PART II - SYNTHESES OF INFORMATION ON SELECTED AFRICAN RESERVOIRS (continued)

PARTIE II - SYNTHESES DE L'INFORMATION SUR CERTAINS RESERVOIRS AFRICAINS (continuer)

VOLTA LAKE (GHANA) (continued)

Table 14. Experimental fishing catch of Clupeids and other species per round during the period December 1969 – April 1971
(Vanderpuye, 1973)

Round (Period)	Type of fish	No.	Weight (kg)	Percentage of total weight for a round
3 (December 1969–May 1970)	Clupeids	145 122	261 404	17
	Other spp.	53 638	1 248 358	83
4 (June–September 1970)	Clupeids	241 044	454 762	25
	Other spp.	43 023	1 401 216	75
5 (October 1970–January 1971)	Clupeids	282 048	556 689	31
	Other spp.	44 534	1 242 159	69
6 (February–April 1971)	Clupeids	132 736	212 374	17
	Other spp.	27 474	1 004 569	83
TOTAL	Clupeids	800 950	1 485 234	23
	Other spp.	168 669	4 896 302	77

Table 15a. Fish biology sampling at Ampem - Species abundance list
(May 1980 - Volta Lake)

Species	No.	Weight (g)	Percentage
Hydrocynus lineatus*	22	2 555	5.46
H. brevis*	24	6 645	14.21
Chrisichthys furcatus	1	300	0.64
C. velifer	28	1 215	2.60
C. walkeri	1	40	0.09
C. auratus	23	815	1.74
Sarotherodon galilaeus	7	3 410	7.29
Chronomidotilapia guntheri	8	225	0.55
Tilapia zillii	5	2 060	4.41
Sarotherodon niloticus	11	4 285	9.16
Hemichromis fasciatus	5	234	0.50
Barbus macrops	1	10	0.02
Lates niloticus	20	8 177	17.49
Heterotis niloticus	1	700	1.50
Alestes macrolepidotus	1	2 250	4.81
Synodontis schall	11	580	1.24
Pellonula afzeliusi	440	210	0.45
Tetraodon fahaka	-	-	-
Auchenoglanis occidentalis	6	2 560	5.48
Mormyrops deliciosus*	2	335	0.72
Distichodus rostratus	1	580	1.24
Petrocephalus simus*	1	25	0.05
Clarias anguillaris	1	250	0.53
Gymnarchus niloticus	6	4 675	10.00
Hyperopisus bebe*	16	4 620	9.88
	642	46 756

* Resurgence of formerly riverine species

Table 15b. Fish biology sampling at Ampem - Species Abundance List
(April 1980 - Volta Lake)

Species	Gillnets
Species	10'	12'	30'	Total
Lates niloticus	6	6	-	12
Hydrocynus brevis*	3	3	13	19
Sarotherodon galilaeus	6	1	-	7
S. niloticus	1	-	-	1
Tilapia zillii	4	1	-	5
Chromidotilapia guntheri	11	11	-	22
Synodontis schall	1	-	-	1
Auchenoglanis occidentalis	1	-	-	1
Hemichromis bimaculatus	3	-	-	3
H. fasciatus	1	3	-	4
Pellonula afzeliusi	630	-	-	630
Hyperopisus bebe*	1	-	-	1
Bagrus bayad	-	2	-	2
Alestes macrolepidotus	1	1	1	3
Synodontis eupterus	-	-	1	1
Heterotis niloticus	-	4	-	4
Chrysichthys velifer	21	10	-	31
C. auratus	12	20	-	32
C. walkeri	1	-	-	1
Gymnarchus niloticus	-	1	-	1
TOTAL	703	63	15	781

* Total weight of fish caught 31 505 g

Table 16. Mesh size range used in the commercial fishery - 1969 (Taylor, 1969)

Mesh size			Best catching mesh size
Inches	mm	No.
2	51	2
2½	63	7
3	76	28	5
3½	89	7
4	102	45	14
4½	114	14	5
5	127	54	2
5½	140	26	32
6	152	50	12
6½	165	27	1
7	178	26	9
7½	191	14
8	203	12	3
9	229	11	4

Table 17. Relative species composition of the annual commercial catch during the period 1970–1972 (Coppola and Agadzi, 1977)

Species	1970		1971		1972
Species	Catch (%)	Cum. (%)	Catch (%)	Cum. (%)	Catch (%)	Cum. (%)
1. Tilapia	37.80	37.80	27.35	27.35	29.16	29.16
2. Lates	16.40	54.20	25.44	52.79	25.75	25.75
3. Labeo	10.48	64.68	13.21	66.00	8.57	63.48
4. Alestes	6.48	71.16	6.09	72.09	6.03	6.03
5. Citharinus	4.54	75.70	5.09	77.18	5.42	74.93
6. Distichodus	3.83	79.53	3.87	81.05	5.01	79.94
7. Bagridae	3.68	83.21	3.79	84.84	4.55	84.49
8. Synodontis	3.31	86.52	3.37	88.21	3.21	87.70
9. Heterotis	3.27	89.79	3.11	91.32	3.03	90.73
10. Schilbeidae	3.23	93.02	2.79	94.11	1.98	92.71
11. Hydrocyon	1.90	94.92	1.87	95.98	1.97	94.68
12. Mormyridae	0.93	95.85	1.05	97.03	0.93	95.61
13. Hemichromis	0.12	95.97	0.27	97.30	0.29	95.90
14. Clupeidae	0.07	96.04	0.10	97.40	0.04	95.94
15. Others	3.96	100.00	2.60	100.00	4.06	100.00

Table 18. Species composition of total catches with experimental gillnets from 21 May 1969 – 21 October 1973 (Rounds 2 – 9)

		Total weight (kg)	%	Cumulative %
1.	Clupeidae	847 158	39.3	39.3
2.	Schilbaidae	375 966	17.4	56.7
3.	Alestes baremose/dentex	250 149	11.6	68.3
4.	Alestes macrolepidotus	163 191	7.6	75.9
5.	Labeo	99 442	4.6	80.5
6.	Lates	87 682	4.1	84.1
7.	Chrysichthys spp.	57 291	2.7	87.3
8.	Alestes nurse/leuciscus	48 461	2.3	89.6
9.	Distichodontidae	42 033	2.0	91.6
10.	Hydrocynus	35 438	1.6	93.20
11.	Mormyridae	31 315	1.6	94.80
12.	Synodontis (incl. Sarotherodon)	29 213	1.4	96.20
13.	Tilapia (incl. Sarotherodon)	28 328	11.3	97.50
14.	Others	44 830	2.1	99.60
	Round	Period
	2	May 1969–Oct. 1969
	3	Dec. 1969–May 1970
	4	June 1970–Sept. 1970
	5	Oct. 1970–Mar. 1971
	6	Feb. 1971–Apr. 1971
	7	May 1971–Sept. 1971
	8	Sept. 1971–Feb. 1972
	9	May 1972–Oct. 1973

Table 19. Catches with experimental gillnets in Volta Lake during the period 21 May 1969 – 21 October 1973 Number and weight of fish (by rounds) (percentage in parenthesis)

ROUNDS		2		3		4		5		6
Family/Species	Total Catch	No.	Wt (gm)	No.	Wt (gm)	No.	Wt (gm)	No.	Wt (gm)	No.	Wt (gm)
1. Clupeidae		135 960	256 557	27 140	47 625	74 322	120 514	76 192	162 922	25 512	63 182
		(92.4)	(57.8)	(76.7)	(24.1)	(84.0)	(39.2)	(88.6)	(47.7)	(78.0)	(31.6)
2. Schilbeidae		8 078	68 228	6 016	36 293	11 235	68 646	8 000	57 297	5 420	12 050
		(5.5)	(15.4)	(17.0)	(18.4)	(12.7)	(22.3)	(9.3)	(16.8)	(16.6)	(6.0)
3. Alestes baremose/dentex		251	24 303	445	25 704	387	36 054	638	57 566	280	18 164
		(0.2)	(5.5)	(1.3)	(13.0)	(0.4)	(11.7)	(0.7)	(16.9)	(0.9)	(9.1)
4. Alestes macrolepidotus		79	23 569	129	20 461	62	22 570	47	15 670	65	21 831
		(0.1)	(5.3)	(0.4)	(10.4)	(0.1)	(7.3)	(0.1)	(4.6)	(0.2)	(10.9)
5. Cyprinidae (Labeo)		29	14 946	50	11 507	23	6 512	42	6 080	84	16 423
		(0.0)	(3.4)	(0.1)	(5.8)	(0.0)	(2.1)	(0.1)	(1.8)	(0.3)	(8.2)
6. Centropomidae (Lates)		14	6 348	45	7 882	42	14 013	55	12 635	71	8 762
		(0.0)	(1.4)	(0.1)	(4.0)	(0.1)	(4.6)	(0.1)	(3.7)	(0.2)	(4.4)
7. Chrysichthys spp.		1 735	28 760	186	7 376	54	3 986	22	630	28	1 636
		(1.2)	(6.5)	(0.5)	(3.7)	(0.1)	(1.3)	(0.0)	(0.2)	(0.1)	(0.8)
8. Alestes nurse/leuciscus		363	734	602	7 573	464	5 662	186	5 328	736	7 476
		(0.3)	(0.2)	(1.7)	(3.8)	(0.5)	(1.8)	(1.2)	(1.6)	(2.3)	(3.7)
9. Distichodontidae		38	4 931	111	4 498	56	6 396	123	3 342	88	3 602
		(0.0)	(1.1)	(0.3)	(2.3)	(0.1)	(2.1)	(0.1)	(1.0)	(0.3)	(1.8)
10. Hydrocynus		1	800	21	5 530	14	6 300	24	5 786	37	5 990
		(0.0)	(0.2)	(0.1)	(2.8)	(0.0)	(2.1)	(0.0)	(1.7)	(0.1)	(3.0)
11. Mormyridae		393	5 481	451	4 882	598	6 224	558	4 914	232	2 118
		(0.3)	(1.2)	(1.3)	(2.5)	(0.7)	(2.0)	(0.7)	(1.4)	(0.7)	(1.1)
12. Mochokidae		14	2 582	19	4 109	16	3 080	24	5 254	41	5 052
		(0.0)	(0.6)	(0.1)	(2.1)	(0.0)	(1.0)	(0.0)	(1.5)	(0.1)	(2.5)
13. Tilapia (including Sarotherodon)		8	2 952	26	9 046	5	2 930	6	170	3	970
		(0.0)	(0.7)	(0.1)	(4.6)	(0.0)	(1.0)	(0.0)	(0.1)	(0.0)	(0.5)
14. Auchenoglanis occidentalis		1	1 280	1	860	-	-	-	-	1	615
		(0.0)	(0.3)	(0.0)	(0.4)					(0.0)	(0.3)
15. Citharinidae		6	1 533	8	691	1	700	5	966	2	50
		(0.0)	(0.4)	(0.0)	(0.4)	(0.0)	(0.2)	(0.0)	(0.3)	(0.0)	(0.0)
Others		85	752	126	3 089	1 154	3 825	90	1 794	84	31 616
		(0.1)	(0.2)	(0.4)	(1.6)	(1.6)	(1.2)	(0.1)	(0.5)	(0.3)	(15.8)
Total		147 073	444 171	35 384	197 266	88 437	307 420	86 034	341 635	32 692	199 727

ROUNDS		7		8		9		TOTAL
Family/Species	Total Catch	No.	Wt(gm)	No.	Wt(gm)	No.	Wt(gm)	No.	Wt(gm)
1. Clepeidae		22 416	59 310	32 700	50 474	53 272	86 574	447 514	847 158
		(76.1)	(27.5)	(81.5)	(24.7)	(94.8)	(34.7)	(83.9)	(39.3)
2. Schilbeidae		4 832	46 180	5 606	50 728	2 094	36 544	51 281	375 966
		(16.4)	(21.4)	(14.0)	(24.8)	(3.7)	(14.7)	(1.0)	(17.4)
3. Alestes baremose/dentex		275	28 804	240	23 256	206	36 298	2 722	250 149
		(0.9)	(13.4)	(0.6)	(11.4)	(0.4)	(14.6)	(0.5)	(11.6)
4. Alestes marcrolepidotus		73	11 892	87	19 228	45	27 970	587	163 191
		(0.3)	(5.5)	(0.2)	(9.4)	(0.1)	(11.2)	(0.1)	(7.6)
5. Cyprinidae (Labeo)		24	2 942	34	15 117	11	25 915	297	99 442
		(6.1)	(1.3)	(0.1)	(7.4)	(0.0)	(10.4)	(0.1)	(4.6)
6. Centropomidae (Lates)		43	16 399	102	16 073	20	5 570	392	87 682
		(0.2)	(7.6)	(0.3)	(7.9)	(0.0)	(2.2)	(0.1)	(4.1)
7. Chrysichthys spp.		169	9 271	94	2 624	48	3 008	2, 336	57 291
		(0.6)	(4.3)	(0.2)	(1.3)	(0.1)	(1.2)	(0.5)	(2.7)
8. Alestes nurse/leuciscus		878	12 496	826	5 040	236	4 152	4 291	48 461
		(3.0)	(5.8)	(2.1)	(2.5)	(0.4)	(1.8)	(0.8)	(2.3)
9. Distichodontidae		85	7 608	62	4 342	53	7 314	616	42 033
		(0.3)	(3.5)	(0.2)	(2.1)	(0.1)	(2.9)	(0.1)	(2.0)
10. Hydrocynus		24	8 182	6	2 850	-	-	127	35 438
		(0.1)	(3.8)	(0.0)	(1.4)			(0.0)	(1.6)
11. Mormyridae		264	4 732	92	1 874	38	1 090	2 626	31 315
		(0.9)	(2.2)	(0.2)	(0.9)	(0.1)	(0.4)	(0.7)	(1.6)
12. Mochokidae		8	2 850	29	3 431	18	2 855	169	29 213
		(0.0)	(1.3)	(0.1)	(1.7)	(0.0)	(1.2)	(0.0)	(1.4)
13. Tilapia (including Sarotherodon)		14	830	23	4 130	20	7 300	105	28 328
		(0.0)	(0.4)	(0.1)	(2.0)	(0.0)	(2.9)	(0.0)	(1.3)
14. Auchenoglanis occidentalis		-	-	3	2 865	3	2 600	9	8 220
				(0.0)	(1.4)	(0.0)	(1.0)	(0.0)	(0.4)
15. Citharinidae		9	1 483	13	1 370	-	-	44	6 793
		(0.0)	(0.7)	(0.0)	(0.4)			(0.0)	(0.3)
Others		340	1 546	134	370	130	1 838	2 143	44 830
		(1.2)	(0.7)	(0.3)	(0.2)	(0.2)	(0.7)	(0.4)	(2.1)
Total		29 476	215 669	40 090	204 372	56 211	249 188	515 389	2 158 377

Table 20. Vertical distribution (by number) of common fish species in Volta Lake (December 1969 – May 1970)

INSHORE
Species	1.5 m	3 m		9 m
		Top	Bottom	Top	Middle	Bottom
Pellonula afzeliusi	15 861	14 286	11 544	27 966	20 939	11 026
Cynothrissa mento	74	134	44	219	218	516
Eutropius niloticus	948	1 211	544	1,414	658	905
Distichodus spp.	112	98	30	41	22	36
Lates niloticus	41	28	34	22	17	16
Alestes leuciscus/nurse	825	440	168	295	148	119
Alestes baremose/dentex	216	240	86	822	190	117
Chrysichthys spp.	137	54	281	36	47	58
Labeo spp.	80	14	19	13	16	26
Sarotherodon galilaeus	231	5	23	87	78	27

OFFSHORE
		3 m		9 m
		Top	Bottom	Top	Middle	Bottom
Pellonula afzeliusi		5 786	4 200	16 149	19 766	8 005
Cynothrissa mento		62	43	110	63	28
Eutropius niloticus		489	294	346	224	295
Distichodus spp.		11	2	13	21	14
Lates niloticus		7	9	7	5	7
Alestes leuciscus/nurse		144	51	28	8	20
Alestes baremose/dentex		108	81	113	92	79
Chrysichthys spp.		2	2	29	3	95
Labeo spp.		21	4	13	25	6
Sarotherodon galilaeus		30	19	30	17	6

Table 21. Lateral distribution of fish in inshore and offshore waters of Volta Lake during the period, September 1971 to February 1972

INSHORE
Area	1.5 m		3m		9 m
	No.	Wt.	No.	Wt.	No.	Wt.
1.	544	5 028	272	10 430	15 286	66 081
2.	188	5 016	1 545	7 928	7 625	36 566
3.	433	4 549	1 669	11 692	2 696	19 026
4.	1 156	6 699	3 988	30 953	3 187	33 486
5.	3 336	15 451	5 964	26 415	3 100	44 487
6.	1 924	17 170	3 535	36 489	1 830	41 188
7.	2 054	12 462	4 447	30 297	1 172	38 131
8	64	3 430	102	3 528	102	16 320
Total:	9 699	69 800	21 522	157 732	34 998	295 285
* Ratios	1.00	1.00	2.22	2.26	3.61	4.23
* The ratios were calculated taking catches by the 1.5m nets as unity.

OFFSHORE
		3m		9 m
		No.	Wt.	No.	Wt.
1.		1 236	4 759	3 943	20 795
2.		536	3 770	3 608	12 445
3.		703	2 545	1 030	4 895
4.		2 704	11 564	4 310	39 900
5.		4 952	22 650	2 772	32 442
6.		1 768	8 822	1 419	11 839
7.		293	9 766	366	16 973
8.		62	3 412	86	6 278
Total:		12 254	67 288	17 534	141 967
* Ratios		1.25	.96	1.81	2.03

* The ratios were calculated taking catches by the 1.5m nets as unity.

Table 22. Average diversity* index of fish species in Volta Lake by rounds (2–9) (May 1969 – 21 October 1973)

AREA	ROUND 2	ROUND 3	ROUND 4	ROUND 5	ROUND 6	ROUND 7	ROUND 8	ROUND 9
1.	0.0333	0.1579	0.0945	0.2096	0.2096	0.0968	0.2954	0.0044
2.	0.1266	0.3807	0.1936	0.0479	0.0978	0.3050	0.3092	0.2116
3.	0.0630	0.2832	0.4153	0.2166	0.1764	0.2742	0.2321	0.1506
4.	0.2626	0.2515	0.2080	0.1377	0.3066	0.3749	0.3236	0.0772
5.	0.1998	0.3627	0.3837	0.3598	0.4965	0.4908	0.2221	0.3044
6.	0.2631	0.3290	0.1552	0.1761	0.1983	0.4029	0.3869	0.2539
7.	0.4124	0.5389	0.4076	0.2048	0.4135	0.5559	0.4263	0.2298
8.	0.5025	0.6847	0.7855	0.8076	0.3169	0.9745	0.6977	0.1609
Lake Ave.	0.2329	0.3736	0.3343	0.2700	0.2770	0.4344	0.3617	0.1741

where s = Number of different species captured during a round and also at each station only fish identified to genus and species are counted (i=1:2…s).

Ni = Catch of number of fish of species i.

Table 23. Classification of common fish of Volta Lake on the basis on principal food habits

Insect-Aufwuchs and Detritus Herbivores Feeders		Piscivores		Semi-pelagic omnivores		Benthic omnivores
Osteeglossidae		Polypteridae		Clupeidade		Mormyridae
	Heterotis niloticus		Polypterus senegalus		Cynothrissa mento		Hyperopisus bebe
					Pellonula afzeliusi		Mormyrus spp.
							Gnathonemus spp.
Distichodontidae		Gymnarchidae		Mormyridae
	Distichodus spp.		Gymnarchus niloticus		Petrocephalus bovei
Citharinidae		Characidae		Characidae		Bagridae
	Cytharinus spp.		Hydrocynus spp.		Alestes dentex		Chrysichthys spp.
			Hepsetus odoe		A. baremose		Auchenoglanis occidentalis
					A. nurse
					A. macrolepidotus
					A. leuciscus
Cyprinidae		Bagridae		Distichodontidae		Claridae
	Labeo spp.		Chrysichthys auratus		Paradistichodus dimidiatus		Clarias anguillaris
			C. walkeri
			C. nigrodigitatus
			Bagrus bayard
Mochokidae		Centropomidae		Cyprinidae		Cichlidae
	Synodontis spp.		Lates niloticus		Barbus spp.		Chromidotilapia guntheri
					Barilius senegalensis
Cichlidae		Cichlidae		Schilbaeidae
	Tilapia spp.		Hemichromis spp.		Schilbe mystus
	Leptotilapia irvinei				Eutropius niloticus
					Physailia pellucida
					Siluranodon auritus
		Tetraodontidae
			Tetraodon fahaka

Table 24. Ichthyomass distribution in Volta Lake (Ichthyomass in kg/ha) (Summarized from Loiselle, 1972)

Area I		Area II		Area III		Area IV		Area V		Area VI		Area VII
Adawso	93.3	Asokoko	286.1	Abotere	46.0	2nd Dodi Island	291.1	Apetsu	46.5	Boaferi	438.7	Lanto No. 1	17.9
Suborni	651.7	Ajena Bay	219.6	Agornyomi No.1	68.6	Tzikpo	569.6	Dumbai	27.6			Lanto No. 2	68.6
K. Jamara	115.0	Ajena Bay	9.6	Agornyomi No. 2	72.9	Brenissi	151.5	Lidza	1.2			Lanto No. 3	70.0
				Mangoase	254.5	Azizakpoe	56.2					Awoyorkope	145.3
												Accra Town	219.9
Average/Area	286.7		171.8		110.5		268.9		25.1		438.7		104.34

Area I – III - Lacustrine Av. = 209.48 kg/ha

Area IV - Interphase between lacustrine and riverine Av. = 268.9 kg/ha

Area V – VII - Riverine Av. = 189.36 kg/ha

Average for lake: 200.86 kg/ha