Earthworm,Eisenia fetida,bedding meal as potential cheap fishmeal replacement ingredient for semi‐intensive farming of Nile Tilapia,Oreochromis niloticus

The study amalgamated earthworm and agro‐industrial wastes through vermicomposting and then evaluated the potential of the bedding (mixture of Eisenia fetida and vermicompost) to replace fishmeal in semi‐intensive farming of Oreochromis niloticus. The bedding was used to substitute fishmeal at inclusion rates of 100, 60, 30 and 0% (D100, D60, D30 and control D0). In triplicates, the four homogeneous diets were fed to quadruplicate groups of 30 g O. niloticus for 112 days. There was no significant difference (p > .05) in mortalities, average length gain and FCR among all tests. Nevertheless, diet D0 had significantly (p < .05) superior amino acid profile, low fibre content and fish carcass crude protein (63.2 ± 0.72% dry matter). Subsequently, D30 and D0 produced fish with significantly higher (p < .05) mean weight gain (256.03 ± 0.4 g) and biomass (369,136 g) respectively. On to the contrary, diet D100 had significantly higher (p < .05) crude lipids content (9.4 ± 0.6% dry matter), economic returns and profit index than the control diet due to the comparatively low cost of producing the earthworm bedding. This simple biotechnology can commercially be upscaled to sustainably produce cheap and nutritious fish feed capable of increasing yields and maximizing profits.     

Predictive thresholds for plague in Kazakhstan

In Kazakhstan and elsewhere in central Asia, the bacterium Yersinia pestis circulates in natural populations of gerbils, which are the source of human cases of bubonic plague. Our analysis of field data collected between 1955 and 1996 shows that plague invades, fades out, and reinvades in response to fluctuations in the abundance of its main reservoir host, the great gerbil (Rhombomys opimus). This is a rare empirical example of the two types of abundance thresholds for infectious disease-invasion and persistence- operating in a single wildlife population. We parameterized predictive models that should reduce the costs of plague surveillance in central Asia and thereby encourage its continuance.     

Influence of pond fertilization and feeding rate on growth performance, economic returns and water quality in a small-scale cage-cum-pond integrated system for production of Nile tilapia (Oreochromis niloticus L.)

The effects of pond fertilization and feeding rate on growth, economic returns and water quality were investigated to develop a low‐cost cage‐cum‐pond integrated system for production of Oreochromis niloticus (L.). Hand‐sexed male fingerlings averaging 19±0.39 and 32±0.69 g were stocked in cages and open ponds at 150 fish cage^?1 and 2 fish m^?2 respectively. Fish were cultured for 114 days in five triplicate treatments. Cages were installed into ponds and caged fish were fed a 24% protein diet at 3% (T1) and 6% (T2) body weight day^?1 (BWD) without pond fertilization, and 6% BWD with pond fertilization (T3). The open water in the fourth treatment (T4) was not stocked but contained caged fish, which were fed 6% BWD for the first 57 days followed by 3% BWD for the remaining period. Ponds in the control (T5) had no cages and were neither fertilized nor open‐pond fish fed. Feeding rate and pond fertilization significantly (P<0.05) affected fish growth, profitability and water quality among treatments. Fish growth, feed utilization, fish yield, water quality and profits were significantly (P<0.05) better in T3 than the other treatments. It was concluded that fish production and economic returns were optimized at 6% BWD in fertilized ponds.     

Population ecology and prey consumption by fathead minnows in prairie wetlands: importance of detritus and larval fish

Abstract –  The fathead minnow Pimephales promelas occurs in high densities in wetlands of the prairie pothole region (PPR) of North America, but food resources sustaining these populations are poorly known. We assessed population dynamics and prey consumption of fathead minnow populations in three PPR wetlands for 2 years. Fish density peaked at 107 fish per m² for all age classes combined. Larval and juvenile fish dominated these populations in terms of abundance and accounted for 83% of total prey consumption. Detritus dominated fish diets, representing 53%, 40% and 79% of diet mass for larval, juvenile and adult fish respectively. Detritus consumption was positively related to minnow density and negatively related to invertebrate abundance, but only for adult fish. Seasonal production:biomass ratios were unrelated to proportions of detritus in the diet for all ages of fish, indicating that detritus is an important food resource capable of meeting metabolic demands and sustaining fish growth in high-density populations. Detritus consumption may also weaken links between abundance of invertebrate prey and minnows, promoting dense fish populations with strong, consistent influences on wetland ecosystems.     

Effects of partial and complete replacement of freshwater shrimp meal (Caridinea niloticus Roux) with a mixture of plant protein sources on growth performance of Nile tilapia (Oreochromis niloticus L.) in fertilized ponds

Despite the well‐documented herbivorous food habits, commercial feeds for production of Oreochromis niloticus usually contain between 7% and 15% animal protein. However, animal protein feedstuffs are expensive, hence the need to search for cost‐effective alternatives in plant‐protein sources. Such alternatives are probably more effective in semi‐intensive systems where natural pond food forms part of the diet. This study evaluated the performance of O. niloticus after feeding diets in which fresh shrimp meal (SM) was gradually replaced by a mixture of plant‐protein sources in fertilized ponds. Three isonitronegenous (24% crude protein) diets containing 12 (control), 6% and 0% SM were fed to three groups of O. niloticus in four replicates per group for 250 days. Fish were fed daily at 2% body weight and sampled monthly to monitor growth and make feed adjustments. Growth, yields, survival and feed conversion ratio were not significantly different (P>0.05) among treatments. Growth of males was double that of females, while the sex ratio was skewed towards females. Although complete substitution of SM by plant protein did not affect the growth of tilapia, production cost was reduced by 36%. In conclusion, animal protein is not required in diets for production of O. niloticus in fertilized ponds.     

Der Einfluß isoosmotischer Lutrol- und Salzlösungen auf die Chlorophyllkonzentration und das Chlorophyll-a/b-Verhältnis bei Phaseolus vulgaris

The influence of isoosmotic Lutrol- and salt solutions upon the chlorophyll-concentration and chlorophyll a/b ratio of Phaseolus vulgaris The behaviour of the chlorophyll status of Phaseolus vulgaris was studied under the influence of different isoosmotic Lutrol and salt solutions in the root medium. Phaseolus seedlings, 12 days old, were raised in a nutrient solution containing isoosmotic concentrations of 0.54 (control); 1.26; 2.82 and 4.68 atm. created by either Lutrol or salts (40% chlorine, 60% sulfate). An increase in the osmotic pressure of the primary and normal leaves generally paralleled the increase in the osmotic pressure of the media with a more pronounced effect in the case of salts than in Lutrol. Mean values of osmotic pressure of both primary and normal leaves during the sampling period were 6.19; 10.35 and 12.98 atm. for control, Lutrol III and salt III respectively. Increasing the osmotic pressure of the media due to salts resulted in a significant decrease of the chlorophyll content of primary leaves (mean value during the sampling period: Cont.: 19.8 μg/cm²; salt II: 12.7 μ/cm²; salt III: 6.3 μg/cm²), accompanied with a decreasing tendency in the chlorophyll a/b ratio. Such effect was only detectable in the case of the highest Lutrol concentration at the end of the experiment. However, the mean values of the sampling period did not show any significant variation from those of controls (Lutrol II: 18.9 μg/cm²; Lutrol III: 16.1 μg/cm²). Both types of osmoticum decreased remarkably the total chlorophyll amount of normal leaves. This behaviour resulted more clearly from a reduction in the leaf area than from the decrease in the chlorophyll concentration. The mechanism of plant response to changes in the osmotic pressure of the medium seemed to depend mainly on the type of osmoticum affecting such variations. In general the changes in the osmotic pressure created by salts affected both mature and developing leaves i.e. primary and normal leaves respectively, whereas such changes in the case of Lutrol affected mainly the latter organs.     

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Waste management in recirculating aquaculture system through bacteria dissimilation and plant assimilation

Wastewater management and disposal in aquaculture is becoming increasingly important due to stringent water regulations regarding waste discharges into natural water systems. Recirculation aquaculture is one of the technologies designed to reduce waste discharge through the nitrification process. However, nitrification results in nitrate accumulation which is normally reduced by dilution through water exchange. Water exchange is only possible with sufficient water. Although nitrification is a conventional process, it has limitations because the autotrophic bacteria require long start-up and multiplication periods. The nitrifiers require high levels of oxygen with relatively higher aeration costs. Moreover, the bacteria are sensitive to rapid changes in pH, temperature, and flow rate. Denitrification can be a solution to the limitations of nitrification since denitrifiers are most abundant in the natural environment and have higher growth rates than nitrifiers. In addition, the process reduces energy costs since there is no need for aeration, water consumption is also reduced drastically since water exchange is minimized. Organic loading can be reduced when fish waste is utilized as a carbon source. An alternative process to manage aquaculture wastes is through anaerobic ammonium oxidation (anammox), where ammonia and nitrite are converted into nitrogen gas. Anammox can efficiently reduce ammonia and nitrites from culture water, but it has not received wide application in aquaculture. Aquaculture wastewater contains nutrients which are essential for plant growth. The plants maintain good water quality by absorbing the dissolved nutrients. Denitrification, anammox, and nutrient uptake by plants are feasible strategies to reduce wastes from aquaculture effluents.     

Population viability risk management (PVRM) for in situ management of endangered tree species—A case study on a Taxus baccata L. population

Population viability risk management (PVRM) provides a framework for explicitly including qualitative information about the possible outcomes of a management decision with regard to the viability of an endangered population in conservation management. Multi-criteria decision-making (MCDM) techniques enables managers to select the most preferred choice of action in a context where several criteria apply simultaneously. In that context a combined approach of the PVRM concept and a MCDM technique is presented for the development, evaluation and finally ranking of the in situ conservation strategies. We discuss the concept based on a case study for the maintenance of a gene conservation forest of an English yew population (Taxus baccata L.) in Styria, Austria. As part of the PVRM the analytic hierarchy process (AHP) is used to evaluate six conservation strategies with regard to the viability of the yew population. The viability of the population is evaluated based on the results of an analysis of the current environmental, social and economical state and a characterization of the ecological parameters of its population. The most significant risk factors (illegal cutting, browsing by game, tree competition, light availability and genetic sustainability) are structured and prioritised according to their impact on the viability of the yew population applying the AHP. Effects of the six conservation strategies on the viability of the yew population are determined through a qualitative assessment of the probability of a decrease of the population along with four different environmental scenarios. In this context strategy IV combining selective thinning, protection measures, game control with public relation activities seems to be the most effective alternative. The benefits of the combined approach of the PVRM concept with the AHP for the rational analysis of conservation strategies for this endangered tree species are discussed.     

Farmers' perspectives of rodent damage and management from the highlands of Tigray,Northern Ethiopian

A farmers' knowledge, attitude and practice (KAP) survey was conducted in the highlands of Tigray, northern Ethiopia, to better understand rodent damage and rodent management from the farmers' perspective. Farmers (n = 191) from Dogu'a Temben district, were interviewed using a semi-structured questionnaire. The large majority of the farmers stated that rodents are the main pests in crop fields (92.1%) and storage (88.5%). The farmers (64.2%) reported they experienced 100–500 kg ha⁻¹ damage in crop fields, which is equivalent to 8.9–44.7% loss in annual production. There was some overlap between the most common crops grown in the highlands and the most common crops susceptible to rodent attack. Farmers identified barley as the crop most susceptible to rodent attack (76.4%) and the booting stage as the crop developmental stage with the highest rodent abundance and damage. Rodenticide application was the most commonly practiced management strategy in crop fields (51.8%); in storage, farmers mainly keep domestic cats around granaries (80.6%). We recommend a reduction in reliance on chemical rodenticide in crop fields and a shift to a more sustainable rodent management approach to reduce rodent numbers and damage.