Now showing items 1-6 of 6

    • Article

      Biology and farming of the green mussel Mytilus smaragdinus 

      WG Yap, C Orano & M Tabbu - SEAFDEC Aquaculture Department Quarterly Research Report, 1977 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Biological investigations were carried out in Sapian Bay, Capiz from November 1975 to December 1976 with samplings conducted fortnightly. Histological studies on the gonad reveal a high percentage of ripe and spent females during the month of April and May, and ripe to near ripe during November to December. However, larval counts were highest on February 25, 1976 with 253 mytilid larvae per haul compared to 0-79 per haul during all other months. The high larval count was followed by the highest spat settlement during the next sampling period two weeks later, with the spat collector set in the water during the February 25 sampling. The four materials tested, blue polypropylene fiber rope, black polypropylene fiber, and coir rope, all had their highest spat counts during this period with an average of 471 spats per standard 10 cm rope piece. The range during the other time periods is 2-283 spats. Of the 4 materials tested, the black fibrillated polypropylene film had the highest larval counts in 15 out of a total of 25 sampling periods. The blue rope was the poorest spat collector. Coconut husk was tested later on and it proved to have a very high catchability, with spats completely enveloping the husk surface. Growth monitored from one cohort in Sapian Bay averaged 10 mm per month. 50-60 mm is considered marketable size. Trial growth experiments with transplanted mussels were also conducted at Igang Bay in Guimaras Island, Makato River in Aklan, and a milkfish pond in Leganes, Iloilo. Survival in Igang was less than 50% after the second week, and the condition of the surviving mussels can be described only as watery with the mantle completely transparent. Mortality was minimal in Makato but the growth rate was only 30% that of Sapian Bay. The pond experiments were terminated due to severe crab predation.
    • Conference paper

      Developments in marine and brackishwater fish culture in Southeast Asia 

      WG Yap - In LMB Garcia (Ed.), Responsible Aquaculture Development in Southeast Asia. Proceedings of the Seminar-Workshop on Aquaculture Development … Southeast Asia organized by the SEAFDEC Aquaculture Department, 12-14 October 1999, Iloilo City, Philippines, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Freshwater, brackishwater, and marine ecosystems are recognized as distinct from each other and aquaculture is often conventionally categorized accordingly. However, the brackishwater aquaculture category is by no means universally recognized. China, India and Japan recognize only two categories: inland and marine aquaculture. Thailand and Vietnam, on the other hand, report production from brackishwater and marine aquaculture together under one category: coastal aquaculture.

      An examination of the species involved would show that there is such a wide overlap between so-called "brackishwater species" and "marine species" so that the two groups are virtually congruent with each other. Brackishwater species are euryhaline and can survive just as well in varying salinity levels and may also be raised and grown in full-strength seawater. So-called marine species, on the other hand, can tolerate slight dilutions in salinity and can be grown just as well in what are technically brackish waters. Furthermore, most, if not all, of the so-called brackishwater species invariably require marine waters for propagation. Thus, it would appear that the distinction between brackishwater and marine aquaculture is meaningless in categorizing aquaculture species.

      Saltwater culture of finfish in Southeast Asia may be characterized by low species diversity; sluggish industry growth, continued use and even dependence for some species on wild-caught seedstock, and heavy dependence either on fresh fish biomass or on fish meal for formulated feeds. There are only a few of finfish species or species groups that are now commercially raised in saltwater: milkfish, tilapia, grouper, and sea bass. Mangrove snapper and rabbitfish are to a certain extent aIready being cultured, but have not yet reached a significant proportion. Relative to other aquaculture commodities, particularly penaeid shrimps and seaweeds, the growth of saltwater fish culture in Southeast Asia has not been particularly spectacular. This is not for lack of market since there is a good intemational and local market for groupers.

      While milkfish and sea bass fry can now be commercially produced in hatcheries, commercial production of grouper fingerlings seedstock remains elusive, despite a long R & D history. There is an urgent need to develop cost-effective feeds with a greatly reduced requirement for fish protein for saltwater aquaculture.
    • Article

      An experimental assessment of the aquaculture potential of the brown mussel, Modiolus metcalfei 

      WG Yap - SEAFDEC Aquaculture Department Quarterly Research Report, 1978 - Aquaculture Department, Southeast Asian Fisheries Development Center
      A study was conducted at Banate Bay, Iloilo, from November 1975 to March 1976. Trials were conducted using spat collectors of four types, but no Modiolus metcalfei spat settled on any of the experimental collectors during the entire study period. Instead they attached to the exposed posterior half of the living Modiolus collected for reproductive cycle studies. The aquaculture potential of the brown mussel is considered to be low. Improvement of its production potential should be approached along the line of resource management rather than aquaculture. This management should be aimed at two objectives: (1) maintenance of enough adults on settlement surfaces, and (2) provision of space to allow new recruitments to grow. A possible solution, therefore, is controlled harvesting or thinning after the peak in the settlement season. In this manner, the chances of the mussel bed recovering year after year may be enhanced.
    • Article

      Limnological features of Lake Buluan: Preliminary findings and observations 

      WG Yap, EA Baluyut & JMF Pavico - Fisheries Research Journal of the Philippines, 1983 - Fisheries Research Society of the Philippines
      A limnological survey of Lake Buluan in Mindanao was conducted to evaluate its potentials for fishpen and fish cage culture. The lake was found to be shallow and highly productive, with the major physicochemical and biological parameters within ranges favorable for fish production.

      The lake has high gross primary production values attributable to high densities of phytoplankton, primarily blue-green algae. It has a high annual yield of 10,000 mt of fish, which when divided by its area of 6,000 hectares, gives an average production of 1.64 mt/ha/yr - the highest open water catch in the Philippines and in Southeast Asia today.
    • Book

      Milkfish production and processing technologies in the Philippines 

      WG Yap, AC Villaluz, MGG Soriano & MN Santos - 2007 - WorldFish Center
      This publication describes the various aspects of milkfish production in the Philippines. It covers these areas 1) technology development from a historical perspective, 2) milkfish seed production 3) grow-out in brackishwater ponds 4) grow-out in pens and cages 5)milkfish processing.
    • magazineArticle

      Principles and concepts of mangrove-friendly shrimp culture 

      WG Yap - SEAFDEC Asian Aquaculture, 2002 - Aquaculture Department, Southeast Asian Fisheries Development Center