Spawning migration of Labeobarbus species was studied from August to December 2013 in some tributary rivers (Qimon, Guanta, Shini, and Chibirna) of Lake Tana. Fish specimens and physico-chemical parameters were measured bimonthly in August and September but monthly from October to December. Adult fish specimens were caught using 6 and 8 cm stretched mesh size monofilament gillnets and 6, 8, 10 and 12 cm mesh size multifilament gillnets. A total of 933 adult Labeobarbus specimens were collected during the study period. Labeobarbus intermedius was the most abundant species followed by L. brevicephalus. The peak spawning season of L. intermedius was from fourth week of August to end of September and for L. brevicephalus it was from fourth week of August to beginning of October. Both species were found to spawn in all sampling rivers. However L. truttiformis spawned only at Guanta and Qimon Rivers during August while L. nedgia in Shini and Chibirna Rivers at the end of September. This implies the presence of micro-spatial segregation among species. Pair-wise comparison of Labeobarbus species showed temporal segregation in all sampling months, except L. brevicephalus and L. nedgia. The present findings showed that small tributary rivers and streams are the main spawning grounds for Labeobarbus species of Lake Tana. Therefore, main spawning grounds or routes should be protected from the deleterious effects of anthropogenic activities like illegal fishing, irrigation and sand mining for wise use of the fish resources.

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The purpose of this study was to determine the concentration of heavy metals in Lake Hayq water and fish muscles samples during dry and wet seasons. Samples of fish organs and water were collected from four sampling sites of Lake Hayq. An optimal procedure required 8 mL of (69%) HNO3 and 6 mL of (30%) H2O2 to mineralize powdered samples in open refluxed digestion vessels: 0.5 g of the fish body for 2:30 hrs at temperature of 130oc.Concentrations of six metals (Pb, Ni, Zn, Cd, Cu and Cr) in water and their accumulation in the edible tissue of Nile Tilapia were determined by FAAS. The results revealed that the average heavy metal concentrations in water samples were; Pb (0.006), Ni (0.018), Zn (0.083), Cd (0.004), Cu (0.1) and Cr (0.003) mg/L in the lake. The average concentration of heavy metals in fish samples were; Pb (2.02), Ni (2.29), Zn (55.52), Cd (1.57), Cu (11.18) and Cr (0.745) mg/Kg. Among the detected metals, zinc (Zn) showed a maximum accumulation in the edible muscle of Nile Tilapia fish from Lake Hayq. The concentrations of the metals (Pb, Zn, Cd, and Cu) were below the recommended limit by WHO, USEPA and FAO. For fish the highest accumulations of nickel (Ni) and chromium (Cr) concentration were observed above the recommended limit by FAO/ WHO. Application of the statistical t-test on heavy metal analysis has shown that there was no significant difference between fish as well as water samples of the lake for all sites.Contribution/Originality: The paper's primary contributions is finding the pollution of the aquatic environment of heavy metals water and fish muscles samples during dry and wet seasons and produce an information of edible fish quality by standards of WHO/FAO, especially concern in South Wollo, Lake Hayq.There are more than ten heavy metals such as cobalt (Co), lead (Pb), mercury (Hg), arsenic (As), thallium (Ti), nickel (Ni),manganese (Mn), zinc (Zn), cadmium (Cd) and chromium (Cr) that have a particular significance in ecotoxicology [5]. Some heavy metals such as copper (Cu), zinc (Zn), iron (Fe), chromium (Cr), manganese (Mn) and nickel (Ni) though essential to human body, are toxic at elevated levels, whereas cadmium (Cd) and lead (Pb) are non-essential metals and are toxic even in trace amounts. Toxicity is highly aggravated by their nondegradability and tendency to bio-accumulate to toxic levels [6]. Heavy metal toxicity can result in lower levels

Contribution/Originality: This study used to contributes in the existing literature to review environmental problem related with domestic, industrial and municipal waste management. This study shows limitation of wastewater treatment using oxidation pond. The primary contribution of this finding is to determine the quality of effluent wastewater to recommend better removal efficiency oxidation pond. INTRODUCTIONWater is an essential component for life on Earth, which contains minerals extremely important in human nutrition and also water is an invaluable resource to man and living things, essential for the sustenance of life (Al Nahyan, 2012). Water is a universal solvent essential to man for various activities such as drinking, cooking, industrial, hydropower, agricultural processes, waste disposal and human recreation. Most wastes contain organic solids, trace heavy metals, salts, bacteria, viruses, other microorganisms and sediment. Well water can be polluted