sustainability Article Fish Communities, Habitat Use, and Human Pressures in the Upper Volta Basin, Burkina Faso, West Africa Paul Meulenbroek 1,* , Sebastian Stranzl 2, Adama Oueda 3, Jan Sendzimir 1,4,5, Komandan Mano 3, Idrissa Kabore 3, Raymond Ouedraogo 6 and Andreas Melcher 5,* 1 WAU Department of Water, Atmosphere and Environment, IHG Institute of Hydrobiology and Aquatic Ecosystem Management, BOKU—University of Natural Resources and Life Sciences, Gregor Mendel Strasse 33, 1180 Vienna, Austria; [email protected] 2 Laboratory for Freshwater Ecology and Inland Fisheries, NORCE Norwegian Research Center, Nygårdsgaten 112, 5008 Bergen, Norway; [email protected] 3 Laboratoire de Biologie et Ecologie Animales, UFR/SVT, Université Joseph Ki-Zerbo, 03 BP 7021 Ouagadougou 03, Burkina Faso; [email protected] (A.O.); [email protected] (K.M.); [email protected] (I.K.) 4 IIASA—International Institute of Applied System Analyses, Schlossplatz 1, 2361 Laxenburg, Austria 5 CDR Centre for Development Research, BOKU—University of Natural Resources and Life Sciences, Dänenstrasse 4, 1190 Vienna, Austria 6 Département Environnement et Forêts, Institut de l’Environnement et de Recherches Agricoles, Ouagadougou, Burkina Faso, 04 BP 8645 Ouagadougou 04, Burkina Faso; [email protected] * Correspondence: [email protected] (P.M.); [email protected] (A.M.) Received: 26 August 2019; Accepted: 26 September 2019; Published: 1 October 2019 Abstract: Human pressures and loss of natural fish habitats led to a decline in fish populations in terms of abundances, biodiversity, and average size in sub-Sahelian Burkina Faso. Little knowledge exists about fish assemblages regarding their composition, their habitat preferences, or their sensitivity to or tolerance of human pressures. This research provides the first data-driven basis for sustainably managing fish and associated aquatic and terrestrial habitats. Surveys in four different regions sampled 18,000 specimens from 69 species during the dry season. Fish communities, available abiotic habitat conditions, habitat use, and human pressures were assessed and analyzed. Fish communities cluster into four distinct types, each dominated by either Cichlidae, Clariidae, Cyprinidae, or Alestidae and accompanied by specific other families and genera of fish. Habitat preferences of four key species (Labeo coubie, Bagrus bajad, Chelaethiops bibie, and Lates niloticus) were linked to ecological habitat conditions. Results show that physical parameters influence fish community composition and abundances and, when indexed according to pressure type, are linked to responses in fish metrics. Relative abundance either dropped (Mormyridae) or increased (Cichlidae, Cyprinidae) with rising pressure intensity, and some sentinel taxa (Auchenoglanis, Hydrocynus) were only found in low-pressure sites. The outcomes of this study provide basic knowledge of habitat availability, habitat use by fish, species associations, and human pressures and therefore provide the basis for effective conservation and management of fish populations. Keywords: habitat preferences; temperature; human pressures; fish assemblages; freshwater; reservoir; river 1. Introduction The Upper Volta basin is located in Burkina Faso, a sub-Saharan landlocked country in the central part of West Africa. It is one of the poorest and the least developed countries in the world, and rising population density is driving an increasing demand for fish protein and is jeopardizing it as an Sustainability 2019, 11, 5444; doi:10.3390/su11195444 www.mdpi.com/journal/sustainability Sustainability 2019, 11, 5444 2 of 21 important source for food security. The country has a tropical climate with two seasons. In the rainy season, from May/June to September, the country receives between 600 and 1000 mm of rainfall per year, decreasing with latitude. In the dry season, high temperatures (up to 45 ◦C) result in massive losses of water due to high evapotranspiration rates (2000 mm/year) [1–3]. This leads to temporal changes in freshwater habitat availability in terms of quantity and quality [4]. The natural habitat conditions are altered by human activities. Frequent pressures on African water bodies include (1) water shortage and water abstraction, (2) pollution (suspended solids, solid wastes, organic and agricultural chemicals), (3) damming, (4) deforestation, and (5) overfishing [5–7]. Similar pressures are also reported in Burkina’s water bodies, e.g., over abstraction, reservoir degradation, and pollution with agricultural chemicals [8]. The Volta Basin has lost almost 97% of its original forest cover [7,9], which is a good indicator for watershed degeneration [10]. As a reaction to severe droughts in Burkina Faso, more than 1400 reservoirs of 1 to 25,000 ha surface area were built since 1950. These are mainly used for agriculture, livestock farming, and fisheries [3]. About 85% of all built reservoirs are smaller than one million cubic meters (Mm3), whereas the two largest ones contribute to more than 60% of the national capacity [11]. The construction of reservoirs increased fishery landings by 15 times since 1950, employing more than 30,000 fishermen and several thousand women for processing and selling the fish [3]. According to Boelee [12] and Mahe et al. [13], more than 50% of the annual discharge of the Nakanbé basin is held in these reservoirs by dams. Many reservoirs are not passable for fish due to lacking or poorly built fish passages [3]. Moreover, large reservoirs have severe downstream effects such as altered flow and sediment regime, a change of water parameters (temperature, oxygen, suspended solids, etc.), erosion, missing flood pulses, decreased fish recruitment, and disturbed river biota [14–16]. The specific composition of communities is mainly influenced by the interaction between animals and their biotic and abiotic environments [17]. Fish habitat encompasses a variety of physical, biological, and chemical features of the environment that affect assemblages, populations, and individuals [18]. The understanding of these interrelations also is crucial with regard to future changes caused by climate change [19–21]. The loss of habitat and human pressures led to a decline in fish populations in terms of total population, biodiversity, and average fish size [3,22]. Native fish species are well adapted to their environment to an extent that some species use the entire river continuum from the headwaters to the estuaries within their life cycle [15]. Because fish cannot easily migrate between aquatic systems, they have to adapt to changing conditions or die. Therefore, they are potential indicators of environmental changes and trends in general aquatic biodiversity, since they interact with other aquatic organisms via predation, nutrient input, and mechanical effects [4]. The knowledge of essential fish habitat for spawning, breeding, feeding, or growth to maturity is an important management tool for a healthy ecosystem and sustainable fisheries [23,24]. Thus far, for Burkinabe and Sub-Sahelian fish species, little knowledge exists about fish assemblages regarding their composition, their habitat preferences, or their sensitivity to or tolerance of human pressures [3,25]. Hugueny et al. [26] noted, already 20 years ago, that fish must become a well-established indicator to support better management that secures an important source of food (protein), especially for Burkina Faso and other less developed countries. This study highlights important findings and generalizations regarding the roles of abiotic factors and human pressures that influence fish community composition and abundances for sub-Sahelian countries. The specific objectives are: (1) to describe fish assemblages, map available habitat parameters, and link them to habitat use by four key species, and (2) to identify typical human impacts on aquatic habitats and associated fish assemblages by proving the response of fish to human induced pressure impacts, eventually leading to modern fisheries management. Sustainability 2019, 11, 5444 3 of 21 2. Materials and Methods Sustainability 2019, 11, x FOR PEER REVIEW 3 of 21 2.1. Study Area ThreeThree large large river river basin basinss (6 (63%3% Volta, Volta, Niger Niger 28 28%,%, Comoé Comoé 99%)%) drain drain the the country. country. The The largest largest and and thethe most most important important is is the the Volta Volta Basin, Basin, covering covering over over 120,000 120,000 km². km2 .Three Three major major rivers, rivers, the the Mouhoun, Mouhoun, thethe Nakanbé Nakanbé, ,and and the the Nazinon Nazinon (respectively (respectively Black Black-,-, White White-,-, and and Red Red Volta) Volta) eventually eventually al alll flow flow into into LakeLake Volta Volta in in Ghana Ghana [27,28] [27,28].. The The study study area area is is located located in in the the Upper Upper Volta Volta (Nakanbé) (Nakanbé) catchment catchment in in BurkinaBurkina Faso Faso between between the the reservoir reservoir of of Korsimoro, Korsimoro, north north of of Ouagadougou, Ouagadougou, and and the the border border with with Ghana Ghana inin the the south south (Figure (Figure 1). The The fish fish sampling sampling took took pl placeace between October and December 2012 in the early drydry season. season. Sampling Sampling areas areas were were selected selected visually visually by by means means of of Geographic Geographic Information Information System System ( (GIS)GIS) andand the the expert expert judgment judgment of of the the local local fishermen, fishermen,