

      AQ Hurtado-Ponce - Botanica Marina, 1994 - Walter de Gruyter
      Gracilariopsis heteroclada grown in fiber glass tanks at four salinity levels was treated with three different concentrations of aqueous NaOH. Yield, gel strength, gelling and melting temperatures of the extracted agar were determined. Plants grown at salinities of 24 and 32 ppt and treated with 3% NaOH produced the strongest gel (850 g cm-2) and weakest gel (300 g cm-2), respectively. Statistically significant differences in gel strength, dynamic gelling and melting temperatures were observed between the various treatments. The interactive effect of salinity and NaOH was significant in gel strength, gelling and melting temperatures of the gel from G. heteroclada.
    • Article

      Assessment of stocks of a natural Gracilaria population on Panay Island, Philippines 

      TR de Castro, NG Guanzon Jr. & MR Luhan - Botanica Marina, 1991 - Walter de Gruyter
      Two peaks in biomass were recorded from natural beds of Gracilaria sp. at Leganes, Iloilo and Batan, Aklan study sites. The major peak occurred in February 1989 for both areas. The minor peak occurred in September 1988 at Batan and October 1988 at Leganes. Highest biomass at Ivisan, Capiz occurred in May 1988. Lowest biomass was recorded in June at Batan and December 1988 at Leganes. At Ivisan, no biomass was recorded from November 1988 to February 1989. Correlation analysis showed no relationship between biomass and temperature or pH at all study sites. However, salinity was negatively correlated with biomass at Leganes and Batan. Rainfall was inversely correlated with biomass. Based on salinity data gathered from the three study sites, Gracilaria sp. is euryhaline and can tolerate a wide range of salinity. The results show a marked seasonality in the biomass of Gracilaria sp.
    • Article

      Changes in Na+, K+-ATPase activity and gill chloride cell morphology in the grouper Epinephelus coioides larvae and juveniles in response to salinity and temperature 

      NB Caberoy & GF Quinitio - Fish Physiology and Biochemistry, 2000 - Springer Verlag
      The activity of the enzyme Na+, K+-ATPase and morphological changes of gill chloride cells in grouper, Epinephelus coioides larvae and juveniles were determined 6–48 h after abrupt transfer from ambient rearing conditions (30–32 ppt, 26.5–30°C) to different salinity (8, 18, 32, 40 ppt) and temperature (25, 30°C) combinations. Na+, K+-ATPase activity in day 20 larvae did not change at salinities 8–32 ppt. Activity decreased significantly (P <0.01) after exposure to 40 ppt at 25–30°C, which was accompanied by an increase (P < 0.05) in density and fractional area of chloride cells. Enzyme activity in 40 ppt did not reach a stable level and larvae failed to recover from an osmotic imbalance that produced a low survival at 25°C and death of all larvae at 30°C. Enzyme activity and chloride cell morphology in day 40 groupers did not change in 8–40 ppt at 25°C and 8–32 ppt at 30°C. A significant decrease and a subsequent increase in Na+, K+-ATPase activity in 40 ppt at 30°C was associated with the increase in chloride cell density resulting in an increased fractional area but a decreased cell size. Enzyme activity and chloride cells of day 60 grouper were unaffected by abrupt transfer to test salinities and temperatures. These results demonstrate that grouper larvae and juveniles are efficient osmoregulators over a wide range of salinities. Salinity adaptation showed an ontogenetic shift as the larvae grew and reached the juvenile stage. This development of tolerance limits may reflect their response to actual conditions existing in the natural environment.
    • Article

      Critical factors influencing survival and hatching of milkfish (Chanos chanos Forsskal) eggs during simulated transport 

      LMB Garcia & JD Toledo - Aquaculture, 1988 - Elsevier
      The effects of loading density, length of transit time, temperature and salinity on milkfish (Chanos chanos Forsskal) eggs during simulated transport were examined. Rocking motion approximating conditions of transport of eggs collected from milkfish broodstock floating net cages to a hatchery was simulated using a laboratory orbit shaker. Loading densities of more than 7000 eggs/l in shipping bags resulted in decreased rates of survival and correspondingly lower hatching rates. Prolonged shaking simulating extended periods of egg transport also resulted in low egg survival and hatching rates compared to fertilized eggs not subjected to simulated transport. Egg survival after simulated transport at 20°C was lower than at 28°C, except at 20 ppt salinity, where survival was equal. Egg survival at 20°C progressively increased with declining salinity levels whereas high egg survival rates were observed after 2 h of simulated egg transport at 28°C and at the three salinities tested. Hatching rates of fertilized eggs after simulated transport were higher at 28°C than at 20°C regardless of salinity. Neither salinity nor its interaction with temperature affected hatching rates of eggs after simulated transport. These results indicate that survival and hatching of fertilized milkfish eggs after simulated transport is influenced by loading density, transport time, temperature and, to some degree, the salinity of the water. Based on these results, guidelines for handling and transporting milkfish eggs are given.
    • Article

      Development of a method for reproducing epizootic ulcerative syndrome using controlled doses of Aphanomyces invadans in species with different salinity requirements 

      ES Catap & BL Munday - Aquaculture, 2002 - Elsevier
      Lesions typical of epizootic ulcerative syndrome (EUS) were induced in three-spot gourami, Trichogaster trichopterus, and sand whiting, Sillago ciliata, injected intramuscularly with controlled doses of Aphanomyces invadans zoospores, the fungal pathogen associated with the disease. Both species of fish exhibited chronic granulomatous response and inflammatory cells, predominantly macrophages and lymphocytes, infiltrated the muscle and skin tissues, at days 6–8 post-inoculation of 65 to 85 spores/fish. Based on the comparative granuloma counts and percentage of cellular infiltration in a sampled lesion area using image analysis, it was shown that the three-spot gouramis mounted a more vigorous response than the sand whiting. It was also observed that lesions in three-spot gouramis exhibited early signs of resolution than those in sand whiting. However, fish mortality was greater in EUS-affected three-spot gourami than in EUS-affected sand whiting. With this technique, we were able to describe and compare the sequential histopathology of EUS lesions in a freshwater (three-spot gourami) and an estuarine (sand whiting) fish species.
    • Article

      Digestibility in milkfish, Chanos chanos (Forsskal): Effects of protein source, fish size and salinity 

      RP Ferraris, MR Catacutan, RL Mabelin & AP Jazul - Aquaculture, 1986 - Elsevier
      The true digestibility of casein, gelatin, fish meal, defatted soybean meal and Leucaena leucocephala leaf meal was measured in 60- and 175-g milkfish (Chanos chanos Forsskal) in fresh- and seawater. The diets contained 45% of these feedstuffs and 1.3% of the indicator substance, chromic oxide. The intestinal dissection method was used to collect fecal material. Results showed that the length of time between initial feeding and fish sacrifice did not significantly affect digestibility. Gelatin was the most digestible (90–98%) protein, regardless of size. Casein, defatted soybean meal and fish meal were moderately digestible (50–90%) and digestibility coefficients tended to increase as a function of fish size. L. leucocephala was the least digestible (−10–40%). The digestibility of most of these feedstuffs was less in the anterior than in the posterior intestine, and tended to be lower in seawater than in freshwater. Rate of food movement was similar in both size groups, but was significantly faster when milkfish were in seawater rather than in freshwater. The effect of salinity on digestibility may in part be due to food motility changes necessitated by alterations in osmoregulatory processes when fish are in seawater.
    • Article

      Effect of salinity on survival of Metapenaeus anchistus juveniles and subadults 

      MJHL Lebata & J Primavera - UPV Journal of Natural Sciences, 1997 - University of the Philippines in the Visayas
      Survival of Metapenaeus anchistus (De Man) juveniles and subadults at 5, 15, 25, 35 (control) and 45 ppt salinity levels was determined and compared. Salinity levels lower than 35 ppt level were prepared by diluting pure seawater with tap water (OPPT) while 45 ppt level was prepared by diluting 85 ppt water with tap water. Survival was observed at 0.5, 1, 2, 3, 6, 12, 18, 24 h after stocking and every 12 hours thereafter until 96 h.

      Shrimp survival was highest at 35 ppt (P<0.01); differences among treatments were first observed at 2 h after exposure with some shrimps dying at 5 ppt. At the end of the experiment, survival was highest at 35 ppt (100%), followed by 25 and 45 ppt (90 and 80%, respectively), 15 ppt (50%) and 5 ppt (0%).
    • Article

      Effect of salinity, dietary lipid source and level on growth of milkfish (Chanos chanos) fry 

      VR Alava - Aquaculture, 1998 - Elsevier
      Six semi-purified microparticulate diets containing coconut oil (CO), cod liver oil (CLO), and their 1:1 combination (CO+CLO) at 9% and 18% levels were fed to milkfish fry or late postlarvae in freshwater (0 ‰), brackishwater (16‰), and seawater (34‰) for 30 days. A three-factor factorial design (3×2×3) with three replicates per treatment was followed. Sixty-five milkfish fry (5 mg, 6 mm) were stocked per 15-l rectangular glass aquarium and fed with the experimental diets at 20% of biomass daily. Water temperature was 28±1°C during the culture period. Survival was not affected by water salinity, and lipid source or level. Among the 18 treatments, freshwater-reared milkfish fry fed with 9% CO+CLO had the highest specific growth rate, but this was not significantly different from those of freshwater-reared fish fed with 9–18% CO and 9% CLO diets or brackishwater-reared fish fed with 9% CO diet (P>0.05). As a main factor, salinity or dietary lipid level, but not lipid source, had significant effects on growth and feed conversion ratio of milkfish fry. Highest growth was observed in fish reared in freshwater and as salinity was increased, growth decreased (P<0.05). Overall, the 9% lipid diets promoted better growth than the 18% lipid diets (P<0.05). Except for the significant interaction between dietary lipid source and level indicating that milkfish fry fed with the 18% CLO was the shortest (P<0.05), no other significant effects of the two- or three-factor interactions were found.
    • Conference paper

      Effects of salinity on growth of young milkfish, Chanos chanos 

      F Hu & IC Liao - In Proceedings of the International Milkfish Workshop Conference, May 19-22, 1976, Tigbauan, Iloilo, Philippines, 1976 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Growth of young milkfish was studied at different levels of salinity over a period 68 days. Results suggested that young milkfish reared in freshwater or less saline sea water grew faster than in sea water. The increase in body weight was neither due to the increase in water content nor increase in feeding rate. The difference in growth rate might be attributed to the deviation from the original acclimating salinity. Mechanisms of the effect of salinity in retarding or accelerating milkfish growth should be investigated in the future.
    • Article

      Enrichment of live food with essential fatty acids and vitamin C: effects on milkfish (Chanos chanos) larval performance 

      RSJ Gapasin, R Bombeo, P Lavens, P Sorgeloos & H Nelis - Aquaculture, 1998 - Elsevier
      The effects of essential fatty acids (EFA) and vitamin C-enriched live food on growth, survival, resistance to salinity stress and incidence of deformity in milkfish larvae reared in tanks were investigated. Larvae were either fed rotifers cultured on Chlorella sp. and newly hatched Artemia nauplii (control), highly unsaturated fatty acid (HUFA)-enriched rotifers and Artemia nauplii or HUFA+vitamin C-enriched rotifers and Artemia nauplii. Milkfish growth in outdoor nursery ponds was also assessed to compare with growth in indoor tanks. Milkfish fed rotifers/Artemia enriched with HUFA (32–48 mg dry weight, DW) or HUFA+vitamin C (33–45 mg DW) exhibited significantly (P<0.05) higher growth than those given unenriched live food (24–27 mg DW) after 40 days of culture. Growth of milkfish in nursery ponds (albeit lower in stocking density) showed similar trends as those reared in tanks. When subjected to salinity stress (Day 25), mortality of the HUFA+vitamin C-treated fish and HUFA-treated fish were significantly lower (P<0.05) than the control fish. Survival of 26-day old milkfish, however, did not differ significantly (P>0.05) among the treatment groups. Forty-day-old milkfish fed HUFA+vitamin C-enriched live food had significantly lower (P<0.05) incidence of opercular deformity (mainly cleft branchiostegal membrane) (8.4–14.7%) compared with those given HUFA-enriched (15.8–23.5%) or unenriched (27.3–33.5%) live food. Results demonstrated the effect of HUFA enrichment in enhancing milkfish larval growth and resistance to salinity stress but not overall survival. Moreover, HUFA and ascorbate supplementation decreased but did not totally eliminate incidence of opercular deformity in milkfish larvae.
    • Book chapter

      The essential nutrients: Lipids and fatty acids 

      OM Millamena - In OM Millamena, RM Coloso & FP Pascual (Eds.), Nutrition in Tropical Aquaculture: Essentials of fish nutrition, feeds, and feeding of tropical aquatic species, 2002 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The objective of this section is to acquaint the reader about common fatty acids, their nomenclature and formulas, and differentiate between saturated and unsaturated fatty acids; to know how environmental factors (temperature, salinity, diet) influence the fatty acid composition of fish; the mechanisms of fatty acid biosynthesis and oxidation, and factors that favor fatty acid biosynthesis and oxidation; the effects of lipid peroxidation and the function of antioxidants; and to understand the importance of fatty acid profiles in fish nutrition, and differences in the essential fatty acid requirements of warmwater and coldwater fishes.
    • Article

      Growth and food consumption of milkfish (Chanos chanos) during dry and wet seasons 

      NS Sumagaysay - International Journal of Tropical Agriculture, 1994 - Serials Publications
      This study was conducted to evaluate the quality of the food consumed by the fish, to estimate the food consumption of the fish in the natural environment during the wet and dry seasons, and to determine the relationship between the growth and food intake. The milkfish fingerlings with the average weights of 4.0 g (wet season) and 9.0 g (dry season) were stocked @ 700 ha-1 in three 1000 sq. m brackishwater ponds. The unfed fish depended on the natural food alone (natural food treatment), while the fed fish were given the supplemental diets containing either 25 per cent protein and 3031 Kcal energy (natural food plus 25% protein diet) or 36 per cent protein and 3344 Kcal energy (natural food plus 36% protein diet). The food consumption increased linearly with the fish growth. Among the environmental factors measured, the salinity varied greatly between the seasons. The caloric and protein intakes for all the fish were higher during the wet season (average salinity, 22 ppt) than during the dry season (average salinity, 36 ppt). Also, the quality of food in terms of the protein and energy levels and the protein energy to total energy ratio was better in the wet than in the dry season. Based on the estimated contribution of the natural food, the rate for the supplemental feeding ranged from 2 to 4 per cent for the body weight during the wet season and from 1 to 2 per cent during the dry season. The feeding during the dry season, however, appeared to have less effect on the growth. It is recommended that the salinity should be maintained below 36 ppt for effective feeding management.
    • Article

      Growth and production of deformed and nondeformed hatchery-bred milkfish (Chanos chanos) in brackishwater ponds 

      NS Sumagaysay, GV Hilomen-Garcia & LMB Garcia - The Israeli Journal of Aquaculture-Bamidgeh, 1999 - Society of Israeli Aquaculture and Marine Biotechnology
      This study evaluated the growth and survival of morphologically deformed and nondeformed hatchery-bred milkfish in brackishwater ponds. It compared the size-frequency distribution of the nondeformed fish with the deformed ones, and determined the effects of different types of deformity on growth. The deformities include the absence of an upper jaw, a folded operculum with gills exposed, a cleft branchiostegal membrane, scoliosis, etc. The results were compared with production of wild stock. Hatchery-bred and wild milkfish fry were grown separately in nursery ponds (500 m2/pond) at 10 individuals/m2. After a month, the juveniles (average weight hatchery-bred 6.0 g; wild 9.5 g) were transferred to seven rearing ponds of 1000 m2 each (stocking density 3000/ha). Three ponds were stocked with selected, nondeformed hatchery-bred fish (unmixed stock), three ponds with a combination of deformed and nondeformed hatchery-bred fish (1:2 ratio; mixed stock), and one pond with wild fish. The final weight, specific growth rate and survival of the nondeformed fish (mixed and unmixed stock) after four months of culture were significantly higher (p<0.05) than those of the deformed fish. Production, however, did not significantly differ between the unmixed nondeformed (433 kg/ha) and the mixed deformed and nondeformed (377 kg/ha) fish. Survival of the deformed stock (56%) was significantly lower (p<0.05) than that of the nondeformed stock (86-88%). Approximately 92% of the deformed stock and 17-20% of the nondeformed were below 150 g. Severe deformities such as the absence of an upper jaw and exposure of all or most of the gills hindered fish growth, while widening of the operculum or branchiostegal membrane, scoliosis, or absence of the anal fin had less effect on growth. To lower the incidence of deformities in grow-out ponds, milkfish fry should be reared to the early juvenile stage in nursery ponds for at least a month. The harsh natural conditions in the nursery ponds (e.g., presence of predators, abrupt changes in salinity, temperature and dissolved oxygen) and stress during transfer to rearing ponds may eliminate most of the weak fish and those with severe deformities.
    • Conference paper

      Growth and survival of Oreochromis niloticus, O. mossambicus and their F1 hybrids at various salinities 

      CT Villegas - In R Hirano & I Hanyu (Eds.), The Second Asian Fisheries Forum: Proceedings of the Second Asian Fisheries Forum, Tokyo, Japan, 17 - 22 April 1989, 1990 - Asian Fisheries Society
      Growth and survival of Oreochromis niloticus, O. mossambicus, and their F1 hybrids were studied at various salinities (0-32 ppt) in net cages inside 12-tonne concrete tanks after acclimation. Growth, measured as weight gain, and survival were assessed after three months of culture. Results showed that although O. niloticus, O. mossambicus, and their F1 hybrids can be acclimated and grown at varying salinities, optimum salinity ranges for good growth varied greatly. The salinity ranges for good growth of O. mossambicus and F1 hybrids were wider than O. niloticus. O. mossambicus had the highest growth rates at 15 and 32 ppt. The optimum salinity range for growth of F1 hybrids was 15-32 ppt, while for O. niloticus it was 0-10 ppt. Salinity up to 20 ppt had no significant effect (P>0.05) on survival of all test strains. However, at 25-32 ppt survival of O. niloticus was significantly lower (P<0.05) than that of O. mossambicus and the F1 hybrids.
    • Article

      Growth of five Asian red tilapia strains in saline environments 

      MRR Romana-Eguia & RV Eguia - Aquaculture, 1999 - Elsevier
      Growth of five Asian red tilapia strains (BFS, NIFI, FAC, PF and HL) were evaluated in brackish and seawater. Eight-week-old juveniles from the five test strains were size-matched with similarly aged Oreochromis mossambicus which served as internal reference. Fish were stocked at a ratio of 15 test:15 reference in 100-l tanks supported by a recirculating system. Commercial feed was given twice daily at 10-20% of the fish biomass. Growth, measured from length and weight increment at 10 weeks, was recorded. Statistical analyses on mean specific growth rates showed significant differences among the strains reared in seawater. The Philippine strain PF grew best in seawater while the Thai strain NIFI performed well in brackishwater. In the Philippines, red tilapias are farmed in intensive freshwater culture systems by few aquaculturists. Results of this study indicate that some Asian strains can be developed for use in more sustainable brackish and seawater culture systems.
    • Article

      Growth response of Nile tilapia fry to salinity stress in the presence of an ‘internal reference’ fish 

      ZU Basiao, RV Eguia & RW Doyle - Aquaculture Research, 2005 - Blackwell Publishing
      Growth of three strains of Oreochromis niloticus L. fry exposed to salinity stress in the presence of an internal reference fish were compared. The Central Luzon State University (CLSU) strain was obtained from the Freshwater Aquaculture Center, CLSU, Philippines. The ISRAEL strain was acquired from the Philippine government's Bureau of Fisheries and Aquatic Resources National Freshwater Fisheries Technology Center (BFAR-NFFTC), Munoz, Nueva Ecija. The National Inland Fisheries Institute (NIFI) strain was obtained from the NIFI, Bangkok, Thailand. Eight to nine full-sib families (replicates) per strain were split into two groups. One group was grown in freshwater for 2 weeks, acclimated to 32 ppt and reared for 2 weeks and finally grown in freshwater for another 2 weeks. Another group was contemporaneously grown in freshwater polyethylene tanks for 6 weeks. Each replicate family included a size-matched internal reference population of red tilapia strain. Two-way analysis of variance (anova) revealed no significant strain differences (P=0.081; r2=0.106). However, analysis of covariance with the internal reference strain used as a covariate showed significant (P=0.049; r2=0.638) strain effects on specific growth (based on standard length measurements). The ISRAEL strain showed consistently better growth rate in both saline and freshwater environments than the NIFI and CLSU strains. We estimated the statistical power of the two-way anova (ϕ=√(k′−1)(factor MS−s2)/(k′s>2); Zar 1984) to be ∼0.30. There was a 70% probability of a Type II error and no true difference in the growth of the three strains was detected. The use of internal reference strain as a covariate improved the r2 from 0.106 to 0.638 and increased the efficiency of the test in detecting a true difference. Other strain comparison studies in our laboratory at the Southeast Asian Fisheries Development Center Aquaculture Department showed that the ISRAEL strain shows better growth than the NIFI and CLSU strains in a crowding stress tolerance experiment, when fed only with rice bran and under restrictive feeding regimes.
    • Article

      Impact of AMPEP on the growth and occurrence of epiphytic Neosiphonia infestation on two varieties of commercially cultivated Kappaphycus alvarezii grown at different depths in the Philippines 

      IAG Borlongan, KR Tibubos, DAT Yunque, AQ Hurtado & AT Critchley - Journal of Applied Phycology, 2011 - Springer
      Two varieties of the carrageenophyte Kappaphycus alvarezii (Tungawan, TUNG; and Giant tambalang, GTAM) from Zamboanga Sibugay, Philippines were used to test the efficacy of Acadian Marine Plant Extract Powder (AMPEP) as source of nutrients for growth, and to determine if applications had any effect on the percent occurrence of an epiphytic infestation of the red alga Neosiphonia sp. at four different depths in the sea. Results showed that the use of AMPEP significantly (P < 0.05) increased the growth rate of both Kappaphycus varieties tested but decreased the percent occurrence of Neosiphonia sp. The percent occurrence of Neosiphonia sp. infection (6–50% at all depths) of both Kappaphycus varieties with AMPEP treatment was significantly lower than the controls (i.e., 10–75% at all depths). Both the growth rate of the cultivated seaweed and the percent occurrence of the epiphytes decreased as the cultivation depth increased. Plants dipped in AMPEP and suspended at the surface had the highest growth rates (i.e., 4.1%, TUNG; 3.1%, GTAM) after 45 days; those without AMPEP dipping had the highest percent occurrence of Neosiphonia infection (viz. 70–75%). The occurrence of Neosiphonia infestation was found to be correlated with changes in irradiance and salinity at the depths observed. The results suggested that both varieties of K. alvarezii used in this study have the fastest growth rate when grown immediately at the water surface. However, in order to minimize damage caused by the occurrence of epiphytic Neosiphonia, K. alvarezii should be grown within a depth range of 50–100 cm. These observations are important for the improved management of Kappaphycus for commercial farming. Furthermore, the use of AMPEP treatments for enhancement of growth and reduction deleterious Neosiphonia sp. infections is encouraging.
    • Article

      Laboratory manipulation of Gracilariopsis bailinae Zhang et Xia (Gracilariales, Rhodophyta) 

      SF Rabanal, R Azanza & A Hurtado-Ponce - Botanica Marina, 1997 - Walter de Gruyter
      Carpospore germination, carposporeling development and tetraspore formation were investigated in Gracilariopsis bailinae Zhang et Xia by manipulating photoperiod, photon flux density, temperature, salinity and nutrients. Laboratory-generated sporelings attained mean growth rate from 4.05 to 10.31% d-1 during the first week of incubation. Duncan s multiple range test (DMRT) showed that growth rates were significantly different (P < 0.05) between the treatment combinations and between weekly intervals. The optimal condition for growth of sporelings, irrespective of culture age, was attained at treatment combinations of 26°C, 11:13 (h. L:D) photoperiod, 100 µEm-2s-1 photon flux density (PFD), 25 µM NH4Cl: 2.5 µM K2HPO4 and 25ppt salinity followed by a treatment combination of 26°C, 11:13 (h. L:D) photoperiod, 100 µEm-2s-1 photon flux density (PFD), 50 µM NH4Cl: 5 µM K2HPO4 and 25 ppt salinity. For the first time in this species, tetraspore formation was induced in the laboratory. The tetrasporophyte produced many tetraspores in almost all branches of the thallus grown at 26°C, 11:13 (h. L:D) photoperiod, 100 µEm-2 s-1, 25 µM NH4Cl: 2.5 µM K2HPO4 and at 30 ppt salinity while those grown at lower light, higher nutrient level and higher salinity had fewer tetraspores. No tetraspores were formed at a higher temperature (30°C), longer photoperiod (13:11 h. L:D), and at 25 ppt salinity and the plants remained vegetative from 4 to 7 months. Logistic regression analysis showed that tetrasporangial induction was significantly affected by nutrients and salinity (P < 0.05).
    • Article

      Lipid and fatty acid composition of milkfish (Chanos chanos Forsskal) grown in freshwater and seawater 

      IG Borlongan & LV Benitez - Aquaculture, 1992 - Elsevier
      The lipid and fatty acid compositions of the various organs of milkfish fed with an invariant diet and reared in seawater (SW) and freshwater (FW) were determined using column chromatography and gas chromatography. Phospholipid content of the gills, kidney, liver, intestines and depot fat was higher in SW than in FW while the organs from fish in FW had higher contents of neutral lipid. Fatty acid patterns of total lipids in the liver, intestines and depot fat of milkfish reared in FW and SW were similar. There were marked differences in fatty acid patterns of gills and kidney. The proportions of saturated to unsaturated fatty acids in gills and kidney were lower in SW than in FW. Likewise, the ratio of n-3 to n-6 fatty acids and total polyunsaturated fatty acids (PUFAs) of gills and kidney were higher in SW than in FW. The fatty acid patterns of the phospholipid fractions showed that SW-reared milkfish have higher total PUFAs, especially of the n-3 fatty acids, than the FW-reared milkfish not only in gills and kidney but in all organs examined. The differences in lipid and fatty acid composition reflect a physiological response to the salinity in which milkfish were reared.
    • Article

      Optimum low salinity to reduce cannibalism and improve survival of the larvae of freshwater African catfish Clarias gariepinus 

      G Kawamura, T Bagarinao, ASK Yong, PW Sao, LS Lim & S Senoo - Fisheries Science, 2017 - Springer Verlag
      The freshwater African catfish Clarias gariepinus is carnivorous and cannibalistic even during the larval and juvenile stages and this behavior causes economic losses in aquaculture. This study examined for the first time the effect of salinity on cannibalism, survival, and growth of African catfish larvae in the hatchery. Larvae (4 days old, median 7.8 mm TL, 2.8 mg BW) of the African catfish were reared for 21 days at nominal salinity 0, 1, 2, 3, 4, 5, 6, and 7 ppt. After 21 days, they grew to 10–39 mm (median 22 mm) and 10–490 mg (median 90 mg), with no significant difference by salinity treatments. Survival ratios were similarly low (24–31%) at 0, 1, 3, and 7 ppt and significantly higher (49–55%) at 2, 4, 5, and 6 ppt. Cannibalism was significantly lower, 15–30% at 4–6 ppt, than the 40–50% at 0–3 and 7 ppt. Size variation was lower at 4–6 ppt and higher at 0–3 and 7 ppt. We recommend hatchery rearing of African catfish at the optimum low salinity of 4–6 ppt rather than in full fresh water at least up to 21 days. This rearing method fosters larval welfare and improves hatchery production.