Survey on diversity, relative abundance and hydrology of fishes in Ayima, Alatish and Gelegu Rivers, of Alatish National Park, Ethiopia

Ethiopia could be called a water tower of Eastern Africa in a continent where its most part is arid. The inland water body of Ethiopia is estimated at about 7,400km2 of lake area and about 7,000km total length of rivers [1]. These water bodies contain large population of commercially important fi sh species. However, the territory of Ethiopia seems to be among regions of the African continent which are least explored in icthyofauna perspectives [2].


Introduction
Ethiopia could be called a water tower of Eastern Africa in a continent where its most part is arid. The inland water body of Ethiopia is estimated at about 7,400km 2 of lake area and about 7,000km total length of rivers [1]. These water bodies contain large population of commercially important fi sh species. However, the territory of Ethiopia seems to be among regions of the African continent which are least explored in icthyofauna perspectives [2].
For conservation and sustainable utilization of biological resources acquiring knowledge and developing skills and systems of conservation and proper utilization is indispensable.
Strategically approaches for conservation and proper utilization process start in stocking and inventory of biological resource, inventory and assessment of root courses problems and option analysis of spatial integrity. However, assessment and conservation effort so far applied are minimal and many areas with diverse biological resources are not well known. Hence, this rapid assessment was targeted to identify hydrological issues of different rivers and icthyofauna of Alatish National park.

Study areas
Gelegu town is a capital of Quara woreda in northern Gondar administrative zone in the west direction from Shinfa town at 62 km distance. Selferede, Dubaba and Gelegu Rivers are rivers, which are potentially rich in fi sh that are found across the main road from Shinfa to Gelegu town (Quara woreda). It needs further investigation of fi sh stocks in these rivers. For this these rapid assessment rivers in Alatish and its bordering area assessed, potential and threats identifi ed.
One of most impressing and unique characteristics of Alatish National Park (ALNP) is its hydrological system.

Materials and methods
Data on fi shing activities at the study areas were collected based on interview of fi shermen while they were fi shing, processing and marketing. Data were collected in two seasons: the wet season (Just after the rainy season that means October, 2008 and the dry season that means January, 2009. Each site was sampled two times (one times in the wet season and one times in the dry season). Samples were collected using gillnets of various mesh sizes (6cm, 8cm, 10cm, 12cm and 14cm stretched mesh) and monofi lament nets with various stretched mesh sizes (5mm-55mm stretched mesh).
An Index of Relative Importance (IRI) and Shannon diversity index (H') were used to evaluate relative abundance and species diversity of fi shes, respectively. An index of relative importance (IRI) is a measure of the relative abundance or commonness of the species based on number and weight of individuals in catches, as well as their frequency of occurrence [3,4]. An index of relative importance (IRI) [3][4][5][6] was used to fi nd the most important species in terms of number, weight and frequency of occurrence in the catches from the different sampling localities. IRI gives a better representation of the ecological importance of species rather than the weight, numbers or frequency of occurrence alone [7]. Index of relative importance (% IRI) was calculated as:

Characteristics of rivers and seasonal wetlands
All rivers have attracting seasonal character. Alatish and Gelegu sink in the golden sandy river course during dry season.
Of which the name of Alatish is given by the indigenous Arabic speaking Gumuz nationalities as the water sinks in the sandy river bed no surface water is seen in dry season (''Moa Altish'').
The Other striking hydrological system of Alatish is the presence of seasonal wetlands (Sambri) and muddy (Mezega) areas that support many life forms and major wildlife and human confl ict is prevalent in the long dry season. Seasonal wetlands of Alatish are characterized by grassy patches of land devoid of woody trees with various size and shape. A thin striped Sambri covers 1-3 km length around Gelegu River in Amejalie to Alga (Figure 3). Where as circular and rectangular shaped Sumbries of a single patch comprises about 0.2 to 3 sq km and interrupted by drained soils. Sambris are used as a main source of fi shing for export to Sudan in a large quantity. To provide estimated quantity, since mostly fi shing is illegal and needs to assess from the middle of wet season (August) to 1/3 of water is remaining (October). Fishing in Sambri is harvested only once a year because of absence of water.
In central and western part of Alatish around Sukul, Yelkuk, Amtish, along Dindir Alatish boarder in Abnun and Amdok fl ood plains are major areas of this land feature ( Figure 4). Fishes in Sumbri are believed to be transported from rivers through the outfl ow of water during extensive fl ooding or specialized in hiding their eggs in residual moisture under soil which requires detail studies on identifi cation and reproduction behavior of hydrological biota.

Fishing in ayima river
Ayima River is found after Gelegu town to Bemur, kebele town of Quara woreda 18 km, again from Bemur 14 km after traveling on foot during wet season sampling period to reach Fetene bahir sampling site (Table 1). It is found at the boundary of Benishangul Gumuz region (Region six) and Quara woreda kebele where Agew and Gumuz ethnic groups are inhabited the area especially Gumuz groups are found just along the river sides, and they are highly engaged by fi sh consumption from Ayima River.
Ayima River arises from Jawi woreda, which is found in Awi zone of region three and the river crosses the country by bisecting two regions (Region three and Benishangul Gumuz, In Ayima river there are two groups of fi shermen organized under cooperatives, but they are not yet functional, this was due to may be inaccessibility of the area (remoteness). From Ayima River, fi shermen sell their catch at Bemur town and the catch transported to Gelegu (a town of Quara Woreda) ( Figure   8). Fishermen after they fi sh together they take to the nearby village of individual house, who is a member of fi shermen and they share their catch and take individually either for home consumption or to earn income. Gumuz individual family who live near Ayima River develope fi shing system, which is permanently built during the dry season called "Guraba".
Fishermen check Guraba everyday early in the morning either it has fi sh or not (Figure 9).
In this system of fi shing fi shermen can get live fi sh at the same time small fi shes and unwanted species would be released to the river and also fi shermen can take fi shes to the market or    to house consumption based on daily needs, the rest will stay for other days without spoilage, used as preservative method.

Diversity and distribution of fi shes
Twenty species of fi sh were identifi ed in Ayima. Because of water turbidity it was diffi cult to sample fi shes in this fi eld assessment from Gelegu. Other hydrological and values are assessed and Fishing in Ayima river is a vital source of both livelihood and economic sources besides its ecological and esthetic value. Similarly several species of fi shes are expected from Gelegu River, but due to turbidity of water it was diffi cult to sample in both sampling periods due to unexpected rains causing fl ooding. Catches from the local fi shermen of Gelegu River two species were identifi ed, Clarias gariepinus and Oreochromis niloticus.
A total of 20 fi sh species were recorded during the present study from Ayima River ( Table 2). These fi shes were represented by a single class Actinopterygii (ray-fi nned fi shes), 5 orders and 9 families ( Table 2). The Siluriformes, Characiformes, and Perciformes were the best represented orders with respect to number of families; with 3, 2, and 2 families respectively and the Cyprinidae, Characidae, were the best represented families with 6, and 4 species respectively (Table 2). Labeobarbus was the best represented genera with 4 species, (  affect biodiversity pattern [9]. River width, catchments area, habitat and substrate structure such as muddy, rocky, sandy, vegetation cover of the surrounding, distance from the source, and depth have also infl uence on the diversity of fi shes (Toham and Teugels). The discharge of water to a river seems    infl uential in Ethiopian river fi sh diversity [10]. Therefore, the fi sh diversity of the studied river may be associated with rich habitat, large volume of water discharge through multiple tributaries, rich vegetation cover of catchment areas and suitable temperature. The possible factor that fi sh diversity was higher during dry season than wet would be high terbidity of rivers, speedy run-off, and low temperature in wet season.

Relative abundance of fi shes
The species caught during all the surveys from October, 2008 to January, 2009 were ranked based on the Index of Relative Importance (IRI) ( Table 3). L. intermedius, L. nedgia and L. forskalii were the most abundant species in Ayima River in order of their importance. These species have 23.9 % IRI, 20.8 % IRI and 18.7 % IRI, respectively (Table 3).

Conclusion and recommendations
The Siluriformes, Characiformes, and Perciformes were the best represented orders with respect to number of families; with 3, 2, and 2 families respectively and the Cyprinidae, Characidae, were the best represented families with 6, and 4 species respectively. Labeobarbus was the best represented genera with 4 species.
Diversity and relative abundance of fi shes in Gelegu and

Alatish Rivers needs further investigation
Prohibited fi shing gears like poisoning with Birbira (Milletia ferruginea), Lalo (Balanites egyptiaca) and the most destructive way of fi shing with illegal fi shing gear have to be restricted before mass destruction of fi sh and other living things in the water body occurs. Therefore, immediate assessment and awareness creation should be done towards this end.
Preservative methods and transporting methods for fi shermen should be designed to enable them to consume and sell their catch in areas where price of fi sh is attractive.
Deforestation of the riparian forest will be an ultimate event by the newly settled farmers taken from most exploited areas to the virgin ones, where those rivers are found, then for cropping and livestock production activities those important fl ora species for the existence of fi sh species grown on the bank of rivers hanging over their branchs at pooled water body will be damaged, therefore, attentions should be given to conserve them.