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Larval Survival Rates (larval + survival_rate)
Selected AbstractsThe effect of vitamin A supplementation in broodstock feed on reproductive performance and larval quality in Penaeus chinensisAQUACULTURE NUTRITION, Issue 5 2004L. Mengqing Abstract The effect of feeding four semi-purified diets A1, A2, A3, A4, containing different vitamin A acetate levels 0, 20, 40, 60 mg kg,1 diet, respectively, on fecundity, egg hatching rate, larval survival rate and vitamin A content in eggs of Chinese shrimp (Penaeus chinensis) broodstock was compared with a fresh clam diet (control) in a 60-day feeding trial. The broodstock shrimp fed the diet with 60 mg kg,1 vitamin A acetate added exhibited significantly higher fecundity (P < 0.01). Hatching rate was highest with diet A4 (P < 0.05), whereas hatching rates were similar fed diets A1, A2, A3. Increasing levels of vitamin A in broodstock diet resulted in improvement in larval quality. The vitamin A levels in shrimp eggs from broodstock fed with diet A4 were higher compared with those from broodstock fed with diet A1, A2 (P < 0.01). The fecundity and hatching percentages were positively correlated with the vitamin A content in eggs in the present study. The results of this study showed that higher level of vitamin A in broodstock diet may have positive effects on fecundity and larval quality in P. chinensis. [source] Influence of water temperature on spawning induction and larval development of the sea squirt Halocynthia ritteri (Oka, 1906)AQUACULTURE RESEARCH, Issue 5 2009Kyoung Ho Kang Abstract In order to establish a large-scale hatchery technique for the sea squirt Halocynthia ritteri, the influences of water temperature on spawning induction, larval development and survival of H. ritteri were studied under laboratory conditions. The larvae of H. ritteri exhibited high sensitivity to changes in temperature. As temperature increased from 10 to 21 °C, the duration of larval stage was inversely related to temperature and the time to reach attached larvae stage decreased from 42.0 to 59.4 h. The biological minimum temperature for the early development of H. ritteri was estimated to be 0.22 °C. In relation to temperature, quadratic equations showed significant fits to the data of spawning rate, fecundity, fertilization, larval survival and attachment. Optimal temperatures for spawning rate, fecundity, fertilization rate, larval survival rate and attachment rate were estimated to be 14.9, 14.7, 13.2, 14.1 and 14.7 °C respectively. It is concluded that the range of 13,15 °C is optimal for spawning and larval rearing of sea squirts. [source] Field efficacy of transgenic cotton containing single and double toxin genes against the Asian corn borer (Lep., Pyralidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2004K. He Abstract:, Insect resistant transgenic cotton (Gossypium hirsutum L.) is expected to provide satisfactory control of lepidopteran species in the cotton field. The Asian corn borer, Ostrinia furnacalis (Guenée) (Lep., Pyralidae), is an important component of the lepidopteran pest complex of cotton in China. Insect resistant transgenic cotton cultivars GK2, carrying cry1A gene, and SGK321, carrying both cry1A and CpTI genes, were evaluated for resistance to Asian corn borer. Field trials were conducted with artificial infestation of Asian corn borer at squaring, flowering and flowering-boll cotton plants, which coincided with the generations of natural Asian corn borer occurrence. Damage ratings were significantly reduced in transgenic cotton cultivars both GK2 and SGK321 compared with their parental non-transgenic cotton cultivars Simian3 and Shiyuan321, respectively. In addition, percentage of plants stem bored and number of tunnels per plant were significantly higher on GK2 than on SGK321 in the second generation. Laboratory bioassays were carried out by exposing neonates to plant tissues collected from the field. Tissues assayed included the new leaves, match-head squares and white flowers, which are the tissues initially attacked by the neonates in the field. Low larval survival rates were observed on SGK321 and GK2, contrasting greatly to the high number of survivors found on their non-transgenic cotton tissue isolated throughout the season. However, larval survival was higher on new leaves isolated from late-season transgenic cotton plants and fruit tissues than on early-season. In addition, higher larval survival was observed on GK2 than SGK321 in assays with the late season tissues. This may be associated with reduced levels of available toxin in plant tissues as they age. Both laboratory and field data indicated that SGK321 and GK2 were highly resistant to Asian corn borer. The high level of efficacy for insect resistant transgenic cotton against Asian corn borer offers the potential for season-long control. [source] Live feeds for early stages of fish rearingAQUACULTURE RESEARCH, Issue 5 2010Luís E C Conceição Abstract Despite the recent progress in the production of inert diets for fish larvae, feeding of most species of interest for aquaculture still relies on live feeds during the early life stages. Independently of their nutritional value, live feeds are easily detected and captured, due to their swimming movements in the water column, and highly digestible, given their lower nutrient concentration (water content>80%). The present paper reviews the main types of live feeds used in aquaculture, their advantages and pitfalls, with a special emphasis on their nutritional value and the extent to which this can be manipulated. The most commonly used live feeds in aquaculture are rotifers (Brachionus sp.) and brine shrimp (Artemia sp.), due to the existence of standardized cost-effective protocols for their mass production. However, both rotifers and Artemia have nutritional deficiencies for marine species, particularly in essential n-3 highly unsaturated fatty acids (HUFA, e.g., docosahexaenoic acid and eicosapentaenoic acid). Enrichment of these live feeds with HUFA-rich lipid emulsions may lead to an excess dietary lipid and sub-optimal dietary protein content for fish larvae. In addition, rotifers and Artemia are likely to have sub-optimal dietary levels of some amino acids, vitamins and minerals, at least for some species. Several species of microalgae are also used in larviculture. These are used as feed for other live feeds, but mostly in the ,green water' technique in fish larval rearing, with putative beneficial effects on feeding behaviour, digestive function, nutritional value, water quality and microflora. Copepods and other natural zooplankton organisms have also been used as live feeds, normally with considerably better results in terms of larval survival rates, growth and quality, when compared with rotifers and Artemia. Nonetheless, technical difficulties in mass-producing these organisms are still a constraint to their routine use. Improvements in inert microdiets will likely lead to a progressive substitution of live feeds. However, complete substitution is probably years away for most species, at least for the first days of feeding. [source] The effect of unilateral eyestalk ablation and diet on the reproductive performance of wild-caught Farfantepenaeus aztecus (Ives, 1891) using a closed recirculating maturation systemAQUACULTURE RESEARCH, Issue 6 2007Ryan L Gandy Abstract Two studies were conducted to evaluate the effects of unilateral eyestalk ablation and diet on the reproductive performance of wild populations of Farfantepenaeus aztecus. In both studies, females in two treatments were unilaterally ablated while those in the control treatment were not. Shrimp in the non-ablated treatment and one of the unilaterally ablated treatments received frozen bloodworms (8% BW day,1) and frozen squid (12% BW day,1). The bloodworm component of the diet of the third unilateral ablation treatment was replaced with frozen adult enriched Artemia sp. Ablated female population spawning per night, in both studies, was higher than non-ablated spawning (8.5 and 8.9 vs. 2.6%; 7.4 and 7.5 vs. 2.7% respectively; P<0.05). Replacement of bloodworms with adult enriched Artemia sp. had no negative effect on the number of eggs spawned per ablated female (124 000 vs. 115 000 eggs spawn,1; 144 000 vs. 151 000 eggs spawn,1 respectively; P>0.05). The life span of ablated females fed adult enriched Artemia sp. was 8 and 40 days longer than ablated females fed bloodworms for the first and second studies respectively. Replacement of bloodworms with adult enriched Artemia sp. resulted in higher hatch and larval survival rates (Nauplius 1 to Zoea 1) (55.0% vs. 46.9% and 44.8% vs. 37.2%), respectively, P<0.05. [source] | ||||||||||