In Ethiopia, particularly in Tana Sub-Basin, irrigation development practice is increasing. However, this development ignored the fisheries; no, enough information about its effects. The sub-basin is rich in fisheries, including the 17 Labeobarbus species (the only remaining cyprinid species in the world). The fishery is also supporting over 6000 fishers. Hence, this study investigated the impact of irrigation practices on the Gilgel Abay, Ribb, and Gumara fisheries. Methods include fish sampling below and above the weirs, expert interviews, key informant interviews, secondary data, and impact significance matrix methods. The data collection time was from July 2019 to June 2020. The analysis of the data was qualitative and quantitative. The existing irrigation system affects fisheries by blocking upstream spawning migration routes (Gilgel Abay Weir and Ribb Dam, for sure catch below the Gilgel Abay Weir, significantly higher than above the weir, Shannon Index (H’), P < 0.001). Besides, according to local sources, after 2007, Gumara and Ribb Rivers became seasonal because of excessive water abstraction for irrigation, resulting in mass fish-killing and the failure of juvenile recruitment to the lake. In one instance, we recorded the deaths of over 930 adults and juveniles on the Gumara and the Ribb Rivers. Succeeding low water volume, even non-fishers collect fish from the pools; and during spawning time, fishers target spawning migratory species at the weirs where the catch is prime is also the other problem. Other threatening elements can also aggravate the impact. Hence, these impacts need to be ameliorated by practicing efficacious water use, catchment treatment, fishery management, fish ladder development, and factor alleviation can be solutions.

Sand and gravel materials are often used in Ethiopia's construction sector. However, the impacts of sand mining on the water body's habitat and biodiversity are not yet considered in the country. In this paper, we study how sand mining activities at Lake Tana and its inflowing rivers affect the environment and spawning grounds of the endemic Labeobarbus species. We measured physicochemical parameters in-situ and developed structured questionnaires to collect primary data on the fishery and sand mining. We found significant differences in conductivity, total dissolved solids and temperature among sampling sites (P < 0.05). Majority (>90 per cent) of the respondents confirmed the drastic physical changes in the rivers and a severe decline in fish production. The study revealed that the ecology of the mined rivers was seriously affected by sand mining, which interfered with migratory routes of fishes and resulted in loss of their spawning grounds. The unregulated sand mining also conflicted with the interests of the fisheries management and environment. Thus, urgent policy intervention is needed to protect the ever-declining Labeobarbus species of Lake Tana and the environment.

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.

This study investigated a possible cause of the low eyed-egg percentage that has occurred recently in pond-reared masu salmon Oncorhynchus masou, at the Kumaishi Fish Hatchery Station, Hokkaido, Japan. Serum cortisol levels of masu salmon during the spawning period were compared between individuals from Kumaishi and those from another station (Mori). Cortisol, thyroxine (T 4 ) and triiodothyronine (T 3 ) hormones were also measured in eyed eggs and their levels were compared to the eyed-egg percentage.Serum cortisol levels were significantly higher at Kumaishi than at Mori. There was a good relationship between serum cortisol and fertilized eggs cortisol levels. As cortisol levels in both ovulated females and in the eyed eggs increased, the eyed-egg percentage decreased, indicating a highly significant negative relationship between cortisol levels and eyed-egg percentage. In contrast, as the T 3 and T 4 levels in eyed eggs increased, the eyed-egg percentage increased. The consistently high cortisol level in serum and eyed eggs observed at Kumaishi may have had a significant effect in lowering the eyed-egg percentage.

Environmental Impact of pump irrigation projects from Lake Tana (Megech - Seraba, Tana Asrate, Tana Mekonta, Tana Wenjeta, and Tana Zegie) was studied from July 2018 to February 2019. Interactions between project activities and environmental parameters were also done by a matrix, and quantitative and qualitative analysis. As a result, identified positive impacts are new job creation, the opportunity to promote traditional agriculture and income increase, whereas land, fisheries and wetland degradation, pollution, deforestation and wildlife, inefficient water use, the decline in soil fertility, erosion, sedimentation, small aquatic animal death, and cumulative impacts are negative ones. Mitigation measures for these impacts to reduce their effects to the minimum level and recommendations have been proposed so that the execution of the projects becomes a success without harming or with the least negative effect on the environment.