The Role of the Liwonde National Park in Conserving Fish Species Diversity

The role of the Liwonde National Park in conserving fish species diversity in the upper Shire River, Malawi 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 Lake Malawi, 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; Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/uast. 132 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 Downloaded from http://read.dukeupress.edu/aehm/article-pdf/21/2/132/847309/132kapute.pdf by guest on 28 September 2021 Kapute/Aquatic Ecosystem Health and Management 21 (2018) 132–138 133 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). Downloaded from http://read.dukeupress.edu/aehm/article-pdf/21/2/132/847309/132kapute.pdf by guest on 28 September 2021 134 Kapute/Aquatic Ecosystem Health and Management 21 (2018) 132–138 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 (Mangochi), 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. Downloaded from http://read.dukeupress.edu/aehm/article-pdf/21/2/132/847309/132kapute.pdf by guest on 28 September 2021 Kapute/Aquatic Ecosystem Health and Management 21 (2018) 132–138 135 Figure 2.

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