Browsing by Author "Encena II, Vincent C."
BookAC Fermin, MR de la Peña, RSJ Gapasin, MB Teruel, SMB Ursua, VC Encena II & NC Bayona - 2008 - Aquaculture Department, Southeast Asian Fisheries Development Center
Series: Aquaculture extension manual; No. 39This manual contains information on abalone hatchery operation, including site selection, design, culture of natural food, broodstock management, spawning, nursery, packing and transport, and profitability analyses.
Evaluation of density and cage design for the nursery and grow-out of the tropical abalone Haliotis asinina Linne 1758 VC Encena II, M de la Peña & VT Balinas -
Journal of Shellfish Research, 2013 - National Shellfisheries AssociationThe effect of stocking density and cage design on the growth, survival rate, and feed conversion ratio was evaluated for the nursery (11–15 mm in shell length) and juvenile grow-out (26–30 mm in shell length) of the tropical abalone Haliotis asinina. Abalone were fed Gracilaria sp. within a randomized 2 × 3 factorial experiment using 2 stocking densities (Tl (500 pieces/m2) and T2 (1,000 pieces/m2)) and 3 cages (D1, box; D2, mesh cage; D3, prefabricated multitier trays). In addition, 3 stocking densities (T1, 50 pieces/m ; T2, 100 pieces/m; T3, 200 pieces/m) were evaluated in the prefabricated multitier trays. We found that, in the nursery experiment, 4-mo-old tropical abalone juveniles reared for 90 d showed no significant differences in growth (shell length and body weight) and survival rates among the 3 nursery cages used (Tukey's post hoc test, P > 0.05). Feed conversion ratio, however, was lowest for the high-density treatment T1D3 (7.8 ± 0.76) and was significantly different from the low density treatment T1D1 (11.32 ± 1.2) and intermediate density treatment T1D2 (12.39 ± 1.12; t-test, P > 0.05). Conversely, at higher densities (T2), the same trend applied with abalone reared in multitier basket systems (T2D3), having the highest growth rates and survival rates (29.3 ± 0.07 mm average shell length (ASL) and 5.16 ± 0.52 g average body weight (ABW)), followed closely by those reared in mesh cages (T2D2) and boxes (T2D1). Feed conversion ratio was also lowest for T2D3 (7.56 ± 0.79) and was significantly lower than T2D1 and T2D2. Between treatments, however, abalone reared at lower densities (T1) had significantly higher growth and survival than those reared at higher densities (T2), regardless of the nursery cage used, indicating an inverse relationship between stocking density, growth, and survival. For the grow-out study, tropical abalone reared in multitier trays at low densities (T1) attained the highest growth in shell length and body weight (49.7 ± 0.11 mm ASL and 29.8 ± 2.6 g ABW, respectively) at 180 d of culture, which was significantly greater than those reared in the high-density treatment (T3) with significantly smaller shell length and body weight (43.8 ± 0.18 mm ASL and 21.2 ± 2.0 g ABW), but not significantly different than the intermediate density treatment. This trend started from day 60 of culture onward when analyzed using Duncan's multiple range test (P > 0.05). Survival rates were not significantly different among stocking density treatments, nor were feed conversion ratios. We recommend, for nursery rearing of abalone juveniles, using multitier trays (D3) or boxes (D1) at 500 pieces/m2 stocking density to attain a grow-out size of 26–30 mm in shell length in 90 days. A stocking density of 100 pieces/m2 is recommended to grow abalone in multitier trays to attain a cocktail size of 50 mm ASL and 30 g ABW in 180 d with survival rates between 85.6% and 83.1%.
BookVC Encena II & NC Bayona - 2010 - Aquaculture Department, Southeast Asian Fisheries Development Center
Series: Aquaculture extension manual; No. 49This manual was written to provide abalone growers a practical guide on how to culture abalone based on the studies and trials conducted by SEAFDEC Aquaculture Department.
ArticleWG Gallardo, VC Encena II & NC Bayona -
Community Development Journal, 1995 - Oxford University PressRapid Rural Appraisal (RRA) was conducted in the fishing village of Lakaran, in the municipality of Dumangas, Iloilo province to identify the resources, livelihood, problems, opportunities, and socioeconomic condition of the villagers prior to the conduct of farmer participatory research on mussel farming. RRA tools such as the construction of the village transect, seasonal calendar and wealth ranking were used.
ArticleThe sex ratio, initial size at sexual maturity, spawning period, time interval between successive spawnings and fecundity of the Donkey's ear abalone, Haliotis asinina were studied. The sex ratio of wild abalone (>60 mm shell length) collected from Panagatan Cays, Antique, Philippines was approximately 1:1. Sexual maturity was first attained at a size of 35.0 mm and 35.9 mm for hatchery-reared male and female abalone, respectively, and 40.6 mm for wild-caught male and female specimens. Based on calculated gonad bulk indices and histological observations, wild-caught abalone appeared capable of spawning during most months of the study period except June for males and May–June for females, during which most specimens collected were at a resting stage. This abalone species is a serial spawner with an asynchronous spawning behavior. Hatchery-reared abalone have short time intervals between successive spawnings of 13–15 days. Ripe females measuring 58.1–69 mm in shell length may release about 150,000 to 600,000 eggs per spawning.