The objective of this study was to understand the microbial flora associated with the hatchery system of giant fresh water prawn, Macrobrachium rosenbergii during an entire rearing cycle. Bacteriological and physico-chemical analysis was done for different samples of water, larvae, and Artemia. The total bacterial load in well water, seawater and inlet water varied from 101 to 105 cfu ml− 1 with higher counts seen in larval rearing tank (LRT) water. The Vibrio count ranged between 101 to 103 cfu ml− 1. Larval samples harboured a bacterial load of 106 to 107 cfu/10 larvae. The bacterial load in Artemia hatching water ranged from 4.90 × 104 to 5.63 × 106 cfu ml− 1 while Artemia had a load ranging from 1.08 × 107 to 2.09 × 109 cfu g− 1. Vibrio count in the LRT water ranged from 101-103 cfu ml− 1 while the count in larvae ranged from 102 to 104 cfu/10 larvae. The bacterial genera were predominantly Gram-negative and comprised of Aeromonas spp., Pseudomonas spp., Vibrio spp. and Bacillus spp. and non-spore formers (NSF) were the dominant Gram-positive bacteria. This study documents the bacterial flora associated with Macrobrachium hatchery system during a regular normal run. Knowledge of the qualitative and quantitative aspects of bacterial flora in the hatchery would help to understand disturbances, if any, brought about during disease outbreaks. 相似文献
The effects of temperature and salinity on the reproductive success of Arctic charr, Salvelinus alpinus (L.), were examined by holding broodstock under the following conditions from mid‐May until the end of September: fresh water at ambient temperature (NFW; 8–16 °C); salt water (25–30‰) at ambient temperature (NSW; 4–10 °C); fresh water cooled to saltwater temperature (CFW; 4–10 °C); or salt water heated to freshwater temperature (HSW; 8–16 °C). The relative fecundity of females was similar among groups (P > 0.05; 2685 ± 706 eggs), but females reared in NSW produced significantly larger eggs than those raised in NFW. The highest spermatozoa concentrations were found in milt from males reared in SW and the highest milt glucose concentration was from males kept under coldwater conditions (CFW, NSW). Eggs from NSW and HSW females contained more proteins than eggs produced by NFW females. Eggs from NSW females also contained 40% more lipids than was observed in the other groups, and total energy content was 27% higher in eggs from NSW females than in eggs from NFW females. When FW was cooled (CFW), females produced eggs with protein contents similar to those in NSW, but the lipid contents remained 30% lower. Finally, the best survival at the eyed stage and at hatch was observed in families produced by NSW broodstock. Intermediate values were observed in families from NFW or CFW while the highest mortality occurred in families from the HSW group. All these results suggest that, under the experimental conditions used in the present study, coastal seawater conditions offered the most favourable summer rearing conditions with respect to the reproductive success of Arctic charr. 相似文献
Marine fish larvae are fragile against physical stress. However, few studies have been conducted to evaluate the flow field in a rearing tank, which is assumed to provide a high degree of physical stress to marine fish larvae. The flow field in a rearing tank (volume of 1 m3) is generated by aerators, which are commonly used to provide oxygen.
This paper is a report on the estimation of stationary flow in the rearing tank of marine fish larvae. The larvae are seven band grouper larvae of Epinephelus septemfasciatus, which have a very low survival rate immediately after the hatching of eggs. The experiments of rearing of seven band grouper larvae were carried out using rearing tanks with four aeration rates (1000, 200, 50 ml/min, and no aeration). The effects of aeration on the survival and floating death of seven band grouper larvae were examined. The experiments confirmed that the mass mortality of seven band grouper larvae depends on the flow rate in the rearing tank. Aeration at 200 ml/min resulted in the highest survival and growth rates of grouper larvae.
Larvae-rearing experiments provided evidence that the flow rates of the rearing tanks are very important design aspects of rearing tanks. The estimation of flow in a rearing tank for an aerating rate of 200 ml/min was carried out by numerical calculation. The computation was simplified by a two-dimensional flow based on experimental results. The calculated flow in the rearing tank was compared with the experimental one. The calculation of the stationary flow in the rearing tank showed good qualitative and quantitative agreement with the experimental results. The numerical estimation of the flow in a rearing tank of marine fish larvae was confirmed to be effective and satisfactory for the design of a tank that would provide optimum performance. 相似文献
The suitability of decapsulated cysts of the fairy shrimp, Streptocephalus dichotomus as a sole diet was evaluated for the ornamental angelfish Pterophylum scalare larvae. Brine shrimp, Artemia sp., and microworms, Panagrellus redivivus, were used as comparison foods. The results indicate an appreciable weight gain of 15.22±1.69 mg and a growth (length) of 0.876±0.03 cm in experimental fish fed decapsulated fairy shrimp cysts compared with the growth and weight of fish fed other foods. The influence of the experimental diets was further reflected in the composition of fatty acid and amino‐acid profiles of the experimental fish. Angelfish larvae readily consumed the decapsulated cysts and utilized them efficiently during the early days of exogenous feeding. 相似文献
Abstract Logistic curves of the average growth in length were elaborated for young-of-the-year perch, Perca fluviatilis L., zander. Stizostedion lucioperca (L.), ruffe, Gymnocephalus cernua (L.), bream, Abramis brama (L.), and roach, Rutilus rutilus (L.), using data from 62 localities. Mean relative deviation from this average growth (MRDAG) is proposed as a simple and reliable indicator of growth rate. The MRDAG for perch, zander, bream and roach showed a significant negative linear relationship with the geographical latitude. 相似文献