Abundance, distribution, and diversity of fishes in Ribb Reservoir, Lake Tana basin, Ethiopia

Figures & data

Table 1. Fish species were previously reported in the longitudinal section of the Ribb River (Getahun et al., 2008)

Family	Genus	Species
Cyprinidae	Labeobarbus	acutirostris (Bini, 1940)brevicephalus (Nagelkerke & Sibbing, 1997)crassibarbis (Nagelkerke & Sibbing, 1997)degeni (Rüppel, 1835)gorgorensis (Bini, 1940)intermedius (Rüppell, 1835)longissimus (Nagelkerke & Sibbing, 1997)macropthalmus (Bini, 1940)megastoma (Nagelkerke & Sibbing, 1997)nedgia (Rüppel, 1835)platydorsus (Nagelkerke & Sibbing, 1997)surkis (Rüppel, 1835)truttiformis (Nagelkerke & Sibbing, 1997)tsanensis (Nagelkerke & Sibbing, 1997)
	Garra	dembeensis (Rüppel, 1835)
	Varicorhinus	beso (Rüppel, 1835)
Clariidae	Clarias	gariepinus (Burchell, 1822)
Cichlidae	Oreochromis	niloticus (Linnaeus, 1758)

Figure 1. The map shows the location of the sampling sites from Ribb Reservoir.

Table 2. Characteristics of the different habitats from Ribb Reservoir

Site	Latitude and longitude	Altitude (m)	Location relative to the reservoir	Characteristics
S1 (Dam)	12^°1ʹ48.69” N 38^°0ʹ9.15” E	1875	Northwestern	There is a high sediment load and the migration of fishes downstream through the dam when the water is released for irrigation purposes due to the lack of iron mesh.
S2 (Middle)	12^°1ʹ20.07” N 38^°1ʹ2.50” E	1879	Middle of the reservoir	Most of the fishermen concentrated here on fishing activity. Water bottom is characterized by muddy and rocky.
S3 (Inlet)	12^°0ʹ41.71” N 38^°1ʹ44.28” E	1876	Eastern part at the entrance of river	The area is mostly influenced by anthropogenic activities (agricultural farmlands).

Table 3. One-way ANOVA of the mean environmental variables in different habitats from Ribb Reservoir

		Site
Parameters	S1 Dam	S2 Middle	S3 Inlet	Mean	p-Value
DO (mg/L)	3.6 ± 0.18^a	4.7 ± 0.4^b	3.5 ± 0.1^a	3.9 ± 0.2^a	0.020*
Temp (°C)	22.7 ± 0.3^a	22.4 ± 0.4^a	22.4 ± 0.4^a	22.5 ± 0.2^a	0.863
pH	8.4 ± 0.1^a	8.5 ± 0.1^a	8.5 ± 0.1^a	8.4 ± 0.1^a	0.732
EC (μS/cm)	178.3 ± 2.7^a	194.5 ± 2.1^b	177.3 ± 2.0^a	183.3 ± 2.7^c	0.001*
Turbidity (NTU)	5.2 ± 0.1^a	4.5 ± 0.4^b	6.0 ± 0.2^a	5.2 ± 0.2^a	0.007*
TDS (ppm)	91.5 ± 1.6^a	89.6 ± 4.1^b	142.3 ± 1.1^c	107.8 ± 7.5^d	0.000*

Note: DO, dissolved oxygen, Temp., temperature, TDS, total dissolved solids, EC, electrical conductivity

*and different superscript letters indicate the mean difference is significant at 0.05 level.

Table 4. Fish species composition from Ribb Reservoir

Family	Species	Catch			Percent (%)
		Male	Female	Total
Cichlidae	O. nilticus (Linnaeus, 1758)	400	352	752	46.2
Cyprinidae	L. intermedius (Rüppell, 1835)	182	316	498	30.6
Clariidae	C. gariepnus (Burchell, 1822)	187	192	379	23.3
Total		769	860	1629	100

Table 5. Fish diversity indices among the sampling seasons and sites from the Ribb Reservoir

Seasons	Species	Individuals	H'	p-Value
Dry	O. niloticus	712	0.98
	C. gariepinus	192
	L. intermedius	425
	Total	1329
Wet	O. niloticus	40	0.907
	C. gariepinus	187
	L. intermedius	73
	Total	300		0.085 ns
Sites	Overall	1629	1.06
Dam	O. niloticus	200	1.04
	C. gariepinus	100
	L. intermedius	106
	Total	406
Middle	O. niloticus	400	1.05
	C. gariepinus	188
	L. intermedius	292
	Total	880
Inlet	O. niloticus	152	1.07
	C. gariepinus	91
	L. intermedius	100
	Total	343		0.075 ns

Notes: H' = Diversity index. Ns stands for no significant at a 0.05 level.

Table 6. Pearson correlation matrix analysis of fish species distribution in relation to physico-chemical water quality parameters from Ribb Reservoir

Variables	DO	Temp	pH	EC	Turb	TDS
DO (mg/L)	1
Temperature (°C)	0.2890.363	1
pH	0.2760.386	0.0200.950	1
EC (μS/cm)	0.813*0.001	0.2550.424	0.0500.878	1
Turbidity (NTU)	−0.430.16	0.1750.586	0.2420.449	−0.6300.028	1
TDS (ppm)	−0.430.16	−0.1940.547	−0.1320.683	−0.4090.186	0.4560.137	1
O. niloticus	0.797*0.002	0.4600.854	0.2900.905	0.886*0.000	−0.750*0.005	−0.5690.053
C. gariepinus	0.801*0.002	0.4760.814	0.2640.844	0.894*0.000	−0.714*0.009	−0.5060.093
L. intermedius	0.799*0.002	0.4850.792	0.2780.810	0.894*0.000	−0.6900.013	−0.4680.125

*Correlation is significant at 0.01 level (two-tailed).

Table 7. Number of fish species and their index of relative importance (IRI) in Ribb Reservoir

Species	No.	%No.	W (kg)	%W	F	%F	IRI	%IRI
O. niloticus	752	46.2	212.9	29.6	18	100	7,580	41.9
C. gariepinus	379	23.3	390.8	54.4	16	88.9	6,907.5	38.2
L. intermedius	498	30.6	114.5	15.9	14	77.8	3,617.7	19.98
Total	1629	100	712.2	100	-	-	18,105.3	100

Notes: No. = number of fish, %No. = fish number (%), W = weight of fish, %W = weight (%), F = occurrence fish, %F = frequency of occurrence (%), IRI = relative importance index, and %IRI = relative importance index of fishes (%).

Figure 2. Percentage fish catch composition by number and weight for each sampling site in Ribb Reservoir.

Table 8. Temporal and spatial distributions of fishes in Ribb Reservoir

Seasons	Species	No.	%No.	W (kg)	%W	F	%F	IRI	%IRI
Dry	O. niloticus	712	53.6	203.4	37.12	10	100	9,072	45.4
	C. gariepinus	192	14.44	256.5	46.8	8	80	6,124	30.6
	L. intermedius	425	31.97	88.1	16.08	6	60	4,805	24.0
	Total	1329	100	548	100	-	-	20,001	100
Wet	O. niloticus	40	13.33	9.5	5.72	6	75	1428.8	7.3
	C. gariepinus	187	62.33	134.2	80.74	8	100	14,307	73.3
	L. intermedius	73	24.33	22.5	13.55	5	62.5	3,788	19.4
Sites	Total	300	100	166.23	100	-	-	19,523.8	100
Dam	O. niloticus	200	49.3	62.4	35.4	14	77.8	6,590.3	50.1
	C. gariepinus	100	24.6	102.6	58.2	10	55.6	4,607.3	34.9
	L. intermedius	106	26.1	11.2	6.4	11	61.1	1,990.4	15.1
	Total	406	100	176.2	100	-	-	13,188	100
Middle	O. niloticus	400	45.5	115.8	29.3	18	100	7,481.3	42.3
	C. gariepinus	188	21.4	234.7	59.3	16	88.9	7,175.6	40.7
	L. intermedius	292	33.2	45.1	11.4	12	66.7	2,975.6	16.9
	Total	880	100	395.6	100	-	-	17,632.3	100
Inlet	O. niloticus	152	44.3	34.7	23.7	12	66.7	4,536.6	35.7
	C. gariepinus	91	26.5	53.5	36.5	8	44.4	2,799.7	22.0
	L. intermedius	100	29.2	58.3	39.8	14	77.8	5,370.3	42.3
	Total	343	100	146.5	100	-	-	12,706.6	100

Table 9. The presence and absence of upstream riverine spawning migratory fish species in Ribb River before and after irrigation dams

		References
		Before the construction of the dam		After the construction of the dam	Present study
Species	Getahun et al. (2008)	Anteneh et al. (2013)	Mequanent et al. (2021) below the Ribb weir	Mequanent et al. (2021) below the Ribb Dam	In the Ribb Reservoir (above the dam)	Below the Ribb Dam
L. acutirostris	x	x	x	x	x	x
L. brevicephalus	✓	x	✓	✓	x	✓
L. crassibarbis	x	x	x	x	x	x
L. degeni	✓	x	x	x	x	x
L. gorgorensis	x	x	x	x	x	x
L. intermedius	✓	✓	✓	✓	✓	✓
L. longissimus	x	x	x	x	x	x
L. macropthalmus	x	✓	✓	✓	x	✓
L. megastoma	x	✓	✓	✓	x	✓
L. nedgia	✓	✓	✓	✓	x	✓
L. platydorsus	x	✓	✓	✓	x	✓
L. surkis	x	✓	x	x	x	x
L. truttiformis	x	✓	✓	✓	x	✓
L. tsanensis	x	✓	✓	✓	x	✓
L. beso	✓	✓	x	x	x	x

✓ = present and x = absent.

Getahun, A., Dejen, E., & Anteneh, W. (2008). Fishery Studies of Rib River, Lake Tana Basin, Ethiopia. A Report Submitted to the World Bank, 116 pp. World Bank. http://documents1.worldbank.org

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Mequanent, D., Mingist, M., Getahun, A., & Anteneh, W. (2021). Impact of irrigation practices on Gilgel Abay, Ribb and Gumara fisheries, Tana Sub-Basin, Ethiopia. Heliyon, 7(3), e06523. https://doi.org/10.1016/j.heliyon.2021.e06523

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