Browsing by Author "Kurokura, Hisashi"
Conference paperJP Altamirano, N Salayo, H Kurokura, H Fushimi & S Ishikawa - In K Hajime, T Iwata, Y Theparoonrat, N Manajit & VT Sulit (Eds.), Consolidating the Strategies for Fishery Resources Enhancement in Southeast Asia. Proceedings of the Symposium … Strategy for Fisheries Resources Enhancement in the Southeast Asian Region, Pattaya, Thailand, 27-30 July 2015, 2016 - Training Department, Southeast Asian Fisheries Development CenterIn central Philippines, the Aquaculture Department of the Southeast Asian Fisheries Development Center (SEAFDEC/AQD), with strong collaboration and support from the Research Institute for Humanity and Nature (RIHN) of Kyoto, Japan, has been looking into the stock enhancement of tiger shrimp Penaeus monodon in the New Washington Estuary (NWE), province of Aklan, central Philippines. The NWE was a productive fishing ground that has been suffering from degenerating brackishwater fisheries and estuarine environment. Average daily catch declined from 24 kg in 1970s to only 0.7 kg at present. Shrimp fisheries, the most important livelihood, declined in quality and quantity. Tiger shrimps were abundant in catch until the early 1990s when these were observed to decline in volume, replaced by smaller and cheaper species. This was coincidental with the rapid decline in mangrove cover for ponds and huge increase in fishing pressure. It is clear that crucial interventions are required to restore the tiger shrimp fisheries in the NWE in order to increase income of local fishers, while promoting reduction of fishing gears and restoration of mangroves. Stock enhancement of tiger shrimps shows good potential in answering these needs. Site-specific assessments were conducted to evaluate prospects of shrimp stock enhancement in NWE. Conservative simulations of capture of released stocks showed that fishers can increase income by 300%. To decrease fishing pressure in the area, number of gears per fisher may have to be reduced but shrimp catches will be relatively high-priced. Comparative experiments using aquaculture techniques were done to identify strategies especially in the delicate intermediate acclimation rearing. Aquaculture protocols like those for pond preparation were also adapted to be used in a mangrove pen nursery rearing system for shrimps. Supplemental feeding with formulated feeds increased carrying capacity of the culture area, while enhancing growth and survival of stocks. Culture experiments showed that shrimps grow to 0.5 g within 1 mo and >1g in 2 mo. High stocking density of 40-60 shrimps m-2 can be used for <2 mo rearing in a mangrove pen. Release experiments showed that 60-d old shrimps have higher chances of survival when released in the estuaries. With strong support from local communities, government and other sectors, together with effective management and law enforcement, aquaculture-based stock enhancement of tiger shrimps can be a viable intervention to restore livelihood and promote estuarine rehabilitation in the NWE.
ArticleJD Toledo, H Kurokura & H Nakagawa -
Nippon Suisan Gakkaishi, 1991 - Japanese Society of Fisheries ScienceCryopreserevation of different strains of Brachionus plicatilis symmetrical stage embryos was conducted. One S-type strain, namely Yashima-S (YS), and three L-type strains, namely Yashima-L (YL), Nagasaki (NG), and Hamana (HA), were used. Symmetrical stage embryos in 10% DMSO-28‰ sea water solution were frozen at -196°C using a two-step freezing procedure; the embryos were first cooled slowly from -5°C to -20°C at a rate of 0.3°C/min and then cooled rapidly by direct transfer to liquid nitrogen. Frozen samples were thawed in a gently stirred water bath at room temperature. A mean survival rate of 36% after 30 days storage in liquid nitrogen of HA strain was significantly lower than YS (55%), YL (58%), and NG (54%), and is due likely to its relatively larger embryo volume. There was no significant difference in the intrinsic rate of increase (r) between strains among clones taken from the cryopreservation or unfrozen control group. The results also indicate that various strains of B. plicatilis embryos can be cryopreserve without seriously altering their reproductive capability. The freezing method described could be of great potential in aquaculture and in future studies on rotifer genetics.
Influence of fishing gears on excessive use of fishing grounds in Batan Estuary, Aklan, central Philippines R Kamiyama, JP Altamirano, K Yoshino & H Kurokura - In LL Tolentino, LD Landicho, S Wun'Gaeo & K Ikegami (Eds.), 4th International Conference : the multidimensionality of energy, economy and environmental crises and their implications to rural livelihoods : September 7-10, 2010, Bicol University, Legazpi City, Albay, Philippines, 2010 - Asian Rural Sociology AssociationThe excessive fishing activities have led to the depletion of many coastal fisheries resources in most of the countries in Southeast Asia. It is therefore necessary to find out the causal factors of excessive fishing in order to build up effective fisheries management system. This paper highlights the results of the study that investigated the overfishing or excessive fishing in Batan Estuary, Aklan, Central Philippines. The data were gathered through an interview of selected households in Barangay Pinamuk-an, Aklan from March 2-26 2010. Of the 93 respondent-households, 67 or 72% is engaged in fishing. The most popular fishing gear was the small set net with synthetic fiber, which was introduced to the community in the latter part of 1970s. The relatively lower cost of this small fishing gear, and a few labor force requirement, including its availability in nearby market made it easier for the fisherfolks to acquire this fishing gear. The small set net with synthetic fiber has been widely used by the fishers, which led to the overuse of the fishing grounds in the Batan Estuary. Thus, this paper argues that the introduction of new fishing gear and method triggered the excessive fishing in coastal areas in Philippines.
ArticleJP Altamirano, JH Primavera, MRN Banaticla & H Kurokura -
Wetlands Ecology and Management, 2010 - SpringerPractical mapping methods employing GPS field surveys and manual image analyses with affordable software were used to assess two mangrove sites in Aklan Province, NE Panay Island, central Philippines. The Jawili mangroves, absent from current maps, actually included 21.5 ha with 24 true mangrove species. On the other hand, the Batan Estuary mangroves, shown to be 4244 ha in available topographic maps, revealed only 406 ha of scattered patches. Actual mangrove data on specific areas worldwide is limited, especially in the Philippines where available maps show discrepancies from actual mangrove distribution. Remote sensing (RS) techniques provide promising results but require expensive setup, particularly for small areas. Therefore, financially limited users need affordable and rapid mapping alternatives. The practical techniques presented here can be immediately implemented at minimal cost and can produce useful estimates of actual mangrove area, fundamental for coastal management. Basic principles used here also have potential applications in other systems and locations. When resources are available though, additional confirmation and precise mapping are also further recommended.