Now showing items 199-218 of 1064

    • Article | Short report

      Early appearance of the retinal tapetum, cones, and rods in the larvae of the African catfish Clarias gariepinus 

      G Kawamura, T Bagarinao, J Justin & CY Chen - Ichthyological Research, 2016 - Springer Verlag
      In the retina of the African catfish Clarias gariepinus, the pigment epithelium and the tapetum were formed in newly hatched larvae, the cones developed within 2 days, and the rods within 3 days after hatching. The retinal tapetum shone under surface light under a light microscope; the shine was located in the apical projections of the pigment epithelial cells. Early appearance of the retinal elements enables African catfish larvae to see and feed well even in dim light.
    • Article

      Early development of Crassostrea iredalei (Faustino, 1932) (Bivalvia: Ostreidae), with notes on the structure of the larval hinge 

      LMM Ver - Veliger, 1986 - California Malacozoological Society, Inc.
      Larvae of the oyster Crassostrea iredalei were reared in the laboratory from eggs through settlement. The oysters were induced to spawn by increasing the temperature by 5-10°C and sometimes by adding stripped oyster sperm to the spawning dishes. Eggs avareaged 48 µm in diameter.

      The straight-hinge veligers appeared 22 to 26 h after fertilization. The larval shell length increased from 64 to 84 µm in the straight-hinge stage, from 85 to 275 µm in the umbo stage, and from 210 to 275 µm in the pediveliger stage. Eye-spotted pediveligers were observed mostly at lengths greater than 225 µm. The hinge line did not increase much with larval growth. Although length was initially greater than height, the increase in height was much faster due to the development of the umbo. Height was greater than length in more advanced larvae. Valve growth was asymmetrical and unequal, with the left valve generally larger. Settlement and metamorphosis occurred 20 days from fertilization at lengths of 270 µm and greater, when the oyster larvae were reared at 26.5 to 30°C and salinities of 30 to 32 ppt.

      The larval hinge structure consisted of minute dentition on the central portion of the provinculum and large rectangular teeth on both ends. These teeth became obscured in advanced larvae due to the skewed development of the umbo.

      Data derived from the laboratory culture of larvae of Crassostrea iredalei may be used in spatfall forecasts for the collection of larvae from the wild and as baseline information for the hatchery culture of oyster larvae.
    • Article

      Early development of fin-supports and fin-rays in the milkfish Chanos chanos 

      Y Taki, H Kohno & S Hara - Japanese Journal of Ichthyology, 1986 - The Ichthyological Society of Japan
      Development of fin-supports and fin-rays was observed in larval and juvenileChanos chanos, Chondrification of the caudal complex started at 4.70 mm SL. Ossification of the caudal elements started at 7.80 mm SL and was nearly completed at about 30 mm SL. Cartilaginous fusion of caudal elements, which occurs in hypurals of higher teleostean fishes but is not seen in lower teleosts, was observed between the neural arch of the preural centrum 1 and that of the ural centrum 1 via a small cartilage bridging the distal tips of the two arches. Caudal finrays began to develop at 6.60 mm SL, and an adult complement of principal rays was attained at 7.35 mm SL. Dorsal and anal pterygiophore elements were first evident at 6.70 mm and 6.65 mm SL, respectively. All proximal radiais were formed at 8.15 mm SL in both fins. Formation of dorsal and anal fin-rays started simultaneously at 8.60 mm SL, and adult fin-ray complements were attained at 10,00 mm and 10.70 mm SL, respectively. In the pectoral fin, the cleithrum, coraco-scapular cartilage and blade-like cartilage (fin plate) had already been formed at 4.65 mm SL. The mesocoracoid was observed to originate from the coraco-scapular cartilage and become detached from it in the course of ossification. Pectoral fin-ray formation started at 13.80 mm SL and was completed in number of rays at 20.00 mm SL. In the pelvic fin, the basipterygium was first evident at 13.00 mm SL. Pelvic fin-rays appeared at 13.80 mm SL and attained their adult count at 17.15 mm SL.
    • Article

      Early effects of nutritional stress on the liver of milkfish, Chanos chanos (Forsskal), and on the hepatopancreas of the tiger prawn, Penaeus monodon (Fabricius) 

      V Storch, JV Juario & FP Pascual - Aquaculture, 1984 - Elsevier
      After periods of food deprivation and subsequent feeding, hepatocytes of Chanos chanos fry and R-cells of Penaeus monodon juveniles were investigated by means of transmission electron microscope. They clearly reflect the quality of different diets and thus can be used as monitor cells. For purposes of comparison, the same diets were offered to land-dwelling isopods which are known to accept a variety of different diets. Thus, this technique could also be used as a method of determining the effectiveness of binders in artificial diets.
    • Article

      Early larval development of the seabass Lates calcarifer with emphasis on the transition of energy sources 

      H Kohno, S Hara & Y Taki - Nippon Suisan Gakkaishi, 1986 - Japanese Society of Fisheries Science
      The early growth, yolk and oil globule resorption, early morphological and behavioral de-velopment, and initial feeding of hatchery-raised Lates calcarifer were studied. Based on the developmental events and the energy the reby utilized, the early life history of this species can be broken down into the following five phases: 1) rapid early growth due to rapid yolk resorption (from hatching to about 15 hr after hatching (TAH); 2) morphological differentiation and slowgrowth based on energy from yolk (to about 50 h TAH when the yolk is exhausted); 3) slow growth with initiation of feeding and swimming activities, based on energy from oil globule and from exogenous food (to about 110 h TAH); 4) accelerated growth and effective feeding and swimming based on the same two sources of energy as in the preceding stage (up to about 120-140 h TAH when the oil globule is exhausted); and 5) accelerated growth, effective feeding and swimming and further development based solely on exogenous energy (beyond 140 h TAIT).
    • Article

      Early postmysis stages of the giant tiger prawn, Penaeus monodon Fabricius 

      H Motoh & P Buri - Researches on Crustacea, 1980 - Carcinological Society of Japan
      The morphological development of the early postmysis stages of the giant tiger prawn, Penaeus monodon are described and illustrated using laboratory-reared specimens and wild ones.

      The first 3 or 4 substages are termed "megalopa" owing to the incomplete branchial formula of the mouth parts, their pelagic or planktonic behavior and their somewhat narrower body. At the 4th or 5th substage, the branchial formula is completed, their behavior is more or less epibenthic, the chromatophores are densely distributed from the tip of the antennular flagella through the ventral side of the abdomen to the tip of the telson. At the beginning of the 7th substage, the chromatophores are distributed over almost the whole body. Thus from the 4th or 5th substage onwards they may be termed juveniles.

      The main characteristics development are as follows : 1) The cempletion of the rostral spine formula appears in the 7th or 8th substage showing 7 dorsal and 3 ventral spines. 2) The endopod of the 1st maxilliped develops again at the 7th substage, although it degenerates with every molt prior to the 7th. 3) From the 1st substage, the distal 3 segments of the endopod of the 2nd maxilliped are bent sharply inwards.
    • Article

      Ecological considerations in milkfish farming in marine pens and cages in the Philippines 

      T Bagarinao - UPV Journal of Natural Sciences, 1998 - University of the Philippines in the Visayas
      Milkfish farming in the Philippines has a long history and great importance, being widely regarded as the way to domestic food security. But the industry has faced new challenges in the past decade, with the advent of many other farmed aquatic species, mostly cash crops and "export winners," and with the increased pressure to intensify production in brackishwater ponds and in marine pens and cages. There are no up-to-date government statistics on the area and production of marine pens and cages, but industry insiders estimate a yearly production of about 25,000 mt of sea-grown milkfish in 1996 - 1998, mostly from Pangasinan, but also from Quezon, Davao, Cebu, Bohol, Panay, Samar, and Negros. High yields (2 -38 kg/m3) were made possible by very high stocking rates (3 -75 fingerlings/m3) and feeding rates (2-4 kg feed per kg of fish). The high production costs and the pollution from feed wastes and fish metabolites have stopped most operations within 1 - 2 years. This paper examines the trends and problems in milkfish farming in marine pens and cages, and discusses the ecological limits and the projected ecological footprint of this farming system. Milkfish farming in marine pens and cages, as presently practised, is not the magic solution to the fish deficit in the Philippines and is not an appropriate technology to promote on a wide scale. The required investment is enormous. Properly made pens and cages set up in suitable clean-water locations cost much. The ability of milkfish to ensure domestic food security is negated by the use of fishmeal-based feeds. Fish feeds use up fish meal and other fisheries and agriculture products used by people and other sectors. If marine pens and cages must be promoted, integrated coastal area management, an informed precautionary approach, better infrastructure, and improved feeding management are important to ensure sustainability.
    • Article

      Ecological role and services of tropical mangrove ecosystems: a reassessment 

      Aim

      To reassess the capacity of mangroves for ecosystem services in the light of recent data.

      Location

      Global mangrove ecosystems.

      Methods

      We review four long-standing roles of mangroves: (1) carbon dynamics – export or sink; (2) nursery role; (3) shoreline protection; (4) land-building capacity. The origins of pertinent hypotheses, current understanding and gaps in our knowledge are highlighted with reference to biogeographic, geographic and socio-economic influences.

      Results

      The role of mangroves as C sinks needs to be evaluated for a wide range of biogeographic regions and forest conditions. Mangrove C assimilation may be under-estimated because of flawed methodology and scanty data on key components of C dynamics. Peri-urban mangroves may be manipulated to provide local offsets for C emission. The nursery function of mangroves is not ubiquitous but varies with spatio-temporal accessibility. Connectivity and complementarity of mangroves and adjacent habitats enhance their nursery function through trophic relay and ontogenetic migrations. The effectiveness of mangroves for coastal protection depends on factors at landscape/geomorphic to community scales and local/species scales. Shifts in species due to climate change, forest degradation and loss of habitat connectivity may reduce the protective capacity of mangroves. Early views of mangroves as land builders (especially lateral expansion) were questionable. Evidence now indicates that mangroves, once established, directly influence vertical land development by enhancing sedimentation and/or by direct organic contributions to soil volume (peat formation) in some settings.

      Main conclusions

      Knowledge of thresholds, spatio-temporal scaling and variability due to geographic, biogeographic and socio-economic settings will improve the management of mangrove ecosystem services. Many drivers respond to global trends in climate change and local changes such as urbanization. While mangroves have traditionally been managed for subsistence, future governance models must involve partnerships between local custodians of mangroves and offsite beneficiaries of the services.
    • Article

      Ecology on the feeding of milkfish fry and juveniles, Chanos chanos (Forsskal) in the Philippines 

      P Buri - Memoirs of the Kagoshima University Research Center for the South Pacific, 1980 - Kagoshima University Research Center for the South Pacific
      An extensive ecological survey was conducted in the Philippines to study the feeding of milkfish, Chanos chanos Forsskal. Types of environments examined included coral reefs, lagoons, mangrove and nipa swamps as well as estuarine systems. It was concluded that organic detritus was the basic nutrient for juvenile milkfish and that depositional environments constitute important nursery and feeding grounds for this spcies. The main pathway of energy flow in these coastal ecosystems through the detritus rather than the grazing pathway. The feeding of milkfish was described in terms of habitat structures, stomach content, feeding chronology and feeding behaviour. The result suggests that a better understanding of the function of the ecosystem will help to improve present aquaculture practices as well as guidelines for resource management.
    • Article

      Economic analysis of an integrated milkfish broodstock and hatchery operation as a public enterprise 

      RF Agbayani, NA Lopez, RE Tumaliuan & GD Berjamin - Aquaculture, 1991 - Elsevier
      The National Bangus (Milkfish) Breeding Program of the Philippines, which was launched by the Philippine government in 1981, had succeeded in spawning milkfish in captivity and in rearing the eggs to fry that were stockable in ponds. The physical productivity and economic viability of an integrated milkfish broodstock and hatchery as a public enterprise is analyzed, using SEAFDEC research findings as bases for analysis.

      Discounted cash flow computations show the repayment schedule for investments in structures and equipment, and operations and maintenance expenses for both broodstock and hatchery operations covering a period of 15 years. Revenues came from the sales of fry. The analysis was based on an annual stocking of 100 milkfish (200–250 g/piece) per cage with a diameter of 10 m. Egg production started during the fifth year. Investment in the hatchery facilities started during the fourth year and expansion occurred in the subsequent years to accommodate the eggs produced for rearing to the fry stage.

      Economic indicators, net present value (NPV) and internal rate of return (IRR), showed negative figures. The trend, however, was upward, starting during the sixth year of operation. Sensitivity analysis was done to determine the effects of changes in operational efficiencies, such as survival rates and stocking densities to the return on investment (ROI) in private hatcheries.
    • Article

      Economic analysis of bottom line and raft monoline culture of Kappaphycus alvarezii var. tambalang in Western Visayas, Philippines 

      GPB Samonte, AQ Hurtado-Ponce & RD Caturao - Aquaculture, 1993 - Elsevier
      A survey was conducted among 72 seaweed (Kappaphycus sp.) farmers in the Western Visayas region, Philippines, from March to July 1990 to assess their culture practices in terms of production and economic efficiency. Yields of 5.8 tons/ha per crop (dry weight) and 7.6 tons/ha per crop (dry weight) were obtained from bottom line and raft monoline methods, respectively. Investment requirement was P27361/ha for bottom line culture, and P56757/ha for raft monoline culture (P25=US$1). The bottom line method was more profitable with net farm income of P33286/ha per crop compared with P26365/ha per crop for the raft monoline method. The bottom line method of culturing seaweed is more cost-efficient compared with the raft monoline method. Production cost averaged P3.32/kg for the former method, and P5.55/kg for the latter method. Return on investment was also higher at 243% for the bottom line method and 93% for raft monoline.
    • Article

      Economic analysis of prawn (Penaeus monodon) culture in the Philippines, I. Hatchery operations 

      R Agbayani, U Hatch & E Belleza - Asian Fisheries Science, 1995 - Asian Fisheries Society
      High prices of prawn (Penaeus monodon) fry, profitability of hatchery operations, and a low cost hatchery design introduced by the Southeast Asian Fisheries Development Center attracted millions of dollars of investments in the mid-1980s. When export prices for prawn fell dramatically in 1989, demand for fry dropped as most prawn growers stopped operations or reduced stocking densities. Natural calamities – typhoons, earthquakes and volcanic eruptions – further depressed conditions in the hatchery sector.

      This paper presents an economic analysis of hatchery operations in the Philippines using data gathered through interviews and structured questionnaires in 1992. Economic indicators estimated include: investment requirements, unit cost, benefit over cost ratios, and internal rates of return. Breakeven and sensitivity analyses of operating hatcheries were employed to determine the degree of risk and changes in profitability levels associated with different scales of operation given changes in output price, input price and production level.

      Results indicate that net income per production run was positive for all scales of hatchery operation in spite of the current adverse market conditions. New hatchery investments, however, should be made in medium- and small-scale facilities because these have a better chance to survive worsening market conditions and periodic spawner shortages. Medium-size operations provide the best returns, and large-scale operations showed negative returns. Large-scale hatcheries are operating below capacity due to scarcity of spawners and low market demand.
    • Article

      Economic analysis of prawn (Penaeus monodon) culture in the Philippines, II: Grow-out operations 

      U Hatch, R Agbayani & E Belleza - Asian Fisheries Science, 1996 - Asian Fisheries Society
      The dramatic fall in prawn (Penaeus monodon) prices coupled with environmental concerns has resulted in a relative stagnation of prawn grow-out operations in the Philippines. Leaders of the Philippine aquaculture sector are concerned that their cost of production is higher than that of their close competitors in Indonesia and Thailand. Also, the environmental and production crash experienced in Taiwan has led to a general perception that intensive culture cannot be sustained. The sector recently experienced a lack of direction and growth, combined with crowded water sheds, excessive use of water bodies, overuse of groundwater and continued destruction of mangrove.

      A field survey of prawn growers was conducted in August-October 1992 using a standardized economic questionnaire that included costs, returns and growers perceptions of constraints. Economic estimates were developed for representative production systems; intensive, semi-intensive, extensive and prawn-milkfish rotation.

      The incentive to expand the prawn pond area is not strong. Existing intensive facilities can be operated efficiently and profitably, but new intensive operations will most likely need to include water treatment capabilities for water entering and exiting grow-out ponds. Canals, reservoirs or ponds used for water quality improvement may be able to concurrently produce a profitable crop, such as milkfish-prawn rotation. Internal rate of return for semi-intensive ponds using earthen ponds was higher than for other culture systems. If, over time, water quality and conservation constraints are sufficiently addressed, stocking densities might be increased. Research and extension programs targeting equity should focus on integrated systems.
    • Article

      An economic analysis of the modular pond system of milkfish production in the Philippines 

      RF Agbayani, DD Baliao, NM Franco, RB Ticar & NG Guanzon Jr. - Aquaculture, 1989 - Elsevier
      In 1980, the annual yield of milkfish ponds in the Philippines was 800 kg/ha while the potential yield is estimated to be 2000 kg/ha. The modular pond system analyzed in this study can largely close the gap between actual and potential yield through more efficient use of pond capacity to increase the number of croppings up to 7 times in 1 year. Pilot-scale production using the modular pond system was done at the Leganes Research Station (LRS) SEAFDEC, Iloilo, and at three cooperating commercial farms. Scale of operation ranged from 2.7 ha to 7.9 ha. From 2 to 7 production runs were recorded with per hectare outputs ranging from 278 kg to 341 kg per run. Input costs were based on actual figures and the ex-farm milkfish price as P21.00 (4 to 6 fish/kg). The average return on investment and payback period for all sites was 68.81% and 1.25 years, respectively.
    • Article

      Economic assessment of commercial hatchery production of milkfish (Chanos chanos Forsskal) fry 

      LMB Garcia, RF Agbayani, MN Duray, GV Hilomen-Garcia, AC Emata & CL Marte - Journal of Applied Ichthyology, 1999 - John Wiley and Sons
      The economic viabilities of two types of commercial hatchery milkfish (Chanos chanos) fry operations were assessed and compared. Based on the actual cost of input, the physical facilities, and the potential production yields, four commercial hatcheries previously used for shrimp (Penaeus monodon fry production were classified as either largeor smallscale operations. Cost-return analysis revealed high profits for both types of operation. The return on investment (54-61 %) and the payback period ( approximately 1.5 years) were comparable between the two types, although a large-scale operation (476 %) had double the working capital return of a small-scale hatchery (221 %). Benefit-cost analysis over a 5-year period also revealed positive and above-baseline discounted economic indicators [net current value = 0.2-2.2 million Philippine Pesos (1 US Dollar = 25 Philippine Pesos); internal rate of return = 88-107 %]. The net benefit-cost ratio of a large-scale operation (2.0) was higher than that of a small-scale hatchery (1.4), suggesting a slight edge in the investment viability of a large-scale hatchery. Compared with a large-scale operation, a small-scale hatchery was more sensitive to changes in the acquisition price of eggs or newly-hatched larvae and in the price of selling hatchery fry. Both types of operation are viable nonetheless when the acquisition cost is P6000 per million eggs or larvae and hatchery fry are sold at P0.50 each. Together, profit and investment in milkfish hatchery fry production appear viable, making milkfish an alternative commodity for production in many abandoned shrimp hatcheries. The limited availability of spawned eggs and larvae for rearing and the quality of hatchery fry are issues requiring urgent attention.
    • Article

      Economic evaluation of grow-out diets for Asian catfish Clarias macrocephalus (Gunther) production 

      EB Coniza, JD Tan-Fermin, MR Catacutan, AT Triño & RF Agbayani - UPV Journal of Natural Sciences, 2000 - University of the Philippines in the Visayas
      The economic feasibility of four grow-out diets for the Asian catfish Clarias macrocephalus was evaluated on a 1000 m2/crop basis. Hatchery-bred catfish juveniles with mean body weight (MBW) of 3.6 g and mean total length (MTL) of 7.8 cm were stocked at 10 fish/m2. Laboratory-formulated diet with 20% crude protein (CP; Diet 1) resulted in net losses. Laboratory-formulated diet with 34% CP (Diet 2), commercial feed pellet with 29% CP (Diet 3), and a mixed diet of blanched chicken entrails (80%) and rice bran (20%) with 32% CP (Diet 4) gave acceptable return on investment (ROI) of 131-326% and return on operating capital of 52-71%. Culture of Asian catfish fed Diet 2, however, attained higher net profit before tax per 1000 m2/crop, ROI (326%), and has the lowest payback period on investment (0.3 yr) or operating capital (1.4 yr) compared with using Diets 3 and 4. Partial budget analysis showed that higher net benefit can be earned by using Diet 2 as feed for C. macrocephalus compared with using Diet 4. Sensitivity analysis done by increasing in feed cost by 20% and decreasing the selling price of fish by 20% showed that ROI were 107-262% and 46-159%, respectively and return on operating capital of 42-57% and 18-35%, respectively. Payback period on investment were 0.4-0.9 yr and 0.6-1.9 yr, respectively while payback period on operating capital were 1.7-2.2 yr and 2.7-4.7 yr, respectively. Results suggest that C. macrocephalus culture is economically feasible with Diets 2, 3 and 4 as feed but the use of Diet 2 is more profitable.
    • Article

      Economic feasibility analysis of the monoculture of mudcrab (Scylla serrata) Forsskal 

      RF Agbayani, DD Baliao, GPB Samonte, RE Tumaliuan & R Caturao - Aquaculture, 1990 - Elsevier
      Mudcrabs, Scylla serrata Forsskal, were monocultured at different stocking densities: 5000, 10 000, 15 000 and 20 000/ha for 90 days. Highest mean weight, survival and relative growth increment (P>0.05) were obtained from a stocking density of 5000/ha. Best feed conversion ratio of 1.72 and corresponding gross production of 1019 kg/ha per crop were attained at the same stocking density. The economic indicators, i.e., return on investment and return on equity, were also highest at 5000/ha stocking density and the payback period was shortest. Partial budgeting showed that no incremental benefit accrued from stocking beyond 5000/ha. Sensitivity analysis showed that even if the value of mudcrab were to decrease by 28%, mudcrab monoculture would still be economically viable.
    • Article

      Economic feasibility of polyculture of tiger shrimp (Penaeus monodon) with Nile tilapia (Oreochromis niloticus) in brackishwater ponds 

      GPB Samonte, RF Agbayani & RE Tumaliuan - Asian Fisheries Science, 1991 - Asian Fisheries Society
      The polyculture of tiger shrimp (Penaeus monodon) with milkfish (Chanos chanos) has been practiced in the Philippines, bit little is known about the possible polyculture of the shrimp with the tilapias in spite of increasing consumer acceptance for tilapias in the country. Shrimp monoculture, two rates of Oreochromis niloticus monoculture, and two polyculture treatments were compared for economic feasibility. The stocking combination of 6,000 ha-1 shrimp with 4,000 ha-1 tilapia generated the highest total production and net income with 283.57 kg ha-1 and P11,849 ha-1, respectively. Two crops per year provided a 70% return on investment and 1.2 years payback. A sensitivity analysis indicated that shrimp polyculture with tilapia is profitable up to a 20% decrease in the selling price of both species.
    • Article

      The economics and marketing of cage-raised finfish and pen-raised mudcrab 

      DD Baliao, MA de los Santos & NM Franco - Aquaculture Engineering, 1998 - Society of Aquaculture Engineers of the Philippines, Inc.
      As part of the technology verification exercise for technologies developed through research, the economics and marketing aspects were investigated before such technologies can be extended to industry practitioners. These were done for groupers raised in marine fishcages, tilapia raised in fishcages set in farm reservoirs, and for mudcrabs raised in pens set in mangroves.
    • Article

      Economics of cultivating Kappaphycus alvarezii using the fixed-bottom line and hanging-long line methods in Panagatan Cays, Caluya, Antique, Philippines 

      AQ Hurtado-Ponce, RF Agbayani & EAJ Chavoso - Journal of Applied Phycology, 1996 - Springer Verlag
      A socio-economic survey was conducted among the Kappaphycus alvarezii planters of Panagatan Cay, Caluya, Antique, Philippines to determine some social information, farming practices and cost and returns of farming the seaweed. Cultivation is dominated by brown and green morphotypes using the fixed-bottom and hanging-long line methods. Approximately 9.3 t d. wt ha−1 and 7.2 t d. wt ha−1 is produced from fixed-bottom and hanging-long lines methods, respectively, after 60–90 days of culture. The former method requires a working capital and total investment of P7490 and P1870, respectively, compared to the hanging-long line which requires P8455 and P25464, respectively (US$ 1 = P26). A higher total revenue (P139500), net income ((P187895), and return of investment 1002%), but a shorter pay back period (0.10 years) were obtained in fixed-bottom than in hanging-long line. A lower total expenses were incurred in fixed-bottom (P21354) than in hanging-long line (P24566). The farming of K. alvarezii in this area has brought tremendous economic impact to the marginal fishermen.