Production of Australian freshwater crayfish in earthen-based systems using pelleted diets and forage crops as food

Juvenile Cherax destructor (commonly called theyabby) were cultured in earthen-based ponds and tanks for 70–105d, and were fed pellets and/or a forage crop of the perennialwhiteclover, Trifolium repens. Three supplementary feedingstrategies were evaluated. Yabby growth on pellets consistently exceeded (by67–159%) that obtained on clover. Base-line yields for extensiveproduction systems are around 400 kg ha^–1. Thesupplementary addition of T. repens produced yields of 635kg ha^–1 (in ponds) to 1086 kgha^–1 (in tanks). The sequential addition of cut-cloverto tanks stimulated growth to levels approaching those achieved on pellets.Yabbies stocked into ponds at 17 m^–2 and fed 33%protein pellets for 100 d, resulted in a yield of 1117 kgha^–1.Pellet inputs at a rate of 129–249 g m^–2(dry matter) and 38–83 g m^–2 (protein) over70–100 d resulted in acceptable growth and feed utilisationindices. Clover inputs of 534–682 g m–2 (asdry matter) or 84–177 g m^–2 (as protein)produced reasonable growth rates but poor feed utilisation indices. Aconsiderable quantity of the dry matter and protein content of clover waseitherinefficiently utilised or directed into other production pathways. In tanks,clover inputs from 113–296 g m^–2 (drymatter) and 24–54 g m^–2 (protein) weresufficient to maintain high growth rates for 4 weeks, while in ponds, inputs of21 g m^–2 (dry matter) and 4.3 gm^–2 (protein) were sufficient for 3 weeks. During theearly weeks of production no growth advantage was gained by providing pelletstoanimals cultured in forage-based systems. Forage depletion occurred after3–4 weeks and was probably a major growth limiting factor.

Preliminary study on the use of synthetic substrate for juvenile stage production of the yabby, Cherax destructor (Clark) (Decapoda: Parastacidae)

Juvenile Cherax destructor (commonly called the yabby) (mean weight 48.3 mg) were cultured intensively (stocking density 360/m²) under controlled conditions for 48 days. The animals were provided with a combination of food (high protein pellets and/or natural feed organisms attached to a conditioned synthetic substrate) and refuge. Fastest growth and highest yield was recorded when both pellets and the conditioned synthetic material were provided. Although the yabbies sheltered in the synthetic substrate, it did not increase survival. Juvenile yabbies (< 200 mg) were able to graze on small organisms attached to the synthetic material but this ability appeared to decline as the yabbies grew to a larger size. The use of artificial substrates in the intensive nursery phase production of juvenile freshwater crayfish is discussed.

On the production of randomly-oriented recrystallization nuclei for selective growth experiments

The ideal starting condition for selective growth experiments is one having a layer of randomly-oriented nuclei adjacent to a matrix with negligible orientational variation but sufficient stored energy to promote growth. In practice, cutting or deformation processes are used in an attempt to approximate these ideal conditions, but the degree to which this is achieved has not been rigorously quantified. In this work, Fe-3wt%Si single crystals were cut or deformed using six different processes. The variation in texture with distance from the cut or deformed surface was measured using electron backscatter diffraction (EBSD) in a field emission gun scanning electron microscope (FEG-SEM) in order to assess the ability of each process to create conditions suitable for selective growth experiments. While grooving with a machine tool produced the best spread of orientations at the cut surface, the suitability of this process is diminished by the presence of a differently-textured deformed layer between the cut surface and the single crystal matrix. Grinding produced a less ideal distribution of orientations at the cut surface, but the presence of these orientations in a very thin layer adjacent to the matrix makes this process preferable for preparing crystals for selective growth experiments, provided the results are corrected for the deviation in the distribution of nuclei orientations from a random distribution.

Principal selection: homosocialibility, the search for security and the production of normalized principal identities

Researchers investigating the decline of potential applicants for principalships have demonstrated that teachers perceive there to be a significant problem in current selection procedures. This article reports an investigation in two Australian states into principal selection. Drawing on a corpus of interviews, two case studies and administrative guidelines, we highlight five key problems in the interview process: (1) the dependence of selection panels on a written application; (2) the dilemma of experience versus potential; (3) the covert rule about the appointment of preferred applicants; (4) the quandary of panel competency; and (5) the evidence of inconsistency of decisions. We argue that the selection process amounts to a reproductive technology which, in the quest for certainty and safety, results in particular kinds of people being successful. This amounts we suggest, whether the selection process is managed by progressive or conservative personnel, to a form of homosociability the tendency to select people just like oneself.

Photocatalytic production of methane and hydrogen through reduction of carbon dioxide with water using titania pellets

This paper presents an experimental study on employing a pellet form of catalyst in photo-reduction of carbon dioxide with water. Water was first absorbed into titania pellets. Highly purified carbon dioxide gas was then discharged into a reactor containing the wet pellets, which were then illuminated continuously for 65 hours using UVC lamps. Analysing the products accumulated in the reactor confirmed that methane and hydrogen were produced through photo-reduction of carbon dioxide with water. No other hydrocarbons were detected. Increasing the temperature in the reactor has showed little change on the amount of methane produced.

Endogenous production of endo-β-1,4-glucanase by decapod crustaceans

The potential ability to produce cellulase enzymes endogenously was examined in decapods crustaceans including the herbivorous gecarcinid land crabs Gecarcoidea natalis and Discoplax hirtipes, the amphibious freshwater crab Austrothelphusa transversa, the terrestrial hermit crab, Coenobita variabilis the parastacid crayfish Euastacus, and the crayfish Cherax destructor. The midgut gland of both G. natalis and D. hirtipes contained substantial total cellulase activities and activities of the cellulase enzymes endo-β-1,4-glucanase and β-glucosidase. With the exception of total cellulase and β-glucosidase from D. hirtipes, the enzyme activities within the midgut gland were higher than those within the digestive juice. Hence, the enzyme activities appear to reside predominantly within midgut gland, providing indirect evidence for endogenous synthesis of cellulase enzymes by this tissue. A 900 bp cDNA fragment encoding a portion of the endo-β-1,4-glucanase amino acid sequence was amplified by RT-PCR using RNA isolated from the midgut gland of C. destructor, Euastacus, A. transversa and C. variabilis. This provided direct evidence for the endogenous production of endo-β-1,4-glucanase. The 900 bp fragment was also amplified from genomic DNA isolated from the skeletal muscle of G. natalis and D. hirtipes, clearly indicating that the gene encoding endo-β-1,4-glucanase is also present in these two species. As this group of evolutionary diverse crustacean species possesses and expresses the endo-β-1,4-glucanase gene it is likely that decapod crustaceans generally produce cellulases endogenously and are able to digest cellulose.

Effects of the extensive culture system as finishing production strategy on biometric and chemical parameters in rainbow trout

The effect of finishing extensive farming period, to reduce fat content and manipulate the fatty acid profile of fish muscle, was evaluated in rainbow trout. Fish were stocked in an artificial lake, in which fish were fed only on naturally available nutrients with no supply of artificial feed, for different lengths of time from 0 to 120 days. No weight loss was noted during the whole finishing period while total length increased from 228±7 to 269±3 mm and the condition factor decreased from 1.41±0.04 to 0.89±0.02. The total fat content of the fillets decreased considerably from 4.7±0.6% at the beginning to 2.4±0.4% and 0.7±0.2% after 45 and 120 days respectively. Fillet fatty acid composition was affected by the time of stocking in the extensive farm. In contrast to the reduction in C18:1n-9, C18:2n-6, total monounsaturated fatty acid and total n-6 percent values, an increase in the C20:5n-3, C22:6n-3, total polyunsaturated fatty acid and total n-3 percent values was observed. It was shown that while other finishing strategies for salmonids have some disadvantages, the extensive culture system seems to be a potentially useful tool for increasing the general quality of the end product.

Enhancing email text production for users with motor impairments

People with motor impairments who use a switch device to interface with computers have poor access to affordable software for email communication. The MultiMail email package was developed with government support to provide email access solutions for these users and for others with a range of disabilities. In this paper, the development of accessible on-screen keyboards and a word prediction program which facilitates email text production is discussed. Technology solutions were informed by people with disabilities through focus group and survey data. The resulting cross-disability design of MultiMail provides innovative and cost-free solutions to email text production.