The role of the in conserving fish species diversity in the upper Shire River, Fanuel Kapute Department of Fisheries Science, Faculty of Environmental Sciences, Mzuzu University, P/Bag 201, Luwinga, Mzuzu 2, Malawi Corresponding author: [email protected]

Tremendous decline of fish catches in , mainly due to uncontrolled fishing, is a clear evidence of challenges of managing a common/open resource. East of the Shire River lies the protected area known as Liwonde National Park about 538 km2. Species diversity around the National Park including the southeast arm of Lake Malawi, Lake Malombe, and the upper Shire River were studied to determine if the moratorium in the park has any impact to the fishery in these areas. Fish samples were collected using a variety of fishing gears including mosquito nets, gill nets, scoop nets, cast nets, and hand lines from southeast arm of Lake Malawi, Upper Shire River, Lake Malombe, and the area near the Liwonde Barrage. Over 40 species belonging to 27 genera and 6 families were sampled compared to 50 species recorded in earlier studies suggesting that, despite the general decline in the fish species diversity, this area still maintains its resilience. The family Cichlidae was the most diverse with 19 genera followed by the Cyprinidae with 4 genera. These results showed that Cichlidae and Cyprinidae fish species that have nearly disappeared in Lake Malawi are still found in considerable abundance in the Shire River especially in areas around the National Park. Most of the determined fish species originated from surrounding areas to the park suggesting that it is a breeding area for fishes that are caught upstream and downstream. Findings underpin the importance of managing and protecting the National Park or even establishing other moratoriums for the same.

Keywords: Lake Malawi, Lake Malombe, moratorium

Introduction proved unsuccessful. The southern and shallow part of the lake where most fishes breed is the Lake Malawi—the lake with the highest fish most affected, signaling fears that the fishery species biodiversity in the world—has only one may eventually collapse. However, fishes tend outlet river, the Shire River. Fish catches in the to migrate between the Shire River and the lake have tremendously declined for many rea- southeast arm of Lake Malawi (Seisay et al., sons, including unabated fishing and use of ille- 1992), an indication of the importance of the gal fishing gears. Several attempts to save the river to the recovery of the fishery in Lake fishery, such as through co-management, have Malawi. Earlier reports (Seisay et al., 1992;

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Aquatic Ecosystem Health & Management, 21(2):132–138, 2018. CopyrightÓ 2018 AEHMS. ISSN: 1463-4988 print / 1539-4077 online DOI: 10.1080/14634988.2018.1457389

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FAO, 2003a,b) suggested that fishes migrate its source in Lake Malawi, the most upper stretch from the Shire River into Lake Malombe (an (Lake Malawi source to Lake Malombe) and from ox-bow lake) then into Lake Malawi. The Shire Lake Malombe to Liwonde Barrage (Figure 1). River is, therefore, an important site for obli- gate, river-breeding fishes from Lake Malawi, hence, most fish fauna in the middle and upper Materials and methods Shire are also found in lakes Malawi and Malombe (State of the Environment Report, A survey was carried out to determine fish species 1998) (Figure 1). Another important feature composition in selected areas from lakes Malawi and within the upper stretch of the Shire River Malombe, and the upper Shire River including the between the southern end of Lake Malombe barrage up to the dam at Nkula Falls. Based on the and Liwonde Barrage is the Liwonde National biophysical environment of the Shire River, there is Park. Situated in the eastern bank of the upper no migration of fish from the Lower Shire River Shire River (Figure 1), Liwonde National Park beyond the falls and rapids, which start at Nkula. As (538 km2) is home to many riverine fish species such, the upper and middle Shire River, including (Bhima and Dudley, 1997). Some of the most Lake Malombe, appear to be an area of major important species include cyprinids such as changes in species composition influenced by the MpasaorLakeSalmon(Opsaridium microlepis) Liwonde National park protected area. and the Shire River Tilapia – (Oreochromis Fish samples were collected from Area A of the shiranus) (www.2011africaguide.com). southeast arm of Lake Malawi, the upper Shire While there is heavy uncontrolled fishing in River (between the source and Lake Malombe), lakes Malawi and Malombe (Banda et al., 2005), Lake Malombe, and the Shire River in the the stretch of the Shire River from Lake Malombe Liwonde National Park, Liwonde Barrage and to the southern boundary of Liwonde National Nkula Falls where the terrain of the river drops Park, is a protected area (FAO, 1993; State of the into rapids before flowing into the Lower Shire Environment Report, 1998). This study was aimed (Figure 1). Fish catches were collected from fish- at assessing the impact of the park (protected area) ermen using a variety of fishing gears including on the species composition in the Shire River from beach seines, gill nets, scoop nets, hand lines, cast

Figure 1. Lakes Malawi and Malombe (a) and Liwonde National Park (b).

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nets and mosquito nets. The area of the Shire River Table 1. Fish species and location collected during the study. in Malawi starts from the southeast arm of Lake Malawi (the source) into Lake Malombe passing Species Location through the Liwonde Barrage down to Nkula Falls Astatotilapia Nkula Falls (Figure 1). The eastern section between Lake Aulonocara Southeast arm Malombe and Liwonde Barrage is the Liwonde Buccochromis Southeast arm National Park, which is a protected area. Chilotilapia Southeast arm Fishes were sorted and identified to species level. Copadichromis Southeast arm, Lake Malombe Standard length (mm) and whole weight (g) was Corematodus Southeast arm, Barrage recorded using a measuring board and a battery oper- Ctenopharynx Southeast arm, Lake Malombe ated electronic weighing scale, respectively. Length- Dimidiochromis Southeast arm, Barrage frequencies and catch data were determined from a Hemitaeniochromis Southeast arm, Barrage sub-sample of the total catch. The type of fishing Lethrinops Southeast arm, Lake Malombe gear and area where fishes were caught were also Mylochromis Southeast arm recorded. Since fish samples were purchased from a Oreochromis Southeast arm, Barrage, Lake single point (place of selling), fishers were asked to Malombe indicate the location of their catch with the aim of Otopharynx Barrage, Southeast arm, Lake tracing the exact origin of the fishes. Malombe The data were analysed for species composition Placidochromis Barrage, Southeast arm (diversity), gear selectivity, size distribution by Protomelas Barrage, Southeast arm species, weight by species and standard length by Pseudotropheus Southeast arm, Lake Malombe gear by plotting length-frequency histograms. Stigmatochromis Barrage, Southeast arm Size-specific selectivity of mosquito nets and Tilapia Barrage, Southeast arm Kambuzi beach seine fishing gears was modeled Trematocranus Barrage, Southeast arm using the logistic model (Butterworth et al., 1989; Bagrus Barrage, Lake Malombe Booth and Punt, 1998) described as: Clarias Barrage, Lake Malombe − Barbus Barrage −ðÞL−L 1 P D 1 C exp 50=δ Engraulicypris Southeast arm Labeo Barrage Opsaridium Barrage where P is the selectivity of the gear on a fish of Synodontis Southeast arm size L, L50 is the size-at-50%-selectivity or the Mormyrus Barrage mean length at which 50% of fishes are retained in the net (mean length at first capture), and d is a parameter related to the size range over which the Results and discussion selectivity changes from values near 0 to values near 1. As d tends to zero, this function approaches At the time of the field survey, the water level in knife-edged selection (Butterworth et al., 1989). Lake Malawi at the southeast arm had receded tre- The size-specific selectivity of scoop-net and mendously as evidenced by wide sandy beaches, hand-line fishing gears was modeled using the which are usually inundated during periods of more gamma distribution function to compensate for the water in the lake. During peak water levels, the vast skewed distribution of catch data from the two sandy beach stretches along the lake are submerged fishing gears. The gamma probability density under water creating breeding areas for Cichlids. function (Malcolm, 2001) is described as: Unfortunately, in the southeast arm of Lake Malawi (), most of these fish-breeding sand beaches have been cleared for holiday resorts, 1 α− −N fxðÞ; α; β D x 1e β βaΓαðÞ which have flourished in recent years. This suggests that, inrespective of whether it is peak or low water level in the lake, fish breeding is still compromised where x is the value at which the distribution is by swimmers, boat landings, and beach seine net- a evaluated, is a parameter to the distribution and ting. The area at the mouth at Lake Malawi is b is a parameter to the distribution. marshy and relatively shallow due to a sand bar.

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Figure 2. Distribution of fish families (left) and genera (right) by weight (%) sampled during the survey.

Common fishing gears in this area are gill nets as (10%) while the least important were the families the muddy and marshy beaches do not favour use of Bagridae and Mochokidae with 4% and 1%, respec- beachseines.Fishinginthisareaisveryactiveespe- tively (Figure 2). The family Cichlidae was the cially Chambo (Tilapia) fish caught with gill nets. most diverse with 19 genera followed by the family The observation during the survey was that the Cyprinidae with 4 genera. These results show that shoreline of the section of the Shire River from most of the catch in the Shire River system as is the Lake Malombe down to Nkula Falls does not have case with Lake Malawi is dominated by Cichlids. an active agricultural industry so that much of the At genus level, the most important in terms of shoreline has not been disturbed. This suggests that biomass were Clarias (17%), Oreochromis (15%), this is an area for fish spawning such as mpasa, san- Mormyrus (10%), Protomelas (9.8%), Otopharynx jika, ntchira and several matemba species. (9%), and Astatotilapia (6%) (Figure 2). Although During this study, it was apparent that the a riverine ecosystem where Cyprinids normally National Park is by far the most important environ- make a good composition of the catch, only a few mental hot spot that requires serious consideration specimens of Mpasa, Matemba and Thamba were in view of the upgrading of the Barrage at Liwonde. identified at the Barrage from fishers who disclosed The Park is home to many fish species by acting as to have illegally caught them from the protected a breeding area. Elsewhere, fishes hardly have a Liwonde National Park. Except for samples from chance to breed because of the uncontrolled heavy the Barrage, no specimen of mpasa was recorded fishing pressure. Over 40 species belonging to 27 from the Shire River explaining the ever increasing genera and 6 families (Table 1) were sampled in scarcity of this commercial IUCN Red List species Lake Malombe, upper and middle Shire River. The (IUCN, 2006). However, it is likely that some fish six families included Cichlidae, Clariidae, Cyprini- species were under-sampled or entirely missed dae, Mochokidae and Mormyridae. The most because of limitations in the efficiency and selectiv- important, based on biomass, were the families ity inherent in fishing gears from which fishes were Cichlidae (61%), Clariidae (17%) and Mormyridae sampled. For example, fishes such as Astatotilapia

6 1.0 5 0.9 0.8 4 0.6 3 0.5 2 0.4 Frequency 1 0.3

Proportion retained 0.1 0 0.0 30 38 45 53 60 68 75 83 90 98 105113120 050100150 Standard Length (mm) Standard Length (mm)

Figure 3. Size distribution and logistic selection curve of Cichlids caught in beach seines.

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6 1.0 5 0.9 0.8 4 0.6 3 0.5 2 0.4 Frequency 1 0.3

Proportion retained 0.1 0 0.0 30 38 45 53 60 68 75 83 90 98 105113120 050100150 Standard Length (mm) Standard Length (mm)

Figure 4. Size distribution and logistic selection curve of Cichlids caught in mosquito nets.

were caught using hand lines, which are highly Lake Malombe. In the upper Shire, the catches from selective. A small difference in the size-distribution hand-line gear were dominated by larger Cichlids ranges and estimated size at capture for the Cichlids such as Copadichromis, Placidochromis and Dimi- caught in both beach seines and mosquito nets was diochromis species, demonstrating the effect of gear observed (Figures 3 and 4). This may support the selectivity in use of hand lines. Also, the small fact that fishers still use very small-meshed beach Cichlid (Kambuzi) fishery is not well pronounced in seines to increase catch effort. A majority of the fish the upper Shire River and the southeast arm of Lake species caught using beach seine were the small Malawi as it is the case in Lake Malombe. At the Cichlids collectively known as Kambuzi (Figure 5) Barrage in Liwonde, scoop nets (Figure 6) are such as Placidochromis, Protomelas, Pseudotro- extensively and intensively employed to catch dif- pheus,andOtopharnx species. These species domi- ferent species. Although partially selective, scoop nate the catches in the southeast Lake Malawi and nets usually catch bigger fish that can maintain

Figure 5. Small Cichlids (Kambuzi) from the southeast arm of Lake Malawi and larger Cichlids from Lake Malombe.

Figure 6. Beach seining on Lake Malawi and using scoop nets in the fast-moving waters at the Barrage.

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5.0 2.5 Astatotilapia calliptera Copadichromis species 3.5 Engraulicypris sardella 4.0 2.0 3.0 2.5 3.0 1.5 2.0 2.0 1.0 1.5 Frequency

Frequency 1.0 1.0 0.5 Frequency 0.5 0.0 0.0 0.0 50 55 60 65 90 70 75 80 85 95 63 67 55 59 71 75 79 83 87 91 95 99 50 53 57 60 64 67 70 74 77 81 84 87 100 105 110 115 103 Standard (mm) Standard Length (mm) Standard Length (mm)

2.5 5.0 Protomelas species Hemitaeniochromis oxyrhynchus 2.5 Placidochromis subocularis 4.0 2.0 2.0

3.0 1.5 1.5

2.0 1.0 1.0 Frequency Frequency 1.0 Frequency 0.5 0.5 0.0 0.0 0.0 50 63 76 89 102 116 129 142 155 168 181 95 97 99 101 103 106 108 110 112 114 116 40 50 60 70 80 90 100 110 120 130 140 Standard Length (mm) Standard Length (mm) Standard Length (mm)

6 Opsaridium microcephalus 2.5 Ctenophyrynx intermedius 8 Otopharynx argyrosoma 5 2.0 4 6 1.5 3 4 2 1.0 Frequency Frequency 1 0.5 Frequency 2 0 0.0 0 70 81 91 102112123133144154165175186 51 62 90 57 96 40 74 79 85 46 68 30 40 50 60 70 80 90 100 110 120 130 Standard Length (mm) 102 107 StandardLength (mm) Standard Length (mm)

Figure 7. Length-frequency histograms of the commonly caught fish species.

position in the strong water current when the Bar- lake, suggesting more migration of fishes from rage doors have been opened. Hand liners’ catch at the Liwonde National Park that borders the the Nkula Falls ESCOM Hydro Electricity Power southern part of Lake Malombe (Seisay et al., generation intake dam generally comprised of Asta- 1992; FAO, 2003a,b). totilapia calliptera (www.cichlid-forum.com). Length-frequency histograms (Figure 7) Beach seines are commonly used on the clear showed that nearly most of the Cichlids caught sandy beaches of Lake Malawi and not in Lake in the Shire River system are small sized proba- Malombe and the Shire River due to the thick bly for two reasons. Firstly, due to overfishing vegetation along the banks which limits the oper- where small-meshed gears, such as mosquito ation of the gear (Figure 7). Gill nets and other nets, dominate resulting into removal of larger smaller traditional gears, such as hand line, scoop sizes. The Kambuzi fishery is characterized by nets, fish traps are used extensively in the Shire use of destructive small-meshed gears, such as River. The fact that the Shire River’s beaches are mosquito net patched purse seines, to increase covered with more vegetation and yet there are the fishing effort. After the collapse of the more Cichlids than riverine species that favor Chambo (Tilapia) fishery in Lake Malombe and such aquatic environment, partly explains the the southeast arm of Lake Malawi due to heavy concept of fish migration from the southeast arm fishing pressure (FAO, 1993), the catch is of Lake Malawi to Lake Malombe (Seisay et al., mainly composed of the small Cichlids (Kam- 1992) (which is part of the Shire River system) buzi) by which the fishery in Lake Malombe is through the upper Shire River. Catches from the identified (Weyl et al., 2004a,b). Secondly, southern part of the overexploited Lake Malombe small fish sizes may be due to the inherently appear better than the rest of the areas of the small size of the fish species that were sampled.

Downloaded from http://read.dukeupress.edu/aehm/article-pdf/21/2/132/847309/132kapute.pdf by guest on 28 September 2021 138 Kapute/Aquatic Ecosystem Health and Management 21 (2018) 132–138 Conclusions References Most of the fishes caught from areas of the Banda, M., Jamu, D, Njaya, F, Makuwila, M. and Maluwa, A. (Eds.), 2005. Proceedings. The Chambo Restoration Strategic Shire River around the Liwonde National Park Plan. WorldFish Center Conference. Penang, Malaysia. appear to migrate from the park, which acts as a Bhima, R. and Dudley, C.O., 1997. The influence of the Shire breeding area. Further, most fishes found in the River on Liwonde National Park, Malawi, with special ref- Shire River, especially upstream from the Barrage, erence to elephant movements. African Protected Area breed in the Liwonde National Park, which is a Conservation and Science 40(2), 9–18. protected area. As long as migration of fish Booth, A.J. and Punt, A.E., 1998. Evidence for rebuilding in the between lakes Malawi and Malombe through the panga stock on the Agulhas Bank, South Africa, Fisheries 15 km upper Shire stretch continues, threats to Research 34, 103–121. Butterworth, D.S., Punt, A.E., Borchers, D.L., Pugh, J.G. and breeding fishes upstream should be minimal. Hughes, G.S., 1989. A manual of Mathematical techniques for line fish assessment. South African National Scientific Programmes Report 160. Recommendations FAO, 1993. Fisheries Management in the South-east arm of Lake Malawi, the Upper Shire River and Lake Malombe, The Liwonde National Park is an important with particular reference to the fisheries on chambo breeding area for fishes that migrate and are caught (Oreochromis spp.). GOM/FAO/UNDP Chambo Fisheries by fishers in the southern part of Lake Malombe Research Project. CIFA Technical Paper. No. 21. Rome, around Mvera area and the stretch of the Shire River FAO. 1993. down to the Barrage at Liwonde. Protecting the fish- FAO, 2003a. FAO Fishery Country Profile: The Republic of Malawi. FID/CP/MLW ery in the park and possibly extending the morato- FAO, 2003b. Management, co-management or no man- rium upstream could have far reaching advantages to agement? Major dilemmas in southern African freshwater the fisheries especially in the middle Shire River and fisheries. 2. Case studies. In: E. Jul-Larsen, J. Kolding, R. southern part of Lake Malombe. Another recommen- Overa, J. Raakjær Nielsen, P.A.M. van Zwieten (Eds.), dation is for further research to look at the early life FAO Fisheries Technical Paper. No. 426/2. Rome, FAO. stages and habitats of the adult fishes under study. IUCN, 2006. 2006 IUCN Red List of Threatened Species. www.iucnredlist.org Malcolm, H., 2001. Modelling and Quantitative Methods in Fisheries. Chapman and Hall, Boca Raton. Acknowledgements Seisay, M.B.D., Turner, G.F., van Zalinge, N.P., 1992. Rela- tionships between the Chambo stocks of Lakes Malombe I thank Mr. G. Z. Kanyerere from the Fisheries and Malawi and the Upper Shire River. GOM/UNDP/FAO Research Unit at Monkey Bay, Malawi for helping Chambo Fisheries Research Project, Malawi. FI: DP/MLW/ with data analysis and providing technical staff 86/013, Field Document 18. who assisted in identifying fish species. State of the Environment Report, 1998. Chapter 5: Fisheries. Department of Environmental Affairs, Lilongwe, Malawi. Weyl, O.L.F., Kazembe, J., Booth, A.J. and Mandere, D.S., Funding 2004a. An assessment of the light attraction fishery in southern Lake Malawi. African Journal of Aquatic Science The study was part of a larger consultancy 29, 1–11. assignment by SMEC International (Australia Weyl, O.L.F., Mwakiyongo, K.R. and Mandere, D.S., 2004b. An assessment of the Nkacha net fishery of Lake Ltd.) hired to conduct an Environmental and Malombe, Malawi. African Journal of Aquatic Science Social Impact Assessment (ESIA) due to the con- 29, 47–55. struction of a new Barrage across the Shire River www.2011africaguide.com Accessed on 20th November, 2011. at Liwonde, Malawi. www.cichlid-forum.com Accessed on 20th November, 2011.

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