Nursery culture of tropical anguillid eels in the Philippines
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This technical publication focused on nursery production of anguillid eels from glass eels to elver using data gathered from eel farm surveys and rearing trials conducted by SEAFDEC/AQD as part of the JAIF (Japan-ASEAN Integration Fund) project on Enhancing Sustainable Utilization and Management Scheme for Tropical Anguillid Eel Resources in Southeast Asia.
Cuvin-Aralar, M. L., Aya, F. A., Romana-Eguia, M. R., & Logronio, D. J. (2019). Nursery culture of tropical anguillid eels in the Philippines. http://hdl.handle.net/10862/3444
PublisherAquaculture Department, Southeast Asian Fisheries Development Center
SeriesAquaculture extension manual; No. 65
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Potential and prospects of southeast Asian eel resources for sustainable fisheries and aquaculture development The world demand for river eels has been increasing mainly because of the market expansion of some delicacies such as the kabayaki (broiled eel with sweet soy sauce) in East Asia. While most of the world’s eel production is derived from aquaculture, it should be noted that eel aquaculture is still dependent on the natural resources. As techniques for the full-life cycle aquaculture of eels have not yet been fully developed for commercial use, the eel aquaculture industry is still solely dependent on wild resources for seed stocks. However, the natural resources had been confronted with various factors that could possibly create negative impacts on the eel resources including habitat alteration, overexploitation, climate change, pollution, and incidence of diseases. Thus, concerns on the sustainability of various eel species in the world have increased in recent years. It should be reckoned that the European and American eels are already threatened to certain degree by pollution and damming (or the construction of dams that prevent their migration to freshwater bodies) leading to almost “close to collapse” of the European eel resources. This situation prompted CITES to list the European eel (Anguilla anguilla) in CITES Appendix II in 2009 and accordingly, trade restrictions of the European eel and its products came into effect. In Southeast Asia, it is known that aquaculture and inland capture fisheries of eel are practiced but data and information on the total production of eel in the region remain very minimal. In this regard, the Southeast Asian countries have been encouraged to report their respective eel production to SEAFDEC in order that the status and trend of the region’s eel resources could be established and the statistics could be appropriately reflected in the Fishery Statistical Bulletin of Southeast Asia produced yearly by SEAFDEC. Meanwhile, in an effort to conserve the eel resources in Southeast Asia, SEAFDEC recently launched a project on Conservation, Management and Sustainable Utilization of Eel Resources in Southeast Asia with funding support from the Trust Fund for SEAFDEC of the Fisheries Agency of Japan.
ArticleThe SS-type rotifer Brachionus rotundiformis is a common initial food for rearing fish larvae with a small mouth. However, there are commercially important fish species whose mouth sizes are too small to feed on SS-type rotifers. In 2004, we isolated a small (body length = 82.7 ± 10.9 μm; body width 40.5 ± 6.4 μm), flexible, and iloricate rotifer, Proales similis from an estuary in Okinawa, Japan. Under laboratory conditions (25 °C, 2–25 ppt) P. similis produced its first offspring on 2.5 to 2.8 days after hatching, and produced 4.3 to 7.8 offspring within 4.0 to 4.7 days life span. Batch cultured P. similis fed Nannochloropsis oculata suspension at 28.8 μg dry weight ml− 1 and cultured at 25 °C, 25 ppt filtered seawater, increased exponentially from 25 to 2400 ind ml− 1 after 11 days of culture with an overall intrinsic rate of natural increase (r) of 0.42 day− 1. The growth rate of P. similis was not significantly different when fed fresh N. oculata and super fresh Chlorella vulgaris-V12®. Total lipid per wet weight of P. similis fed by N. oculata and C. vulgaris were 2.4 and 2.6%, respectively. The compositions of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (ARA) of P. similis fed N. oculata were 23.2, 0.0 and 5.3%, respectively, while these were 11.0, 17.5 and 0.5% respectively, when fed C. vulgaris. The use of P. similis to feed small mouth fish including seven-band grouper Epinephelus septemfasciatus, rusty angelfish Centropyge ferrugata, and humphead wrasse Cheilinus undulatus showed that it is an excellent starter food for these species because of their high selectivity index and improved survival. In addition, P. similis was ingested by Japanese eel Anguilla japonica larvae with a complicated digestive system. The use of P. similis as starter feed for small mouth fish larvae is highly recommended.
ArticleTo test the effect of Vibrio anguillarum extracellular products (ECP) on Japanese eels (Anguilla japonica ), test fish were injected intramuscularly with ECP at a dose of 1 mg protein/100 g body weight of fish.At 3,6,12,24 and 36 h post-injection, blood samples were collected for haematocrit, haemoglobin, and serum protein determinations and tissues were fixed in Bouin's solution. Histopathological observations 24 h post-injection revealed that the ECP caused severe damage to muscle tissue, characterized by extensive muscle liquefaction and haemorrhaging. In addition, extensive haemosiderin deposits were observed in the spleen, with lesser deposits occurring in the kidney and liver. Haematocrit, haemoglobin, and serum protein values were lower in ECP-treated fish than in the untreated controls.