Now showing items 1-19 of 19

    • 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

      Assimilation of aquatic macrophytes in Penaeus monodon. 

      MR Catacutan - Journal of Aquaculture in the Tropics, 1993 - Taylor & Francis
      The macrophytes Najas graminea and Ruppia maritima are common aquatic plants found in brackishwater ponds in the Philippines. The assimilation efficiencies of these plants by male and female Penaeus monodon (30-40 g wet wt.) were determined using the ash-free method of Conover (1966). Ruppia maritima was assimilated significantly better (70-76%) than N. graminea (40-47%). The assimilation efficiency values were significantly higher in the female shrimp for both plants.
    • 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

      Effects of salinity, aeration and light intensity on oil globule absorption, feeding incidence, growth and survival of early-stage grouper Epinephelus coioides larvae 

      JD Toledo, NB Caberoy, GF Quinitio, CH Choresca & H Nakagawa - Fisheries Science, 2002 - Springer Verlag
      A series of experiments were conducted to examine the effects of salinity, aeration and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage Epinephelus coioides larvae. Newly hatched larvae were transferred to 40-L aquaria at a density of 1500 individuals/aquarium. Larvae were exposed to different levels of aeration (0 mL/min per L, 0.62 mL/min per L, 1.25 mL/min per L, 2.50 mL/min per L, or 3.75 mL/min per L); salinity (8 ppt, 16 ppt, 24 ppt, 32 ppt, or 40 ppt); and light intensity (0 lx, 120 lx, 230 lx, 500 lx, or 700 lx) for 4–6 days. Twenty larvae were sampled daily at 11:00 hours to measure for total length (TL), oil globule volume, and feeding incidence. Survival rates were determined by counting the total number of larvae remaining in each aquarium at the end of the experiment. Significantly higher survival rates (P < 0.05) were observed at aeration levels of 0.62 mL/min per L and 1.25 mL/min per L, at salinity levels of 16 ppt and 24 ppt, and at light intensities of 500 lx and 700 lx. The influence of aeration level, salinity and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage grouper larvae are discussed.
    • Book chapter

      Evaluation of fertilizer use and milkfish yields in Palawan 

      EB Dumada-ug & R Sevilleja - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      Milkfish yields in Palawan in 1993–94 were low, only 595 kg/ha-yr on average and ranged 100–700 kg/ha-yr in 35 of 50 farms surveyed. Only seven farms had yields between 1,000 and 1,800 kg/ha-yr. Yields were higher in deeper ponds, and shallowness of ponds was a major constraint to high yields. Farm -gate prices of milkfish ranged from P25 to P55 and averaged P42. The prices of milkfish were on average 43x greater than the price of organic fertilizers (chicken manure) and 6x more than the price of inorganic fertilizers. The income from milkfish made up 10-95% and averaged 53% of the total income of the farmers. One crop cycle a year was the practice in 28 of the 50 farms; 20 farms had two crops, and two farms went for 3–4 crops a year. A crop cycle was 3–4 months long in 14 farms, 5–6 months in 29 farms, and 7–9 months in 7 farms. Crop cycles started with draining and drying the ponds and applying fertilizers to grow natural food. Most of the farms were supplied by tidal water and water exchange in the ponds was done every spring tide in 33 farms. The other farms changed water once a month, once or twice in a crop cycle, or once a year. Application rates of organic fertilizers were mostly less than 1 ton/ha-yr and averaged 515 kg/hayr, but three farms used as much as 1,250 kg/ha-yr, and one farm used 3,000 kg/ha-yr. Half as much inorganic fertilizers were used; the average for the 50 farms was only 211 kg/ha-yr, but one farm used as much as 1,350 kg/ha-yr. The fertilizers encouraged natural food to grow in the ponds. Two of the farms grew mostly plankton, 15 grew the benthic mat lablab, and 33 grew the green filamentous algae lumut. None of the farms used commercial feeds. Stocking rates varied widely among the farms, ranged from 1,000 to 60,000 fry or fingerlings per hectare per year and averaged 8,000/ ha-yr. Two-thirds of the farms stocked less than 7,000/ha-yr, but eight farms stocked fry or fingerlings at much higher rates of 13,000–60,000/ ha-yr. An input use variation model showed that milkfish yield was a function of the ratios of prices of milkfish to prices of organic and inorganic fertilizers; pond water depth and salinity; milkfish income as percent of total income; family size; membership in aquaculture association; and contacts with government‘s extension services and information dissemination system. The surveyed farms ranged from 3 to 40 years old, with 92% under 20 years; they had been in operation 1–23 years, 76% of them for less than eight years. Of the 50 farms in the survey, only nine were private (titled) lands, 34 were covered by fishpond lease agreements (FLA issued by the Bureau of Fisheries and Aquatic Resources), and the others had only survey documents or no papers at all. Farm sizes ranged 0.8–50 ha (average 12.5 ha), and 52% of them were smaller than 6 ha. The private farms were small, only 1–7 ha except one that was 25 ha. The FLA farms were much larger, and 23 of them were 5–50 ha. Large parts of the large farms were not operational, and 90% of the farms used effective areas of less than 7 ha. The low lease fees for FLAs evidently did not encourage farm development to increase yields. The farms had mostly shallow ponds 25–100 cm deep (average 68 cm).
    • 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.
    • Influence of salinity on survival and molting in early stages of three species of Scylla crabs 

      FD Parado-Estepa & ET Quinitio - The Israeli Journal of Aquaculture-Bamidgeh, 2011 - Society of Israeli Aquaculture and Marine Biotechnology (SIAMB)
      Early instars of three mud crab Scylla species were reared in different salinities and survival and growth were compared. Scylla olivacea were reared in salinities of 12, 16, 20, 24, and 32 g/l (control). Scylla serrata and S. tranquebarica were reared in salinities of 8, 16, 20, 24, and 32 g/l (control) After 75 days, survival of S. olivacea and S. serrata was not affected by salinity but survival in S. tranquebarica was significantly higher in 8-20 g/l than in 24 and 32 g/l. The molt interval was shorter in S. olivacea, and more animals attained the fifth molt, than in the other species. The molt interval was shorter in 12-20 g/l than in 24 and 32 g/l for S. olivacea, did not vary among test salinities for S. serrata, and was shortest in 20 and 24 g/l in S. tranquebarica where fewer animals attained a fourth molt in 32 g/l than in 8-20 g/l. The molt increment was influenced by salinity only in S. olivacea. At the end of the test, all three species exhibited lower internal carapace width and mean body weights in 32 g/l. Among the three species, S. serrata was most versatile in tolerating a wide range of salinities during nursery culture.
    • 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.
    • Book chapter

      Parameters in site selection and monitoring 

      SMS Santander - In Training Handbook on Rural Aquaculture, 2009 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Before starting an aquaculture venture, it is necessary to first select an appropriate project site. Doing this ensures that money invested in the project is not later wasted because the site does not meet the requirements of the culture organism. It also makes sure that the environment is not compromised and will be able to sustain the aquaculture activities.

      Two major parameters are considered during site selection. These are the 1) physico-chemical; and 2) environmental parameters. Physico-chemical parameters affect the health of the culture organisms while the environmental parameters will give insights on the sustainability of the aquaculture venture. However, the task does not end with site selection. Monitoring of the aquatic environments is also essential to note any changes in the environment that may affect the aquaculture project and the environment itself.
    • Article

      Population dynamics of the calanoid copepod, Acartia tsuensis in a brackish-water pond in the Philippines 

      MSN Golez, A Ohno, JD Toledo, Y Tanaka & T Ishimaru - Fisheries Science, 2002 - The Japanese Society of Fisheries Science
      The occurrence pattern and population dynamics of Acartia tsuensis were investigated in a brackish-water pond in Panay Island in central Philippines by implementing both bi-monthly and daily sampling schemes. A. tsuensis occurred in the pond during the dry season (November-April) when the salinity of the water is in the range of 14 ~ 40 ppt but was completely absent at lower salinities. An almost constant rate of development from the nauplius 2 through to copepodite 5 stages of A. tsuensis was observed both in the pond and in the laboratory. The generation time ranged from 5.9~11.3 days. Fecundity had a positive linear corelation with chlorophyll a. Salinity and chlorophyll a affect the stage duration, mortality, and fecundity of A. tsuensis in the pond.
    • Conference paper

      Preliminary notes on the salinity preference of milkfish, Chanos chanos, fry 

      JV Juario & WE Vanstone - In Proceedings of the International Milkfish Workshop Conference, May 19-22, 1976, Tigbauan, Iloilo, Philippines, 1976 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Vertical salinity gradient columns were used to investigate the salinity preference of milkfish fry. Newly captured fry showed a preference for 32‰ salinity. Fry which had been in captivity for one to five days, at 12 or 22‰ salinity, had no salinity preference between waters of 12, 22 or 32‰ salinity.
    • Article

      Salinity tolerance of larvae of the mangrove red snapper (Lutjanus argentimaculatus) during ontogeny 

      CB Estudillo, MN Duray, ET Marasigan & AC Emata - Aquaculture, 2000 - Elsevier
      Salinity tolerance and the effects of salinity on growth, condition factor and chloride cell (CC) densities were evaluated for Lutjanus argentimaculatus larvae during ontogeny. Tolerance of L. argentimaculatus larvae to abrupt changes of salinity from 32 ppt varied with age. Periods to 50% mortality (LT50) were significantly (P<0.05) longer for 0-day-old larvae than for 7-, 14- and 21-day-old larvae. Tolerance of abrupt salinity change increased remarkably, starting on day 28. Although abrupt transfer to test salinities caused substantial mortalities, L. argentimaculatus larvae, regardless of age (0-, 7-, 14-day-old), showed significantly longer LT50 when abruptly transferred to 8 and 16 ppt than for transfers to 24 and 40 ppt (P<0.05). Growth of L. argentimaculatus larvae at 16, 24, 32 (control) and 40 ppt was not significantly different either at the end of the first rearing phase (days 0–21) or second phase of rearing (days 22–50). Survival was significantly lowest at 40 ppt (4.3%) at the end of first phase of rearing (P<0.05). There were no significant differences in survival rates at the end of the second phase of rearing; however, the condition factor (K) of larvae reared at lower salinities was significantly higher than that of fish at 40 ppt (P<0.05). Gill epithelia of 42- and 50-day-old larvae showed increasing density of CC with increasing salinity.
    • Article

      Studies on the causative organism of Sarotherodon niloticus (Linnaeus) fry mortalities - 2. Identification and characterization of the physiological properties of Pseudomonas fluorescens 

      RC Duremdez & GD Lio-Po - Fish Pathology, 1985 - Japanese Society of Fish Pathology
      Identification and examination of the physiological characteristics of Pseudomonas sp. isolated from fry of Sarotherodon niloticus (L.) was conducted. Based on morphological and biochemical tests, the bacterium was identified to be a strain closest to Pseudomonas fluorescens. In vitro physiological growth patterns at varying temperatures, NaCl concentrations, and pH were observed for a maximum of eleven days incubation while growth of the test bacterium into various water media were observed for a maximum of 148 days. Bacterial growth occurred between 10° to 41°C with optimum growth at 25° to 30°C. The bacterium tolerated NaCl concentrations of 0 to 50 ppt. Optimum growth, however, was obtained from 0 to 15 ppt. It was found that growth was possible only at pH 5.0 to 9.7. Optimum growth occurred at pH ranging from 5.7 to 8.4. Inoculation of the test bacterium into different freshwater media obtained from various sources resulted in growth and rapid multiplication. Viability was maintained throughout the 148 day incubation period. Growth in the brackishwater medium was observed only until 50 days. No growth was observed in the seawater medium.
    • Article

      Survival and settlement rates of Haliotis asinina larvae at different salinity levels 

      JRH Maquirang, RD Caturao, JH Maquirang & FL Pedroso - IAMURE International Journal of Ecology and Conservation, 2013 - IAMURE Multidisciplinary Research
      The study was conducted to determine the optimum salinity levels (24 ppt, 28 ppt, 32 ppt, 36 ppt and 40 ppt) for the survival and settlement rates of H. asinina in a complete randomized design with three replicates each. The experimental animals were reared in 15 glass aquaria for the first run and in plexiglass for the second run. Feeding of Navicula spp. was done once a day. Temperature and dissolved oxygen were monitored throughout the experiment. Data were analyzed using One-Way ANOVA to determine significant difference among treatments at 0.05 level of significance using Social Package for Social Science. Result of the first run showed that 32 ppt had the highest mean survival (1.50%) and mean settlement rate (1.84%). Similar result was also observed in 32 ppt with highest mean survival (9.72%) and mean settlement rate (16.42%). Significant difference existed among treatments during the second run of the experiment. Results showed that 28 ppt and 32 ppt were the optimum salinity levels for survival and settlement rate of H. asinina. Further study should be conducted to determine the tolerance and settlement rates of H. asinina larvae to lower salinities until it reaches juvenile stage with first respiratory pore appearing.
    • Article

      Survival of Penaeus monodon postlarvae and juveniles at different salinity and temperature levels. 

      FD Parado-Estepa - The Israeli Journal of Aquaculture-Bamidgeh, 1998 - Society of Israeli Aquaculture and Marine Biotechnology
      Penaeus monodon postlarvae (PL1, PL5, PL10, and PL15) and juveniles (0.2 and 2 g mean weights) were acclimated gradually within 6 h to test temperatures of 22°, 28°, and 33°C. After 24 h, the postlarvae were abruptly transferred to salinity levels of 8, 16, 24, 32, 40, or 50 ppt, and juveniles to 0, 4, 8, 16, 20, 24, 28, 32, 40, 50, or 60 ppt. All test animals were previously reared in 32 ppt sea water at a temperature of 27-29°C. Survival rates were compared after four days for PL1, PL5, and PL 10, and 10 days for PL 15. Tests for juveniles lasted seven days. Length and total (TPI) or mean (MSI) population stage indices were compared for postlarvae.

      Survival rates of postlarvae and juveniles were generally lower at 33°C. Length and MSI of postlarvae were higher at 33°C than at 22°C. TPI at PL10 and PL15 were not significantly affected by salinity. Optimal salinity ranges for postlarvae and juveniles were identified based on the different parameters measured.
    • Technical Report

      Weather observation at Tigbauan, Iloilo, Philippines from 1977 to 1980 

      H Motoh, N Solis, E Caligdong, M Gelangre & F Boblo - 1981 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Series: Technical report / SEAFDEC Aquaculture Department; no. 8
      The observations include: (1) air and sea water temperatures; (2) cloud cover; (3) rainfall; (4) wind direction and speed; (5) salinity; (6) sea wave condition.
    • Book chapter

      Yield and agar quality of three red seaweed Gracilaria species grown in tanks at three salinities 

      MSR Ferrer & AN Marasigan - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      Gracilaria changii, G. firma and G. tenuistipitata were collected from the eastern coast of Sorsogon in southeastern Philippines and grown in concrete tanks at the SEAFDEC Aquaculture Department in Iloilo in May-June and in September-October 1994 at a stocking density of 1 kg/m2 and at three salinities (15, 25, and 35 ppt). In the first run, the highest specific growth rates per day were 2.5% at 25 ppt for G. changii, 3.6% at 35 ppt for G. firma, and 3.2% at 15 ppt for G. tenuistipitata. In the second run, the highest daily growth rates were 1.4% for G. changii, 1.2% for G. firma, and 3.3% for G. tenuistipitata, all at 15 ppt. Nutrient and light limitation in the second run led to lower and even negative growth rates. Gracilaria changii and G. firma were euryhaline but grew best at 25–35 ppt; G.tenuistipitata was not euryhaline and grew best at 15 ppt. The highest growth rates in tanks were at salinities close to those in the natural habitat: G. changii at 25 ppt, G. firma at 35 ppt, and G. tenuistipitata at 15 ppt. The estimated potential production (dry weight kg/m2-yr) in tanks was 1.65 kg G. changii at 25 ppt, 2.49 kg G. firma at 35 ppt, and 2.35 kg G. tenuistipitata at 15 ppt.

      Agar yields from three Gracilaria species varied from 5% to 23%, on average lowest in G. tenuistipitatata, and were generally higher at 25 ppt and 35 ppt than at 15 ppt. Agar gel strengths were also strongly affected by salinity and were highest at 35 ppt. Gracilaria tenuistipitata had very high gel strength (average 782 g/cm2 but as high as 1,082 g/cm2 comparable to agarose), well above the specified 750 g/cm2 for the international market. Gracilaria changii and G. firma had average gel strengths of 516 and 558 g/cm2, well within the range (400–600 g/cm2) for commercial agar used in the food industry. The sulfate contents were lower at 15 ppt and were even 0% in several instances, especially in G. tenuistipitata. The gelling temperature of 32°C and melting temperature of 97.3°C qualifies G. tenuistipitata for the international market. Gracilaria changii and G. firma had melting temperatures of 93–95°C but gelling temperatures of just 29°C. Farming techniques for these seaweeds should be developed to produce enough raw material for profitable commercial processing.