The Decline of the Lake Tana (Ethiopia) Fisheries: Causes and Possible Solutions

Abstract

This article reviews major findings of a vast body of scientific studies on the ecology of the fish community and the fisheries in Lake Tana over the past 25 years. There are three commercially important fish taxa in the lake: Nile tilapia, African catfish and Labeobarbus spp. The catch per unit of effort for all the three taxa declined during the last two decades: total catch 177 kg/trip in 1993,140 kg/trip in 2001 and 56 kg/trip in 2010. But the most drastic reduction was observed for the Labeobarbus species: 63 kg/trip in 1993, 28 kg/trip in 2001 and only 6 kg/trip in 2010. Most probably, both recruitment overfishing and increased recession farming contributed to the decline. The migrating Labeobarbus spp. were heavily affected by irrigation and dam constructions causing destruction of breeding and nursery habitats in the spawning rivers. We conclude that implementation of the fisheries legislation gazetted in 2003 and the lake management plan adopted in 2015 is crucial to prevent the collapse of the Lake Tana fishery. Suspended silt from erosion and land degradation, caused by deforestation in the catchment, increased the turbidity of the lake water. The current Maximum Sustainable Yield is approximately 10–20 kg ha−1 y−1, which is low compared to other African lakes. The low productivity seems to be caused both by both light limitation and nutrient limitation. Soil erosion is probably limiting primary production. Appropriate land use management and soil conservation around Lake Tana, such as afforestation and implementing zero‐grazing practices, are urgently needed. Copyright © 2017 John Wiley & Sons, Ltd.

A Drivers-Pressure-State-Impact-Responses Framework to Support the Sustainability of Fish and Fisheries in Lake Tana, Ethiopia

“…In many cases, wastes are discharged indiscriminately into the nearby waterbodies without any treatment, intensifying the Ethiopian water resources problems [90]. This is not different from Lake Tana, Ethiopia's largest lake, where fish communities are rapidly declining due to anthropogenic activities [1,10,11]. Illegal fishing coupled with environmental degradation has already led to drastic stock reduction of the endemic Labeobarbus species.…”

“…The CPUE for the endemic Labeobarbus species has declined from 63 kg/trip in 1993 [80] to 6 kg/trip in 2010 [82]. Likewise, the CPUE for all the commercially important fish including Labeobarbus species has also declined from 177 kg/trip in 1993 to 56 kg/trip in 2010 [10].…”

“…For instance, damming and sand mining are detrimental to spawning grounds of the migratory endemic Labeobarbus species in Lake Tana [11,15]. Moreover, flood recession agriculture is negatively affecting the habitat and nursery sites of many fish species in the lake [10]. Therefore, degradation of these areas could have a large impact on the survival of the fish species in the lake (Table 1) [29,30].…”

GIS modeling of potentially suitable sites for aquaculture development in the Lake Tana basin, Northwest Ethiopia

“…The population density is about 228 people/km 2 , which implies that resources are being severely exploited that in turn leads to eutrophication. This could ultimately cause off-flavor of Nile tilapia, declining of the endemic Labeobarbus fish species, and watershed degradation in the basin [29,30]. The basin is also coined as a biodiversity hotspot because the lake harbors 15 unique species flock of Labeobarbus, the only remained cyprinid species flock in the world [31]; Nile Tilapia and African catfish, which are important aquaculture fish species and are widely cultivated in Africa, are inhabiting with good breeding capability.…”

“…However, the fish resources are highly threatened by fishing pressure. The total catches of commercial interest have been seriously declining during the last two decades, particularly the endemic Labeobarbus fish species [2]. Currently, the annual fish catch in the lake is about 10,000t from which Nile tilapia accounted for more than 50% by volume [3].…”