Mechanised Fisheries of Lake Malawi

1. INTRODUCTION

Commercial trawling was introduced to Lake Malawi by Maldeco Fisheries in 1968. Management of the trawl fisheries is presently based on a system of allocation of licenses for 8 areas (see FAO 1976) in southern Lake Malawi. Allocation of trawling units to these areas has been based on biomass estimates resulting from experimental trawling by FAO (1976), where the maximum sustainable yield was calculated as 45% of virgin stock biomass. These estimates were clearly stated to be tentative (FAO 1976). No differentiation between trawling techniques was made in the allocation of units, except insofar as different techniques use vessels of different fishing power. Subsequently, Tweddle & Magasa (1989) have assessed the state of the pair trawl fishery in Area A (S. of Boadzulu Island), and of the ringnet and trawl fisheries for chambo in the SE Arm.

In the course of the Chambo Fisheries Research Project, it became apparent that different trawling techniques may exploit different fish species and that analysis of the species composition of the catch was required before it could be determined which trawling techniques exploit the same fish stocks within a particular area. Additionally the possibility that some species are exploited by both artisanal and trawl fisheries has been investigated.

In this report, the present state of the trawled fish stocks is assessed, in the light of statistics from more recent fishing activities, and of in-depth analysis of the species composition of the catches. The economic implications of these assessments are considered by Turner & Mdaihli (1992).

2. PRESENT MANAGEMENT STRATEGY

2.1 Regulations

The number of trawling licenses issued for each of the 8 license areas is based on tentative biomass estimates made by FAO (1976). At present 9 pair trawl units and three stern trawlers operate in the SE Arm, 10 pair trawlers in the SW Arm and Salima and one in Domira Bay.

In addition to the limitation of licenses, the following regulations are in force:

1. Trawling is prohibited in the hours of darkness.

2. A minimum cod-end mesh size of 38mm is permitted for trawls.

3. Trawlers are prohibited from fishing within 1.6km (one mile) from the shore.

4. Commercial fishing companies are required to submit monthly catch returns to the Fisheries Department.

2.2 Implementation

Although the FAO (1976) estimates were clearly stated to be tentative, the Fisheries Department does not routinely perform analysis of catch-effort returns to monitor the state of the stocks, but rather considers that the stocks are underexploited if total yields are below the tentative MSY levels suggested by FAO.

Fishing units generally ignore the boundaries of their license areas. For reasons of economy, most units fish close to their landing sites. Units licensed for Area B often fish in Area A, while those licensed for Area C usually fish in Area B.

Trawling by night generally does not take place.

Mesh size regulations are ignored by pair trawlers, which use meshes of 22mm or double bag the cod-end. In any case, pair trawlers generally make a single pull of around 12 hours duration which results in clogging of the net meshes and renders mesh size restrictions irrelevant.

Fishing within 1.6km from the shore is universally practised.

Monthly catch returns are submitted regularly, although generally several months late, by Maldeco Fisheries. In the case of pair trawl operations, catches are recorded by Fisheries Department scouts, unless, as often happens, landings are not made at Fisheries Department jetties, in which case they are not recorded.

3. SPECIES COMPOSITION ANALYSIS

3.1 Relationships between Haplochromine and Chambo Fisheries

From analysis of commercial catch returns and of traditional fisheries data collected by the MTF system (Alimoso et al 1991), it can be seen that in the south-east arm of Lake Malawi only the midwater trawl and, to a lesser extent, the gillnet fisheries, catch large quantities of both chambo and other species (Table I). In the case of the gillnet, the gear is selective for large fishes and mainly exploits kampango (Bagrus meridionalis) and clariid catfishes in addition to chambo. These species mature at larger sizes than chambo and so any management measures which protect chambo will also be beneficial for fisheries based on these catfish species.

The other species caught by the midwater trawl are small-maturing haplochromine cichlids and thus increases in mesh size aimed at protecting immature chambo would lead to a loss of this large 'by-catch'. Thus, before framing any management recommendations for the chambo trawl fisheries it is necessary to know: (i) what non-chambo stocks are exploited by the midwater trawl: (ii) are these stocks exploited by other fishing techniques; (iii) what is the state of exploitation of these stocks.

Table I

Interactions Between Fisheries for Chambo and Other Species
(SE Arm, Total Catches, in tonnes, 1991- MTF & Commercial Returns)

3.2 Interactions Between Artisanal and Mechanised Chambo Fisheries

In the past separate stock assessments have been carried out on artisanal and mechanised chambo fisheries in the south-east arm of Lake Malawi (Tweddle & Magasa 1989; Tweddle et al. ms). Citing the observations of Lowe (1952), it had been assumed that mechanised fisheries operating in deep water would exploit mainly Oreochromis lidole, while artisanal fisheries would mainly catch Oreochromis squamipinnis and O.karongae. However, it should be noted that Lowe found considerable overlap in the species composition of catches by different gears, including the ringnet which was already operational by the 1940s. In any case, fishing techniques have changed greatly since Lowe's study and none of the subsequent studies have recorded the species composition of chambo catches by any gear.

In a year-long stratified sampling programme, more than 150 samples, totalling more than 20,000 fish, were examined from all the major chambo catching gears (Table II).

Table II
Species Composition of Chambo Catches
(% weights)

Data: October 1990– September 1991: thrice monthly sampling of midwater trawl catch; monthly sampling of ringnet, bottom trawl & pair trawl, monthly sampling in each of four minor strata for gillnet and chambo seine.

It was found that midwater trawl and ringnet catch mostly O.lidole, but also significant amounts of O.squamipinnis. Bottom trawl and pair trawl mainly exploit O.squamipinnis, but with substantial numbers of O.lidole and O.karongae respectively also being taken. No single species dominates the gillnet and chambo seine catches. Thus, there is no justification for performing separate assessments of the artisanal and mechanised chambo fisheries. An assessment of the chambo fisheries of the south-east arm is reported elsewhere (Seisay et al. 1992).

Since all species of chambo are also heavily exploited by the artisanal fisheries, catches of chambo must be excluded from any assessment of the haplochromine trawl fisheries.

3.3. Relationships Between Different Haplochromine Trawl Fisheries

To investigate the interactions between haplochromine trawl fisheries, 54 commercial trawl catches were examined, and the numbers and weights of each species caught determined. The percentage contribution of the 20 most important species or species groups (taxa) is given on Table III.

Table III
Species Composition of Trawl Catches in the S.E.Arm
(percentage weights, excluding chambo & large catfish)

Note: *= less than 1%, blank= not recorded

There is clearly very little overlap between the species exploited by the three fishing techniques. In fact, subsequent studies have indicated that these data over-estimate the interaction between the fisheries: nine of the taxa distinguished (2,7,9–14 & 17) consist of two or more species, in most cases with different habitat preferences and likely to be exploited in different proportions by the three techniques.

Midwater trawling mainly exploits pelagic Diplotaxodon spp. (ndunduma) and Rhamphochromis spp. (ncheni), which are generally, and erroneously, recorded in fisheries statistics as utaka or chisawasawa.

Bottom trawling, while also catching large amounts of pelagic species, is principally based on large Lethrinops spp. which dominate the demersal communities at depths of 50m depth of more.

Pair trawling mostly exploits small shallow water demersal species. In the Malawi commercial fisheries statistics, most of the fish recorded as ‘others’ are adults of large demersal haplochromine cichlids, which should properly be combined with the catches of small species marketed as chisawasawa. It is not known if the pelagic Rhamphochromis spp. exploited by this gear are the same species as are caught by the other two techniques.

Thus, there is justification for assessing each of these fisheries separately.

4. GEOGRAPHICAL LIMITS OF STOCKS

Since few previous studies have distinguished different haplochromine cichlids in Lake Malawi, little is known of the boundaries of the major stocks. Most demersal species appear to have restricted depth distributions and probably also substrate preferences (Eccles & Lewis 1977, 1978, 1979; Eccles & Trewavas 1989, Turner et al. 1993), and some utaka (semi-pelagic species) also appear to have restricted distributions (Konings 1991). Factors limiting the distributions of pelagic species are not known, but since these stocks are presently exploited principally by a single midwater trawler, this does not pose a problem at present.

The pair trawl fishery in Area A operates over a large area of shallow gently-shelving bottom, less than 40m deep. Waters of this depth are restricted to narrow bands along the edges of Areas B & C. Heavy fishing since the early 1970s has produced significant changes in species proportions within the haplochromine community (FAO 1976; Turner et al. 1993)- these changes have been less marked in other areas. Thus, Area A can be considered as a limnological and biological unit for the assessment of haplochromine fisheries.

From a consideration of the topography of the south-east arm, there is no reason to regard Areas B & C as separate: the boundary between the areas is wide and cuts across all depths, except for the very deep waters below 70m, which are not presently exploited, and where the fish density is low. The species composition of bottom trawl catches in Areas B and C are similar. Shallow water fish stocks on of west coast of Area B are probably largely isolated from the east coast of Areas B & C, but a separate assessment of these is not possible as fish catches from the east and west coasts are not distinguished on catch returns.

The productive shallow waters of south-west arm are separated from the shallow waters of the south-east arm by the steeply-shelving headland of the Nankumba Peninsula. It seems unlikely that demersal species favouring depths of less than 70m would freely cross the extensive rocky slopes of the peninsula. Since, at present, only pair trawlers fishing in shallow waters (less than 50m) operate in the south-west arm, these can be considered to exploit separate stocks from those in the south-east arm. There are no natural boundaries within the south-west arm: the present division into areas D and E is arbitrary and can be ignored for the purposes of stock assessment. Similarly there is no reason to separate catches from Salima from those of the south-west arm.

Although there is no known habitat boundary between Salima area and Domira Bay, the strikingly different catch rates reported suggest that the stocks exploited by pair trawling in Domira Bay are largely isolated.

5. STOCK ASSESSMENT

On biological (section 3) and geographical (section 4) grounds, mechanised fisheries in Lake Malawi can be divided into seven separate fisheries: (i) the chambo fishery of the south-arm, which is shared between mechanised and artisanal operation; (ii) the midwater trawl haplochromine fishery of the south-east arm; (iii) the bottom trawl fishery of the south-east arm; (iv) the pair trawl fishery of Area A, i.e. the south-east arm south of Boadzulu Island; (v) the pair trawl fishery of Areas B & C, i.e. the south-east arm, north of Boadzulu Island; (vi) the pair trawl fishery of Areas D, E, & F, i.e. the south-west arm and Salima; (vii) the pair trawl fishery of Area G, Domira Bay.

Since the pair trawl fishery of Domira Bay has only been in operation since 1990, no stock assessment in possible as yet, but the economics of this fishery are considered in Turner & Mdaihli (1992).

5.1 The Midwater Trawl Haplochromine Fishery

Since the introduction of midwater trawling in the early 1970s, a single vessel, Maldeco's Crystal Lake, has employed this technique. Two mesh sizes, 102mm and 38mm have been employed. Since few haplochromine cichlids are large enough to be caught be the 102mm gear, only catch and effort statistics for the 38mm net can be used to assess the haplochromine stocks. Catch and effort data since 1976 are given on Table IV.

Table IV
38mm Midwater Trawl Haplochromine Fishery

Surplus productions models were fitted (Table V) to the data for catches of haplochromine cichlids (‘others’ in Table IV).

Table V
Midwater Trawl Haplochromine Fishery Surplus Production Models
(asterisk indicates best-fitting model)

The highest correlations between CPUE and effort were obtained using a 2-year running mean of effort (Table V, see also Figure 1), suggesting that the main exploited species has an average generation time of two years. The Schaefer model predicts that MSY could be obtained at an effort slightly below the present level, while the Fox Model indicates that a slight increase could be permitted.

Thus, the midwater trawl haplochromine fishery is estimated to be fully exploited in the south-east arm, and might perhaps benefit from a small reduction in fishing effort.

5.2 The Bottom Trawl Fishery

Since the inception of this fishery in 1973, the Dennis Sanudi (Maldeco Fisheries Ltd.) has exploited this fishery continuously. However, 5 other vessels have also fished this stock at various times. The relationship between their fishing power and that of the Dennis Sanudi is given on Table VI.

Table VI
Bottom Trawl Fishery: Fishing Power of Vessels

For the purpose of stock assessment, the fishing effort of all other craft was standardised, by dividing the CPUE of the Dennis Sanudi into the total catch by all craft exploiting the same stocks (Table VII).

Table VII
Bottom Trawl Fishery, SE Arm

NB: Effort in boat days, catch in tonnes

Table VIII
Bottom Trawl Haplochromine Fishery Surplus Production Models
(asterisk indicates best-fitting model)

All models indicate an MSY of around 1400 tonnes (Table VIII), but the best fit is obtained if a three-year average of fishing effort is used, indicating a three-year generation time for the main exploited species (as found by FAO 1976). At present yields are considerably below MSY. From Figure 2, it is apparent that bottom trawl stocks have been over-exploited since 1983, when Fatch's trawler was licensed for Area C. Since Fatch's trawler rarely manages to fish for more than 220 days per year, and the Dennis Sanudi usually fishes for around 330 days, optimal exploitation of these stocks could be achieved if only these two vessels were permitted to employ bottom trawls in the south-east arm. However, given that these demersal cichlids appear to be slow growing fish with low fecundities, it may take several years of low fishing effort before stocks recover from present densities of 1.2 tonnes per standard boat day to the predicted MSY equilibrium levels of 2.5 t/d.

5.3 Pair Trawl Fisheries

Catch and effort data for the pair trawl fisheries of the south-east and south-west arms are shown on Table IX. Pair trawling has been carried out intensively in the Area A and in the south-west arms, but operations have been inconsistent in Areas B & C.

Table IX
Pair Trawl Fisheries in the S.E. and S.W. Arms

NB: Catch figures exclude chambo and large catfish, and are in metric tonnes, effort is given as boat days

Surplus production models have previously been fitted to the catch and effort data for pairs trawls in Area A (FAO 1976; Tweddle & Magasa 1989). A statistically significant relationship was found when using the complete data set from the initiation of this fishery in 1968.

However, the accuracy of surplus yield models in fisheries stock assessment is highly sensitive to the assumption that the stocks are in equilibrium (Pitcher & Hart 1982). Even in a single species fishery, stocks cannot be considered to be in equilibrium during the first few years of exploitation: in an unfished population there is a considerable number of old fish. These will be rapidly removed by fishing, and an equilibrium age structure will develop, assuming that exploitation does not reach excessive levels within the first few years.

The situation is further complicated when there is a multispecies fishery in which large, slow-maturing fish are replaced by smaller species. Such species changes were documented by FAO (1976) between 1971 and 1975. A change in mesh size from 25 to 38mm was introduced in 1977.

Thus, catch and effort statistics for 1968 to 1977 should not be used for stock assessment- from Figure 3, it can be seen that a regression of CPUE on effort would be strongly influenced by the inclusion of the year 1968, the first year of exploitation. Thus, MSY estimates of FAO (1976) and Tweddle & Magasa (1989) should be treated with caution.

Using catch returns for the years 1978–1991, attempts were made to fit both Fox and Schaefer Models, using 1, 2, and 3 years of effort data, for the three areas exploited by pair trawlers over the whole time period. In no case was a significant correlation found (Table X). In fact in 10 of 18 calculations there was a positive correlation (but non-significant) between catch and effort, which would mean that fish stocks increased as fishing effort increased- this is clearly impossible!

Table X
Pair Trawl Fisheries Correlations Between Catch and Effort

Closer inspection of the data for Area A for the years 1978 to 1991 (Figure 4) indicates that the pair trawl fishery has moved through three phases, each with a different relationship between cpue and effort. The third phase, lasting from 1987 to the present, suggests a potential for very high yields at reduced effort levels, but that a collapse of stocks could occur with a relatively small increase in effort. No such trends were apparent in other areas.

Possible explanations for the phase changes in the pair trawl fishery are:

1. a decrease in mesh size: the legal minimum of 38mm is not enforced- 22mm meshes are used, and the practice of double-bagging the codend is reported;

2. an increase in the length of pulls leading to clogging of the net: presently pair trawlers in Area A make a single pull of 10–12 hours duration. This keeps the catch fresh, as there are no refrigeration facilities on these open boats. It also prevents the crew from selling part of the catch out of sight of the owner, who does not generally accompany the fisherman during their operations. Previous practices have not been documented;

3. a change of fishing ground: at present, trawling within one mile (1.6km) of the shore is legally prohibited, but this is not enforced. During experimental fishing cruises, the majority of pair trawlers observed were fishing close to the shore: this is consistent with the species composition of the catch. Previous practices have not been documented;

4. a change in species composition of the catch: samples taken by experimental trawling (Demersal Fisheries Reassessment Project, funded by the Overseas Development Administration, UK) indicate that since the FAO report of 1976, changes in the species composition of the demersal cichlid communities have continued. Large cichlid species preferring depths of 30m or deeper had already declined by 1975- many of these have declined further, or become locally extinct. More recently, populations of large species in shallow waters have also diminished (Table XI).

Table XI
Change in Species Composition of Cichlid Communities in Area A

Notes: * indicates period of greatest change in relative abundance (Data from ODA Demersal Fisheries Project-Turner et al. 1992)

Thus the pair trawl fishery in Area A appears to be in a dangerously unstable state. As it is not possible to determine the maximum sustainable yield or optimum fishing effort for this fishery, future developments need to be monitored closely, and corrective action taken swiftly, through limitation of fishing effort or temporary closure of the fishery.

Before any increase or redistribution of fishing units is performed, potential trawling grounds in Areas B & C should be resurveyed, taking into account (i) that pair units generally operate in waters of less than 40m depth, (ii) that single boat bottom trawlers operate between 50 and 70m depth-deeper areas can be excluded, (iii) that units licensed to fish in these areas will continue to fish as far south as possible for economic reasons, (iv) that much of the coast near Makanjila is rocky and cannot be trawled, and (v) that many species now extinct in Area A are confined to the S.E.Arm and would probably become entirely extinct if pair trawl operations were to reach a similar intensity in Areas B & C.

References

Alimoso, S.B., Seisay, M.B.D., & van Zalinge, N.P. (1991) An efficient method for catch-effort sampling of the artisanal chambo fisheries of the south east arm of Lake Malawi, the Upper Shire River and Lake Malombe. FI:DP/MLW/86/013 Field Document 6.

Eccles, D.H. & Lewis, D.S.C. (1977) A taxonomic study on the genus Lethrinops Regan (Pisces: Cichlidae) from Lake Malawi. Part 1. Ichthyol. Bull. J.L.B. Inst. Ichthyol. 36.

Eccles, D.H. & Lewis, D.S.C. (1978) A taxonomic study on the genus Lethrinops Regan (Pisces: Cichlidae) from Lake Malawi. Part 2. Ichthyol. Bull. J.L.B. Inst. Ichthyol. 37.

Eccles, D.H. & Lewis, D.S.C. (1979) A taxonomic study on the genus Lethrinops Regan (Pisces: Cichlidae) from Lake Malawi. Part 3. Ichthyol. Bull. J.L.B. Inst. Ichthyol. 38

Eccles, D.H. & Trewavas, E. (1989). Malawian Cichlid Fishes: the classification of some haplochromine genera. Lake Fish Movies: Herten, Germany.

FAO (1976) Promotion of integrated fishery development, Malawi. FI:DP/MLW/71/516 Technical Report 1., based on the work of J. Turner. 73pp.

Konings, A (1990) Cichlids and all the other fishes of Lake Malawi. TFH Publications: New Jersey.

Lowe, R.H. (1952) Report on the Tilapia and other fish and fisheries of Lake Nyasa. Fishery Publications of the Colonial Office 1:1–126.

Pitcher, T.J. & Hart, P.J.B. (1982) Fisheries Ecology. Croom Helm: Beckenham, UK.

Seisay, M.B.D., van Zalinge, N.P. & Turner, G.F. (1992) Population dynamics and stock estimates of chambo (Oreochromis spp.) in the south-east arm of Lake Malawi and Lake Malombe-length-based approach. FI:DP/MLW/86/013 Field Document 19.

Turner, G.F. & Mdaihli, M. (1992). A bioeconomic analysis of the industrial and semi-industrial fisheries of southern Lake Malawi. FI:DP/MLW/86/013 Field Document 22.

Turner, G.F., Tweddle, D. & Makwinja, R.D. (1993) Species composition changes of demersal cichlid communities as a result of trawling in southern Lake Malawi. In: The Impact of Species Changes in African Lakes, Edited by TJ Pitcher. Chapman & Hall: London, UK.

Tweddle, D. & Magasa, J.H. (1989) Assessment of yield in multispecies cichlid fisheries of the South East Arm of Lake Malawi. J.Cons.int.Explor.Mer. 45, 209–222.

	Figure 1. The midwater trawl haplochromine fishery is fully exploited. At effort levels of 250–350 days catches of around 500–750 tonnes have been made.
Figure 2. The bottom trawl haplochromine stock has declined due to heavy fishing pressure in the late 1980s. Although fishing effort has subsequently been reduced, catches have remained low.
	Figure 3. The pair trawl fishery in Area A (south of Boadzulu Island) initially showed large fluctuations in cpue and effort, before stabilising from 1978 onwards. Any apparent relationship between cpue and effort is the result of a few data points from the early years of exploitation.
Figure 4. Since 1979, the pair trawl fishery in Area A has moved through three phases, each characterised by a  different relationship between cpue and effort. The present phase, which began in 1987, shows great instability. This phase has not lasted long enough to justify an attempt to fit a surplus production model.

GLOSSARY

Artisanal Fishery: a small-scale commercial fishing operation, using various nets and small planked boats or canoes, powered manually or by outboard engine. (chambo & kambuzi seine (qv) nets, nkatcha net (qv), chirimila net (qv), gillnet). Generally referred to in Malawi as ‘Traditional Fisheries’.

Bottom Trawl: Demersal trawl operated by a single boat, usually in water deeper than 50m.

Chambo: 3 endemic species of tilapiine cichlids classified within the subgenus Nyasalapia of the genus Oreochromis.

Chambo Seine: a large-meshed beach seine targeted on chambo (qv).

Chirimila Net: a small seine net used clear of the bottom to catch usipa (qv), utaka (qv) and ncheni (qv).

Chisawasawa: chichewa name for some categories of demersal haplochromine cichlids (qv): (i) large species caught by gillnets; (ii) small species caught by pair trawls (qv); (iii) all species caught by Maldeco Fisheries (qv).

Copadichromis: small zooplankton-feeding haplochromine cichlids (qv). Mostly found inshore in shallow waters, a few metres above the bottom (‘semipelagic’).

CPUE: catch per unit effort. Weight of fish caught in a given unit of time by a standard type of fishing craft. A direct measure of the density of fish in the environment.

Diplotaxodon: a genus of haplochromine cichlids (qv) endemic to Lake Malawi, confined to waters with a bottom depth greater than 20m. Most species are undescribed. The most important food fishes are small pelagic zooplankton feeders-ecological counterparts to Limnothrissa of Lake Tanganyika.

Endemic: naturally-occurring exclusively within a specific area (NB not to be confused with indigenous, which means naturally-occurring within a specific area, but not necessarily only that area).

Fatch: Mr.F.Fatch. Prior to 1992, the only semi-industrial (qv) fishing operator to use a technique other than pair trawling (qv). Owner of a bottom trawl (qv) unit in the S.E.Arm and a pair trawl unit in the S.W.Arm.

Fox Model: a surplus production model for the calculation of the MSY (qv) of a fishery. It is based on a regression of the logarithm of cpue on effort. Appropriate for fish stocks which do not collapse suddenly at high levels of exploitation.

Fmsy: Fishing effort required to produce the MSY (qv).

Haplochromines: demersal, pelagic and semipelagic cichlids of the haplochromine tribe of the family cichlidae. Mostly, but not all, small species.

Industrial Fishery: fishing operation with a high degree of capitalisation, including considerable investment in onshore landing, processing, repair and transport facilities.

Kambuzi: small cichlids caught by seine nets. Mostly small demersal species, but also including juveniles of larger demersal and pelagic species.

Kambuzi Seine: a small-meshed beach seine targeted on kambuzi (qv), usipa (qv) or immature chambo (qv).

Kampango: Bagrus meridionalis, a large predatory catfish.

Lethrinops: a genus of haplochromine cichlids (qv) endemic to Lake Malawi and associated water bodies. Includes most of the important demersal species exploited by trawl fisheries.

Maldeco: Maldeco Fisheries Limited, a subsidiary of Press Incorporated. The only industrial fishing (qv) company presently operating in Malawi.

Mbaba: chichewa name for large demersal haplochromine cichlids (qv) caught by seines or pair trawls (qv).

Mechanised Fishery: a fishery operated by larger craft, using inboard engines (includes both industrial (qv) and semi-industrial (qv) fisheries). Generally referred to as ‘Commercial Fisheries’ in Malawi.

Midwater Trawl: a semipelagic trawl, in which heavy otter boards are set to drag the bottom, but the net is weighted to float clear of the substrate.

MSY: Maximum sustainable yield. The largest weight of fish which can be caught in a given time period (usually one year), without causing a reduction in catch rates in future years.

Ncheni: chichewa name for haplochromine (qv) cichlids of the genus Rhamphochromis (qv).

Ndunduma: chichewa name for haplochromine (qv) cichlids of the genus Diplotaxodon (qv).

Nkatcha Net: a seine net operated from two boats, which is hauled along the bottom and closed (‘pursed’) by a diver.

Pair Trawl: a demersal trawl, without otter boards, pulled by two craft.

Rhamphochromis: a genus of haplochromine cichlids (qv), endemic to Lake Malawi & associated water bodies. Surface-living fish-eaters. Some species are truly pelagic, others inshore-living. Ecological counterparts to Luciolates stappersi and Bathybates of Lake Tanganyika.

Ringnet: a purse seine operated by Maldeco Fisheries (qv). Presently operated by pairs of inboard-powered boats and manually-hauled. Mostly used with 102mm mesh and catching almost exclusively adult chambo (qv).

Schaefer Model: a surplus production model for the calculation of the maximum sustainable yield of a fishery. Based on a linear regression of cpue on effort. Appropriate for fish stocks which show dramatic declines at high fishing effort.

Semi-Industrial Fishery: a mechanised (qv) fishing operation characterised by little or no investment in onshore facilities.

Subsistence Fishery: small scale fishing operation, using inexpensive gears, and producing small catches, often mainly for home consumption (fish trap, handline, longline, cast net, scoop net).

Usipa: a small pelagic cyprinid, Engraulicypris sardella, endemic to Lake Malawi and associated water bodies. Ecological counterpart to Rastrineobola in Lake Victoria and Stolothrissa in Lake Tanganyika.

Utaka: chichewa name for small zooplankton-feeding haplochromine (qv) cichlids, mostly of the genus Copadichromis (qv). Mostly found inshore in shallow waters, a few metres above the bottom, and thus referred to as ‘semipelagic’.

LIST OF CHAMBO FISHERIES RESEARCH REPORTS

A. FIELD DOCUMENTS

1. STATISTICAL AND COMPUTING ASPECTS IN DEVELOPING STATISTICAL SYSTEMS IN MALAWI by C. Stamatopoulos. Field Document 1, July 1989.

2. PREPARATION OF A BASELINE SURVEY OF THE ARTISANAL FISHERIES ON LAKE MALAWI by B. Horemans. Field Document 2, February 1990.

3. STATISTICAL AND COMPUTING ASPECTS OF THE CHAMBO FISHERIES by R. Mahon. Field Document 3, June 1990.

4. A DATABASE FOR THE TRADITIONAL CHAMBO FISHERIES STATISTICAL SURVEY by R. Mahon., S. Alimoso, C. Stamatopoulos, and N.P. van Zalinge. Field Document 4, June 1990.

5. FRAME SURVEY OF THE SOUTH EAST ARM OF LAKE MALAWI, THE UPPER SHIRE RIVER AND LAKE MALOMBE by S.B. Alimoso, M.B.D. Seisay, N.P. van Zalinge, M. Mdaihli and S. Donda. Field Document 5, July 1990.

6. AN EFFICIENT METHOD FOR CATCH-EFFORT SAMPLING OF THE ARTISANAL CHAMBO FISHERIES OF THE SOUTH EAST ARM OF LAKE MALAWI, THE UPPER SHIRE RIVER AND LAKE MALOMBE by S.B. Alimoso, M.B.D. Seisay and N.P. van Zalinge. Field Document 6, March 1991.

7. MTF - MALAWI TRADITIONAL FISHERIES, COMPUTER USER MANUAL by C. Stamatopoulos. Field Document 7, March 1991.

8. ESTIMATION OF CONVERSION FACTORS FOR CONTAINERS USED IN TRADITIONAL FISHERIES FOR CHAMBO by M.B.D. Seisay and J. Phiri. Field Document 8, July 1991.

9. PRELIMINARY NOTE ON THE DECLINE OF THE CHAMBO CATCHES IN LAKE MALOMBE by N.P. van Zalinge, S.B. Alimoso, S.J. Donda, M. Mdaihli, M.B.D. Seisay and G.F. Turner. Field Document 9, March 1991.

10. FISH MARKETING IN THE MANGOCHI AREA OF MALAWI by D.S. Liao. Field Document 10, November 1990.

11. FISHERMAN-ENTREPRENEURS - A BASELINE SURVEY by M. Mdaihli and S. Donda. Field Document 11, July 1991.

12. THE ECONOMIC STATUS OF CREW MEMBERS by M. Mdaihli and S. Donda. Field Document 12, June 1991.

13. THE ROLE OF WOMEN IN CHAMBO FISHERIES by M. Mdaihli and S. Donda. Field Document 13, June 1991.

14. AN EVALUATION OF THE MALAWI CATCH ASSESSMENT SURVEY SYSTEM FOR TRADITIONAL FISHERIES by G.F. Turner, M.B.D. Seisay and N.P. van Zalinge. Field Document 14, March 1992.

15. VALIDITY CHECK IN CATCH EFFORT SAMPLING IN THE TRADITIONAL CHAMBO FISHERIES IN THE SOUTH-EAST ARM OF LAKE MALAWI, THE UPPER SHIRE RIVER AND LAKE MALOMBE by M.B.D. Seisay, H.J. Phiri and P.K. Mpezeni. Field Document 15, October 1991.

16. FISH MARKETING IN LAKE MALOMBE, THE UPPER SHIRE RIVER AND THE SOUTH-EAST ARM OF LAKE MALAWI by M. Mdaihli, M.M. Hara and M.C. Banda. Field Document 16, March 1992.

17. PROFITABILITY OF FISHING IN LAKE MALOMBE, THE UPPER SHIRE RIVER AND THE SOUTH-EAST ARM OF LAKE MALAWI by M. Mdaihli and S.J. Donda. Field Document 17, July 1992.

18. RELATIONSHIPS BETWEEN CHAMBO STOCKS OF LAKES MALOMBE AND MALAWI AND THE UPPER SHIRE RIVER by M.B.D. Seisay, G.F. Turner and N.P. van Zalinge. Field Document 18, July 1992.

19. POPULATION DYNAMICS AND STOCK ESTIMATES OF CHAMBO (OREOCHROMIS SPP.) IN THE SOUTH-EAST ARM AND LAKE MALOMBE - LENGTH BASED APPROACH by M.B.D. Seisay, N.P. van Zalinge and G.F. Turner. Field Document 19, July 1992.

20. AGE AND GROWTH PARAMETERS OF CHAMBO (OREOCHROMIS SPP.) IN THE SOUTH-EAST ARM OF LAKE MALAWI, AS DETERMINED FROM OPERCULAR BONES by M.C. Banda. Field Document 20, July 1992.

21. DISTRIBUTION AND BIOLOGY OF CHAMBO (OREOCHROMIS SPP.) IN LAKES MALAWI AND MALOMBE by G.F. Turner and N.C. Mwanyama. Field Document 21, July 1992.

22. A BIO-ECONOMIC ANALYSIS FOR SOME OF THE INDUSTRIAL AND SEMI-INDUSTRIAL FISHERIES OF SOUTHERN LAKE MALAWI by G.F. Turner and M. Mdaihli. Field Document 22, July 1992.

23. MECHANIZED FISHERIES OF LAKE MALAWI by G.F. Turner. Field Document 23, July 1992.

24. PREDICTIVE MODEL FOR THE LAKE MALOMBE FISHERIES by N.P. van Zalinge, M. Mdaihli, G.F. Turner, and M.B.D. Seisay. Field Document 24, July 1992.

25. REPORT ON FISHERIES LEGISLATION IN MALAWI by A. van Houtte. Field Document 25, July 1992.

26. THE MANAGEMENT PLAN FOR THE COMMERCIAL FISHERIES OF LAKE MALOMBE, THE UPPER SHIRE RIVER AND THE SOUTH-EAST ARM OF LAKE MALAWI by the Ad-Hoc committee established at the Chambo Fisheries Research Project's workshop on 11 July 1992. Field Document 26, October 1992.

B. TECHNICAL PAPERS

1. FISHERIES MANAGEMENT IN THE SOUTH-EAST ARM OF LAKE MALAWI, THE UPPER SHIRE RIVER AND LAKE MALOMBE, WITH PARTICULAR REFERENCE TO THE FISHERIES ON CHAMBO (OREOCHROMIS SPP.). REPORT ON THE WORKSHOP HELD AT MANGOCHI, 8–11 JULY 1992. Technical Paper 1, August 1992.

C. OTHER REPORTS

1. IDENTIFICATION OF OREOCHROMIS SPECIES FROM LAKE MALAWI USING MITOCHONDRIAL DNA by D.M. Reid, R.N. Zaba and T.J. Pitcher, FAO, Rome 1990.