Challenge 03: Sustainably feed the global population
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Ocean Decade
Challenge 03:
Sustainably feed the global population
Generate knowledge, support innovation and develop solutions to optimize the role of the ocean in sustainably nourishing the world’s population under changing environmental, social and climate conditions.
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- Survival, growth and food conversion efficiency of Panulirus ornatus following eyestalk ablationJuinio–Meñez, Marie Antonette; Ruinata, Jesselita (Elsevier BV, 1996-11)The viability of eyestalk ablation as a means to enhance the growth of juvenile spiny lobsters in commercial growout cultures was investigated in a 4-month experiment. Three replicate groups of small-sized (86.3–94.4 g total weight; 44.1–46.6 mm carapace length (CL)) Panulirus ornatus were subjected to three experimental treatments: unablated/control, unilateral and bilateral eyestalk ablation. Only animals which were initially at the intermolt stage were used in the experiments. The average food conversion efficiency (12–17%) and monthly growth rates of bilaterally ablated lobsters, based on both total weight (42.0–64.0 g) and carapace length (6.7–7.0 mm CL) increments, were significantly higher than lobsters in the two other treatments during the first 2 months of the experiment but declined thereafter. At the end of the experiment, only 6% of the bilaterally ablated lobsters (n = 48) survived compared with 73% and 75% for unilaterally ablated and unablated lobsters, respectively. The extreme sensitivity of bilaterally ablated lobsters to water quality and diet renders bilateral ablation impractical for commercial growout culture. The high survivorship and generally higher growth rates of unilaterally ablated lobsters compared with unablated lobsters resulted in the highest gross yield among the three treatments. The results indicate that unilateral ablation may be a viable option to consider in accelerating the growth of small juvenile P. ornatus to a marketable size of 200–300 g.
- Clonal propagation of Eucheuma denticulatum and Kappaphycus alvarezii for Philippine seaweed farmsDawes, C. J.; Trono, G. C.; Lluisma, A. O. (Springer, 1993-06)Technique improvement and cost reduction of branch culture, micropropagation, and callus production of carrageenan-yielding seaweeds Kappaphycus alvarezii and Eucheuma denticulatum is presented. Low cost branch culture is possible by enriching seawater with 0.1% coconut water with 1 mg l−1 indole-3-butyric acid for 24 h wk−1 or continuous culture with 0.01% Algafer, a Philippine fertilizer. Micropropagation of 0.5 cm explants had almost 100% new branch production demonstrating the viability of callus regenerated plants. The use of carrageenan as a media for callus production was not effective when compared to agar. Propagules of both species, transferred from the University of the Philippine Marine Science Institute (UPMSI) culture facility to the field, showed daily percent growth rates of 5 to 5.5% d−1 over 84 days. Based on the costs of the UPMSI laboratory, a culture facility in the seaweed farming area is estimated to cost about U. S. $22000 during the initial year and 58% less the second year.
- Electrophoretic evidence for extensive hybrid gene introgression into commercial Oreochromis niloticus (L.) stocks in the PhilippinesMacaranas, J. M.; Taniguchi, N.; Pante, M. J. R.; Capili, J. B.; Pullin, R. S. V. (Hindawi Limited, 1986-10)The usefulness of isozyme and protein markers in identifying tilapia species and their hybrids is demonstrated. Genetic characterization of Oreochromis niloticus populations from commercial farms, experimental stations, and government hatcheries in Luzon, Visayas and Mindanao in the Philippines indicates well-established introgression with O. mossambicus. Genetic differentiation of the O. niloticus stocks, measured by Nei's genetic distance, was highly correlated with O. mossambicus gene content. The implications of these results for tilapia genetic improvement are discussed.
- Spontaneous maturation and spawning of milkfish in floating net cagesMarte, Clarissa L.; Lacanilao, Flor (Elsevier, 1986-04)Milkfish (Chanos chanos Forsskal) reared from wild-caught fry and from hatchery-bred fry matured at 3.5–5.5 years (2.3–4.9 kg). Maturation and spawning of the hatcherybred fish marks the first time the milkfish life-cycle has been completed in captivity. Milkfish at various stages of gonadal development were obtained in July–October 1980 and March–June 1981 derived from wild-caught fry, and in February–June 1983 from the hatchery-bred fish. The fish were held in floating net cages 9 m and 10 m diameter by 3 m deep, located in 7 m deep water off Igang, Guimaras Island, Philippines. Annual ranges of temperature and salinity were 25–33°C and 25–38 ppt, respectively. The fish were fed commercial feed pellet (42% protein) at 1.5–2% of body weight twice daily. Sexual maturation occurred during the natural breeding season of wild milkfish in the nearby waters. Gonadosomatic index (GSI) of mature males was 0.32–3.95 (wild-caught, 0.32–3.95; hatchery-bred, 1.71–3.85). For mature females it was 1.24–8.12 (wildcaught, 1.56–7.62; hatchery-bred, 1.24–8.12). Two spawnings were recorded in August 1980 and eight in May–July 1981 from the broodstock derived from wild-caught fry, with 342–6293 eggs collected from each spawning, while 14 spawnings were observed in May–June 1983 from the hatchery-bred fish, with 770–114 000 eggs collected. The time of spawning was between 23.00 and 02.00 h. Fertilization rate was 55–99% for the broodstock from wild-caught fry and 47–100% for the hatchery-bred fish. Hatch rate varied from 9 to 80%. Factors affecting spontaneous maturation, spawning and rematuration are discussed. Although slight improvements in egg collection were obtained, further innovations in egg collecting techniques will have to be developed. The results indicate the potential for hatchery production of milkfish fry from captive broodstock and for restocking of waters deprived of naturally occurring fry.
- Genetic improvement of farmed tilapias: Biochemical characterization of strain differences in Nile tilapiaMacaranas, Julie M.; Agustin, Liza Q.; Ablan, Ma. Carmen A.; Pante, Ma. Josefa R.; Fukushima, A.; Pullin, Roger S. V. (Springer, 1995-03)Four African wild strains (Egypt, Ghana, Senegal and Kenya) and four established Asian farmed strains of Nile tilapia, Oreochromis niloticus (popularly known in the Philippines as ‘Taiwan’, ‘Thailand’, ‘Singapore’ and ‘Israel’) were analysed electrophoretically at 30 protein loci to estimate genetic differences among the strains. All strains shared alleles at 14 monomorphic and 16 variable loci. Among the African strains, characteristic allele frequency differences were observed at AAT-1 * 46 for Ghana and Senegal, ADH * 83 for Kenya, ADH * 120 for Senegal, G3PDH-2 * 300 for Egypt, IDDH * 67 for Senegal, sMDH-1 * 120 for Kenya and SOD * 150 for Senegal. Genetic distance values among the strains revealed a clustering of the farmed strains with Egypt and Ghana O. niloticus, a slight separation of the Senegal strain and a larger separation of the Kenya strain. This profile may reflect the origins of the few founder populations of this species previously introduced to Asia. It also confirms the wider genetic divergence of the Kenya strain (O. niloticus vulcani) from the others studied here, which are all O. n. niloticus. Observed heterozygosities of the strains ranged from 0.026 to 0.071, with the African wild strains the lower values (mean Ho = 0.036) and the farmed strains the higher ones (mean Ho = 0.056). The implications of these results to the ongoing tilapia genetic improvement programme in the Philippines are discussed.