Status of fish stocks and fisheries of thirteen medium-sized African reservoirs

Table 1.1 List of reservoirs studied, including data on area and potential fish yields (after Crul, 1992)

Name	Country	Area	Pot. yield (t/y)
Kafue Flats/Gorge	Zambia	4 340.0	18 476
Kossou	Côte d'lvoire	1 600.0	7 378
Jebel Aulia	Sudan	1 500.0	6 952
Buyo	Côte d'lvoire	900.0	4 345
Lagdo	Cameroon	700.0	3 448
Mtera	Tanzania	610.0	3 038
Manantali	Mali	600.0	2 992
Mbakaou	Cameroon	500.0	2 530
Mwadingusha	Zaire	446.0	2 278
Selingue	Mali	409.0	2 103
Itezhitezhi	Zambia	360.0	1 870
Maga	Cameroon	360.0	1 870
Bamendjing	Cameroon	300.0	1 582

Table 2.1 Summary of limnological data for some Cameroonian rivers

Source: river; location;	De Kimpe (1980a) Benue Lagdo	SOGREAH, 1983
Source: river; location;	De Kimpe (1980a) Benue Lagdo	Benue Lagdo	Logone Bongor	Sanega Nachtigal
pH	7.2	7.5	7.7	7.1
Conductivity mho/cm	80.0 μS/cm	122	50	30
HCO₃ mg/l	55	55	45.7	16.3
Cl mg/l	3	3.0	-	0.7
NO₂	0	-	-	-
NO₃	4.9	-	-	-
PO₄	0	-	-	-
Ca	9.0	9.0	5.6	3.1
Mg	2.0	2.0	2.1	1.0
Na	3.9	3.9	3.5	1.8
K	3.0	3.0	1.8	1.6
NH₄	0	-	-	-
SiO₂	20	20	-	14.4
SO₄	-	-	0	0.8
Fe	-	-	-	0.78
TDS	-	-	-	39.0

TDS = total dissolved solids

Table 2.2 Fishermen, boats and gear by ethnic group around Lake Lagdo, February 1990 (after Van der Knaap et al., 1991a)

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19
Subtotal for Djoukoun/Agatou	263	536	66	0	25	20	19	1	1	257	7	0	0	280.0	782.0	20600	20	154	64
Subtotal for Fishermen from Far North	801	839	74	1	49	12	10	0	2	862	1	3	0	901.5	1575.5	700150	60	61	3
Subtotal for Haussa/Kabawa	271	238	46	1	19	19	7	0	0	293	17	1	2	134.0	623.5	488070	939	41	1
Subtotal for Local fishermen	597	2846	0		0	5	1	0	0	401	211	9	0	315.0	893.0	153051	91	46	4
Subtotal for Fishermen from Mali	28	12	7	0	5	1	1	0	0	26	0	0	0	9.0	35.0	0	299	0	0
TOTAL	1960	1909	199	2	98	57	38	1	3	1839	236	13	2	1639.5	3909.0	1361871	1409	302	72

1. Masterfishermen
2. Assistants
3. Outboards
4. 5 HP
5. 8 HP
6. 15–16 HP
7. 25 HP
8. 30 HP
9. 40 HP
10. Plywood canoes
11. Dugout canoes
12. On foot
13. Gourd
14. 200 mesh net
15. 400 mesh net
16. Hooks
17. Traps
18. Nile perch net
19. Castnet

Table 2.3 Annual fish production by fishing enterprise at Lake Lagdo (after Van der Knaap et al., 1991b)

Year	Production (t)	Number of enterprises	Annual production (t) by enterprise
1985/1986	7 656	1 193	6.42
1986/1987	13 404	1 486	9.02
1987/1988	12 876	1 800	7.15
1989	10 500	1 659	6.33
1990	12 289	1 960	6.27

Table 2.4 Annual fish production by unit area at Lake Lagdo (after Van der Knaap et al., 1991b)

Year	Production (t)	Mean surface (km²)	Production (kg/ha)
1985/1986	7 656	381	201
1986/1987	13 404	395	339
1987/1988	12 876	436	295
1989	10 500	600	175
1990	12 289	600	205
1991	10 675	600	178

Table 2.5 Monthly average catch rates for gillnets of various mesh sizes (mm) (after Van der Knaap et al., 1991b)

Month	40–99	No.	100–129	No.	130–223	No.
January	8.86	21	12.97	42	49.05	1
February	5.95	5	17.08	24	10.10	1
March	5.47	17	10.57	63	16.89	11
April	7.12	7	8.93	33	-	0
May	7.62	4	14.45	35	7.15	1
June	7.78	7	32.30	34	6.36	8
July	8.55	7	25.60	35	24.03	6
August	9.69	13	19.89	46	11.24	6
September	4.83	18	15.09	29	5.53	11
October	8.38	7	9.19	32	-	0
November	5.90	1	8.08	4	-	0
December	3.07	11	5.19	25	-	0

Table 2.6 Species composition for three categories of gillnets, based on mesh size

Species	Mesh > = 130 mm	%	Mesh 100 < = x < 130 mm	%	Mesh 40 < = x < 100 mm	%
SCHILBE MYSTUS	0.01	0.04	0.01	0.03	0.21	1.57
LABEO SENEGALENSIS	0.18	0.65	0.46	1.50	2.41	17.97
SAROTHERODON GALILAEUS	15.66	56.33	25.44	82.81	2.55	19.02
SAROTHERODON NILOTICUS	0.36	1.29	1.59	5.18	0.23	1.72
BARUS BAYAD	0.25	0.90	0.26	0.85	0.47	3.50
SYNODONTIS SPP	0.02	0.07	0.18	0.59	0.74	5.52
CHRYSICHTHYS SPP	0.15	0.54	0.16	0.52	3.85	28.71
CLARIAS LAZERA	0.04	0.14	0.02	0.07	0.02	0.15
TILAPIA ZILLI	0.03	0.11	0.05	0.16	0.11	0.82
ALESTES NURSE	0.04	0.14		0.00	0.44	3.28
AUCHENOGLANIS OCCIDENTALIS	0.54	1.94	0.68	2.21	1.00	7.46
GYMNARCHUS NILOTICUS		0.00		0.00		0.00
ALESTES MACROLEPIDOTUS		0.00	0.01	0.03	0.58	4.33
HEPSETUS ODOE		0.00		0.00	0.01	0.07
CTENOPOMA SPP		0.00		0.00	0.03	0.22
HEMICHROMIS SPP		0.00		0.00	0.01	0.07
CITHARIUNS CITHARUS	4.00	14.39	1.23	4.00	0.18	1.34
HYDROCYNUS SPP	5.92	21.29	0.17	0.55	0.13	0.97
HETEROTIS NILOTICUS	0.18	0.65	0.13	0.42	0.03	0.22
CHANA OBSCURA	0.01	0.04		0.00		0.00
POLYPTERUS SPP		0.00		0.00	0.10	0.75
PROTOPTERUS ANNECTENS		0.00		0.00		0.00
MORMYRUS AND MORMYROPS SPP	0.13	0.47		0.00		0.00
TETRAODON FAHAKA	0.02	0.07	0.07	0.23	0.08	0.60
HETEROBRANCHUS BIDORSALIS		0.00		0.00		0.00
LABEO COUBIE	0.01	0.04	0.02	0.07	0.01	0.07
HYPEROPISUS BEBE	0.05	0.18	0.02	0.07		0.00
DISTICHODUS SPP	0.08	0.29	0.01	0.03		0.00
CLAROTES SPP	0.02	0.07	0.03	0.10		0.00
EUTROPIUS NILOTICUS		0.00		0.00		0.00
GNATHONEMUS SPP		0.00	0.02	0.07	0.04	0.30
EPIPLATYS SPP		0.00		0.00		0.00
TYLOCHROMIS JENTINKI		0.00		0.00		0.00
BARILIUS SPP		0.00		0.00		0.00
LATES NILOTICUS	0.08	0.29	0.15	0.49	0.15	1.12
MALAPTERURUS ELECTRICUS	0.02	0.07	0.01	0.03	0.02	0.15
ALESTES BARILIUS		0.00		0.00	0.01	0.07
TOTAL	27.80	100	30.72	100	13.41	100

Table 2.7 Frame survey results of Maga Reservoir, Cameroon (Dr Baba Malloum Ousman, pers. comm.)

Year	Fishermen	Canoes	Nets	Longlines	Traps
1986/1987	839	435	1 153	1 465	-
1987/1988	1 120	912	1 483	2 172	-
1988/1989	1 480	946	1 624	10 820	300
1989/1990	1 480	956	1 624	10 820	300
1990/1991	1 811	694	1 403	1 569	97
1991/1992	1 811	694	1 404	1 569	97

Table 2.8 Fish production from Maga Reservoir (Dr Baba Malloum Ousman, pers. comm.)

Year	Tonnes
1984	2 603
1985	2 623
1986	700
1987	1 229
1988	3 642
1989	3 585
1990	1 161
1991	1 241
1992	1 766

Table 2.9 Summary of figures on fishery potential of four reservoirs in Cameroon

Reservoir	Fishery potential t/year 1)	Fishery potential t/year 2)
Bamendjing	500	1 582
Mbakaou	3 500	2 530
Lagdo	2 900	3 448
Maga	1 500	1 870

1) Summarized from Vanden Bossche and Bernacsek (1990b) who compiled data from Balarin (1985), who in his turn modified data after SOGREAH, 1983 b; Laclavere and Loung, 1980; Aubray, 1976.
2) Summarized from Crul (1992).

Table 2.10 List of fish species caught in the Maga Reservoir and Logone River, including their vernacular names (after De Kimpe, 1980b)

	MASSA	MOUSGOUM	FOUFOULDE
Heterotis niloticus	Heraouhina		Laréou
Hyperopisus bebe	Mourana	Avri	Soudao
Mormyrus sp.	Binendanada	Do'ni
		Ankoï
Gnathonemus sp.	Binendanada	Moukoum say
Petrocephalus sp.	Moudina		Soudao
Gymnarchus niloticus	Sinilda	Mounkou	Yaouni
Tetraodon	Mamouk	Korkoto	Bagoulidi
Hydrocynus	Chekah'la	Goé	Sagaie
		Yiehou
Alestes dentex	Djiod'ha	Ania	Ketchaperado
Alestes baremoze		Hackdi	Pelepelekou
Alestes macrolepidotus		Gerken'kou
Ichthyoborus		Botchenchebekou	Yarendeou
Citharinus		Madaraï	Falia
		Abade
Distichodus	Dakaouasna	Tchenchebako	Siaké
		Bedjef
Barbus sp.	Koulay Souleina		Dabalabala
Bidé
Labeo sp.	Blara	Girgila	Bidé
Bagrus	Lacturendi	Malao	Blagi
Auchenoglanis	Pinina	Gougourou	Nakaset
Clarias	Non'nan	Hoedei	Moubalao
Schilbe	Nerek'ma	Kotobo	Solet
		Bezné
Eutropius	Nerek'ma	Bezné	Solet
Synodontis	Guémila	Kokoye	Kouroungou
Malapterurus electricus		Ambournini	Feféoundé
Lates niloticus	Goeklof'na	Maldang	Akaltao
Tilapia sp.	Silaïdjaraïna	Asougouni	Faraoré
Polypterus	Challa	Yam	Bodiou
Protopterus	Soïda	Moukouloum	Boyénaou
		Abd'haï

Table 3.1 Summary of information on water level, surface and volume of Lake Kossou

Year	Level (m ASL)		Surface (km²)		Volume (km³)
Year	minimum	maximum	minimum	maximum	minimum	maximum
1971	157.89	183.45	-	485	-	3.
1972	183.15	186.15	475	590	3.7	5.
1973	184.10	187.93	505	680	4.15	6.
1974	186.50	190.44	610	825	5.6	8.
1975	-	192.87	-	863	-	9.
1987	184.00	188.00	500	700	3.9	6.

Table 3.2 Summary of physico-chemical parameters for Lake Kossou (after Bearez, 1988)

Water temperature	: average 29°C, range 29–33°C
Transparency	: range 130–280 cm
Conductivity (20°C)	: 100 μ S/cm
Alkalinity	: 50 ppm CaCO

Dissolved oxygen	: seldom over 5 mg/l
pH	: range 7.5 – 8.0

Table 3.3 Development of the fishery at Lake Kossou for the period 1972–1975 (estimated from data collected by Bazigos and Begin) (after Entz, 1984)

Mean annual number of full-time fishermen

Year	Lake surface	Fishermen trained by AVB	Ivorians attracted	Total Ivorians	Foreign fishermen	AVB canoes	Gillnets	Production (t/y)
1971	480	83	(?)	(?)	(?)	41	600	(?)
1972	600	226	500	726	645	185	(10 000)	5 640
1973	680	812	541	1 353	669	863	16 800	4 905
1974	810	1 548	768	2 316	654	1 184	20 902	7 355
1975	625	1 623	907	2 530	0	1 305	15 728	-
(June)

(AVB: ‘Autorité pour l'aménagement de la vallée du Bandama’ or Bandama Valley Management Authority)

Table 3.4 Number of fishing gear sets, boats, fishermen and fishing camps by administrative region (after Bearez, 1988)

Administrative region	Number of fishing gear					Number of canoes	Number of fishermen		Number of fishing camps
Administrative region	Seines	Gillnets	Longlines	Traps	Castnets	Number of canoes	Foreign	Ivorian	Number of fishing camps
YAMOUSSOUKRO TIEBISSOU	106 40	605 460	130 135	1 450 1 450	54 8	260 240	220 200	35 20	20 25
TOTAL	146	1 065	265	2 900	62	500	420	55	45

Table 3.5 Annual fish yield estimates at Lake Kossou (after Bearez, 1988)

Year	Production (in tonnes)	Yield (kg/ha/year)
1972	5 430	106
1973	4 695	82
1974	7 355	89
1975	5 105	67
1976	7 335	102
1977	9 315	147
1978	7 518	129
1987	8 000	133

Table 4.1 Summary of baseline limnological data from Bafing River (after Anne et al., in press).

	April 1977	October 1978
Electric conductivity μ S/cm	44.1	48.5
pH	6.6	8.2

O₂ (ppm)	6.0	8.4
iron (ppm)	0.03	0.06

ammonium (ppm)	0.09	0.13
silicates (ppm)	8.7	9.2
phosphate (ppm)	<0.01	<0.01

Table 5.1 Summary of physico-chemical data for Jebel Aulia Reservoir (various sources as quoted by Vanden Bossche and Bernacsek, 1991 and Khalid, 1990

		Vanden Bossche et al., 1991		Khalid, 1990
			Source		Source
Surface temperature		21.0 – 29.5°C	Welcomme, 1972	16–31°C	Asma, 1985
Transparency				45–85 cm	Ponedelko et al, 1964
				12.5–52 cm	Asma, 1985
Dissolved solids		180 mg/l - dam end	Welcomme, 1972
		120 mg/l - river end
Dissolved oxygen				5.0–6.5 mg/l	Ponedelko et al, 1964
				4.1–10.8 mg/l	Asma, 1985
pH		9.2 - dam end	Welcomme, 1972	8.35–8.40	Ponedelko et al, 1964
		7.5 - river end	Brook and Rzoska, 1954	7.4–8.6	Asma, 1985
		8.0–8.3 at centre	Talling, 1957
Conductivity				160 – 330 μS/cm	Asma, 1985
Ionic composition mg/l			Talling, 1957
	Ca	8 – 11
	CaCO₃	65 – 70
	Cl	3 – 7
	SO₄	1
	SiO₂	6.11
	Fe	0.1 – 0.5
	NO₃-N	0.02 – 0.06		0.05 mg/l	Ponedelko et al, 1964
	NH₃-N	0.04 – 0.06
	PO₄-P	0.04 – 0.10

Table 5.2 List of commercial species caught in Jebel Aulia Reservoir, their contribution to the total production, and their local names (Asma, 1985)

Scientific name	% of catch	Vernacular name
Hydrocynus forskalii	5.6	Kas
Chrysichthys auratus	5.2	Abu Reyala
Labeo horiae	5.0	Tutkum
Alestes baremose	4.8	Kawara
Eutropius niloticus	4.6	Schilbaya Arabi
Oreochromis niloticus	4.6	Bulti
Hydrocynus lineatus	4.4	Kas
Synodontis schall	4.4	Gargour

Table 6.1 List of fish species caught in the Great Ruaha River and its tributaries

Mormyrus longirostris
Gnathonemus livingstoni
Gnathonemus macrolepidotus
Gnathonemus sp.
Petrocephalus catostoma
Hippopatamyrus discorhynchus
Mormyrid sp. 1
Mormyrid sp. 2
Alestes affinis
Hydrocynus vittatus
Distichodus petersii
Distichodus rufigiensis
Barbus macrolepis
Barbus zanzibaricus
Barbus jacksonii
Barbus innocens
Barbus paludinosus
Barbus kerstenii
Barbus neumayeri
Barilius loveridgei
Labeo spp.
Bagrus orientalis
Synodontis maculipinna
Synodontis matthesi
Schilbe mystus
Eutropius mobiusii
Pareutropius longifilis
Clarias mossambicus
Tilapia urolepis
Haplochromis gr. ‘bloyeti’

Table 6.2 Summary of available data on number of fishermen, boats and gear as well as on fish production (t) for the Mtera Reservoir (after Lyimo, pers. comm.)

Number		Year 1986	1987	1990	1991
Fishermen		1 238	1 493	1 815	1 716
Boats		1 044	1 204	1 472	1 478
Gillnets (")		10 825	10 825	3 657	3 657
	2	175	175
	2.5	873	873	238	238
	3	4 237	4 237	360	360
	3.5	2 402	2 402	2 946	2 946
	4	2 817	2 817	307	307
	4.5	287	287
	5	34	34	58	58
	5.5
	6			24	24
	6.5			10	10
	7			21	21
Hooks		29 172	29 172	10 321	10 321
Traps		182	182	52	52

Production		3 254	3 361	3 761	5 025

Table 7.1 Summary of available physio-chemical data for the Mwadingusha Reservoir

Surface temperature	:25–26°C in rainy season
Conductivity	:K₂₀ 128–309 μS/cm
pH	:7.1–8.2; 7.5–8.4 (Konare, 1984)
Oxygen	:15.0 mg/l, Jan.; 2.0, April; 21.0, July (Konare, 1984)
Ionic composition:	mg/l
Na	3.07–6.0
K	0.78–1.56
Ca	11.04–49.07
Cl	0.71–2.49
SO₄	0.19–5.0
SiO₂	14.06–21.06
NO₃-N	3.01–11.02
PO₄-N	9.0–18.0

Table 7.2 Summary of existing annual catch figures for the Mwadingusha Reservoir

Year	Total catch (t)	No. of fishermen	No. of boats
1953	314	-	-
1954	2 354	-	-
1955	7 991	-	-
1956	674	-	-
1957	1 359	-	-
1958	4 223	-	-
1959–60	-	-	-
1961	6 115	-	-
1962–77	-	-	-
1978	1 500	-	-
1979–81	-	-	-
1982	4 350	-	-
1983	3 106*	1 410	1 583**

* 1 606 t marketed fish + 1 500 t fishermen consumption
** Konare, 1984