Diversity, Relative Abundance and

Some Aspects of the Biology of Fishes

below the Tisisat Fall of the Blue Nile

River, Ethiopia

Author

Tadlo Awoke Mengesha

Department of Animal Production and Extension, Gondar, Ethiopia

Publication Month and Year: November 2019

Pages: 60

E-BOOK ISBN: 978-81-944644-2-6

Academic Publications

C-11, 169, Sector-3, Rohini, Delhi, India

Website: www.publishbookonline.com

Email: publishbookonline@gmail.com

Phone: +91-9999744933

Acknowledgement

This thesis work could not have been successful without the contribution of

many individuals and institutions. I have no words to express my deepest

gratitude and sincere appreciation to my research advisors, Dr. Minwyelet

Mengist from Bahir Dar University; Fisheries, Wetlands and Wildlife

Management Department, and Abebe Getahun from Addis Ababa University

for their unreserved scientific advice, guidance and the accomplishment of

this study. Their critical constructive comments starting from the proposal

until the thesis writing and supply of related literature facilitated the smooth

completion of this study.

Indeed, it is quite difficult to me to express my internal feeling with the

languages I know so far to acknowledge Dr. Minwyelet Mengist

contributions to the realization of this study. He was seriously committed

right from the beginning by suggesting the research area. He was also

supplied me the necessary field materials in time. He is so friendly and has

helpful attitude, which I consider it was an important quality.

I am grateful to the staff members of the Bahir Dar Fish and Other

Aquatic Life Research Center for their technically assist during my filed and

allow the laboratory works. Especially Biniam Hailu and Temesgen for their

support in both the field and the laboratory work.

I would like to thanks Bahir Dar University for Budget and logistic

support, which is required for fieldwork for my thesis. I am grateful to my

friends Shewit G/Medium and Marcos Buddha for their hospitality and

encouragement in my two-year stay and in accessing their computer.

My due thanks go to my family, especially my father Awoke Mengesha

and my mother Fenty Teshager their sympathy and sensitive follow up while

I was in fieldwork.

Finally yet importantly, peoples of Fich, Angar and Wazir Ki Bela and

Amhara National Regional State police commission working are duly

acknowledged for their unreserved efforts in providing valuable information

and support letters for the study.

Almighty god, thank you! You make everything possible for me. Save

my family and help me to realize my dreams.

Contents

S. No. Chapters Page No.

1. Introduction 01-06

1.1 Freshwater bodies in Ethiopia 01

1.2 Fish species diversity in main drainage basins of

Ethiopia 02

1.3 Justification 05

2. Objectives 07-07

2.1 General objective 07

2.2 Specific objectives 07

3. General Description of the Study Area 08-13

3.1 Climate 10

3.2 Fauna 12

4. Materials and Methods 14-18

4.1 Site selection and sampling 14

4.2 Laboratory studies 15

4.3 Species diversity and relative abundance 15

4.4 Shannon index of diversity (H') 16

4.5 Length-weight relationship 16

4.6 Condition Factor (Fulton Factor) 16

4.7 Sex Ratio 17

4.8 Fecundity 17

4.9 Data analysis 18

4.10 Species description 18

5. Results and Discussion 19-39

5.1 A biotic Parameters 19

5.2 Fish species composition in the upper part of Blue

Nile River 20

5.2.1 Diagnostic and descriptive characteristics of

fishes 23

5.2.2 Species diversity and abundance 27

5.2.2.1 Species diversity 27

5.2.2.2 Relative abundance of fish during wet and dry

seasons 29

5.2.2.3 Length frequency distribution of the dominate

fish species 33

5.3 Some biological aspects of the dominant fish

species 34

5.3.1 Length-weight relationship 34

5.3.2 Fulton’s condition factor (FCF) 36

5.3.3 Some aspect of reproductive biology 37

5.3.3.1 Sex ratio 37

5.3.3.2 Fecundity 38

6. Fishing Activity and Its Problems in the Study Area 40-42

6.1 Fishing activity 40

6.2 Problems in fishing activities 42

7. Limitation of the Study 43-43

8. Conclusion and Recommandations 44-46

8.1 Conclusion 44

8.2 Recommendations 45

References 47-53

Appendixs 54-60

List of Tables

Table No. Tables Page No.

1. Number of fish species and endemic species in the

main drainage basins of Ethiopia 05

2.

Sample sites and there codes, estimation distance from

the Tisisat fall elevation, habitat, width of the river and

coordinates 10

3. Macroscopic description of various gonadal stages 17

4.

A biotic parameters in the sampling sites with their

Means ±SE in both dry and wet seasons (Mann-

Whitney U test) 19

5. Fish species composition and local name in amharic

according to the local people 20

6. Fish species presence in sampling sites (present, +,

absent, -) 21

7. Fishes specie composition compression above and

below the Blue Nile Fall (+, present and -, absent) 22

8. Fish distribution among the sampling sites both dry

and wet seasons (+: present; -:absent) 27

9. Shannon diversity index (H') and number (N) of fish

species in dry season 28

10. Shannon diversity index and number of fish species in

wet season 28

11. Number and total biomass (kg) of fish during wet and

dry season 29

12.

Species number and percentage composition of both in

dry and wet season in sampling sites (One way

ANOVA) 30

13. Percentage index of relative importance of fish species

in dry season 31

14. Percentage index of relative importance of fish species

during wet season 31

15. Pooled catch of IRI and H' values in both dry and wet

seasons at all the sampling sites 33

16.

Mean and Standard deviation of Fulton condition

factor both by sex and season: P= significance

difference (Mann-Whitney U test) between sex and

seasons of dominant fish species 36

17. Number of males, females and the corresponding sex

ratio 38

List of Figures

S. No. Figures Page No.

1. Map of study area 09

2. Mean maximum and minimum air temperature 11

3. Mean monthly rain fall 12

4. Lateral view of Labeobarbus intermedius 23

5. Lateral view of Labeobarbus crassibarbis 24

6. Lateral view of Labeobarbus nedgia 24

7. Lateral view of Clarias gariepinus 25

8. Lateral view of Mormyrus kannume 25

9. Lateral view of Bagrus docmak 26

10. Lateral view of Labeo forskalii 26

11. Lateral view of Oreochromis niloticus 27

12. Shannon diversity index (H') and Number of fish

species in both dry and wet seasons

28

13. Percentage IRI of dominant fish species in sampling

sites during dry and wet season

32

14. Length frequency distribution of L. intermedius 34

15. Length-weight relationship of L. intermedius, L.

forskalii and M. kannume respectively

36

16. ABC Absolute fecundity with total length, total weight

and Gonad weight relation in L. intermedius

39

17. Farmers fishing time in the study area 41

Page | 1

Chapter - 1

Introduction

1.1 Freshwater bodies in Ethiopia

Ethiopia is water tower of East Africa and has a number of lakes and

rivers in which the majority of the rivers and lakes are situated in Rift Valley

of Africa (Leykun Abunie, 2003). There is about 7,000 km length of flowing

(rivers and streams) and 7, 400km2 area of standing waters 7,700 km2

(MOA, 2003). In addition, minor water bodies such as crater lakes and

reservoirs make up about 400km2 area (Tesfaye Wudneh, 1998).

The main drainage basins of Ethiopia flow away from the rift system

either towards the Nile system in the west or to the Indian Ocean in the

southeast. Ethiopia has seven drainage basins that include Abay, Awash,

Wabeshebelle-Ghenale, Omo-Gibe, Baro-Akobo, Tekeze and Rift Valley

basins (Mesfin Wolde Mariam, 1970): which can be categorized under three

main drainage systems.

The first drainage system is the western drainage system, which includes

the sub-drainage systems of Baro-Akobo, Blue Nile and Atebara-Tekeze.

Rivers Didessa, Dabus, Beles, Gelgel Beles, Beshilo, Dura and Ardi are

tributaries of the Blue Nile that drain the southwestern parts of the western

highlands of Ethiopia (Abebe Getahun and Stiassny, 1998).

The second drainage system is the Rift Valley system, which is

composed of awash sub-drainage system that drains in to Lake Abbe, at the

Ethio-Djibouti border and it is a closed system. Omo- Gibe sub drainage

system flows to the south to Lake Turkanna (Rudolf) at the border with

Kenya. The Rift Valley Lakes are again categorized into three-sub system on

the bases of the similarities of their fish fauna. These are Southern Rift

Valley Lakes (Chamo, Abaya and Chew Bahir), Central Rift Valley Lakes

such as Hawassa, Shalla, Abijata, Langeno and Ziway (LFDP, 1996) and the

Northern Rift Valley lakes such as Afambo, Gamari, Afdera, Asale, and parts

of Abbe.

The third main drainage basin is the Wabi Shebelle-Juba drainage

system. It is composed of sub-drainage system of Ghenale, Dawa and Weyb

Page | 2

Rivers that join Shebelle River and drain to southwestern parts of the eastern

highlands. The Wabi Shebelle River is called Juba in Somalia. The major

rivers in this drainage system arise from the eastern highlands in the Bale

Mountains of Ethiopia and flow into the Indian Ocean (Roberts, 1975).

Four major river systems originate in the Ethiopian highlands. The

Awash arises in Shoa and flows northwards following the Great Rift Valley

where it disappears in the desert near the Djibouti border. The Omo begins in

Kafa and drains into Lake Turkana, in the south, on the border with Kenya.

The Wabi Shebelle originates in the Bale Mountains and flows in a

southeastern direction towards Somalia. The most impressive river, however,

is the Nile, which flows MOR than 6,000 km from its source (Lake Tana) to

the shores of the Mediterranean (De Graaf, 2003). The Nile River is

principally fed by two great rivers, the White Nile and the Blue Nile, which

fuse at Khartoum, Sudan's capital city.

1.2 Fish species diversity in main drainage basins of Ethiopia

Ethiopia has a rich diversity of ichthyofauna in its lakes, rivers and

reservoirs, although they are poorly known (Abebe Getahun and Stiassny,

1998). Even though, Ethiopian has high production potential and notable

fishery investigation has been carried out only in a few of numerous

freshwater bodies. The territory of Ethiopia encompasses parts of the

catchment areas of two oceans, separated by the north portion of the Great

African Rift. Two major biogeographic units, the Nilo-Sudan and the east

coast ichthyofauna provinces are in contact to this region (Golubtsov et al.,

2002).

Shibru Tedla (1973) has listed 94 species of fish in Ethiopia. Although

extensive review work is in progress, it appears that there are 153 valid

indigenous fish species included in 25 families in Ethiopia freshwater

(Abebe Getahun, 2002). According to Golubtsov and Mina (2003), the total

number of valid species in Ethiopia inland waters is about 168 to 183

including 37 to 57 countrywide endemics. There are also 10 exotic fish

species introduced from abroad into Ethiopian fresh waters (Shibru Tedla

and Fisseha H/Meskel, 1981). Currently results of various studies indicate

that the number of fish species could increase to 200 and above (JERBE,

2007).

The freshwater fish fauna of Ethiopia is a mixture of Nilo-Sudanic, East

African and endemic forms (JERBE, 1995; Abebe Getahun and Stiassny,

1998; Abebe Getahun, 2007). The Nilo-Sudanic forms are represented by

many representative species. For example, the genera Alestes, Bagrus,

Page | 3

Citharinus, Hydrocynus, Hyperopisus, Labeo, Malapterurus, Mormyrus,

Polypterus and Protopterus are some of the representatives from Baro

Akobo, Omo-Gibe and Abay basins. The Nilo-Sudanic forms are related to

West African forms and are believed to occur here due to past connection of

the Nile to Central and West African river systems. According to Abebe

Getahun (2002), some of the elements of Nilo-Sudanic species are reported

from southern rift valley lakes (Chamo and Abaya). These include the

families Mormyridae, Cyprinidae, Bagridae, Clariidae and Mochokidae.

Wabi Shebele and Jube basins also have element of Nilo-Sudanic forms.

The highland East African forms are found in the northern rift valley

lakes (Lake Awassa, Ziwai and Langano), highland lakes (Lakes Hayq and

Tana) and awash drainage basin. The genera include Labeobarbus, Clarias,

Garra, Oreochromis and Varicornis. They are related to fishes of Eastern and

Southern Africa and Arabian Peninsula (Skelton et al., 1991).

Fish fauna of Ethiopian high lands are dominated by species of fish in

the family Cyprinidae (Roberts, 1975). The fishes of the high mountain

torrential streams largely belong to Cyprindae (Abebe Getahun and Stiassny,

1998) adapted to the swiftly flowing floodwaters that occur seasonally. Two

genera of fishes (Barbus and Garra) are dominant in these streams. It

appears that there is high endemism of fish, but fauna is not well known.

Endemic fishes of the genus Garra (e.g. G. dembecha, G. duobarbis) have

been described recently (Abebe Getahun, 2002). Some of endemic fish

species are found in Abay basin: Labeobarbus zephyrus Boulenger 1906, V.

beso and some Garra species (Golubtsov and Mina, 2003).

Some of the family of fish identified within the Nile basin and its

tributary rivers are Mormyridae, Characidae, Cyprinidae, Bagridae,

Schilbeidae, Mochokidae, Clariidae and Cichlidae (MoWR, 1998). Moges

Beletew (2007) assessed fish diversity in Beshilo, Ardi and Dura Rivers of

Abay basin and found twelve species of fishes. These represent by five

families i.e. Cyprinidae, Clariidae, Bagridae, Mochokidae and Cichlidae.

Some of the species were L. intermedius, L. nedgia, C. gariepinus, V. beso,

O. niloticus, S. schall, R. loti, B. docmak, B. bajad, L. forskalii and H.

longfillus. According to Zeleke Berie (2007) a total of 22 species of fishes

were recorded from Beles and Gelgel Beles Rivers of Abay basin. Seven

families represent these: Cyprinidae, Clariidae, Bagridae, Mochokidae,

Characidae, Mormyridae and Cichlidae, represent these.

There is no clear, complete list and description of the diversity of the

fish fauna of Ethiopia. Many of the drainage basins especially the rivers are

Page | 4

not exhaustively explored (Abebe Getahun, 2002). There are 38 endemic

species and sub species to Ethiopia (Abebe Getahun, 2005a). Lake Tana

from Abay drainage basin exclusively has large number of endemic fish

species in the country (Abebe Getahun, 2005a).

The Abay basin is one of the tributaries of Nile and consists of 36

species (Abebe Getahun, 2007) of fish of which 23 are endemic (Golubtsov

and Mina, 2003; Abebe Getahun, 2007). Most of the endemic species of

Blue Nile basin occur exclusively in Lake Tana. Lake Tana is a lake in the

northern high lands of Ethiopia and is the source of the Blue Nile. The Blue

Nile descends from Lake Tana to Tissisat Falls (ca. 40 m high), effectively

isolating the lake’s fresh water fauna from the rest of the Nile (Thieme and

Brown, 2007). It was formed by a volcanic blockage that reversed the

previously north-flowing river system. The isolation of the lake from all but

in flowing rivers has led to an endemic freshwater biota. Fish species in the

lake are most closely related to those of the Nilo-Sudan biogeographic

region.

Seventeen species of large barbs have been described from Lake Tana

(Nagelkerke & Sibbing, 1998 & 2000). Eight of the large barbs are

piscivorous, and Barbus humilis and the newly described, Barbus

tanapelagius, are thought to be the major prey species (de Graaf et al.,

2000).

About 70% of the fish species in this highland lake are endemic,

including 20 endemic Cyprinids. The tilapia of Lake Tana belongs to a wide

spread species but is described as an endemic subspecies, Oreochromis

niloticus tana (Eshete Dejen, 2003; Thieme et al., 2007).

The family Cyprinidae is the only group of fish that is more diverse in

the Blue Nile drainage system than in White Nile system. All other forms

occurring in the latter system are represented by few species or absent in the

former system. This might be the lack of flood plain in the Blue Nile system

as was suggested by Golubtsov and Mina (2003).

According to Golubtsov and Mina (2003), the fish diversity in Atbara-

Tekeze is less in comparison with Blue Nile and White Nile due to

accessibility in the former system. JERBE (2008) reported 34 fish species

belonging to 10 families and 22 genera from Atebra-Tekeze basin system.

That means two to three times fewer species than Blue Nile and Whit Nile

system respectively. The JERBE recorded 22-23 fish species from Abaya-

Chamo system, 12-14 fish species for Chew Bahir, 12 species for Zwai-

Langano, Abijata-Shalla system, 6-7 fish species for Awassa-Shalla system

Page | 5

and 13-25 fish species for Awash and its adjacent enclosed basins (Golubtsov

and Mina, 2003).

The highest fish diversity recorded, among Ethiopian main drainage

basins, is from the Baro basin. According to Golubtsov and Mina (2008), 113

fish species belonging to 26 families and 60 genera were recorded from

Baro-Akobo basin. However, the basins are low level of endemism as

compared to other Ethiopia drainage basins. Low level endemism is

probably because of the Baro basin have connections (past and present) with

the Nile and West and Central African river systems and as a result of all the

fish fauna represent widespread Nilo-Sudanic forms (Abebe Getahun, 2007).

According to Golubtsov and Mina (2003), 33 fish species belonging to

12 families and 21 genera were recorded from Wabi Shebelle and Juba

drainage basins within the limits of Ethiopia. This region is inhabited by

most distinct ichthyofauna within the country. A number of East African fish

taxa occur in this basin such as the Characid Alestes affinis, the Cyprinid,

Neobola bottegoi, the Schilbeidae irvine orientalis, the loach catfish

Amphilius species, the Cichlid Oreochromis spilurus. There are 2-3

introduced fish species in this drainage system (Golubtsov and Mina, 2003).

The highest fish species diversity in Ethiopia has been recorded from

Baro basin, followed by Abay, Wabi Shebelle and Omo-Gibe basins.

However, endemicity seems to be highest in Abay and Awash basins. This is

attributed, in the former case, to the endemic species flock of Labeobarbus

in Lake Tana (Abebe Getahun, 2002) (Table 1).

Table 1: Number of fish species and endemic species in the main drainage basins of

Ethiopia (Abebe Getahun, 2007)

Abay 36 23

Awash 15 6

Baro 87 1

Omo 26 2

Rift valley lakes 32 7

Wabi Shebelle 26 4

Drainage basins No. of species No. of endemics species

1.3 Justification

Knowledge on diversity, population structure, distribution and

population of the Ethiopian ichthyofauna and biology of fish species has

been poorly known: relatively a number of small, medium and even some

large rivers have not been well studied and explored (Abebe Getahun,

Page | 6

2005b). Therefore, further study on rivers is a time demanding phenomena.

Blue Nile River originates from Lake Tana and flows down approximately

35 km in the southeast direction where it forms the famous Tisisat falls. This

river especially below the fall has not been given adequate attention with

regard to the study of the diversity, abundance and biology the fish fauna due

to the presence of some harsh geographical features, inaccessibility for

transportation, security and logistic problems. The purpose of the study is,

therefore, to answer the following research question with the objectives

mentioned.

What is the fish composition of the Blue Nile River below the

Tisisat fall?

Do species vary in their relative abundance?

What are some aspects of the biology of the dominant fish species

found in this river?

Is there some fishing activity around this river?

Page | 7

Chapter - 2

Objectives

2.1 General objective

Major objective of the study is to generate baseline scientific

information about fish species found in upper part of Blue Nile River below

the “Tisisat” fall for management and sustainable utilization of the fish

resources and recommend ways of conserving the diversity of ichthyofauna

of the River.

2.2 Specific objectives

To identify fish species composition of the Blue Nile River below

the Tisisat fall.

To assess relative abundance of fish species in the river.

To determine some aspects of the biology (Length-weight

relationship, Condition factor, Sex ratio and Fecundity) of the

dominant fish species.

To investigate the fisheries activities and recommend appropriate

resource utilization strategies.

Page | 8

Chapter - 3

General Description of the Study Area

The Nile River is the longest in Africa and the second longest in the world. It

flows 6,700 km from its source in the equatorial lake basin to the

Mediterranean Sea north of Cairo, Egypt. In between, it receives flows from

a major tributary, the Blue Nile from the Ethiopian highland plateau, which

contributes significantly to the Nile River’s total annual flow of almost 84

billion m3 per year at Aswan, Egypt (UNECA, 2000). The catchment area of

over 3 million km2 of the Nile cuts across ten African countries namely,

Burundi, the Democratic Republic of Congo, Rwanda, Tanzania, Kenya,

Uganda, Ethiopia, Eritrea, Sudan and Egypt. This catchment area represents

over 10% of the total land surface area of the African continent. The sources

of the Nile are located in humid regions of Ethiopian highlands and the Great

Lakes of East-Central Africa with an average rainfall rate of over 1,000 mm

per year (UNECA, 2000).

The out flow from Lake Tana is the main source of Blue Nile River. The

Blue Nile River flows the Eastern outskirts of the city of Bahir Dar at the

Southern end of the Lake Tana flows down approximately 35 km in a

southeast direction where it forms the famous Blue Nile Fall to drop in to a

gorge having a depth of about 45 m (Yihun Dile, 2009).

Blue Nile River basin lies in the west of Ethiopia between latitude 7°45'

and 12°45' N, and longitude 34° 05' and 39°45' E (MoWR, 2010). River

Didissa, Dabus, Beles, Gelgel Beles, Beshilo, Dura and Ardi are tributaries

of Abay (Blue Nile) that drain the southwestern parts of the western

highlands of Ethiopia (Abebe Getahun and Stiassny, 1998). The Bashilo rises

near Magdala and drains eastern Amhara; the Jamma rises near Ankober and

drains northern Shoa; the Muger rises near Addis Ababa and drains south-

western Shoa; the Didessa, the largest of the Abay's affluents, rises in the

Kaffa hills and has a generally south-to-north course; the Dabus runs near

the western edge of the plateau escarpment. All these are perennial rivers.

The right rising mostly on the western sides of the plateau have steep slopes

and are generally torrential in character. The Beles, however, is perennial,

and the Rahad and Dinder are important rivers in flood-time.

Page | 9

Blue Nile basin shares common boundaries with the Tekeze basin to the

north, the awash basin to the east and southeast, the Omo-Gibe basin to the

south, and Baro-Akobo basin to the west (MoWR, 2002). The total area of

the basin is 199,812 km2 including Lake Tana which has an area of about

3200km2. About 46, 31 and 23% of the total basin area falls in Amhara,

Oromiya and Benishangul-Gumuz, respectively (MoWR, 2002). The River

basin’s elevation ranges from 500 m to 4261 m and the total mean annual

flow from the River basin is estimated to be 54.8 billion m3 (Seleshi Bekele

et al., 2007).

The study was conducted in the upper part of the Blue Nile River

(Starting from the Blue Nile Fall/Tissisat Fall to the border between East and

West Gojjam). It lies between West Gojjam and South Gondar zones,

specifically the adjacent Kebeles are Tis Abay, Wajir, Anigar, Gibish, Fichi

and Dibaye (Figure 1).

Fig 1: Map of study area

Source: GIS Case Team Bureau of finance and economic at Bahir Dar

Page | 10

Table 2: Sample sites and there codes, estimation distance from the Tisisat fall

elevation, habitat, width of the river and coordinates. Here on wards, Se, Ab and Wm

refers to the sampling code

Site Code Distance

(km) Elevation Habitat Width

Coordinate

(GPS)

Sefania Se 8 1548m Clear water and

rocky, sandy Medium

110 27.7' 07" N

E ״60 '37.9 37

Abenaze Ab 30 1528m Turbid muddy Wider 110 24.3' 06'' N

370 40' 71'' E

Wotetomider Wm 60 1493m Clear water and rock

gravel Medium

110 31.5' 03" N

370 72.9' 48" E

3.1 Climate

According to Conway (1999), the local climate classification in Ethiopia

is based on elevation and temperature. In other words, depending on

elevation for any area there is associated mean annual temperature range.

This enables identifying traditional climate zone of a given area. The three

traditional climate zones of Ethiopia are: Kola (elevation less than 1800 m

A.M.S.L and mean annual temperature 20-28 oC), Woina Dega (elevation

between 1800 m and 2400m A.M.S.L and mean annual temperature 16-20 oC), and Dega (elevation between greater than 2400m A.M.S.L and mean

annual temperature 6-16 oC). Based on the above local climate classification

the climate zone of the study area is Kola (elevation is less than 1800m

A.M.S.L).

The maximum and minimum mean monthly air temperatures of upper

part of Blue Nile basin are 26.29 oC and 10.78 oC respectively at the Adet

station and 25.39 oC and 11.31 oC at the Bahir Dar station (Fig. 2). The mean

monthly rainfall was 141.5 mm at Adet station and 105.22 mm at Bahir Dar

station. The main rainy season of this basin is between May and end of

October (Fig. 3).

Page | 11

(A)

(B)

Fig 2: Mean maximum and minimum air temperature (a) at Adet station and (b) at

Bahir Dar from 2006- 2010 (Ethiopian Meteorological Agency, Bahir Dar Branch,

2011)

Page | 12

(C)

(D)

Fig 3: Mean monthly rain fall (c) at Adet station and (d) at Bahir Dar station from

2006-2010 (Ethiopian Meteorological Agency, Bahir Dar Branch, 2011)

3.2 Fauna

Blue Nile River below the Tissisat fall besides fishes there are other

vertebrate animals found in the river. These are Crocodile, Snakes, “Arjano”

(Monitor lizard) and different species of amphibians and birds. Species of

Page | 13

birds observed during the study period were Cattle egrets (Bubulcus ibis),

Great white pelican (Pelecanus onocrotalus), Grey heron (Ardea cinerea),

Sacred ibis (Threskiornis aethiopicus) and African Jacana (Actophilornis

africana).

3.3 Flora

There is high deforestation in the Blue Nile River basin below the

Tissisat fall mainly hillside farming is devastating the forest and soil.

Farmers in this area cultivate two crops a year and perennial crop farming is

practiced. The changes in vegetation patterns result from land degradation

along the Blue Nile basin below the Tissisat fall that may lead to unexpected

abnormal floods and reducing soil nutrients of the basin. The other factors

that a lead to deforestation is because of all of the residents do not have

access to the electricity. The people use kerosene lamp and fuel wood as a

source of light and for cooking. Therefore, the villagers continue to denude

the remaining shrubs and trees for their daily consumption. Shrubs and trees

mainly cover vegetations on either side of the riverbank. The dominant trees

are Syzygium guineense (“Dokma”), Mimusops kummel (“Eshe”), Olea

europaea (“Woyira”) and Ficus (“Shola”).

Page | 14

Chapter - 4

Materials and Methods

4.1 Site selection and sampling

A reconnaissance survey was conducted to fix the sampling sites. The

survey was conducted in three woredas along the River. Three sampling sites

were selected taking into consideration; the velocity of the flowing river,

interference by human beings and other farm animals, substrate type of

sediments and accessibility, depth of water, and access to road. These sub

areas are namely; Wotetomider site found in Wotetomider village at Fichi

kebele, which is about 60 km down stream of Blue Nile fall, Abenaze site

found in Abenaze village at Anigar kebele, which approximately 30km far

from Blue Nile fall and Sefania site found in Wojir kebele, which is

approximately 8km far from Blue Nile Fall. These sites were found in West

Gojjam Zone under three woredas namly Gonje Kolela, Yelmanadensa and

Bahir Dar Zuria, respectively. Data on fishing activity were collected using

semi-structured questionnaires (Appendix 10.3). Conductivity, temperature,

pH, Total dissolved solid (TDS) were measured using standard multi -meter

and transparency was measured using secchi disk 20 cm in diameter. In

addition to this cast, net was used in unsuitable areas of the river. Fish

samples were collected in both wet season (November 2010) and dry season

(March 2011). Each site was sampled two twice (one time in the wet season

and one time in the dry season). Samples were collected using gillnet of

various mesh sizes (6, 8, 10 and 12 cm stretched mesh) and monofilament

nets with various stretched mesh size (5, 10, 15, 20, 25, 30, 35, 40, 45, 50

and 55 mm). In all studied sites, monofilaments were set during the daytime

for two hours. Gill and monofilament nets were set, using swimmers, across

the width of the river during dry sampling period when the water volume is

less and parallel to the river flow during wet season when the water

discharge is high. Gillnets were set late in the afternoon and collected in the

water for 14 hours at deeper parts of the river and collected in the following

morning. Cast net was also used by selecting an appropriate site.

Immediately after capture, a gentle pressure was applied on the abdomen to

check whether reproductive maturity has occurred or not. Then total length,

fork length, standard length, total weight and gonad weight of all specimens

Page | 15

of fish were measured to the nearest 0.1 cm and 0.1 g precision for length

and weight, respectively. Picture of fish specimen was taken for each

species. After dissection, gonad maturity of each fish specimen was

identified using a five-point maturity scale (Nikolsky, 1963). Four specimens

were preserved by 5% formalin from each species and transport to Bahir Dar

Fish and Other Aquatic Life Research Center for morphometric study and

comparison with previously identified specimens available.

4.2 Laboratory studies

Specimens were soaked in tap water for one day to wash the formalin

from the specimens and then specimens were identified to species level

using taxonomic keys found in Boluenger (1909-1916) and Golubtsov et al.

(1995). The specimens were also compared with previously identified

specimens, especially Labeobarbus species, available at Bahir Dar Fish and

Other Aquatic Life Research Center.

4.3 Species diversity and relative abundance

Estimation of relative abundance of fish was made by taking the

contribution in number and weight of each species in the total catch in each

sampling effort. An Index of Relative Importance (IRI) and Shannon

diversity index (H') were used to evaluate relative abundance and species

diversity of fishes, respectively. 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 (Kolding, 1989, 1999). IRI

gives a better representation of the ecological importance of species rather

than the weight, numbers or frequency of occurrence alone (Sanyanga,

1996).

Index of relative importance (% IRI) was calculated by the following

formula:

IRI = X 100

Where % Wi and %Ni are percentage weight and number of each

species of total catch, respectively. % Fi is percentage frequency of

occurrence of each species in total number of settings. % Wj and % Nj are

percentage weight and number of total species in total catch. % Fj is

percentage frequency occurrence of total species in total number of setting. S

is total number of species.

Page | 16

4.4 Shannon index of diversity (H')

The Shannon index of diversity is a measure of the number of species

weighted by their relative abundance (Begon et al., 1990). Shannon index of

diversity (H’) was calculated using the formula:

H' =

Where:

H' = the Shannon diversity index

Pi = fraction of the entire population made up of species i

S = numbers of species encountered

∑ = sum from species 1 to species S

Shannon’s diversity index (H') was used to indicate diversity at different

sampling sites and/or rivers. A high value indicates high species diversity.

4.5 Length-weight relationship

The relationship between total length and total weight of the most

dominant fish species was computed using power function as in Bagenal and

Tesch (1978) as follows:

TW= a X TLb

Where

TW= Total weight (gm)

TL= Total length (cm)

a = Intercept of the regression line

b = Slope of the regression line

4.6 Condition factor (Fulton factor)

The well-being or plumpness of each dominant species was calculated

as total weight in percent of total length cube (Lecren, 1951; Bagenal and

Tesch, 1978). Fulton Condition Factor (%) was calculated as:

FCF = X 100

Where,

FCF = Fulton condition factor

TW = total weight in grams

TL = total length in cm

Page | 17

4.7 Sex ratio

The ratio between the number of female and male. Sex ratio was

determined using the formula:

Sex ratio=

4.8 Fecundity

Fecundity was determined gravimetrically method (MacGregor, 1957),

by weighing all the eggs from each of the ovaries of gravid fish species

(gonad maturity stage IV). Three sub-samples of 1 gm eggs were taken from

different parts of ovary and counted and the average was calculated. The

total number of eggs per ovary was calculated by extrapolation from the

mean calculated. The relative fecundity was calculated by dividing the total

number of eggs per fish weight. The relationship of fecundity with total

length, total weight and ovary weight was determined. Fecundity was

determined by the following formula.

F = aTLb

F = aTWb

F = aGwb

Where

F-Fecundity

TL-Total length (cm)

TW-Total weight (g)

GW-Gonad weight (g)

a. Constant

b. Exponent

Table 3: Macroscopic description of various gonadal stages, (Nikolsky, 1963)

Maturity

stage Male Female

I

Immature, virgin-A pair of small

thread-like, colourless organs (with

slightly serrated edges, in C.

gariepinus). Difficult to distinguish

between the sexes (except in C.

gariepinus).

Immature virgin-A pair of small,

thread-like colourless organ. Difficult

to distinguish between the sexes in B.

tsanensis and O. niloticus. In C.

gariepinus (size >18 cm) the ovary is

discernible as tiny, bulb-like and

pinkish in colour.

II Developing virgin or recovering Developing virgin or recovering

Page | 18

spent-Long thin, up to 1/2 length of

body cavity but distinct opaque

white in B. tsanensis and O.

niloticus and translucent white in

C. gariepinus, with distinct serrated

edges and shorter.

spent- Long thin, up to 1/2 length of

body cavity thicker than the testis and

translucent yellowish-white in B.

tsanensis and O. niloticus and pink in

C. gariepinus. Recovering spent has

larger gonad size and athicker wall.

III

Maturing or ripening-Long and

thicker, 2/3 body cavity (or 1/2 in

C. gariepinus), firm and more

solid. Colour white in B. tsanensis,

cream or beige in O. niloticus and

greyish-white in C. gariepinus.

Maturing or ripening-Long and

thicker, 2/3 body cavity Colour

yellowish in all. Ova discernible in

all.

IV

Ripe and Running-Large thick and

slimy. Milky white in B. tsanensis,

creamy in O. niloticus and white in

C. gariepinus. Sperm easily flows

when pressed or cut. C. gariepinus

testis has smoother edge.

Ripe and running-Ovary large,

yellow, almost filling the peritoneal

cavity in all. Ova well developed and

large may flow out when pressed.

V

Spent-testis shrunk and flaccid.

Numerous folds appear in O.

niloticus, and serrated edges revert

to original sharpness and colour

changes grey in C. gariepinus

Spent-Ovary shrunk and flaccid.

Some remnants of disintegrating,

opaque and ripe eggs appear in ovary

of O. niloticus and sometimes in B.

tsanensis; rarely in C. gariepinus.

Colour changes translucent in O.

niloticus and B. tsanensis but in C.

gariepinus the ovary changes colour

to greyish-red.

Description of gonads

4.9 Data analysis

Data collected were collated and analyzed using descriptive statistic

(mean, standard error and percentage). Statistical comparison of data

between and within zones was carried out using SPSS Version 16, analysis of

variance (ANOVA), Mann-Whitney U test and line graphs using Origin 6

and excel statistical package (2007). Sex ratio of the fish was studied using

Chi-square test (χ2) and values were tested using 95% confidence level.

Correlation analysis was used ascertain the significance of these

relationships. The exponents (b) of length weight relation were tested for

departure from isometry (b=3) using t- statistics

4.10 Species description

The morphometric data have been converted into percentages with

respect to standard length and head length. Standard univariate statistics

methods (mean, standard deviation, maximum and minimum) have been

used to summarize the morph metric and meristic data.

Page | 19

Chapter - 5

Results and Discussion

5.1 A biotic parameters

A biotic factor land organisms, aquatic populations are also highly

dependent upon the characteristics of the aquatic habitat, which support all

their biological functions (reproduction, growth, feeding and sexual

maturation). Thus, factors are the controlling factors for the aquatic life,

since they shape most the biological functions of aquatic life (Murdoch and

Martha, 1999). Cyprinids species as they lack parental care, fast flowing,

clear and highly oxygenated water, and gravel-bed streams or rivers are

generally their spawning ground requirements (Rodriguez-Ruiz and Granado

Lorencio, 1992; Baras et al.,1996; Baras, 1997), due to their critical

important in the development of eggs and larvae (Tomasson et al., 1984).

Deposition of eggs in the gravel or pebble beds protect them from being

washed away by riffle, and clear water will not cover them with affirm of

obstructing the diffusion of oxygen (Lowe-McConnell, 1975).

Environmental factors such as temperature, vertical transparency

(Secchi dept), pH, conductivity and TDS were compared among sampling

sites (Table 4). Physical and chemical parameters were analyzed using

nonparametric test (Mann-Whitney U). There was no significant difference

(P>0.05) in pH, temperature, transparency, conductivity and TDS among all

sampling sites (Table 4). However, there was significant difference between

dry and wet seasons in pH, conductivity, transparency, TDS and temperature

in all the sampling sites (P<0.001) (Appendix 10.1).

Table 4: A biotic parameters in the sampling sites with their Means ±SE in both dry

and wet seasons (Mann-Whitney U test)

pH

Se 5.56±0.69

Ab 5.96±0.09 0.251ns

Wm 6.88±0.34

Average 6.14±0.32

Temperature Se 20.9±0.700

Ab 23.3±0.50 0.063ns

Page | 20

Wm 24.0±0.50

Average 22.73±0.65

Transparency

Se 37.50±12.50

Ab 32.00±8.00 0.935ns

Wm 33.50 ±11.50

Average 34.33 ±4.96

Conductivity

Se 176.32±4.67

Ab 193.60±5.00 0.144ns

Wm 177.20±4.80

Average 182.31±4.12

TDS

Se 87.50±3.50

Ab 82.50±6.50 0.73ns

Wm 87.30±3.70

Average 85.77 ±2.37

Physico-chemical Site Mean ± SE Sig.

Note: ns (P<0.05), (Average = Mean of mean)

5.2 Fish species composition in the upper part of Blue Nile River

A total of eight fish species were identified during the present study in

the upper part of the Blue Nile River below the fall. These were

Labeobarbus intermedius, Labeobarbus nedgia, Labeobarbus crassibarbis,

Labeo forskalii, Mormyrus kannume, Bagrus docmak, Clarias gariepinus

and Oreochromis niloticus. These fishes representing by a single class

Actinopterygii (ray-finned fishes), four orders, and five families (Table 5).

The Cyprinidae were the dominant families. The freshwater fish fauna of

upper part of Blue Nile River contains a mixture of Nilo-Sudanic (e.g., M.

kannume, B. docmak and L. forskalii) and highland East African (e.g., L.

intermedius, L. nedgia, L. crassibarbis, C. gariepinus and O. niloticus). L.

intermedius, L. nedgia, L. crassibarbis, L. forskalii, B. docmak and M.

kannume were present in all the sampling sites (Table 6). However, C.

gariepinus was found in Sefania and Abenaze sampling sites but O. niloticus

was found only in Sefania site.

Table 5: Fish species composition and local name in Amharic according to the local

people

Species name local name family order

L. intermedius Nech Assa Cyprinidae Cypriniformes

L. forskalii Tubemate » » » »

L. crassibarbis Source » » » »

L. nedgia Mota » » » »

Page | 21

M. kannume Aishe Mormyridae Osteoglossiformes

B. docmak Fergus Bagridae Siluriformes

C. gariepinus Ambaza Clariidae » »

O. niloticus Koroso Cichlidae Perciformes

Table 6: Fish species presence in sampling sites (present, +, absent, -)

Sampling sites

Fish species Se Ab Wm

L. intermedius + + +

L. forskalii + + +

L. nedgia + + +

L. crassibarbis + + +

M. kannume + + +

B. docmak + + +

C. gariepinus + + _

O. niloticus + - -

The fish species composition in upper part of the Blue Nile River during

the study period was low as compared to results obtained by other workers in

the Blue Nile and Tekeze drainage basins. Mohammed Omer (2010),

reported 17 species from head of Blue Nile River (Lake Tana to Tisisat fall),

Genanaw Tesfaye (2006), 10 species identified from Sanja, and Angereb

Rivers, Moges Beletew (2007) 17 species from Beshilo, Dura and Ardi

Rivers, Zeleke Berie (2007) 23 species from Beles and Gelegel Beles, Dereje

Tewabe (2008) 27 species in Guang, Ayima, Gondwana and Shinfa Rivers,

Tesfaye Melak (2009) 59 species from Baro and Tekeze Basins. Flow

variability has an effect on fish assemblage, sometimes-high flows for

instance can destroy fish habitat and can wash the eggs of the fish that have

been already laid. On the other hand, during the dry season when the flow is

low and when the water is reduced, the fishes are trapped in very small

shallow pools that cause stress on fish and make very visible.

Below the Tisisat fall of Blue Nile River, fish species compositions were

different from head of Blue Nile River and Lake Tana fish species

composition as compared Mohammed Omer (2010) and (Nagekerke, 1997)

works, respectively (Table 7). These result due to high waterfalls (40 m) at

Tissisat ('smoking waters'), 30 km downstream from the Blue Nile outflow,

effectively isolate the lake’s ichthyofauna from the lower Nile basin (de

Graaf, 2003). In the present study L. forskalii, M. kannume and B. docmak

were identified which were not recorded from de Graaf (2003) in Lake Tana

and Mohammed Omer (2010) in head of Blue Nile River (Table 7).

Page | 22

Labeobarbus nedgia and L. crassibarbis previously were reported only in

Lake Tana (de Graaf, 2003). Mohammed Omer (2010) also identified these

species from the head of Blue Nile River and Dereje Tewabe (2007) reported

from Gondwana, Guang and Shinfa Rivers. Moreover, Dereje Tewabe et al.

(2008) reported from survey of Tekeze hydropower dam and in the present

study of the Blue Nile River below Tisisat fall. There was preliminary survey

done by Golubtsov and Mina (2003), about 4-5km downstream from Tis

issat falls that recorded four typical Nilotic species: Morymurs hasslequistii,

Labeo forskalii, Raiamas senegalensis and Bagrus docmak. There was

species composition variation between the present study and Golub tsov and

Mina (2003), reported. Golubtsov and Mina (2003) recorded M. hasslequistii

and R. senegalensis fish species but it was not found in the present study. M.

kannume was recorded in the present study but Golubtsov and Mina (2003)

did not record it. There might be variation in sampling habitats, fishing

effort, type of gear they used and gill net efficiency, sampling seasons and

altitude difference that contributed the variation in the catches.

Table 7: Fishes specie composition compression above and below the Blue Nile Fall

(+, present and -, absent)

List of Species Lake Tana head of Blue Nile below the fall

L. intermedius + + +

L. nedgia + + +

L. crassibarbis + + +

L. surkis + + -

L. longissimus + + -

L. platydorsus + + -

L. gorgorensis + + -

L. brevicephales + + -

L. tsanansis + + -

L. acutirostris + + -

L. megastoma + + -

L. gorguri + + -

L. daniellii + + -

L. macrophthalmus + - -

L. trust forms + - -

G.. dembecha + + -

V. beso + + -

C. gariepinus + + +

O. niloticus + + +

Small Barbus + - -

Page | 23

B. docmak - - +

L. forskalii - - +

M. kannume - - +

(Nagelkerke, 1997) (Mohammed Omer, 2010 (Present study, 2011)

5.2.1 Diagnostic and descriptive characteristics of fishes

Labeobarbus intermedius (Banister, 1973) (Fig 4)

Diagnosis: It has variable body shape and heads, has characteristics of

most L. intermedius species.

Description: It has variable body shape and head, has characteristics of

most Labeobarbus species. Head naked, variable in dorsal profile. Mouth is

terminal and protractile. Its HL 17.5-15.43% in SL. Depth of the body is

little greater than head length; its depth 25.68-27.43% SL. It has medium eye

24.87-26.55% in HL. Its DFL and AFL are 20.61- 27.38% and 15.48-22.57%

of SL respectively. Lip development is variable. Lower lip is interrupted and

sometime continuous. Have two barbells on each side of the head. Its caudal

peduncle length is greater than depth.

Coloration: Olive above yellow or pinkish beneath fins first brown or

olive.

Distribution: The species is widely distributed in Ethiopian freshwater

for example in Gibe, Megech, Sanja and Angereb, Borkena and Mille Rivers.

Fig 4: Lateral view of Labeobarbus intermedius

Labeobarbus crassibarbis (Nagelkerke & Sibbing, 1997) (Fig. 5)

Diagnosis: It has irregular dorsal, head profile.

Description: Body depth is greater than head length (its depth 15.30-

49.05% SL). It has small eye (its diameter, 14.71-19.77). Its snout length and

interorbital width is 27.45-35.44 and 27.45-35.46% in HL respectively.

Coloration: Mostly silver white beneath, the fins are whitish; but it

differs depending on the habitat.

Distribution: It was reported from Tekeze River by Genanaw Tesfaye

(2006) and Dereje Tewab (2008) and Lake Tana. (de Graaf, 2003).

Page | 24

Fig 5: Lateral view of Labeobarbus crassibarbis

Labeobarbus nedgia (Ruppell, 1836) (Fig. 6)

Diagnosis: Lips strongly developed both upper and lower, produced into

a rounded or sub triangular lobes. It has fleshy rounded lobe on upper lip that

curls back over the snout.

Description: Depth of the body is little greater than length of head (its

depth 21.08-22.76% in SL). Its eye diameter is 22.5-32.36% in HL. Caudal

peduncle length is grater than its depth (31.34-31.74% in SL).

Coloration: Fins olive or greenish above yellow beneath fins

Distribution: It was reported from Lake Tana, Angereb, Sanja, Omo,

Dedessa, Beles, Gelegel Beles and Borkena Rivers.

Fig 6: Lateral view of Labeobarbus nedgia

Clarias gariepinus (Burchell, 1822) (Fig. 7)

Diagnosis: It has no adipose fin and scales in caudal peduncles and

lateral line.

Description: depth of the body is less than length of the head (its depth

8-12.95 in % SL). The upper surface of head more or less distinctly

granulate; occipital process angular. Its Eye is very small, its diameter of

4.44-6.02% in HL. It has wide interorbital width (30-31.91% in HL). Mouth

is terminal and large Pectoral spin.

Coloration: Dark, grayish-black above and creamy-white underside.

Distribution: All Ethiopian freshwater.

Page | 25

Fig 7: Lateral view of Clarias gariepinus

Mormyrus Kannume (Forsskål, 1775) (Fig. 8)

Diagnosis: Snout at least nearly as long as postorbital part of head;

dorsal in advance of base of ventral fins with rays; anal rays; scale in lateral

line.

Description: Depth of the body is less than length of head (its depth

20.71-23.41% in SL). Upper profile of head is descending in straight line. It

has small eye (14.4 -19.67% in HL). Paired and vertical fins all present;

narrow caudal peduncle depth (6.82-9.39% SL) and deeply forked caudal

fin. Dorsal fin rays 51-59, Anal fin rays 22-23. Dorsal and anal fins are

opposite each other on the posterior part of body.

Coloration: Brownish or olive above and white in beneath.

Distribution: Gendewuha, Guang, Omo, Angereb, Ayima and Gibe

Rivers.

Fig 8: Lateral view of Mormyrus kannume

Bagrus docmak (Forskalii, 1775) (Fig. 9).

Diagnosis: Body is slightly elongated. It has long barbells.

Description: Depth of the body is almost equal to head length (18.9-

26.33% SL). Its head much depressed and smooth above. It has short snout

length (7.94-10.61% in HL). It has relatively small eye (10-14.22% HL).

Barbell length is much greater than head length. Caudal peduncle length is

greater than its depth. Caudal is deeply forked.

Page | 26

Coloration: Grayish blue to dark olive above, white beneath.

Distribution: Guang, Omo, Sanja, Angereb, Ayima, Beles and Gelegel

Beles Rivers.

Fig 9: Lateral view of Bagrus docmak

Labeo forskalii (Rüppell, 1835) (Fig. 10)

Diagnosis: Labial folds well-developed sucker around the mouth

distinguishes this species, rostral flap large and horny tubercles on the snout.

Description: Body more or less compressed, its depth 19.02- 20.99%in

SL. Snout is swollen with distinct curved transverse groove above. Snout

length is greater than head length (its length 41.12 – 54.55%in HL). It has 11

to 12 dorsal fin rays and 18 to 21 caudal fin rays.

Coloration: Dark olive above and on the sides, whet beneath.

Distribution: Dubus, Angereb, Sanja, Tekeze, Baro, Omo, Gendewuha,

Guang, Ayima and Gibe, Beles and Gelgel Beles Rivers.

Fig 10: Lateral view of Labeo forskalii

Oreochromis niloticus (Linnaeus, 1758) (Fig. 11)

Diagnosis: The most distinguishing characteristic of O. niloticus species

is the presence of regular vertical stripes throughout the depth of caudal fin.

Description: Depth of the body is greater than the length of head (its

depth 34.97-43.56% SL). Snout rounded, with straight or slightly convex

upper profile. It has relative large eye, its diameter 16.37-24.07% in HL. The

pectoral and pelvic fin length is 28-34.25 and 21.33-25.56% SL respectively.

Page | 27

Coloration: Brown or grey to dark olive color.

Distribution: Almost all Ethiopian freshwater.

Fig 11: Lateral view of Oreochromis niloticus

5.2.2 Species diversity and abundance

5.2.2.1 Species diversity

Labeobarbus intermedius, L. nedgia and L. forskalii were common in all

the sampling sites in both seasons. However, M. kannume and B. docmak

were found in all the sampling sites during wet season but it was absent

during dry season at Wm site (Table 9). Clarias gariepinus was found both

in Se and Ab sites during the dry and wet seasons but absent in Wm site at

both sampling periods. Oreochromis niloticus did not found in both Ab and

Wm sites during the dry and wet seasons. The number of fish species is

higher at Se sampling site and lower in Wm sampling site (Table 9). Eight

species at Se and six species from Wm sampling sites were recorded (Table

8). Blue Nile River below the Blue Nile Fall was dominated by the Family

Cyprinidae and mainly by the genus Labeobarbus.

Table 8: Fish distribution among the sampling sites both dry and wet seasons (+:

present;- :absent)

Sampling sites

Se Ab Wm

Fish species family dry wet dry wet dry wet

L. intermedius Cyprinidae + + + + + +

L. nedgia Cyprinidae + + + + + +

L. crassibarbis Cyprinidae + + + + + +

L. forskalii Cyprinidae + + + + + +

M. kannume Mormyridae + + + + _ +

B. docmak Bagridae + + + + _ +

C. gariepinus Clariidae + + + + _ _

O. niloticus Cichlidae + _ _ _ _ _

Page | 28

Shannon diversity index (H') was used to evaluate species diversity of

sampling sites. Shannon diversity index explains both variety and the

relative abundance of fish species (Naesje et al., 2004). The species diversity

in Se site showed more diversity than Abenaze and Wotetomider in dry

season but it is the lowest in wet seasons (Table 9 &10 and Fig 14). The H'

was higher in Se sampling site with the values of (H' = 1.44) followed by Ab

(H'= 1.33) and Wm (H' = 1.23) in dry season sampling period (Table 9).

However, the H' was higher in Wm sampling site with the values of (H' =

1.62) followed by Ab (H' = 1.60) and Se (H’ = 1.58) in wet season sampling

period (Table 10).

Table 9: Shannon diversity index (H') and number (N) of fish species in dry

season

H'/N Sampling sites

Se Ab Wm

H' 1.44 1.33 1.23

N 8 6 4

Table 10: Shannon diversity index and number of fish species in wet season

H'/N Sampling sites

Se Ab Wm

H' 1.58 1.60 1.64

N 7 7 6

Fig 12: Shannon diversity index (H') and Number of fish species in both dry and wet

seasons

During the study period, 128 kg and 232 kg total biomass of specimens

were collected during wet and dry seasons, respectively (Table 11). The

Page | 29

number of fish species was higher in dry season than wet season. However,

Shannon diversity index (H') value was higher in wet season in all the

sampling sites (Fig 12).

Table 11: Number and total biomass (kg) of fish during wet and dry season

Season Total weight (kg) Total number

Dry 232 553

Wet 128 304

Dry season showed higher values than wet season in terms of weight

(kg) and number of specimens of fishes. The reason would probably be

during wet seasons there is high turbidity of river, speedy run-off, and low

temperature that attributed less number of fish catch in wet season. During

wet season, there is also higher water discharge; fishes could be highly

dispersed in the large volume of water than dry season and it becomes

difficult to catch them. In addition to the variation in catches between wet

and dry seasons might be variation gill net efficiency and time of setting of

gill net might also contribute to variation in the catches. The efficiency of

gill nets could be decreased by logs, leaves, roots that were brought by

flooding.

5.2.2.2 Relative abundance of fish during wet and dry seasons

The species composition of gillnet and monofilament catches both in dry

and wet season ranked based on the IRI value for different sampling site

(Table 12 and 13). Labeobarbus intermedius was the most abundant species

during the study period and constituting of 39.67% in the total number of

catch. L. forskalii and M. kannume were found in relative abundance of

27.77% and 11.67% respectively (Table 12). The other species, L. nedgia, B.

docmak, L. crassibarbis, C. gariepinus and O. niloticus were found in

9.59%, 5.13%, 3.5%, 1.98% and 0.70%, respectively.

There was significant difference in fish specimen abundance between

dry and wet season except L. crassibarbis, B. docmak and C. gariepinus

(Table 12). Labeobarbus intermedius was the most important fish species in

both dry and wet season in all sites (Table 12 and 13). Labeo forskalii was

very important in all sampling site except Wm during the wet season.

Mormyrus kannume was important in all sites except in Wm in wet season

but was less important in all sites during dry season.

Labeobarbus intermedius and L. forskalii showed very highly

significant variation in number of catch between dry and wet season

(P<0.001). Mormyrus kannume and L. nedgia showed significant variation in

Page | 30

number of catch between dry and wet season (P<0.01) and (P< 0.05)

respectively (Table 12). However, B. docmak, C. gariepinus, L. crassibarbis

and O. niloticus did not show significant variation in number of catch

between dry and wet season (P>0.05).

Table 12: Species number and percentage composition of both in dry and wet season

in sampling sites (One way ANOVA)

Seasons

Fish species dry wet total percentage composition sig.

L. intermedius 243 97 340 39.67 0.000***

L. forskalii 179 59 238 27.77 0.000 ***

L. nedgia 52 30 82 9.57 0.015*

L. crassibarbis 14 16 30 3.50 0.715 ns

M. kannume 31 69 100 11.67 0.00 **

B. docmak 17 27 44 5.13 0.132 ns

C. gariepinus 11 6 17 1.98 0.225 ns

O. niloticus 6 0 6 0.70-

Note: *(P<0.05) (significant), **(P<0.01) (highly significant), ***(P<0.001) (very

highly significant), and ns (P>0.05) (non-significant)

The species collected were analyzed based on the Index of Relative

Importance. Accordingly, L. intermedius % IRI values (58.82%, 54.54%, and

48.05%) and (30.55%, 42.17%, 43.58%) in Se, Ab and Wm during wet and

dry seasons respectively given in Table (13and 14). The percentage IRI of L.

forskalii in dry season was (24.56%, 37.27% and 22.41%) in Se, Ab and

Wm, respectively. The percentage IRI value of L. forskalii was higher both

in dry and wet season in all the sampling sites (Table 13 and 14). The % IRI

value of M. kannume was higher in Se and Ab sites during wet season.

Nevertheless, it had small % IRI value in Wm site during wet season and in

all sampling sites during dry season (Table 13 and 14). During dry season L.

intermedius, L. forskalii and L. nedgia were the most important species with

in Se and Wm sampling sites whereas in Ab site the most important species

were L. intermedius, L. forskalii and M. kannume. Percentage IRI value from

the pooled catch in sampling sites for L. intermedius (51.92%), L. forskalii

(29.14%), L. nedgia (6.81%) and M. kannume (5.99%) were in order of their

decreasing importance (Table 15).

Page | 31

Table 13: Percentage index of relative importance of fish species in dry season

Sites Fish N %N W% %WF F IRI % IRI

Se L. intermedius 11 41.9 56184 48.2 7 21.21 1915 58.82

L. forskalii 95 35.2 35714 30.78 4 12.12 799.5 24.56

L. nedgia 19 7.04 6818 5.88 6 18.18 234.8 7.21

L. crassibarbis 4 1.48 5438 4.69 2 6.06 37.38 1.55

M. kannume 18 6.67 4281 3.69 4 12.12 125.5 3.86

B. docmak 9 3.33 4074 2.04 3 9.09 62.22 1.91

C. gariepinus 6 2.22 2364 1.01 4 12.12 51.63 1.59

O. niloticus 6 2.22 1171 100 3 9.09 29.38 0.90

Total 270 100 116044 51.43 - - 32.55 -

Ab L. intermedius 74 45.12 31355 31.84 6 31.6 3049 54.54

L. forskalii 56 34.15 19411 2.67 4 21.1 2084 37.27

L. nedgia 8 4.88 1626 4.08 2 10.5 79.42 1.42

M. kannume 13 7.93 2486 6.10 3 15.8 189.5 3.39

B. docmak 18 4.88 3716 3.89 2 10.5 115.5 2.07

C. gariepinus 5 3.05 2369 100 2 10.5 73 1.31

Total 164 100 60963 48 - - 5590 -

Wm L. intermedius 56 47.1 26447 15 6 26.09 2483.55 48.05

L. forskalii 28 23.5 7978 17 7 30.43 1158.12 22.41

L. nedgia 25 21 9204 21 7 30.43 1149.32 22.23

L. crassibarbis 10 8.4 11304 3 13.04 378.02 7.31

Total 119 100 54933 100 - 5169.01 -

Table 14: Percentage index of relative importance of fish species during wet season

Sites Fish N %N W% %WF F IRI % IRI

Se L. intermedius 32 29.09 12702 29.74 5 18.52 1089.94 30.55

L. forskalii 20 18.18 8314 19.74 7 25.93 976.06 27.37

L. nedgia 3 2.73 968 2.27 2 7.41 36.99 1.04

L. crassibarbis 6 5.43 6827 15.98 2 7.41 158.80 4.45

M. kannume 38 34.45 9237 21.63 5 18.52 1040.22 29.17

B. docmak 8 7.27 3210 7.52 4 14.81 219.08 6.14

C. gariepinus 3 2.73 1454 3.40 2 7.41 45.42 1.27

Total 110 100 42712 100 - - 3565.98 -

Ab L. intermedius 43 36.75 18361 34.77 6 22.22 1589.29 42.17

L. forskalii 24 20.51 9794 18.54 7 25.93 1012.60 26.87

L. nedgia 5 4.27 4666 8.83 1 3.70 48.55 1.29

L. crassibarbis 4 3.42 6257 11.85 2 7.41 113.08 3.00

Page | 32

M. kannume 27 23.08 7048.6 14.78 5 18.52 701.03 18.60

B. docmak 11 9.40 4488 8.50 4 14.81 265.18 7.04

C. gariepinus 3 2.56 1442 2.73 2 7.41 39.22 1.04

Total 117 100 52813 100 - - 3768.95 -

Wm L. intermedius 22 28.57 8606 27.75 7 31.82 1728.44 43.58

L. forskalii 15 19.48 5401 16.16 4 18.18 648.03 16.34

L. nedgia 22 28.57 8598 25.73 4 18.18 987.25 24.89

L. crassibarbis 6 7.79 6490 19.42 2 9.09 247.34 6.24

M. kannume 4 5.19 755 2.26 2 9.09 67.76 1.71

B. docmak 8 10.39 3570 10.68 3 13.64 287.34 7.24

Total 77 100 33420 100 - 3966.20

Percentage IRI of L. intermedius was higher at Se and lower at Wm in

dry season and it was higher at Wm and lower at Se site in wet season.

Percentage of IRI of L. forskalii was higher at Ab and lower at Wm in dry

season and it was higher at Se and lower at Wm (Table 13 and Fig 13).

Percentage IRI of M. kannume was higher during wet season and lower

during dry season in all sampling sites.

Fig 13: Percentage IRI of dominant fish species in sampling sites during dry and wet

season

There might be several reasons for changes in abundance between wet

and dry seasons. Variation in available nutrients and habitats, fishing effort,

fish behavior, size and life history stages of fishes might all contribute to

variation in abundance of the catches. Moreover, water level (Karenge and

Kolding, 1995) and turbidity of water may also affect abundance.

Page | 33

Table 15: Pooled catch of IRI and H' values in both dry and wet seasons at all the

sampling sites

Sites N %N W% WF %F IRI % IRI H’

L. intermedius 340 39.67 153655 42.69 37 24.50 2018.22 51.92 0.37

L. forskalii 238 27.77 86612 24.06 33 21.82 1132.83 29.14 0.36

L. nedgia 82 9.57 30912 8.59 22 14.57 264.54 6.81 0.22

L. crassibarbis 30 3.50 36316 10.09 11 7.28 99.01 2.55 0.12

M. kannume 100 11.67 24563.6 6.82 19 12.58 232.70 5.99 0.25

B. docmak 44 5.13 19058 5.30 16 10.06 110.51 2.84 0.15

C. gariepinus 17 1.98 7629 2.12 10 6.62 27.17 0.70 0.08

O. niloticus 6 0.70 1171 0.50 3 4.00 4.82 0.12 0.03

Total 857 - 359916.6 - - - 3887.01

5.2.2.3 Length frequency distribution of the dominate fish species

The length frequency distribution of the most dominant species of L.

intermedius, L. forskalii and M. kannume are showed in (Figure 14).

Labeobarbus intermedius the most dominant species had total length rage

from 17 to 52.3 cm, with the mean and standard error of total length was

32.5±0.50 (Fig 14). Labeo forskalii is the second most abundant species with

total length range from 13.8 to 46.5 cm with mean and standard error of 34.3

±0.39 (Fig 14). Mormyrus kannume is the third abundant species had total

length rage from 25.2 to 40.8 cm with mean and standard error of 32.2± 0.44

(Fig 14).

Page | 34

Fig 14: Length frequency distribution of L. intermedius (N= 340), L. forskalii

(N=238) and M. kannume (N= 100) respectively

5.3 Some biological aspects of the dominant fish species

5.3.1 Length-weight relationship

The relationship between total length and total weight for most

dominant species of L. intermedius, L. forskalii and M. kannume were

curvilinear and showed significant variation (P<0.001).

In fishes, the regression coefficient b=3 describes isometric growth,

when the value becomes exactly 3, if the fishes retain the same shape and

their specific gravity remains unchanged during their life time (Ricker,

1975). If the weight increased according to the fish length, it is said to be

isometric growth (Mansor Mat Isa S.A.S.A., 2001). However, fishes may

have “b” value greater or less than 3, a condition of allometric growth

(Bagenal and Tesch, 1978). A value less than 3.0 shows that the fish becomes

lighter (-ve allometric) or greater than 3.0 indicates that the fish become

heavier (+ve allometric) for a particular length as it increases in size

(Wootton, 1998; Zafar et al., 2003). L. intermedius in the upper part of Blue

Nile River showed nearly isometric growth, which means the weight of these

Page | 35

fishes increases as the cub of length because the b value is nearly 3 for these

fish species in river (Fig 15). This value was close to the values reported for

some freshwater fish species by Genanew Tesfaye (2006), in Angereb and

Sanja Rivers, Wassie Anteneh (2005), in Dirma and Megech Rivers, Abebe

Getahun et al., (2008) in Rib River, Assefa Tessema (2010), in Borkena and

Mille Rivers and Mohammed Omer (2010), in head of Blue Nile River. On

the other hand the b values obtained in this study area for L. forskalii and M.

kannume show negative allometric growth unlike that reported by Dereje

Tewabe (2006) in Gendewuha, Guang, Shinfa and Ayima Rivers and

Genanaw Tesfaye (2006), in River Angreb. However, the result obtained in

this study b value for L. forskalii in upper part of Blue Nile River is in

agreement with the values obtained by Zeleke Berie (2009) from Gelegel

Beles River.

Page | 36

Fig 15: Length-weight relationship of L. intermedius, L. forskalii and M. kannume

respectively

5.3.2 Fulton’s condition factor (FCF)

The mean Fulton condition factor value obtained in the present study for

L. intermedius in the Blue Nile River below the Tisisat fall was 0.99, which

was less than reported by Genanaw Tesfaye (2006), from Angereb and Sanja

Rivers with a value of 1.06, Dereje Tewabe (2008), from Gondwana, Guang

and Shinfa Rivers with a value of 1.12, Assefa Tessema (2010), with a values

of 1.23 and 1.31 in Borkena and Mille Rivers. Nevertheless, it is higher than

the result obtained by Mohammed Omer (2010), with value of 0.87 in a head

of Blue Nile River. The present FCF value of L. intermedius was similar to

that reported by Zeleke Berie (2009), in Gelegel Beles River. The

measurement of fish condition can be linked to the general health, fat and

lipid content prey or food availability, reproductive potential, environmental

condition and water level fluctuation. In general, higher condition is

associated with higher energy (fat) content, increasing food base,

reproduction potential or more favorable environmental condition (Pauker

and Cottle, 2004).

Table 16: Mean and Standard deviation of Fulton condition factor both by sex and

season: P= significance difference (Mann-Whitney U test) between sex and seasons

of dominant fish species

Fish Sex Mean ± SD P Season Mean ± SD P

L. intermedius

F

M

Average

0.99±0.16

0.97±0.09

0.99±0.15

ns Wet

Dry

0.97±0.14

0.99±0.16

0.98±0.15

ns

L. forskalii

F

M

Average

0.83±0.09

0.86±0.18

0.84±0.11

ns

Wet

Dry

0.80±0.06

0.850.12

0.83±0.11

***

Page | 37

M. kannume

F

M

Average

1.00±0.00

1.00±0.00

1.49±0.050

ns Wet

Dry

1.00±0.00

1.00±0.00

1.32±0.047

ns

Note: ** =P<0.01, ns =P>0.05, (Average =Mean of mean)

The mean Fulton condition factor of L. intermedius did not show

significant variation in sex and season respectively (Table 16). The mean

Fulton condition factors of L. forskalii in dry season was (0.85±0.12) which

is higher than wet season (0.80±0.06). There was significant variation in

Fulton condition factor of L. forskalii between dry and wet season (P<0.01),

but it did not showed significant variation between sexes (Table 16). This

result is in agreement with Genanaw Tesfaye (2006) that reported significant

variation (P<0.05) for L. forskalii between dry and wet seasons in Sanja and

Angereb Rivers. Labeo forskalii was in better condition in dry season than in

wet season. The mean Fulton condition factor of M. kannume was

(1.49±0.05) and (1.32±0.047) in sex and season, respectively. There was no

significant variation between Fulton condition factor by sex and seasons. The

low Fulton condition factor of fishes of the river is probably because of

fluctuation in factors such as food quantity and quality, water level and flow

rate and temperature.

5.3.3 Some aspect of reproductive biology

5.3.3.1 Sex ratio

From total number of 857 specimens of fish collected from upper part of

Blue Nile River during the study period, 17 (1.98%) specimens were

unsexed, hence excluded from sex ratio study. Totally 840 (98.02%)

specimens were sexed of which 619 (73.69%) were females and 221

(26.31%) were males. In general, females were numerous than males. The

chi-square test showed that there were significant variations between number

of male and female fish species of L. intermedius, L. forskalii, L.

crassibarbis and B. docmak (Table 18). The sex ratio of L. intermedius, L.

forskalii and L. crassibarbis showed significant variation (χ², P<0.001). B.

docmak showed significant variation (χ², P<0.01) between number of male

and female (Table 18). However, L. nedgia, M. kannume, C. gariepinus and

O. niloticus did not show significant variation between male and female.

During the study period, the highest deviation in sex ratios was observed in

L. crassibarbis (6.50:1) and the second one was O. niloticus (5:1) (Table17).

Page | 38

Table 1: Number of males, females and the corresponding sex ratios (pooled from all

sites) (One way ANOVA)

Species F M Sex ratio χ² P (F: M)

L. intermedius 248 77 3.22:1 89.97 0.000***

L. forskalii 196 41 4.87:1 101.37 0.000***

L. nedgia 47 34 1.38:1 2.09 0.185ns

L. crassibarbis 26 4 6.50:1 16.13 0.000***

M. kannume 51 49 1.04:1 0.04 0.841ns

B. docmak 33 11 3.00:1 11 0.001**

C. gariepinus 13 4 3.25:1 4.76 0.225ns

O. niloticus 5 1 5.00:1 2.67 0.102ns

Note: **highly significance (P<0.01), *** Very highly significance (P<0.001), (ns)

not significant (P>0.05)

The imbalance of female to male ratio was most probably related to

different biological mechanisms such as differential maturity rates,

differential mortality rates and differential migratory rates between the male

and female sexes (Sandovy and Shapiro, 1987; Matsuyama et at., 1988).

5.3.3.2 Fecundity

Absolute fecundities of the most dominant fish species (L. intermedius)

was determined based on number of eggs per total length, total body weight

and gonad weight. Eleven specimens of L. intermedius with total length

ranging from 25.5 to 47.4 cm, mean and standard error of 38.7 and 2.35 had

mean absolute fecundity (AF) of 3705 and ranged from 1345 to 7235 eggs.

The relationship between AF with TL, TW and Gonad Weight of L.

intermedius was linear. In general, absolute fecundity of L. intermedius was

strongly positive correlated with TL. TW and GW (Fig 16).

The information about fecundity of large Barbus fish species in Africa is

scarce (Marshall, 1995). There was few data on the fecundity of Ethiopian

large Barbus. Alekseyev et al. (1996) and Wassie Anteneh (2005) studied

fecundity of large Barbus in Lake Tana and its tributaries. The absolute

fecundity of L. bervicephalus and L. truttiformis ranged from 1284 to 4563

and 1732 to 8134 eggs, respectively in Lake Tana (Wassie Anteneh, 2005).

Compared to Lake Tana Labeobarbus species a similar sized female L.

intermedius in the Blue Nile River below the Tisisat fall have more or less

similar number. The absolute fecundity of L. intermedius reported by Dereje

Tewabe (2008) ranged from 542 to 13769 in Gendewuha, Guang, Shinfa and

Ayima Rivers. In Borkena and Mille Rivers reported the absolute fecundity

of L. intermedius ranged from 2736-12124 (Assefa Tessma, 2010).

Page | 39

(A)

(B)

Fig 16: ABC Absolute fecundity with total length, total weight and Gonad weight

relation in L. intermedius (n= 11)

Page | 40

Chapter - 6

Fishing Activity and Its Problems in the Study Area

6.1 Fishing Activity

Questionnaires were developed and interviewed the local inhabitant of

villages near the River: Sefania, Abenaze and Wotetomider to know the

fishing activity of the farmers and identify major problems. The information

obtained from the questionnaires and from personal communication was

used to state about the fishing activity in the river and identify its problems.

There were 30 farmers in the study area that were selected and

interviewed. The farmers’ source of income is crop and animal farming.

Fishery was an additional source of food. They fish for their own

consumption and as a gift for relatives. The entire farmers in upper part of

Blue Nile River were seasonal and the fishing activity takes place only from

the river. They usually start fishing activities in the river in the middle of

November. They start during this time because in most cases the water level

starts to lower.

The fish catch data from upper part of the Blue Nile River was not

available. The farmers fishing activity takes place at night. However, rough

estimates can be made from the observations I had and interviews made with

the farmers. Accordingly, fishing activity takes place at about three sites

along the stretch of the river. It takes place for about six months (15

November to end of May) sometimes in June and July. Farmers catches fish

on average four day per week and 17 days per month. They estimated their

daily catch up on average five fish/night/person (about 10 kg/night/person).

From each site 204kg of fish harvest per six months per person per site. In all

sampling site an average of 18.36 quintals of fish has been harvest annually

from the three sampling site. The method I used to estimate based on

interview result. Fishing intensity in the study area was higher starting from

January to May (Fig 17). Fish potential of the river is decline from time to

time due to environmental fluctuation (personal communication). According

to Gebru Asrat (personal communication), few species extinct from the river

for example, L. horie in local language “Assam nalbari”. This fish was

present in the river few years ago and they were catch frequently but now it

Page | 41

does not found. The probable reason they put was fluctuation of the river

volume year-to-year and other environmental variations. For example, in

2010 the river was total blocked at the source in Lake Tana, during this time

there was numerous fish massive fish death and also catch by the local

people using hand. In addition, huge amount of fish was dead on October

(2010) after heavy ran fall. The reason of this the rainfall is mixe up with

snow. This leads to increase the coldness of the river.

0

5

10

15

20

25

30

35

Sept

Oct

Nov

Dec

Juan

Feb

Mar

Apr

May

Jan

Jul

Aug

Month

Nu

mb

er

of

resp

on

dan

t

Fig 17: Farmers fishing time in the study area

There is no as such any technical assistance (extension service) for the

local community with regard to utilization and management of the fish

resource. There is no any modern fishing gear in the area. Most local

fishermen use hook and line (Local name is mekatin) and Castnet (Local

name is mereab) for catching fish. The hook and line has got three size

categories (Large, medium and small). Those local fishermen used part of

the flesh of fish as bait. Some of the local fishermen used locally made gill

nets with mesh size of approximately 12cm.

When the volume of the river is becoming low there is high fishing

intensity by local community and the fish prey by other aquatic animals such

as birds and crocodiles. Most of the respondents are willing to cooperate in

any measures that would lead to sustainable utilization of the fish resources.

They are also eager to get modem fishing gear like gillnets.

Farmers identify some of the fish species with their local names: "Nech

Assa" (L. intermedius), "Tubemate" (L. forskalii), "Source" (L. crassibarbis),

"Mota" (L. nedgia), “Aishe” (M. kannume),”Fergus” (B. docmak), "Ambaza"

(C. gariepinus), "Koroso" (O. niloticus, Nile tilapia). They very well

Page | 42

understand that there is diversity of fish in upper head of Blue Nile River.

Almost all of the respondents said that more than, 90% of the catch is

composed of L. forskalii, M. kannume, L. intermedius, and B. docmak (this

especially used after drying). Among the above fish, species the farmer

prefer to consume L. intermedius and L. forskalii. They prefer the two

species because they assume high quality and the fishes are attractive when

seen externally. All of the respondents do not have storage facilities but they

have tried to improve the shelf life of the fish by sun drying methods by

making a strip of the flesh of catfish and Bagrus docmak

6.2 Problems in fishing activities

Main problems mentioned by respondents in upper part of Blue Nile

River were: Lack of proper fishing gears; almost all of them use hook and

line and castnet for fishing, lack of knowledge in fishing and fish processing,

lack of infrastructure and market, especially those local fisherman live far

from woreda town, lack of post-harvest technology in case of excess

production. As a result, the fishermen catch fish only for household

consumption purposes. There is no extension service that assists the fishery

activities.

Page | 43

Chapter - 7

Limitation of the Study

Data were collected only in two seasons due to logistic and budget

constraints and hence it was difficult to collect enough information on

reproductive biology of dominant fish species: L. intermedius, L. forskalii

and M. kannume. In addition to this, sampling duration and sampling sites

were limited due to budget and rugged topography location so that the

chance of obtaining many new species in the rivers became low. The

efficiency of fishing gears was also another limitation for my current study.

Page | 44

Chapter - 8

Conclusion and Recommandations

8.1 Conclusion

Eight species of fishes included in 5 families and 4 orders were

investigated from upper part of Blue Nile River.

Diversity of the fish fauna of the River is dominated by cyprinid

fish species. L. intermedius, L. forskalii and M. kannume were the

most dominant fish species in number and total biomass during the

study periods.

Sefania site had higher fish diversity in dry season than the other

sampling sites. But it had lower diversity in wet season as compared

to Abenaze and Wotetomider. Shannon diversity value (H’) of

Sefania was (1.44) in dry and (1.58)in wet season, where as

Abenaze and Wotetomider had 1.33 and 1.23 in dry and 1.60 and

1.62 in wet season respectively.

L. intermedius, L. forskalii and M. kannume were the most

important fish species during wet season with IRI value of 46.64%,

17.69% and 16.87%, respectively. Whereas L. intermedius, L.

forskalii and L. nedgia were the most dominant fish, species during

dry season with IRI value of 57.32%, 28.96% and 8.27%,

respectively.

L. intermedius, L. forskalii and M. kannume were with highest

diversity, with the Shannon diversity index value of 0.37, 0.36 and

0.25, respectively.

L. intermedius, L. forskalii and M. kannume were the most

important fish species in the upper part of the Blue Nile River. Their

compositions from the total catches were 39.67%, 27.77% and

11.67% respectively.

The length weight relationships for L. intermedius, L. forskalii and

M. kannume were curvilinear. L. intermedius showed nearly

isometric relation, but L. forskalii and M. kannume showed negative

allometric relation.

Page | 45

There was significant difference in Fulton condition factor for L.

forskalii between dry and wet seasons (P<0.01).

Fulton condition factor of L. forskalii in dry and wet seasons was

(0.85±0.12) and (0.80±0.06), respectively. Therefore, L. forskalii

was in better condition in dry season than wet season.

The chi-square test analysis showed that there was significance

variation in number of male and female of L. intermedius and L.

forskalii with (P< 0.001). However, M. kannume did not showed

significant variation in number of male and female.

Fecundity was found to have linear relation with total length, total

weight and gonad weight for L. intermedius.

The upper part of Blue Nile River has a number of fish species and

the people in this area have fish consuming habit.

L. intermedius, L. forskalii, M. kannume and B. docmak are the

most subsistence fish species in of Blue Nile River below the Tisisat

fall.

L. intermedius and L. forskalii are the most preferred fish species

consumed by the local people.

8.2 Recommendations

Detailed studies and investigations are required on:

The diversity, abundance and biology of fish species was carried

out only in upper part of the River only in two seasons over

relatively short period of time. Besides, the study was conducted

only at three sites. For comprehensive assessment on the magnitude

of fish, diversity in these river investigations should be conducted

throughout the year using more sites and different sampling

methods. Investigations should also be done along the river until the

border of Sudan by selecting many more suitable sampling sites.

Food and feeding behaviors of the fish species in the river.

Ecological issues specially that of catchment area of the rivers.

There are indications of severe degradations of the river basins

particularly the upper part of the river catchment area. Major threats

to the basins are related to deforestation and erosion. This issue

requires scientific study so that sustainable utilization of the

resources is designed.

The water released from Lake Tana should be constant, so that it

does not affect the natural flow of the regime.

Page | 46

There is lack of information on the fish and fisheries in the river.

This should be given emphasis by the respective institutions or

organizations so as to introduce appropriate extension systems to

identify and exploit the fishery resources in a sustainable manner.

Fishermen need to be encouraged through training and provision of

appropriate fishing gears, since crocodile problem for gillnet is

paramount in the area. Organizing fishermen in cooperatives with

strong extension network with expertise is recommended.

The government should be implement fisheries legislation to

encourage the fishermen

Awareness creassion should be given for fishermen’s about fishing

activity and supply appropriate fishing gears.

Integrated watershed management should be done in the river

drainage basins.

Fish species of L. nedgia and L. crassibarbis were required further

identification because of previously the two species are endemic to

Lake Tana only.

Page | 47

References

1. Abebe Getahun (2002). The Nile basin: Riverine fish and Fisheries,

Department of Biology Addis Ababa University, Ethiopia 19pp.

2. Abebe Getahun (2005a). Fresh water eco-regions of Ethiopia. In:

Theime et al., (eds) Freshwater eco-region of Africa. Aconservation

assessment/ Island press, Washington, D.C., U.S.A.

3. Abebe Getahun (2005b). An over View of the diversity and conservation

status of Ethiopian freshwater fish fauna. In proceeding of the Pan.

Africa fish and fisheries society, Cotonou, Benin, Nov.2003.

4. Abebe Getahun (2007). An overview of the diversity and conservation

status of the Ethiopian freshwater fish fauna. J. Afrotropical Zoology

special Issue: 87-96.

5. Abebe Getahun and Stiassny, M.L.J. (1998). The freshwater

Biodiversity Crisis: the case of Ethiopian fish fauna. SINET. Eth. J. Sci

21(2):207-230.

6. Abebe Getahun, Eshete Dejen and Wassie Anteneh (2008). Fishery

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Appendixs

Physico chemical parameters of the river at sampling site both in dry

and wet seasons

Parameter Site Mean ±SE Sig

Cond Se 76.32±4.67 0.000***

Ab 193.4±5.00 0.000***

Wm 177.20±4.80 0.000***

Temp Se 20.9±0.70 0.000***

Ab 23.30±0.50 0.000***

Wm 24.00±0.50 0.000***

TDS Se 87.50±3.50 0.000***

Ab 82.50±6.50 0.000***

Wm 87.30±3.70 0.000***

Trans Se 37.50±12.50 0.000***

Ab 32.00±8.00 0.000***

Wm 33.50±11.50 0.000***

pH Se 5.56±0.69 0.000***

Ab 5.96±0.09 0.000***

Wm 6.88±0.34 0.000***

Note: ***(Very highly significant)

Morphometric and merstic measurements of Fishes

Morphometric and Merstic characteristics of L. intermedius

Character n mean SD Max Min

% SL

HL 4 16.85 0.96 17.52 15.43

BD 4 26.23 0.80 27.43 25.68

Pc.FL 4 16.98 1.00 17.62 15.48

Pv.FL 4 14.83 3.55 18.22 10.56

DFL 4 23.83 3.19 27.38 20.61

AFL 4 19.26 3.29 22.57 15.48

CPL 4 34.95 4.90 39.90 30.56

CPD 4 8.75 0.49 9.11 8.02

%HL

SnL 4 26.69 0.89 27.96 25.87

Page | 55

HD 4 71.96 4.26 75.39 66.12

ED 4 25.71 0.84 26.55 24.87

IOW 4 26.38 1.15 27.14 24.67

Merstic

DFR 4 9.75 0.5 10 9

CFR 4 20.75 0.5 21 20

LLS 4 32.25 1.71 34 30

Morphometric and merstic characteristics of L. forskalii

Character n mean SD Max Min

% SL

HL 4 20.79 1.92 23.3 18.93

BD 4 20.11 0.88 20.99 19.02

Pc.FL 4 22.43 0.82 23.26 21.4

Pv.FL 4 21.28 1.74 22.63 18.84

DFL 4 34.16 3.41 39.15 31.28

AFL 4 18.75 1.66 21.08 17.28

CPL 4 11.15 1.02 11.79 9.63

CPD 4 38.08 4.48 43.05 32.56

%HL

SnL 4 48.65 5.72 54.55 41.12

HD 4 72.3 8.83 79.55 60.28

ED 4 16.36 3.61 20.45 11.98

IOW 4 45.93 3.66 50 41.9

Merstic 4

DFR 4 11.5 0.58 12 11

CFR 4 20 1.41 21 18

LLS 4 41.25 0.5 42 41

Morphometric and merstic characteristics of L. nedgia

Character n mean SD Max Min

% SL

HL 4 18.22 1.86 20.62 16.09

BD 4 21.92 0.85 22.76 21.08

Pc.FL 4 19.43 3.69 22.17 13.98

Pv.FL 4 17.12 3.02 20.83 13.80

DFL 4 23.32 3.72 26.21 18.37

AFL 4 18.45 3.28 20.94 13.89

CPL 4 9.18 0.76 10.52 9.12

Page | 56

CPD 4 31.53 0.20 31.72 31.34

%HL

SnL 4 28.52 4.08 34.63 26.18

HD 4 60.98 11.37 74.45 51.5

ED 4 26.15 4.29 32.36 22.5

IOW 4 28.44 3.91 34.30 26.43

Merstic 4

DFR 4 10.5 0.58 11 10

CFR 4 20.75 1.5 22 19

LLS 4 31.5 1.29 33 30

Morphometric and merstic characteristics of M. kannume

Character n mean SD Max Min

% SL

HL 6 23.81 1.09 25.69 22.81

BD 6 21.96 1.12 23.41 20.72

Pc.FL 6 16.42 1.76 17.96 13.06

Pv.FL 6 11.46 0.27 11.83 11.15

DFL 6 48.27 2.46 51.70 45.36

AFL 6 16.68 2.09 19.46 13.66

CPD 6 6.36 0.42 6.81 5.71

CPL 6 10.35 0.99 11.45 8.67

%HL

SnL 6 27.27 3.80 33.93 22.89

HD 6 46.88 5.34 55.36 40.96

ED 6 16.98 1.82 19.67 14.46

IOW 6 27.24 1.66 28.57 24.09

Merstic

DFR 6 54 2.68 59 51

CFR 6 22.5 0.55 23 22

LLS 6 - - - -

Morphometric and merstic characteristics of B. docmak

Character n mean SD Max Min

% SL

HL 4 23.76 1.25 25.1 22.4

BD 4 21.81 3.33 26.33 18.9

P.F.L 4 14.9 1.89 16.73 13.21

Pe.FL 4 15.21 2.05 17.11 13.31

Page | 57

DFL 4 23.38 0.91 24.33 23.31

AFL 4 16.81 2.30 18.63 13.69

CPL 4 46.64 3.77 50.2 41.33

CPD 4 8.57 1.18 9.39 6.82

%HL

HD 4 74.20 3.49 79.37 71.69

ED 4 12.56 1.94 14.22 10

SnL 4 8.85 1.20 10.61 7.94

IOW 4 30.89 7.56 39.39 21.63

BL 231.47 32.30 267.86 190.61

Merstic 4

DFR 4 10.5 0.58 11 10

CFR 4 19.5 0.58 20 19

LLS 4 - - - -

Morphometric and merstic character of L. crassibarbis

Character n mean SD Max Min

% SL

HL 4 20.35 7.46 34.87 13.23

BD 4 26.72 11.52 49.05 15.30

PcFL 4 19.81 7.81 26.01 13.85

PvFL 4 16.45 7.73 35.46 10.55

DFL 4 18.51 7.66 33.69 11.99

AFL 4 18.93 7.98 34.87 12.82

CPL 4 41.87 15.04 62.64 21.09

%HL

SnL 4 30.26 2.76 35.44 27.45

ED 4 16.85 1.82 19.77 14.71

IOW 4 31.61 3.87 35.31 27.11

Merstic

AFR 4 6.67 0.52 7 6

LLS 4 31.67 0.52 32 31

Morphometric and merstic characteristics of C. gariepinus

Character n mean SD Max Min

% SL

HL 4 22.10 3.83 25.76 15.63

BD 4 10.44 2.27 12.95 8.19

PcFL 4 9.42 1.97 11.66 6.33

Page | 58

PvFL 4 7.28 1.53 8.63 4.65

DFL 4 47.33 8.16 55.98 35.53

AFL 4 34.02 5.61 41.28 26.42

CPL 4 3.15 0.13 3.3 3.04

CPD 4 6.95 1.02 7.69 5.22

%HL

SnL 4 5.54 2.22 8.89 3.23

ED 4 5.13 0.70 6.02 4.44

IOW 4 30.83 0.83 31.92 30.00

Merstic

DFR 4 - - - -

CFR 4 - - - -

LLS 4 - - - -

Morphometric and Merstic characteristics of O. niloticus

Character n mean SD Max Min

% SL

HL 4 28.95 1.73 31.11 26.99

BD 4 38.19 1.44 43.56 34.97

PcFL 4 31.19 2.26 34.25 28

PvFL 4 22.88 1.67 25.56 21.33

DFL 4 58.24 4.19 64.42 54.63

AFL 4 26.01 1.65 28.63 24.54

%HL

SnL 4 17.10 2.86 20.83 12.96

ED 4 20.79 3.52 24.07 16.37

IOW 4 36.80 3.69 41.67 32.74

Merstic

ARF 4 10.8 0.45 11 10

LLS 4 30.8 4.09 14

Questionnaires

Date __________

Name of respondent ___________

1. Age of respondent _________

2. Sex _____________

3. Educational Background.

A. Basic

Page | 59

B. Elementary

C. Secondary

D. above

4. Marital status_________

A. Single

B. Married

5. Total number of family___________?

6. Income per month in ET. Birr _____________?

7. What is your Source of Income?

A. Animal farming

B. Crop farming

C. Mixed farming

D. Fishing

E. All

F. Other___________.

8. Do you engage fishing activity?

A. Yes

B. No

9. If your answer is yes for Q.7. Where do you fish?

A. River

B. Pond

C. Lake

D. other_________.

10. When do you actively involved in fishing (within a day)?

A. Morning

B. Midday

C. Late day

D. Night

E. Other__________.

11. When did you start fishing__________?

12. What type of fishing gear you use?

Page | 60

A. Gillnet

B. Hook and line

C. Castanet

D. Other__________

13. How much the mesh size you use for fishing__________?

14. What types of fish you fish? ____________

15. How many days do you fish per month____________?

16. How many kg of fish you catch per week__________?

17. Which type of fish you prefer to eat____________?

Why_________

18. Which type of fish consumers prefer to buy__________?

Why__________

19. When do you fish more fish within a year___________?

Which type of fish___________?

20. Do you use prevention methods of fish spoilage?

A. Yes

B. No

21. If your answer is yes, what type of prevention method you

use__________?

22. How much the Price of each fish that you fish__________?

23. How is trend of the price?

A. Increasing

B. Decreasing

C. Constant

24. How much is income generated from fishing_________?

25. What are the major changes occurred in fishery__________?

26. What are the major problems to stay in this business_________?

27. Do you know the type of fish that has become extinct in this area?

A. Yes

B. No

28. If your answer yes for Q.28 which type of fish are extinct?