Preliminary observations on the tank and pond culture of the glass eels of the Australian shortfin eel, Anguilla Australis Richardson

There is expanding interest in the culture of the Australian shortfin eel Anguilla australis Richardson; however, there is a lack of fundamental biology and husbandry information necessary to further develop an industry within Australia. The present study was undertaken to gain a preliminary understanding of basic husbandry requirements for rearing of juvenile A. australis (glass eels and elvers) in tanks and earthen ponds. Newly caught glass eels were successfully acclimated to culture conditions. During tank culture trials, specific growth rates (SGR) and survival rates ranged from −2.1 to 2.8% day⁻¹ and 52% to 100% respectively. Glass eels weaned onto a commercial eel diet exhibited a significantly greater SGR and survival rate than those weaned onto a commercial trout diet. Glass eels weaned onto an eel diet over a 15-day period grew slightly faster than eels weaned over a 5-day period, but survival rates were not significantly different for each treatment. SGRs (up to 2.8% day⁻¹) were significantly higher for glass eels fed at 9 and 12% day⁻¹ than at 6% day⁻¹. Stocking densities between 2.5 kg m⁻³ and 30 kg m⁻³ did not influence either SGR or survival rates. SGRs were significantly higher for glass eels cultured at 25 °C than at lower temperatures. During pond culture trials, SGRs and survival rates ranged from 1.36 to 1.65% day⁻¹ and 39% to 77% respectively. The SGR and survival rates of juvenile eels stocked into ponds receiving supplementary feeding with a commercial eel diet were not significantly different to those of eels stocked into ponds that did not receive supplementary feeding.

Citrus peel influences the production of an extracellular naringinase by Staphylococcus xylosus MAK2 in a stirred tank reactor

Staphylococcus xylosus MAK2, Gram-positive coccus, a nonpathogenic member of the coagulase-negative Staphylococcus family was isolated from soil and used to produce naringinase in a stirred tank reactor. An initial medium at pH 5.5 and a cultivation temperature of 30°C was found to be optimal for enzyme production. The addition of Ca⁺² caused stimulation of enzyme activity. The effect of various physico-chemical parameters, such as pH, temperature, agitation, and inducer concentration was studied. The enzyme production was enhanced by the addition of citrus peel powder (CPP) in the optimized medium. A twofold increase in naringinase production was achieved using different technological combinations. The process optimization using technological combinations allowed rapid optimization of large number of variables, which significantly improved enzyme production in a 5-l reactor in 34 h. An increase in sugar concentration (15 gl^-1) in the fermentation medium further increased naringinase production (8.9 IUml^-1) in the bioreactor. Thus, availability of naringinase renders it attractive for potential biotechnological applications in citrus processing industry.

Shared beliefs, expectations and surprises: adaptation decisions of village tank farmers in Sri Lanka

This study examined adaptation decisions of village tank farmers in Sri Lanka, focusing on how commonly held beliefs on local rainfall influence their adaptation choices. Findings suggest that farmers’ have shared beliefs consistent with local pattern of rainfall variability that help to explain short-, medium- and long-term decisions of adaptation.

Evaluation of an evaporation suppressing monolayer system in a controlled wave tank environment: a pilot investigation

Due to long-term drought conditions coupled with the apparent influence of global warming, compounding water loss has been a very serious issue across the vast majority of the Australian continent. During these drought conditions, the evaporative effect outweighs the amount of precipitation being received on a year to year basis. Several methods have been introduced in recent history to inhibit the amount of evaporative loss from various types of water bodies such as the application of thin layer chemical films (monolayers). A series of solvent, solid and suspension derived prototype monolayers, based on ethylene glycol monooctadecyl ether (C18E1), are examined in this current study as an approach to eliminate the problems seen to occur with the previous types of monolayers. This research evaluates the fundamental effect of wind and wave based activity upon these prototype monolayers in an atmospherically controlled enclosure positioned over a large extended water tank using real-time environmental measurements. Selected performance results for the prototype monolayers as measured within the enclosed water tank were compared to results measured from a control monolayer film based on a commonly used octadecanol suspension film. The results show that under varying wind and wave conditions the prototype monolayers inhibit evaporation at a level similar to or better than the octadecanol standard, even when delivered at lower raw dosages.

The "Sensory Deprivation Tank": an interpretative phenomenological analysis of men's expectations of first-time fatherhood

Few studies have investigated expectations of fatherhood in men without children, and none within the age bracket most often associated with new fatherhood. Therefore, the objective of this qualitative study was to gain in-depth understanding of young men's beliefs and perceptions of that role. Interpretative Phenomenological Analysis (IPA) of interview transcripts identified 3 key themes: The contemporary model father, perceived threat to life as we know it, and, the central theme, an unforeseeable future. Analysis revealed that while participants held broad expectations to be emotionally and physically involved as well as economically responsible fathers, their views often lacked specificity, consideration of meaning, and practical notions about how expectations could be fulfilled. We explain the lack of development in men's conceptualization of fatherhood across emerging adulthood through hegemonic masculinity, identity theory, and life course perspectives. The current study provides a rationale for promoting increased discussion around fatherhood in the preconception period to help lessen the turbulent nature of men's transition through pregnancy. (PsycINFO Database Record

Competitive interactions between the Australian native fish Galaxiasmaculatus and the exotic mosquitofish Gambusiaholbrooki,in a series of laboratory experiments

Competitive interactions between Galaxias maculatus, native to southeastern Australia, and Gambusia holbrooki, an exotic pest, were examined in relation to two types of artificial cover and a food source. Experiments were performed in an 800 l tank using photographic techniques. The relative distance of G. maculatus from cover or food source before and after the introduction of G. holbrooki were compared. Also, the proportions of the species were altered to examine the effects of unequal numbers on dominance behaviour. It was found that G. holbrooki was unable to out compete G. maculatus for either cover or food. The distance of G. maculatus from a food source was seen to increase following the introduction of G. holbrooki, when they outnumbered G. maculatus by 3 to 1. Although the distance from the food of G.maculatus increased following the introduction of G. holbrooki, in all cases the mean distance of G.␣maculatus from cover or food was less than that of G. holbrooki. Significant intra-species competition appeared to occur between G. maculatus and it may be that this competition had a greater effect than the competitive pressure G. holbrooki was able to place on the natives. This study revealed that the exotic pest species, G. holbrooki, could not out compete a small native Australian fish species.

Use of plastic and textile media in polishing primary treated effluent

The majority of on-site sewage management systems in Australia fail to perform to expectations. About 60% to 80% of on-site systems reportedly fail to produce acceptable effluent quality, and there is an increaed concern about the risks associated with public health and environmental pollution. In Victoria, a large proportion of septic tank installations have been reported to discharge highly polluted waste to drains and streams. Users, often considered by regulators as operators, have to bear the costs of upgrade/replacement of their old systems to meet stringent water quality guidelines. Some of the common problems include clogging of the disposal fields due to solids and organic overloading and surfacing of highly polluted effluent. Large land application area is subsequently required for irrigating the effluent and/or installation of upgraded disposal fields.
This paper investigates the effectiveness of various types of textile and plastic media, in polishing primary tank effluent, downstream from a typical two-compartment septic tank system. Results to date show that high biochemical oxygen demand removal rates are achieved from the textile and plastic media (up to 86% and 83% respectively). At these removal levels, the performance of a combined conventional septic tank system and plastic/textile filters is comparable to that of an advanced aerated wastewater treatment system. This approach, subject to further investigation, could provide a less costly upgrade.

Induced spawning, larval development and rearing of two indigenous Malaysian mahseer, Tor tambroides and T. douronensis

The Mahseers (Tor spp.) are highly valued freshwater fishes across the Himalayan and South-east Asian regions. Over exploitation of natural stocks because of high demand and the deteriorating environmental conditions have resulted in marked decline of mahseers in the wild. Malaysian mahseers, T. tambroides (Bleeker) and T. douronensis (Valenciennes), locally known as empurau, kelah or belian and semah, respectively, have significant cultural and economic importance but both species are now threatened in the wild because of environmental degradation and over fishing. A captive breeding programme was instigated to attempt to propagate these two species artificially for conservation and aquaculture purposes. Both pond-reared and tank-held T. tambroides and T. douronensis reached sexual maturity in captivity and were successfully induced to spawn using hormone treatments. Ovaprim (0.5 mL kg⁻¹) was the most successful hormone treatment for both species. Pre-treatment of fish with Ovaplant (28–68 μg kg⁻¹, 2–7 weeks before spawning induction) greatly improved the success rate of spawning induction. Repeat spawning (within 4 months of initial spawning) was induced in some captive fish. Use of formalin baths improved hatching by preventing fungal infections. Embryonic development and hatching are described. Juveniles were reared in static greenwater ponds. Tor tambroides reached 142–179 g (max 270 g) in 60 weeks. These results represent the first successful captive spawning and rearing of both species. Options for future research to improve production are discussed.

Solar heating systems for recirculation aquaculture

The literature over the past 25 years indicates that there has been a continued interest in using passive and active solar technologies to reduce the conventional energy required to maintain water temperatures in small recirculation aquaculture systems. Although all of the experimental systems reviewed report favourable results, there is little information available to guide system designers. This paper describes the use of a simulation model to predict the annual conventional energy consumption of a 10.6 m3 RAS enclosed in a double layer polyethylene greenhouse in two different climates. The water was maintained at 22.5 °C and the recirculation rate was 10% of tank volume per day. Simple unglazed solar collectors have also been combined with the greenhouse to further reduce energy consumption. The effect of increasing collector area on the solar fraction and utilization of useful energy was predicted. Finally, the model was used to investigate the relationship between the occurrence of condensation on the inner cover, ventilation rates and energy use. It was found that in a hot dry climate, the greenhouse alone was sufficient to reduce the conventional energy requirements by 87%; while in the cooler temperate climate reductions of 66% were possible. When solar collectors were added to the system, conventional energy requirements were reduced further and depended on the area of collector used. For example, in the temperate climate location, conventional energy requirements were reduced to 23% of a RAS enclosed in a non-solar building when 26 m2 of solar collector inclined at the optimum angle for winter energy collection were used. Although condensation could be successfully reduced by ventilation of the greenhouse, this increased conventional energy requirements because the potential for evaporation was increased. Covering the tanks at night was found to be a more effective strategy because it reduced condensation and conventional energy use simultaneously.

Domestic drinking water in rural areas : are water tanks on farms a health hazard?

The aim of the research was to gain a better understanding of the relationship between drinking water quality, householders' knowledge and maintenance practices of private water supplies and drinking water-related public health risk on farms. Samples of drinking water were taken from 100 farming households. The Colilert-18 method was used for the detection of total coliforms and Escherichia coli (E. coli) as indicators of water quality. Each household completed a questionnaire about their knowledge and practices relating to a safe water supply. Coliforms were present in 52 water samples and E. coli was present in 38. Seven households reported minor illnesses in the previous three months and two households reported gastroenteritis. Some tank maintenance occurred in 86 households, but tank maintenance activities varied considerably. Four of the households had published guidelines on water quality. None of the participating households had their drinking water tested regularly. There was no obvious relationship between drinking water quality, householder knowledge, maintenance practices and drinking water-related health risk on farms.

Design and simulation of an interdigital-chaotic advection micromixer for lab-on-a-chip applications

This paper presents the design and simulation of a novel passive micromixer. The micromixer consists of two inlet tanks, one mixing channel and two outlet channels. In order to maximise the mixing efficiency, the following considerations are made: (i) The inlet tanks are followed by a series of microchannels, in which the flow is split. The microchannels are arranged in an interdigital manner to maximise the contact area between the two flows. (ii) The microchannels attached to the lower inlet tank have an upward slope while those attached to the upper tank have a downward slope. The higher-density flow is fed to the lower inlet tank and gets an upward velocity before entering the mixing channel. (iii) Two triangular barriers are placed within the mixing channel to impose chaotic advection and perturb the less-mixed flow along the top and bottom surfaces of the channel. (iv) Finally, two outlet channels are incorporated to discard the less-mixed flow. Three-dimensional simulations are carried out to evaluate the performance of the micromixer. Simulations are performed in the absence and presence of the gravitational force to analyse the influence of gravity on the micromixer. Mixing efficiencies of greater than 92% are achieved using water and a 1011'density biological solvent as the mixing fluids.

Optimization of medium and process parameters for the production of inulinase from a newly isolated Kluyveromyces marxianus YS-1

A newly isolated strain of Kluyveromyces marxianus YS-1 was used for the production of extra cellular inulinase in a medium containing inulin, meat extract, CaCl₂ and sodium dodecyl sulphate (SDS). Fermentation medium pH 6.5, cultivation temperature 30 °C and 5% (v/v) inoculum of 12 h-old culture were optimal for enzyme production (30.8 IU/ml) with a fermentation time of 72 h at shake flask level. Raw inulin (2%, w/v) extracted from dahlia tubers by processing at 15 kg/cm² for 10 min was optimum for bioreactor studies. Maximum enzyme production (55.4 IU/ml) was obtained at an agitation rate of 200 rpm and aeration of 0.75 vvm in a stirred tank reactor with a fermentation time of 60 h.