Modeling the potential of periphyton based fish production in pond culture system

To evaluate the potential of fish production from Periphyton-based aquaculture system, a simple dynamic simulation model was constructed. The model consists of three state variables, periphyton biomass (PB; g), fish biomass (FB; g) and nutrient stock and six rate variables (nutrient inflow, nutrient uptake by periphyton, periphyton grazing by fish, periphyton degradation rate, fish harvesting and mortality rates). In the model, it was assumed that PB is minimum before fish were stocked and that fish grazing would cease whenever PB would be lower than that minimum biomass. This model was implemented in Stella 8 and run with a time- step of 0.05 day. Parameter values were derived from the literature. We assumed a maximum periphyton density of 100 g dm m-2. PBmax was derived from this value by multiplying with the substrate area. Simulated PB increased from 10 g m-2 initially to 100 g m-2 after 24 days. Before day 30, periphyton productivity was greater than the consumption of the periphyton by fish. After day 105, fish grazing exceeded periphyton productivity as a result of increased FB and PB decreased steadily until reaching a value of about 75 g m-2 on day 182. The scenario in the model also showed that the optimum application rate of nutrient is at 15 g m-2 urea per two weeks. In the model a 1:1 ratio of substrate area to pond size tends to produce larger FB which was 1000 kg ha-1. Therefore, periphyton can increase the productivity and efficiency of aquaculture systems; however more research is needed for optimization

First limnological records of highly threatened tropical high-mountain crater lakes in Ethiopia

Lakes Dendi, Wonchi and Ziqualla are among the few remnants of undisturbed crater lakes in the central highlands of Ethiopia, and have never been investigated reliably owing to seclusion and inaccessibility. As the lakes offer a pristine environment in a beautiful landscape and are located in the vicinity of the capital city Addis Ababa, they are highly threatened by unsustainable tourism, shoreline and crater rim modifications, water abstraction and land grabbing. We provide a first limnological description to establish baseline data against which future environmental and biological changes can be monitored. The lakes are located above 2,800 m elevation with no surface outflow and generally show low concentrations of ions, displaying an equal distribution of readily soluble components like Na or K throughout the water column, but distinct oxygen depletion in greater depths linked to rising concentrations of Fe and Mn, which indicates subterranean springs. Based on nutrients, chlorophyll a, and water transparency, lakes Dendi and Wonchi are classified as oligotrophic and Ziqualla as oligo-mesotrophic. The phytoplankton community is dominated by coccal green algae, desmids and dinoflagellates in lakes Dendi and Wonchi, typical for unpolluted dilute waterbodies; whereas chlorococcales, in particular Botryococcus braunii and benthic diatoms, prevail in Ziqualla. The zooplankton fauna is depauperate, comprising a total of 11 rotifer taxa and 13 crustaceans. Copepods were the most abundant group and contributed over 60% to the total zooplankton abundance in all three lakes, followed by rotifers and cladocerans. The conservation significance of these lakes lies predominantly in their representation of dilute, nutrient–poor highland lake systems that support diverse biota assemblages like desmids and daphnids, which are highly sensitive to eutrophication

Effect of supplementary feeding of agro-industrial byproducts on the growth performance of Nile tilapia (Oreochromis niloticus L.) in concrete ponds

This study was conducted to evaluate the effect of supplementary feeding of wheat bran, noug cake and brewery waste on the growth of Oreochromis niloticus in concrete ponds. The feeding trial was conducted in eight concrete ponds of about 50 m2 each. The control and experimental groups were run in duplicate with stocking density of 2 fish/m2. The treatment groups were fed at 5% of their body weight with the respective test feeds and the control group was left to feed on endogenous phytoplankton diet. The results of the experiment showed that fish given supplemental diets grew much faster (ANOVA, P<0.001) than the control group. Although no significant growth differences were observed between the test feeds (ANOVA, p=0.81), fish raised in brewery waste (0.4 g/day) and noug cake (0.37 g/day) showed better growth rate than wheat bran (0.34 g/day). Differences in growth rates between the control and test feeds as well as among the test feeds can be attributed to both direct and indirect effects of supplementary feeds given to the fish. Direct intake of feeds by the fish provides more nutrients resulting in better growth and production. Moreover, addition of supplementary feeds can elevate the level of organic nutrients that favour the growth of flagellate phytoplankton which are good quality food for the fish. We therefore concluded that all supplementary feeds nearly doubled the growth of O. niloticus in ponds. In addition to feed ingredients, information on digestibility, palatability and levels of anti-nutritional substances should be determined under different agro-ecological conditions. Keywords/phrases: Agro-industrial byproducts, Growth, Oreochromis niloticus, Phytoplankton, Pond experiment, Production, Supplementary feedsEthiop. J. Biol. Sci. 11(1): 29-41, 201

Prevalence of high bloodpressure, hyperglycemia, dyslipidemia, metabolic syndrome and their determinants in Ethiopia: Evidences from the National NCDs STEPS Survey, 2015

<div><p>The prevalence of diabetes, dyslipidemias, and high blood pressure is increasing worldwide especially in low and middle income countries. World Health Organization has emphasized the importance of the assessment of the magnitude of the specific disease in each country. We determined the prevalence and determinant factors of high blood pressure, hyperglycemia, dyslipidemias and metabolic syndrome in Ethiopia. A community based survey was conducted from -April to June 2015 using WHO NCD STEPS instrument version 3.1. 2008. Multistage stratified systemic random sampling was used to select representative samples from 9 regions of the country. A total of 10,260 people aged 15–69 years participated in the study. Blood pressure (BP) was measured for 9788 individuals. A total of 9141 people underwent metabolic screening. The prevalence of raised blood pressure (SBP ≥140 and/or DBP ≥ 90 mmHg) was 15.8% (16.3% in females and 15.5% in males). The prevalence of diabetes mellitus (FBS ≥ 126 mg /dl) including those on medication was 3.2% (3.5% males and 3.0% females). The prevalence of impaired fasting glucose was 9.1% with ADA criteria and 3.8% with WHO criteria. Hypercholesterolemia was found in 5.2%, hypertriglyceridemia in 21.0%, high LDL cholesterol occurred in 14.1% and low HDL cholesterol occurred in 68.7%. The prevalence of metabolic syndrome using IDF definition was 4.8% (8.6% in females and vs. 1.8% in males). Advanced age, urban residence, lack of physical exercise, raised waist circumference, raised waist hip ratio, overweight or obesity, and total blood cholesterol were significantly associated with raised blood pressure (BP) and diabetes mellitus. Increased waist- hip ratio was an independent predictor of raised blood pressure, hyperglycemia and raised total cholesterol. Our study showed significantly high prevalence of raised blood pressure, hyperglycemia and dyslipidemia in Ethiopia. Community based interventions are recommended to control these risk factors.</p></div

Prevalence of raised blood pressure, hyperglycemia and their determinants, WHO STEPs study, 2015, Ethiopia.

<p>Prevalence of raised blood pressure, hyperglycemia and their determinants, WHO STEPs study, 2015, Ethiopia.</p

Mean and SD values of total cholesterol, blood glucose, diastolic and systolic blood pressure, Ethiopia NCD steps, 2015.

<p>Mean and SD values of total cholesterol, blood glucose, diastolic and systolic blood pressure, Ethiopia NCD steps, 2015.</p

Prevalence of dyslipidemia, WHO STEPS survey, Ethiopia 2015.

<p>Prevalence of dyslipidemia, WHO STEPS survey, Ethiopia 2015.</p

Prevalence of raised total cholesterol level and metabolic syndrome, and their determinants WHO STEPS survey, Ethiopia 2015.

<p>Prevalence of raised total cholesterol level and metabolic syndrome, and their determinants WHO STEPS survey, Ethiopia 2015.</p

Bivariate and multivariate analyses of demographic and clinical risk factors for raised blood pressure, raised blood sugar, raised total cholesterol level, Ethiopia NCD Steps 2015.

<p>Bivariate and multivariate analyses of demographic and clinical risk factors for raised blood pressure, raised blood sugar, raised total cholesterol level, Ethiopia NCD Steps 2015.</p