Some of the earliest recorded observations of the Chad Basin fisheries are to be found in Migeod (1925) and Monod (1928), followed by Welman (1948) spanning a period when the “Normal” sized Lake Chad predominated, the fisheries were undeveloped and most of the catch was consumed locally. Annual fisheries production during this period is estimated by these authors to have been 10–20,000t.
After 1960, the number of appraisals increased as attempts to develop the fishery by government and international agencies, such as FAO, expanded. Blache et al. (1962) provided the first comprehensive overview of the fisheries in the period prior to development. This work includes an inventory of the diverse range of traditional fishing techniques used to exploit the equally diverse and variable local fishery resources. Dajet (1962) provides a similiar account for the Chad Basin fisheries located in Niger.
Fisheries are included in a number of early reports by the FAO which consider the potential for developing the water resources of the Chad Basin (FAO, 1973; Degand, 1974), although the main focus here is irrigation agriculture and livestock, and the possibilities for drought control (FAO, 1974). Chad Basin fisheries are also included as an integral part of an expert review of Sahelian fisheries and their problems by the FAO (1975) - the impact of the Sahel drought on the fisheries and future prospects are considered. As part of this review, Ardizzone (1975) assembled a bibliography on the hydrobiology and fisheries of the Chad, Niger and Senegal Basins. Following on from this, an expert consultation meeting was held by FAO in 1978 to promote the FAO Fishery Development Programme in the Sahel; Aubray (1978) reviewed the situation in Chad. Durand (1977) also provided a report on the status of the Chad Basin fisheries for FAO; by this time Lake Chad, the influent rivers and associated fisheries had been significantly reduced in size due to the severe Sahel Drought at that time.
The present and future impact of the Sahel Drought on the Chad Basin fisheries is also considered in a detailed appraisal of the fisheries development potential in Chad carried out by Hill (1976) for USAID. Recommendations to facilitate future development include education and training, development of the National Fisheries Service and new forms of fishing equipment. An effective overview of Chad Basin fisheries and the potential for development, based on the work of ORSTOM is provided by ORSTOM (1977), Benech et al. (1979) and Quensiere (1979). Once again, the impact of the Sahel drought and the complexity of the fisheries are emphasized. Much of this information is included in the Lake Chad Basin Commission Report of 1981, also in Stauch (1973, 1978).
Sagua (1983, 1986) provides a detailed review of the economic importance of the Chad Basin fisheries and the impact of the Sahel drought (1980–85). The Federal Department of Fisheries (Nigeria) report (1986) also briefly emphasizes the importance of the fisheries. Neiland (1987, 1990a) provides an update on the status of the fisheries in the post-drought period identifying the growing significance of the commercial trade as the fisheries show signs of rejuvenation in the post-Drought period. Finally, a comprehensive bibliography of of the Chad Basin by Leveque (1988) provides an excellent overview of the status of fisheries research in relation to other subject areas. In particular it is is worth nothing the large quantity of information available on the limnology of the Chad Basin - a subject-area excluded from this fisheries bibliography.
The most comprehensive account of the fisheries resources and their exploitation is given by Durand (1983): “The exploitation of fish stocks in the Lake Chad Region”, Chapter 13 in Carmouse et al. (1983), based largely on the research of ORSTOM.
Early descriptions of traditional fisheries, including the regulation of activities, are provided by Guilland (1955) and Stauch (1956, 1960f), prior to their development. However, soon afterwards Stauch (1960d, 1961a) was considering suitable schemes for regulating the expansion of fishing activity in Northern Cameroun through a government licencing system and the collection of taxes. By 1967, Hopson had recorded that there had been an intensification of fishing effort on Lake Chad, and a fall in CPUE since 1963 and the introduction of nylon gill-nets.
The fishery of the intermittent river, the El Beid, which connects the North Cameroun floodplain (Grand Yaere) and Lake Chad was studied by Durand (1970a, 1970b, 1971). Over 95% catch of this traditional, seasonal fishery was young fish migrating between breeding grounds (Yaere) and the feeding areas (Lake Chad). The important relationship between the seasonally-inundated floodplain and fisheries production in both Lake and river environments was also examined by Iltis (1974), Quensiere (1981) and Vidy (1983).
However, Durand (1973b) emphasizes that the unpredictable nature of the hydrological cycle in the Chad Basin, and the difficulty therefore of estimating stock size and yield, represents a serious and fundamental problem to fisheries management in this system. Durand also recorded that from 1963 to 1971 (Fig.3.), landings in the now unregulated fisheries of Lake Chad rose from 20,000t to over 100,000t as total effort increased. However, CPUE fell during this period (Durand, 1973c). The fishery was stimulated, in-part, by the expansion of commercial trade with southern Nigeria (Fig.4.)
From 1971 to 1974, landings increased at an even faster rate, reaching 220,000t in 1974 when Lake Chad had been greatly reduced in size due to the Sahel Drought and fish stocks were increasingly concentrated and easier to catch (Stauch, 1977; Stauch et al. 1974; Durand, 1980). Much of these estimates are based on statistics collected by Stauch (1977) who established a road traffic census in Nigeria and Cameroun to monitor the trade in processed fish. Best estimates of landings have been made from these statistics taking into account weight loss in processing, post-harvest losses and auto-consumption. Stauch (1977) demonstrated a strong correlation between landings and drought, and stressed the instability of fisheries production in the Chad Basin.
Durand (1980) calculated that the annual maximum sustainable level of production for Lake Chad will vary between 100,000t (“small state”) up to 180,000t (“normal state”), based on fish density measurements. Sagua (1982), Bukar (1985) and Bukar et al. (1985) have reported a continued reduction in the size of Lake Chad since 1980 and the establishment of major swamp fisheries for Clarias catfish and Tilapia species. Fishing effort, although not quantified, is thought to be very high and unregulated. Annual production is estimated to be c.20,000t, guaged from the level of commerce. Formal fisheries statistics are not collected and the traffic census has ceased. If Lake Chad was to experience a re-juvenation in the near future, the re-establishment of the fisheries would certainly depend upon the effective control of fishing effort. The enforcement of formal regulations would, however, be unworkable given the size of the Chad Basin and the limited financial resources available to the fisheries authorities of the riparian countries.
Although there are only 6 publications included in this section, it is worthwhile identifying a number of the major resource survey programmes that have been carried out in the Chad Basin for future reference.
The ORSTOM research team, while based in N'Djamena carried out a series of detailed sampling programmes in the major aquatic environments. Benech et al. (1974, 1975a, 1975b) provides details of the net-fishing sampling programmes carried out between 1966 and 1975 in Lake Chad (Archipelago and Northern Basin) and the associated influent rivers. This includes the equipment used, locations and catch data by species. This information is also summarised by Durand et al. (1972), and forms the basis of many of the subsequent publications on Chad Basin fish populations produced by the ORSTOM workers.
The Lake Chad Research Institute (LCRI) station at Baga in Nigeria has undertaken a fish population sampling programme in Lake Chad on a continuous basis since 1963. Some of the original work here was reported by Hopson (1967). It is unclear whether the LCRI publishes the results of its surveys on a regular basis, although a number of workers including Bukar et al. (1985) have used the results to report on interesting observations such as the decline of species diversity with the shrinkage of Lake Chad associated with the Sahel Drought.
Finally, it is worth noting that Durand (1983) emphasizes the difficulties of sampling the fish populations in this very dynamic system, and indicates that in attempting to develop a fish stock monitoring system for future management purposes, it might be more appropriate to monitor the limited number of commercial fish trade routes through which a large quantity of the fish landed is eventually moved. The road traffic census organised in the 1970s in Nigeria proved to relatively easy to operate and the trade recorded was considered to be representative of the overall fisheries production (Stauch, 1977).
Studies of the biology of particular fish species constitute 30% of all publications in this bibliography, by far the largest number in any single subject area. However, of the 100 endemic fish species found in the Chad Basin less than 10 have been studied in any great detail.
Table 1., below, provides an overview of the species which have been studied; the number of publications and their subject areas are also indicated.
Table 1.
Fish Biology Studies in the Chad Basin by Genus and Subject-Area.
| Genus | %Publications | Subject Areas |
| (a) Fish spp. (General) | 9 | E/G/Gr/L/M/S |
| (b) Alestes | 15 | E/G/Gr/L/M/Mi/Mo/N/P/R/S |
| (c) Brachysynodontis | 6 | E/G/Mo/N/P/R |
| (d) Clarias | 7 | M/Mo/P/S |
| (e) Lates | 9 | E/G/Gr/N/P/R |
| (f) Micralestes | 7 | E/Gr/Mo/N/R |
| (g) Tilapia | 7 | G/L/Mo |
| (h) Others | 26 | E/G/Gr/M/Mi/N/P/R |
| 100 |
Key: E = Ecology;
G = Descriptive accounts;
Gr = Growth
L = Length/weight keys;
M = Morphology;
Mi = Migration;
Mo = Mortality;
N = Nutrition;
P = Population studies;
R = Reproduction;
S = Systematics.
The characin Alestes baremoze, an abundant and commercially-important species was the subject of a major investigation by the ORSTOM team based at N'Djamena during the 1970s and is best known. Many aspects of the biology of this species are given in the papers of Durand et al. (1967–71) and Lauzanne (1969–73). A comprehensive presentation of the biology and population dynamics of this species is provided by Durand (1978). In addition, Durand (1983) also demonstrates the use of biological information in modelling the population dynamics of the Alestes stock, and the likely impact of fisheries exploitation levels and hydrological influences on yield.
Durand (1983) emphasizes that, while it was possible to model the reasonably discrete single fish stock represented by the migratory Alestes population in the Chad Basin, the information requirements were significant. At the present time, however, it is not feasible to attempt working on a multi-species predictive model for fish production in the Chad Basin, given our limited knowledge of the numerous species present, and their inter-specific interactions.
Although the other fish species detailed above have not been studied to the same extent as that for Alestes, there is still a significant quantity of information available on many aspects of their biology. Works which present a general overview of Chad Basin fish biology include Blache et al. (1964) and more recently, Daget and Durand (1981). Growth and nutrition have been examined for many species. Length-weight keys for most species have been prepared by Durand et al. (1973). The nutritional habits of species such as Lates niloticus are well-known (e.g. Hopson, 1972b). Lauzanne (1972, 1976, 1983) provides an invaluable overview of the feeding and trophic relationships in the major fish communities.
Although the publications in this section could have been included under FISH BIOLOGY (no.3), by treating them separately it is possible to highlight some of the key findings on the ecology of the multi-species fish communities found in the Chad Basin.
All but two of the works included here arise from research undertaken by the ORSTOM team which was based at N'Djamena until 1981. Comprehensive coverage of this work is given in the two relevant chapters of the book “Lake Chad: Ecology and productivity of a shallow tropical ecosystem” (Ed. Carmouze et al., 1983): Chapter 10, “Fish communities of Lake Chad and associated rivers and floodplains” (Benech et al.) and Chapter 15, “Trophic relations of fishes in Lake Chad” (Lauzanne, 1983).
Carmouze (1983) represents a detailed examination of the fish communities based on fieldwork between 1965–75. Special emphasis is given to the impact of the drought and the transition from “Normal” to “Lesser Chad”, and the resultant replacement of lacustrine species by swamp species in both Lake Chad and the major rivers. Lauzanne (1983) in his overview of trophic relationships identifies two major food chains (plant and detritus based) and nine major food types. Both food chains are energetically efficient and influenced by hydrological and environmental changes.
The impact of the severe Sahel drought on the fish communities was the focus of a number of earlier studies. Changes in fish community composition, structure and distribution in Lake Chad and the River Chari, with the replacement of lacustrine species by swamp species were studied by Benech (1975a), Quensiere (1976) and Lek et al. (1978a). Quensiere (1976) noted a direct correlation between the drought and falling catches in the River Chari delta fishery, associated with a deterioration of the environment and a destabilisation of the fish populations. Significant fish mortalities in Lake Chad due to decreasing water levels at the time of the drought were noted by Benech et al. (1976). Benech et al. (1981) also made observations on 16 species at this time and noted that those species with high resistance to water deoxygenation (e.g. Clarias catfish and Tilapia) were able to survive.
Other studies (Lauzanne, 1972, Lauzanne, 1976, 1977; Tobor, 1972) have examined the food, feeding habits and trophic relationships of the fish populations in both Lake Chad and the major rivers. The complex and extensive fish migrations between Lake Chad, the El Beid channel, the N. Cameroun Floodplain (Yaere) and the river Logone have been investigated by Benech et al. (1981, 1982, 1983). Downstream migrations (river - lake) appear to be organised on three interacting levels: seasonal, lunar and diurnal, which vary with the hydrological patterns. The traditional fishing communities have an expert knowledge of the fish migrations and have adapted their fishing practices accordingly. Juvenile fish are the basis of a significant fishery when moving from the floodplain to the lake through the El Beid channel.
A general overview of the fish community ecology in Lake Chad is also given by De Merona (1979) and Leveque et al. (1979).
Fishing technology in the Chad Basin has undergone a number of significant changes between 1960–90 including the widespread adoption of nylon gillnets, and the use of wooden canoes and some mechanisation. In general there has been an increase in catching capacity and a decline in the diversity of methods employed.
A number of early studies (Monod 1928; Stauch, 1961; Blache et al. 1962) provide detailed description of the traditional fishing gear and practices. The main methods included fixed gillnets, drifting gillnets, nets of large mesh size, unbaited multiple longlines, fish traps and fish fences. Blache et al. (1962) demonstrated that the traditional fishing techniques were well-adapated to this diverse aquatic system. Undoubtedly, the large variety of techniques resulted from the local differences in the hydrological cycle.
Nylon gillnets first appeared on Lake Chad in 1958, and by 1961 there was a well-established gillnet fishery (Hopson, 1968). This initiated a rapid increase in total fishing effort; Durand (1973b) estimated that fishing effort in the northern basin increased by 50 times and total production by 5 times between 1967–72.
Early trials using nylon nets on the rivers of N. Cameroun were undertaken by Stauch (1957, 1958). The demonstrable success of these new nets encouraged local fishermen to adopt them. Subsequent trials of nets have been undertaken by Thomas (1967), Franc (1975), Dupuis et al. (1977) and Bukar (1979), although the information-base on the performance and optimal use of new net fishing technology is not very extensive. More recently, the use of Malian fish traps in the shallow waters and swamp areas of Lake Chad, and the impact on juvenile fish has been examined briefly by Gubio et al. (1982).
The FAO has sponsored a number of projects since 1963 to examine the development of fishing boat technology on Lake Chad, where the papyrus-built kadei was once dominant. Designs, construction facilities and finance for suitable wooden (plank) craft with outboard engines were proposed by Anderson et al. (1963), Fyson (1966), Gulbrandsen (1968), Christenson (1969), Richards (1979) and Langford (1981). By the late 1960s the kadei had been almost completely replaced by wooden fishing boats. Interestingly though, many of the designs above were subsequently modified by local boat-builders. Although outboard motors were used in the Lake Chad gillnet fishery during the late 1960s and early 1970s, the widespread adoption and persistance of this technology has been hindered by poor technical support and the cost of spare parts. Many craft in the Chad Basin today lack motorization.
Fish processing in the Chad Basin has traditionally involved a number of different methods, often used in combination and including smoking, char-burning and sun-drying. Much of this activity has been located in the fishing camps of the Lake Chad archipelago, on the north Cameroun floodplain and along the major river channels. With the rapid development of the fisheries from 1960 onwards, it was recognised that the traditional processing methods were not appropriate for the volume of accompanying trade. The processed products were highly variable in quality and promoted significant post-harvest losses during distribution. Specific studies on fish processing have attempted to (a) identify the nature and cause of post-harvest losses, and (b) investigate methods by which processing might be improved.
Azeza (1979a, 1979b, 1982, 1983, 1986), a scientist at the Lake Chad Research Institute (Nigeria), identified that insect infestation and bacterio-fungal decay are a major problem promoted by the fact that the fish was processed in the open and inadequately dried before packaging. It was observed that the fish products suffer significant breakage and decay during transit to distant Nigerian markets, and that this could significantly reduce market and nutritional value. Although suspected, Azeza (1983) failed to demonstrate that processors were using pesticides to reduce insect infestation. In an earlier study, Stauch (1958) examined the extensive and unregulated use of pesticides by processors in N. Cameroun and the implications for human health.
It was shown, however, that improvements in product quality could be achieved by using various methods; re-smoking proved to be particularly effective in extending storage time (Azeza, 1979b). Azeza (1986) reviewed possible methods and strategies for reducing post-harvest losses in Lake Chad fish. New processing methods and research priorities were also considered in general in an earlier work by Azeza and Maembe (1981).
An FAO-supported project between 1979–82, “Improvement of fish processing and transport on Lake Chad”, attempted to address the problems of post-harvest losses (FAO, 1982). Taylor (1980) identified insect infestation as a major problem in the processed fish destined for Nigerian markets. Carleton (1980) examined possible solutions. Maembe (1982a) calculated the post-harvest loss to be as high as 60% of total processed fish production. A number of technical recommendations were made to reduce the problem including the use of new kilns, as well as ice and brine (Moes, 1980; Maembe, 1982b). Both Carleton and Maembe proposed the establishment of a fishermans' cooperative to co-ordinate improvements. Others studies include an examination of transportation methods for processed products across Lake Chad (Wilder, 1981) and the design and implementation of appropriate statistical surveys (Herman, 1982). The terminal report for this project summarizes the findings of the various investigations and the recommendations for improvements which arose (FAO, 1982). Following on from this work, ice-making facilities and new smoking kilns were provided at Baga, but their impact has been minimal.
More recently, Neiland (1987, 1990a, 1990b) reports that traditional fish processing methods, high post-harvest losses and vigorous commercial activity persist at Lake Chad. In addition, there is a serious threat of deforestation due to the demand for fuelwood; processors are even using the locally abundant poisonous shrub Calotropis.
Although this section represents a mere 5% of the total publications, there is a reasonably complete record of observations concerning the commerce and marketing of Chad Basin fish products dating from 1958 onwards. Aspects of fish commerce and marketing have often been included in other subject area studies as shown in the Secondary Index (5.2.).
Early work by Stauch (1957, 1959, 1960b, 1960g) examined the trade in processed fish products (banda and salanga) in N. Cameroun and to markets in S. Nigeria during the phase of fisheries development. Particular attention was given to the operation of the marketing system and to the role of the new road infrastructure in promoting commercialisation. Stauch also voiced some concern that the trade was becoming dominated by certain groups of merchants to the detriment of the community as a whole. However, he also noted that the new infrastructure allowed greater distribution of fish to local food markets. Mann (1961a, 1962), in more local studies in Nigeria, surveyed trade in the Wulgo area (S.E. Lake Chad), and along the full length of the western shore of the Lake, prior to the rapid development of the fishery soon afterwards.
By far the most comprehensive studies of fish commerce and marketing in the region are given in Couty (1964a, 1968) and Couty and Duran (1968). Based on extensive surveys these works detail and evaluate every aspect of this commercial activity in north Cameroun and Chad respectively. Information is provided on the activities of merchants and fish-traders, markets and their organisation, trade routes and transportation, and the significance of fish in the local and national economies. Prospects for the future and constraints are also included. Unfortunately, such detailed information is not available for Nigeria, the main focus for the Chad Basin fish trade.
A road traffic census, organised by the Lake Chad Basin Commission and the Nigerian Federal Department of Fisheries, along main export routes for processed fish into Nigeria, has until recently provided the best estimate of the significant trade passing into the main Nigerian markets (Stauch, 1977). For example, between 1970 and 1976, the total quantity of banda which left the Chad Basin by road was 145,000t (dried wt.), with Lagos being the single largest final destination, accounting for over 30% of this (Fig.4.). A strong correlation was also demonstrated between fish production and the Sahel drought. Although the data-set is not complete, it has been used to determine total fisheries production for the Chad Basin between 1970 and 1980 (Durand, 1983).
Since 1977, there have been no comprehensive studies of fish commerce and trade in the Chad Basin. However, from studies such as that by Maembe and Gubio (1981) and more recently Neiland (1987), it is evident that processed fish products from the Chad Basin are economically significant to the riparian countries, and particularly Nigeria, despite the impact of the Sahel drought on fisheries production. However, very little is known of the economic impact of commercialization on the fishing communities and the general distribution of benefits within a regional economy which has traditionally valued fisheries production as an integral part of the agricultural production cycle.
Besides two preliminary studies by Verlet (1964) and Meeren (1980), this subject area has been largely ignored by researchers. The former study identified some of the characteristics of the fishing communities and the relationships between the major tribes involved. The other study by Meeren was conducted as part of the FAO project on improvement of fish processing and transport on Lake Chad. An attempt was made to undertake a socio-anthropological analysis of the fishing communities with a view to assessing the potential for establishing fisheries cooperatives.
Reference to the ethnic characteristics of fishing activity is made in at least ten other publications. Of particular interest is Blache et al. (1962) which describes in some detail, with many fine diagrams, the fishing activity (methods and gear) of the major fishing tribes, and ORSTOM (1977) which provides an overview of the fishing communities in Chad. In addition, early work by Stauch (1960c, 1960e, 1961) again provides detailed description of the traditional organisation and methods of fishing activity in the Chad Basin prior to extensive commercialisation. Stauch (1960e) gives an interesting account of traditional fishing rights among the main tribes.
There are no contemporary studies in the field of fisheries anthropology or social organisation, besides the two mentioned above, which might allow a greater understanding of the fisheries activities which have emerged over the last 20 years in the Chad Basin. Interestingly a number of studies looking at agricultural communities in the region were carried out in preparation for Chad Basin irrigation scheme, and although not directly related to fisheries, do provide some insight into the associated and neighbouring agricultural communities3.
Specific studies in this area have investigated the problems of sampling fish populations in the different biotopes of Chad Basin (Benech, 1978) and the potential use of electrified nets to achieve a representative sample (Benech, 1978; Benech et al, 1978). Earlier studies by Loubens (1969, 1970) had assessed the effectiveness of natural and synthetic ichthyotoxins as means of sampling fish populations. This was found to be effective on a small-scale, albeit highly destructive.
Others studies in this section have included that of Durand (1973a) who analysed catch composition using correspondance factorial analyses, which was found to be useful in explaining variation according to biotope and season, and Gras et al. (1982) who in examining Ivelv's electivity index, found this not to be useful in representing the degree of prey selection by fish. A new index was proposed for this purpose. Finally, with reference to the collection of fisheries statistics, Loubens et al. (1972) investigated existing methodology and made recommendations for further research.
Although this section contains a limited number of studies, it must also be pointed out that many of the other studies in the various sections which include the collection of primary data, often contain a description of the research methods used as well as some comment on their usefulness.
