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The study involved three groups of six broodstock with a 1:1 male-to-female ratio. They were injected with 13 µg/kg LHRHa to stimulate spawning. We fed the broodstock three diets: a control diet without selenium, a diet containing 0.3 mg of nano-selenium /kg (N-Se), and a diet containing 4 mg of organic selenium /kg (O-Se). The broodstock diet consisted of equal parts of dry feed (45% protein), sardines, and squid. After being laid, the eggs were obtained from the collection ponds at the General Authority for Fisheries Development's fish hatchery and incubated until hatching. The larvae were given a micro diet containing 51.7% crude protein and live food (Rotifer and Artemia). Rotifer density increased from 5/ml to 15/ml by day 22 dph, Artemia nauplii increased from 0.2 to 4 ind./ml, from 7 to 35 dph then decreased to 0 at 55 dph, and micro-diets increased from 100-200 µ at 16 dph to 200-400 µ at 23-40 dph to 300-500 µ at 55 dph, and 500-1000 µ until the experiment ended. Three different diets in three replicates were tested: A micro diet free of selenium as a control diet (C), A micro diet with 0.3 mg of nano selenium (N-Se) kg-1, and A micro diet supplemented with organic selenium 4 mg (O-Se). Each group was taken from the three Broodstock groups respectively. Sixteen days after hatching, the three experimental micro diets were introduced to the larvae and continued for 76 days post-hatch. Larvae (260,000 per tank) were placed in fiberglass tanks with 4 m3 of water at a temperature of 19±2°C for optimal conditions. The larvae fed the N-Se diet had significantly better survival rates (75.0 ± 1.2 %), final body weight (240.0 ± 5.8 mg), weight gain (239.00 ± 5.8 mg), average daily gain (3.98±0.1mg), total length (39.0±0.06 mm), specific growth rate (9.133±0.04 %/day), feed intake (471.67±0.01 mg), and better feed conversion ratio (1.97±0.01) than the other groups (P < 0.05). The group provided with N-Se also had the highest levels of glutathione peroxidase enzyme (GPx) content in the whole larval body, whereas the control diet without Se supplementation recorded the lowest value of (14.8 ± 0.1 U/mg protein). The number and length of folds in the stomach and esophagus of sea bass post-larvae fed on diets fortified with selenium in both forms, nanoparticles or organic, showed a significant (P < 0.05) enhancement on the larval gastrointestinal (GI) tract. Moreover, selenium has an anti-inflammatory action in sea bass post-larvae. This study concluded that using N-Se as an antioxidant supports the growth and survival of European seabass D. labrax, gastrointestinal development and antioxidant efficacy during critical weaning. [ABSTRACT FROM AUTHOR]

The efficacy of using agar-bound microparticulate diet (A-MPD) as alternative food for abalone Haliotis asinina Linne post-larvae in large-scale culture was investigated. Larvae sourced from the hatchery-bred (HB) and wild-sourced (WS) broodstock were fed with either diatoms (TMT1-NF), agar-bound microparticulate diet (TMT2-A-MPD), or a combination of both feeds (TMT3-NF + A-MPD) in six 2-m tanks replicated over time. Three hundred thousand veliger larvae were stocked/tank containing 80 corrugated plates with mucus trails hanging on bamboo poles. Feeds were given at 0900 h starting at day 3 with seawater flow through introduced every 1400 h starting day 5. Two-way analysis of variance determined significant differences ( p < 0.05) in survival and shell length between larval sources and feed types. Tukey's post hoc test established differences among treatment means. At day 30, survival for HB- and WS-sourced larvae was significantly higher (42%) in TMT3 compared with TMT2 having 35% for HB and 38% for WS ( p < 0.05). Larvae fed with TMT1 had significantly lowest survival among the three treatments. Survival at 60 and 90 days did not show significant difference for TMT2 and TMT3 regardless of broodstock source. Post-larval shell growth (90 days), from both sources fed with TMT2 and TMT3, was significantly higher than TMT1 ( p < 0.05). Larval performance did not show any significant interactions between HB and WS broodstock. The use of A-MPD alone or in combination may elicit improvement in survival and shell length growth in abalone larvae regardless of larval sources. A-MPD may be used as full or partial replacements to diatoms as alternative food for abalone post-larvae in large-scale culture. [ABSTRACT FROM AUTHOR]

Settlement, metamorphosis, survival, and growth of Haliotis asinina larvae exposed to settlement surfaces coated with biofilms of four local diatom species ( Navicula seminulum, Navicula parva, Nitzschia alexandria, Amphora coffeaeformis) were assessed. After 24 h and 72 h, N. alexandria induced the highest settlement rate ( p < 0.001). Larval settlement rate on slats coated with N. seminulum, and A. coffeaeformis was significantly higher after 72 h than after 24 h ( p < 0.001). Metamorphosis was not higher than control after 24 h ( p > 0.05) for any diatom treatment, but after 72 h, all diatoms induced a significantly higher metamorphosis rate than the control ( p < 0.001). N. alexandria induced the highest metamorphic rate (15.71 %). Shell length of post-larvae was not significantly different on day 4 and day 10 ( p > 0.05) in diatom film treatments, relative to control. By day 20, post-larvae survived best on slats with N. alexandria (79.86 %). Survival among treatments was the lowest on slats with N. seminulum (54.91 %), and no live larvae were found in the control. Post-larvae on slats with A. coffeaeformis showed the highest daily growth rate of shell length (DGsl) (87.44 μm d). Post-larvae on slats with N alexandria showed the lowest DGsl (55.66 μm d). Commercial nursery slats seeded with N. alexandria will result in high and consistent settlement, metamorphosis, and survival, while slats with A. coffeaeformis will ensure sufficient food for rapid growth of the H. asinina post-larvae. [ABSTRACT FROM AUTHOR]

The effect of supplemented commercial diets with crystalline l-tryptophan (TRP-5, 10 and 20 g TRP kg) on cannibalism, survival and growth parameters of pikeperch post-larvae ( Sander lucioperca) was evaluated. Fifteen-day-old pikeperch larvae (mean weight-6.8 mg) were reared during the next 28 days (20.5 °C, 16L:8D) in glass aquaria in a recirculating aquaculture system. The enzyme-linked immunosorbent assay showed that TRP-supplemented diets were effective in increasing the levels of serotonin (5-HT) in the body tissue of pikeperch. TRP supplementation resulted in a slight decrease in both types of cannibalism, although the reduction in cannibalism impact did not amount to more than a few percent. TRP treatment had no significant influence on the final survival of pikeperch post-larvae (ranged from 20.1 ± 12.4 to 29.0 ± 12.9 %). However, contrary to the earlier studies conducted on other fish species, no significant difference in the growth rates and feeding behavior of pikeperch between TRP-fed and control group were found. The final body weight and growth rate ranged from 0.211 ± 0.014 to 0.243 ± 0.016 and from 12.19 ± 0.38 to 12.76 ± 0.35 % day, respectively. To our knowledge, this is the first study reporting the effects of TRP supplementation on the cannibalism-survival-growth relations in fish in the post-larval stage. [ABSTRACT FROM AUTHOR]

In order to optimize Pecten maximus larval performance and post-larval yield, larvae were fed five algal concentrations in the range 3-20 cells μL in 2,800-L flow-through tanks without prophylactic antibiotics. Competent larvae were transferred to a commercial hatchery for settlement and provided uniform conditions for 4 weeks to observe effects. Increased diet concentration increased the sum of fatty acids (FA) in the total larval population, reaching 7 and 25 ng FA larvae at 3 and 16 cells μL, respectively. The FA level in competent larvae was not affected by diet concentration and ranged from 30 to 46 ng larvae. Increased diet concentration increased larval growth rate, and the larvae were ready to settle 5 days earlier when fed 16 cells μL compared to 3 cells μL. Larval ingestion rate increased during life span and with increased larval diet concentrations, but a considerable amount (40-60 %) of the added algal cells was lost from the larval rearing tanks due to the seawater flow. There was no effect on larval survival, final post-larval shell height, % of competent larvae transferred to settlement, or total yield of post-larvae. Final mean post-larval shell height was 509 μm and 25.5 % of competent larvae settled, resulting in a final post-larval yield between 6.9 and 17.6 % of the initial number of d3 larvae. Competent larvae with similar FA content produced similar numbers of post-larvae independent of diet concentration, even if higher diet concentrations resulted in higher rates of larval development and metamorphosis. [ABSTRACT FROM AUTHOR]