Die gesamte Deutsche Akademikerschaft gegen den Bolschemismus

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Comparison of the lipid properties of healthy and pansteatitis‐affected African sharptooth catfish,Clarias gariepinus (Burchell), and the role of diet in pansteatitis outbreaks in the Olifants River in the Kruger National Park,South Africa

Pansteatitis has been identified in wild populations of sharptooth catfish, Clarias gariepinus (Burchell), and Nile crocodiles, Crocodylus niloticus Laurenti, inhabiting the same waters in the Olifants River Gorge in the Kruger National Park, South Africa. Mesenteric and pectoral fat tissue was investigated microscopically and by fatty acid analysis in healthy and pansteatitis‐affected catfish from both captive and wild populations. Variation in fatty acid composition between pectoral and mesenteric fat was noted. Composition of mesenteric fat differed between fish from various localities as a result of differences in diet. Pansteatitis in the captive population, resulting from ingestion of high amounts of dietary oxidized fat, reflected higher levels of unsaturated fatty acids within the mesenteric fat. Mesenteric fat of pansteatitis‐affected wild catfish was characterized by an increase in moisture content, a decrease in fat content and a decrease in stearic and linoleic acids. The n‐3 to n‐6 fatty acid ratio of mesenteric fat was higher in pansteatitis‐affected wild catfish than in healthy catfish from the same locality, reflecting higher polyunsaturated fat intake by pansteatitis‐affected fish. The possible role of alien, invasive, phytoplankton‐feeding silver carp, Hypophthalmichthys molitrix (Valenciennes), in the aetiology of pansteatitis in both catfish and crocodiles in the Olifants Gorge is discussed.     

Advances in hatchery and grow-out technology of cobia Rachycentron canadum (Linnaeus)

This paper describes advances in hatchery and grow‐out technology of cobia (Rachycentron canadum, Linnaeus). In 2007, methods for capture, transport, acclimation, sampling, conditioned spawning, larval rearing, fingerling production, nursery, shipping and grow‐out have been perfected. Survival rates ranging from 17.5% to 35% were achieved from egg to shipping size fingerlings (1.0 g) in 2007 at the University of Miami Experimental Fish Hatchery, with production of approximately 20 000 fingerlings per 12 000 L tank. Wild and F1 broodstock cobia have been conditioned to spawn through temperature manipulation producing viable eggs for experimental and production level larval rearing trials in several hatcheries. Brood fish have also been induced to spawn using hormones. Cobia appear to be susceptible to infestations by parasitic protozoa such as Amyloodinium ocellatum and to infections caused by deleterious bacteria such as Photobacterium spp. and Vibrio spp. Prophylactic methods used to prevent and control epizootic diseases at the hatchery are summarized. Improved techniques for cage management were implemented, and both novel designs of submerged cages deployed in exposed areas and traditional gravity cages in protected areas have been used for commercial ongrowing of cobia in the Americas and the Caribbean region.     

Laboratoriumsuntersuchungen über den Einfluß von konstanten und varrierenden Temperaturen,relativer Luftfeuchtigkeit und Licht auf die Embryonalentwicklung vonPolychrosis botrana

Ohne Zusammenfassung Mit 10 Abbildnngen) (Fortsetzung)     

Exponential growth model of Nile tilapia (Oreochromis niloticus) strains considering heteroscedastic variance

The objective of this research was to evaluate the initial growth of Nile tilapia of Thai and commercial strains, being the latter derived from GIFT program (Genetically Improved Farmed Tilapia). A set of weight/time data to an exponential model had been fitted. The fish were cultivated in cages of 2.7 m³, arranged on a dam of Parque Ecológico Cidade da Criança in Presidente Prudente — SP, Brazil. Each cage received 250 fingerlings of a single strain. With the fish growth, five random samples of 20 fish from each strain were taken, weighed and the model to the adjustment was weighted by inverse weight variances in each sample. The values of the initial weights were overestimated in the unweighted model in relation to the initial means values observed. Although the Thai strain had presented higher estimate of the initial weight than the Commercial strain, it obtained lower growth rate. In the weighted model, this difference in the growth rate was 32.27%, 10.85% bigger than in the unweighted model. In this experiment, this model described adequately the growth of the Thai and Commercial strains. However, it should be applied only with the intention of comparing the species or strains and not as a generalized growth model. The weighted model by the inverse weight variances had the best adjustment, estimates and confidence parameters. In this cultivation form, the Commercial strain can be the most indicated to farmers and resellers that deal with fish up to 200 g.     

Demonstrating the Use of Risk Programming for Aquacultural Farm Management:

A risk programming method that evaluates production plans based on expected income and risk was demonstrated using representative data from Panama. Results illustrate the usefulness of the program in presenting production choices to decision makers and evaluating those choices under changing conditions.
Less experienced or less financially secure farmers may select farm plans that differ quite importantly from those chosen by more experienced or more financially secure farmers. If farm survival is in doubt, more conservative farm plans will generally be adopted. Without consideration of the potential losses, it will often appear that all farmers should pursue the most intensive farm plan within their farming capabilities. However, many farmers will employ less intensive management strategies if the potential for losses associated with more intensive strategies is perceived to be excessive.
The model indicated that management strategies were sensitive to changes in shrimp price and feed cost, but less sensitive to the costs of post larvae or energy. Also, shrimp farm managers should give serious consideration to not producing in the dry season due to relatively high risk and low expected returns. Farmers should be most concerned with quality and availability of post larvae, not price. If hatcheries can address these concerns, the higher price of hatchery post larvae will be justified.