Table 7 shows the percentage composition by weight of the processed fish species in the commercial fishery in 1991. Tilapia is the dominant species (25.9%) closely followed by Chrysichthys spp. (23.1%) and Synodontis spp. (15.8%). Clupeids - which did not exist at all in the commercial fishery in the earlier days - now generally constitute 0.5% of the total catch. The dominance of Tilapia in the commercial catches is the result of the use of the wangara net (gill net combined with traps) which is specific for Tilapia. Species composition of the commercial catches differed per stratum in 1991. For six strata, the four most important species are given in Table 8. Tilapia appears in all strata, while Chrysichthys appears in 5 and Hydrocynus in 4 strata.
The main species in the fresh fish landings in 1991 were Chrysichthys (32.9%), Synodontis (23.5%) and Tilapia (12.4%). A survey by Loiselle (1972) of the inshore habitats gave a similar species composition, indicating that most fishermen are fishing in inshore waters.
In experimental gill nets catches in the Akosombo gorge (Stratum II) in 1989, 39 fish species from 28 genera and 13 families were found (Table 9). The catches were dominated by Characidae (52.4%), followed by Mochokidae (10.7%), Mormyridae (8.2%), Bagridae (8%) and Cichlidae. Almost 90% of the gill net catches in the Akosombo gorge came from gill nets with mesh sizes between 15 mm and 63.5 mm (Table 10), while the 63.5 mm gill nets produced the highest catches (Ofori-Danson 1990). This indicates that all main commercial fish species in Volta Lake are overexploited.
Yamamoto (1991) listed the species composition of catches from experimental gill nets with various mesh sizes in the Yeji area (Stratum VII). Catches of 4-inch nets were dominated by Bagridae (Chrysichthys spp.) (27.8%) and Mochokidae (Synodontis spp.) (20.7%), followed by Mormyridae (18.1%). Gill nets of 1 inch (25 mm) mesh size and below caught predominantly clupeids (63.6 – 71.8%) and nets with bigger mesh sizes caught fish species belonging to the families Bagridae, Mochokidae, Mormyridae and Cyprinidae.
Braimah (1991) conducted efficiency tests on newly designed gill nets (88 mm mesh size) at ten fishing sites in Stratum VII (the Yeji part of the lake). Main species in the catches were Synodontis spp. (54.2%), Chrysichthys spp. (18.1%) and Mormyridae (7.6%).
Comparison of the species composition of the commercial and experimental catches revealed large differences. Vanderpuye (1984) found a high correlation between experimental and commercial catches, and experimental catch data proved to be a good indicator of trends in commercial catches. However, due to the selectivity and species specificity of newly introduced gears, experimental catch data can no longer be used to predict commercial catches.
Table 8 Four most important species in commercial catches in six strata
| STRATUM AND STATION | ||||||
|---|---|---|---|---|---|---|
| II: Dzemeni | III: Kpando | IV: Kwame-krome | V: Dambai | VII: Yeji | VIII: Bupei | |
| 1 | Tilapia | Tilapia | Tilapia | Tilapia | Chrysichthys | Synodontis |
| 2 | Chrysichthys | Bagrus | Chrysichthys | Chrysichthys | Tilapia | Tilapia |
| 3 | Hydrocynus | Hydrocynus | Hydrocynus | Synodontis | Synodontis | Chrysichthys |
| 4 | Lates | Synodontis | Bagrus | Citharinus | Labeo | Labeo |
Table 9 Checklist of species in the Akosombo Gorge area of Volta Lake in 1989–90, based on gill net catches
| FAMILY | SPECIES | ||
|---|---|---|---|
| 1) | Clupeidae | 1) | Pellonula afzeliusi |
| 2) | Cynothrissa mento | ||
| 3) | Sierrathrissa leonensis | ||
| 2) | Osteoglossidae | 4) | Heterotis niloticus |
| 3) | Mormyridae | 5) | Mormyrus deliciosus |
| 6) | Mormyrus rume | ||
| 7) | Hippopotamyrus pictus | ||
| 8) | Pollimyrus isidori | ||
| 4) | Characidae | 9) | Brycinus nurse (= Alestes nurse) |
| 10) | Brycinus leuciscus (= A. leuciscus) | ||
| 11) | Brycinus macrolepidotus (= A. macrolepidotus) | ||
| 12) | Hydrocynus forskahlii | ||
| 13) | Hydrocynus lineatus | ||
| 5) | Cyprinidae | 14) | Labeo coubie |
| 15) | Raiamas senegalensis | ||
| 6) | Bagridea | 16) | Bagrus docmac |
| 17) | Bagrus bayad | ||
| 18) | Chrysichthys nigrodigitatus | ||
| 19) | Chrysichthys walkeri | ||
| 20) | Chrysichthys auratus | ||
| 21) | Auchenoglanis occidentalis | ||
| 7) | Mochokidae | 22) | Synodontis gambiensis |
| 23) | Synodontis ocellifer | ||
| 24) | Synodontis schall | ||
| 25) | Synodontis eupterus | ||
| 26) | Synodontis velifer | ||
| 8) | Schilbeidae | 27) | Schilbe myatus |
| 28) | Siluranodon auritus | ||
| 9) | Malapturidae | 29) | Malapterurus electricus |
| 10) | Centropomidae | 30) | Lates niloticus |
| 11) | Cichlidae | 31) | Sarotherodon galilaeus (= Tilapia galilaea) |
| 32) | Oreochromis niloticus (= Tilapia nilotica) | ||
| 33) | Tilapia zilii | ||
| 34) | Chromidotilapia guentheri | ||
| 35) | Leptotilapia irvinei | ||
| 36) | Hemichromis bimaculatus | ||
| 12) | Anabantidae | 37) | Ctenopoma kingsleyae |
| 13) | Tetradontidae | 38) | Tetraodon fahaka |
Table 10 Experimental fishing distribution of CPUE by mesh size of gill nets used in Akosombo Gorge during the dry and wet season in 1989
| Stretched mesh size of net (mm) | Catch per unit effort (CPUE) | |||
| in wet season (October) | in dry season (December) | |||
| Number | Weight | Number | Weight | |
| 15.0 | 10.5 | 249.1 | 5.5 | 276.8 |
| 20.0 | 5.0 | 387.0 | 11.5 | 621.6 |
| 25.0 | 4.5 | 301.0 | 1.5 | 143.0 |
| 30.0 | 7.0 | 69.0 | 1.0 | 65.8 |
| 40.0 | 0.0 | 0.0 | 1.0 | 164.3 |
| 63.5 | 2.5 | 1 781.0 | 1.5 | 432.1 |
| 101.6 | 0.0 | 0.0 | 0.5 | 182.1 |
| 114.3 | 0.0 | 0.0 | 0.0 | 0.0 |
| 127.0 | 0.5 | 375.0 | 0.0 | 0.0 |
| 139.7 | 0.0 | 0.0 | 0.0 | 0.0 |
| 152.4 | 0.0 | 0.0 | 0.0 | 0.0 |
| 177.8 | 0.0 | 0.0 | 0.0 | 0.0 |
(Source: Ofori-Danson, 1990)
While in the 1970s and early 1980s the common fishing gears were gill nets (producing 80% of the catch), cast nets, lines and traps, other, more efficient gears, have been recently introduced, including purse seines (winch), beach seines (adranyi), bamboopipe fishing and drive-in gear (wangara). Small-meshed purse seines and beach seines contribute between 65–70% of the total commercial landings (unpublished IDAF report, 1990). Bamboo-pipe fishing - introduced in 1991 - is specific for Chrysichthys spp. and is responsible for the sudden rise in percentage contribution by body weight of Chrysichthys spp. to the commercial landings (23.1%), while the gill net combined with traps (nifa nifa) is specific for Tilapia.
Analysis of the experimental and commercial catches clearly reveals that most commercial fish species in Volta Lake are overexploited.
Vanderpuye (1976) concluded from his work on species distribution that some species were mainly limited to estuarine or to riverine environments, e.g., Hydrocynus spp., Labeo spp., mormyrids, schilbeids, Cynothrissa mento, Brycinus nurse, Alestes baremose, Alestes dentex and Citharinus spp.
However, data on the commercial fish landings along the lake show that some of these species have penetrated into what were originally described as lacustrine strata (I, II and III). Table 11 shows that some of the species are almost uniformly distributed throughout the lake. This may indicate that conditions in the lake have become uniform and that the lake has more or less stabilized.
Table 11 Percentage composition per stratum of riverine species in commercial catches (processed fish) in 1991
| Station | Buipe | Yeji | Makango | Dambai | Tapa-Abotose | Kwame-krom | Kpandu | Dzemeni |
| Stratum | VIII | VII | VII | V | IV | IV | III | II |
| Hydrocynus | 0.4 | 0.4 | 0.2 | 3.7 | 15.4 | 13.8 | 13.4 | 12.5 |
| Mormyridae | 2.8 | 2.9 | 2.3 | 2.8 | 2.7 | 1.8 | 2.7 | 2.4 |
| Alestes | 2.5 | 0.6 | 0.5 | 1.3 | 0.0 | 0.1 | 0.2 | 0.4 |
| Synodontis | 26.8 | 14.5 | 14.8 | 15.3 | 17.2 | 10.6 | 9.7 | 8.5 |
Commercial catches comprise only 18 genera. The recording does not include a breakdown of the different species. In the absence of experimental catch data for the lake, commercial fish landings might give an insight into the size of the components of the eco-groups described by Vanderpuye (1984). Using his categorization, the insect-aufwuchs and detritus herbivore feeders predominate (52.9%), with Tilapia alone contributing 25.9%, while the piscivores were the second ecogroup (37.8%), followed by the benthic-omnivores (5.7%) and the semi-pelagic omnivores (3.6%) (Table 12).
Table 12 Main feeding group categories as percentage composition based on fresh weight equivalent (FWE) fish landings, 1991
| Insect-aufwuchs, detritus feeders and herbivores | Piscivores | Semi-pelagic omnivores | Benthic-omnivores | ||||
| Species | % | Species | % | Species | % | Species | % |
| Heterotis niloticus | 2.8 | Polypterus senegalus | Clupeidae | 0.5 | Mormyridae | 2.7 | |
| Distichodus | 0.5 | Gymnarchus niloticus | Schilbeidae | Auchanoglanis | 0.6 | ||
| Citharinus | 4.7 | Hydrocynus spp. | 4.5 | Alestes | 0.9 | Clarias | 2.4 |
| Labeo | 3.2 | Chrysichthys spp. | 23.1 | Distichodus | 0.5 | ||
| Synodontis | 15.8 | Bagrus spp. | 6.4 | ||||
| Tilapia spp. | 25.9 | Lates niloticus | 3.2 | ||||
| Tetradon fahaka | |||||||
| Total % FWE | 52.9 | 37.8 | 3.6 | 5.7 | |||
The survey by Loiselle (1972) showed that the highest ichthyomass was in the interphase between the lacustrine and riverine parts of the lake (Stratum IV), followed by the southern lacustrine (Strata I, II and III). The poorest area was the northern riverine part (Strata V to VIII). To a certain degree, catch per unit effort (CPUE) data for these areas should reflect the ichthyomass distribution, but this could not be observed in the compiled CPUE data for 1991 (Table 13) (Braimah, 1992). The CPUE figures are uniform, which might indicate that the ichthyomass distribution is also uniform. This may be further evidence that the lake has stabilized, although fluctuation in lake level will always be a major destabilization factor affecting fish species composition and fish landings.
Table 13 Average CPUE per day stratum (kg/canoe/day) on a monthly and annual basis
| Stratum and Station | ||||||||
| VIII Buipe | VII Yapei | VII Yeji | V Dambai | IV Tapa-Abotase | III Kpando-Tor | II Dzemeni | Whole Lake | |
| Jan. | 18.10 | 10.70 | 9.27 | 19.59 | ||||
| Feb. | 17.40 | 6.19 | 7.14 | 9.69 | ||||
| Mar. | 10.20 | 6.28 | 7.29 | 8.00 | ||||
| Apr. | 13.60 | 12.86 | 8.80 | 8.58 | 11.11 | |||
| May. | 9.30 | 6.41 | 7.93 | 8.63 | 11.38 | |||
| Jun. | 10.50 | 6.98 | 8.07 | 8.67 | 19.92 | |||
| Jul. | 8.40 | 7.01 | 12.07 | 9.91 | 8.80 | |||
| Aug. | 7.20 | 3.89 | 12.05 | 12.66 | 3.81 | |||
| Sep. | 7.40 | 3.59 | 8.21 | 10.95 | 3.40 | |||
| Oct. | 3.10 | 15.00 | 4.75 | 9.62 | 2.93 | |||
| Nov. | 5.00 | 5.19 | 8.76 | 11.48 | 5.38 | |||
| Dec. | 4.80 | 4.90 | 12.28 | 11.40 | 2.74 | |||
| Total | 115.00 | 65.83 | 106.17 | 115.60 | 94.15 | |||
| Annual Average | 7.83 | 8.40 | 9.58 | 7.30 | 8.85 | 9.63 | 7.85 | 8.49 |
It is estimated that nearly 10% of the total catch from the lake is eaten fresh (Yeboah, 1974; Maembe, 1991) and the balance is processed.
The main processing methods continue to be smoking, salting, sun drying and fermentation.
In general, 18 species of commercial importance are processed (Table 7). Cylindrical and rectangular Fanti ovens are extensively used for smoking, with the cylindrical ones more preferred (58 to 61%). Maembe (1991) counted 1 881 cylindrical ovens and 1 315 rectangular ones in 34 villages with 6 993 housing units. Agyenim-Boateng (1989) recorded 6 569 fish processors in Stratum VII, while Maembe (1991) recorded 9 328, representing a 42% increase in two years.
The fishing business has become complex and now is conducted by what is termed the ‘company’ system. The company has an investor, a group of fishermen and one or two fish processors working as a unit by agreement for a set period (2 years), after which profits accrued are share in an agreed ratio. The Ntumu system, which is the marketing strategy, is now well established. It involves the use of middle-women to facilitate the marketing of the processed fish, and has developed to become a socio-economic convenience for the middle-woman and the distant fish traders on one hand and the middle-women and the fisherwomen from the fishing villages on the other. Pricing of fish is based on the season of the year, fish species and the bargaining skill of the buyer. The initial price is fixed by the fisherwoman from the village, based on costs in the week of fishing, processing and transportation, with a 25–50% mark up.
The fish price per kilogram in 1978 was ¢ 2.06 ($US 0.75 at the time) and in 1992 it was ¢ 300 ($US 0.71). The high cost of fish today is therefore attributable to inflation, which is perpetuating itself through high costs of inputs of production.
In 1991, there were 31 fish markets, of which 11 were major markets, against 20 in 1975 (Coppola and Agadzi, 1976). The order of importance of these lakeside fish markets has changed over the years. Whereas the 1975 frame survey showed that the largest fish market on the lake was Kwame-krome, followed by Yeji and Kpando-Torkor, the 1991 fish market data on processed fish showed that the Yeji market was now the largest fish market, followed by Buipe market and Kpando-Torkor. Kwame-krome market had dropped to sixth position.
The fish markets are mainly for domestic trade. The Yeji market attracts fish traders from the Brong Ahafo, Northern, Upper East, Central, Western, Greater Accra, Ashanti, Eastern and Volta Regions. Fish from the lake is also exported to neighbouring countries: Togo, Côte d'Ivoire and Burkina Faso (Salome-Anshong, 1990).
The effects of deforestation have been becoming increasingly obvious in recent years, making the lot of the fishing communities even harder. Fishermen have exploited what is within their reach for fish processing, and now have to rely on the indigenous tribeswomen to bring firewood in exchange for fish. The result is the beginning of a barter trade which is of tremendous importance to the indigenous tribesfolk, who have no other work during the farming off-season. In the areas owned by the Gonja tribe along the lake, the exploitation of firewood is reserved for the Gonja women. This measure is providing an extra income to these women. However, the resultant effect is that settler tribesmen now go to the lake to cut submerged trees for firewood. This particular wood, incidentally, is preferred by fish processors and therefore it has become a lucrative business to cut and sell the wood, which could have highly significant implications for the fisheries in the future.
Besides the research activities of the former Volta Lake Research and Development Programme (LVRDP) and Volta Lake Research Project (VLRP) of the University of Ghana (1964–1970), hydrobiological monitoring of the Onchocerciasis Control Programme (OCP) was started in 1974 by the Institute of Aquatic Biology and sponsored by the Onchocerciasis Control Programme of the World Health Organization.
The (on-going) programme includes the monitoring of daytime invertebrate drift, night-time drift and analyses of Surber samples. Some abiotic parameters (Ph, temperature, turbidity, current speed and river height) are recorded regularly. The monitoring protocol includes two-monthly sampling aimed at assessing changes in CPUE, catches of main fish species on the individual rivers, the condition of principal fish species of individual rivers on a monthly basis, length frequency distribution of main fish species in individual rivers, and, where applicable, evaluation of the food habits of some important fish species.
The UNDP/FAO project Integrated Development of Artisanal Fisheries (IDAF) started in 1989 and, inter alia, research programmes in biology, fish processing and marketing and gear development have been undertaken. The project is currently in its second phase (1992– 1996).
The experience of the fishery complex in Kpando-Torkor has been incorporated into the plans for the establishment of the Yeji Community Fisheries Centre (CFC). One of IDAF's primary objectives since it started in 1989 has been to facilitate the construction of the CFC. Feasibility studies have been concluded and a master plan has been finalized. The first phase of IDAF committed funds for landfill activities in preparation for the actual construction to be executed in the second phase (1992–1996).
In the area of construction of fish processing facilities, the IDAF Project has already commenced construction of communal processing facilities in some fishing villages under the Village Assistance Programme. One was completed in 1990 in Jaklai village (3 km from Yeji Town) and is fully operational. The facility comprises a mosquito-proof storeroom, a chamber for ovens (Chorkor ovens only) and a third room for washing and preparing fish. Five more units are planned in other villages.
The IDAF Project has re-incorporated the embryonic cold storage in its programme for the second phase. In this way the project intends to install an ice machine with the aim of promoting the fresh fish trade. Feasibility studies indicate that the venture would be economic.
A boatbuilding component is attached to the CFC. Even before the construction of the boatbuilding workshop, a scheme for providing better tools and machines to the artisans was initiated. There are plans to install a slipway for easy launching of boats from the boatyard.
Fishery development activities undertaken include:
Fishery complexes
Apart from the Kpando-Torkor complex, the Yeji complex is to be constructed. An amount of $US 300 000 has been provided by UNDP for the landfill work on the proposed site, and $US 4 million will be donated by the Japanese Government as a grant aid for the construction itself.
Fish processing demonstration programme
The IDAF Project was starting the construction of village fish processing facilities in six villages. The Jaklai facility already constructed cost nearly ¢ 177 000 ($US 500). The Chorkor oven - which has been rarely used in the fishing villages - was to be used for extension work to improve the quality of fish products and save costs on firewood. One standard double chamber oven with a complement of 5 trays cost $US 71.
Fishery Schools
The Kpando Torkor Fishery School had trained 81 youths (aged between 17 and 21) and 32 young women (aged between 16 and 21) by 1991. Other fishery schools are the Mobile Fishery School, with a station at Kpando Torkor serving 26 settlements, and the Fishery Services Centre, based at Ampem and serving 35 settlements, both with a annual budget of $US 32 000.
Floating jetty programme
Permanent ramps have proved better than the floating jetties and were incorporated in the Yeji Complex, at a cost of $US 28 800.
Net Revolving Fund Programme
In the second phase of the IDAF project, and linked with the Japanese aid grant, the Net Revolving Fund Programme of $US 1 million will be re-activated.
Fishery extension service
The IDAF Project already has already initiated the development of improved gear to replace outmoded and illegal gears currently deployed on the lake. Improved boat construction techniques are also being taught to boat builders as an on-the-job training activity.
Loans to Fishermen
The scheme of providing inputs on credit to trainees is being revived by the IDAF project. The inputs will be paid back in instalments.
Lakeside fishermen cooperative development programme
The Mobile Training School at Kpando-Torkor and the Fishery Services Centre at Ampem are actively involved in the formation of cooperatives. Seven fishery cooperatives already exist. In order to establish confidence by entrusting them with the capital necessary for them to expand their businesses, the IDAF project intends to create a revolving fund as a means of extending credit to the various user groups who would have been re-vitalized, trained and promoted into registered cooperatives by the Department of Cooperatives.
• Water supply and irrigation
The creation of the Head pond at Kpong (24 km downstream from Akosombo) provided a reliable water supply for the Akosombo Township, and some parts of the Greater Accra Region. This facility enabled the establishment of a very large irrigation project behind the Kpong Head pond in the Accra plains. From 1992, the Irrigation Development Authority (IDA) has operated two sprinkler irrigation projects on the Afram wing of the lake, at Amate and Dedeso. Currently, almost 35% of the drawdown area is being cultivated.
• Generation of electricity
With the sustained improvement in the water level in the reservoir, total energy sales in 1991 were projected to be 5 580 Gwh in addition to the previously installed capacity already on line, an increase of 1.0% over the 1990 level of 5 537 Gwh. Revenue from the sale of electricity in 1991 was expected to increase by 13.7% over the 1990 level of ¢ 37 200 million ($US 120 million) to ¢ 42 300 million ($US 140 million). The major part of the electricity is sold and exported (5 540 Gwh) to Togo, Benin and Côte d'Ivoire. The major internal consumers are Volta Aluminium Company Limited (VALCO) (2 788 Gwh) and Electricity Corporation of Ghana (ECG) (1 560 Gwh).
The government has started a rural electrification scheme in which, by the end of 1992, all regional and district capitals were to have been connected to the National Grid, and over 90% of the country was expected to receive power from Akosombo by 1995. By the year 2000, the coverage was expected to be 100%.
• Bauxite development project
The total cost of the project was considered high and the project was deferred.
• Volta Lake Transport
The Volta Lake Transport system now comprises the following subsystems:
a multi-purpose, break-bulk cargo system for transport of all commodities (except for mineral oil products) and a small number of passengers;
a specialized bulk-cargo system for contract transport of mineral oil products; and
a passenger transport system.
The company's income rose from ¢ 381 million in 1989 to ¢ 656.7 million in 1990, with a concomitant rise of expenditure from ¢ 325 million to ¢ 511.7 million. The declared cash profit was ¢ 145 million in 1990, compared with ¢ 56 million in 1989.
• Wildlife
The Digya National Park, with a total area of 31 000 km2, was established along Volta Lake by Legislative Instrument 710 of September 1991.
• Forestry
The proposed forestry programme for the lake had not materialized at the time of writing. Selected areas were to have been forested with fast-growing tree species for the establishment of a charcoal industry and to help arrest soil erosion.
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