Egg size and larval size among teleosts: implications to survival potential
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A survey of the early life history characteristics of 135 teleost fishes from freshwater, marine, tropical, temperate and boreal habitats show the influence of egg size and larval size on survival potential. Marine species have smaller eggs and larvae than freshwater species at similar temperatures. Coldwater species tend to have larger eggs and larvae than warm water species. Egg diameters are positively correlated with larval lengths (Lh) and weights at hatching. The times from fertilization to onset of feeding (tf), to yolk and oil resorption (ty) and to irreversible starvation (ts), increase linearly with Lh and decrease exponentially with temperature. Both tf and ts are positive linear functions of ty. Thus, larger larvae with much yolk that lasts for a relatively longer period feed later and if not fed, will starve later than small larvae with little yolk. Larger larvae will thus have the advantage under conditions of limited or variable food supply. Moreover, large larvae tend to have large mouths and are thus capable of ingesting large high-calorie prey. They also tend to have higher swimming speeds and greater potential to encounter food and avoid predators. There is no definite relation between growth rates and Lh, but tropical species with small eggs and larvae tend to have high growth rates. Survival potential has implications in the recruitment to natural stocks and in seed production in hatcheries.
In: Maclean, J.L., Dizon, L.B., Hosillos, L.V. (eds.). The First Asian Fisheries Forum. Proceedings of the First Asian Fisheries Forum, 26-31 May 1986, Manila, Philippines. Manila, Philippines: Asian Fisheries Society. pp. 651-656
PublisherAsian Fisheries Society
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Size measurement and nutritional condition evaluation methods in sandfish (Holothuria scabra Jaeger) S Watanabe, JM Zarate, JG Sumbing, MJH Lebata-Ramos & MF Nievales -
Aquaculture Research, 2012 - WileyThe aims of this study were to establish an accurate size measurement method and a nutritional condition evaluation method of Holothuria scabra (Jaeger). Although 0.5% KCl and 0.05% MgSO4 did not induce anaesthesia, 2% menthol–ethanol for 20 min was found to be effective and harmless. The anaesthetization significantly reduced the coefficient of variation of the mean body length and weight by 68% and 43% respectively. During starvation, body size and weight decreased concomitantly, resulting in an unchanged condition factor (body weight/volume), suggesting that the condition factor cannot be used as an index of nutritional condition. Protein, cholesterol and carbohydrate concentrations in the body fluid were analysed to study the relationship with starvation. As the protein and cholesterol concentrations initially increased and then decreased during the starvation period, it is difficult to use them as an index of nutritional condition. The carbohydrate concentration showed a gradual one-fold increase during 10 days of starvation, and it may be used as a proxy for nutritional condition; however, further physiological studies are needed. Body fluid density and volume relative to body size gradually increased and decreased, respectively, during starvation. These methods may be used to correctly monitor the conditions of H. scabra in studies for aquaculture and stock enhancement techniques.
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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%.