J. Bio. & Env. Sci. 2020 Journal of Biodiversity and Environmental Sciences (JBES) ISSN: 2220-6663 (Print) 2222-3045 (Online) Vol. 16, No. 4, p. 121-132, 2020 http://www.innspub.net RESEARCH PAPER OPEN ACCESS Inventorying the ichthyologic fauna of Ahémé Lake and its Channels (South-West Benin, West Africa) Christian Comlan Viaho*1,3, Djiman Lédéroun1, Thierry Matinkpon Agblonon Houelome1, Delphine Adandedjan1, Ahouansou Montcho2, Hippolyte Agadjihouèdé2, Martin Gbedey3, Philippe Lalèyè1 1Laboratory of Hydrobiology and Aquaculture, Faculty of Agricultural Sciences, University of Abomey-Calavi, Cotonou, Benin 2Laboratory Research in Aquaculture, Biology and Aquatic Ecology; School of Aquaculture, National University of Agriculture (UNA), Kétou, Benin 3Integrated Development for Economic Zone of Ahémé Lake and its Channels Agency (ADELAC), Sègbohouè, Kpomassè, Sègbohouè, Bénin Article published on April 30, 2020 Key words: Inventorying, Fish fauna, Experimental fishing, Lake, Channels Abstract The present study aims at contributing to a better understanding of Lake Ahémé and its surroundings together with its channels through an update of its fish fauna. The study covers twelve months, from May 2016 to April 2017. Fish specimens which were examined were collected from catches by fishermen as well as from monthly experimental fishing at 19 stations. A total of 73 fish species belonging to 59 genera and 38 families were identified. The Gobiidae family is the most represented with 6 species; the Carangidae and Cichlidae families are next, with 5 species each; then comes the Clupeidae with 4 species; and the Eleotridae, Clariidae, and Lutjanidae families with 3 species each. Strictly estuarine species (E) dominate the population and account for 87.7% of the total species richness *Corresponding Author: Christian Comlan Viaho [email protected] 121 | Viaho et al. J. Bio. & Env. Sci. 2020 program aims at rehabilitating Ahémé Lake and its channels through dredging. Integrated Development Introduction for Economic Zone of Ahémé Lake and its Channels Estuaries and lagoons are ecosystems of great Agency (ADELAC), is a Government office which ecological importance. They play an interface role charge to execute this Program. between continental and marine environments. However, functional complexity varies widely from But dredging can potentially lead to disturbances in the one environment to another (Charbonnel et al., 1995). aquatic ecosystem. On the other hand, no scientific They are diverse, productive habitats that are rich in work has been carried out to date on the fish species of nutrients. These nutrients support the establishment those water bodies. So, the purpose of the present and growth of many animal populations, such as study is to develop an inventory of those fish species marine fish species, crustaceans, and other species before the upcoming dredging and provide the lacking such as planktonic communities and macro scientific information regarding the fish species of the invertebrates (Cardona, 2000; Adandédjan, 2012). study area. Specifically, this study will collect, identify, These environments play a vital role in the life cycle of and conserve specimens from all fish species obtained many biological species. They are home to important in the study area. This will serve as reference data for animal and plant biological diversity (Ahouansou, all aquatic ecosystems involved in this dredging. 2011). On the other hand, fish fauna is an important source of protein and income for the populations Material and methods (Jouffre, et al., 2005). Study area Benin has an important hydrographic network Lake Ahémé and its channels, located in southwestern comprising four systems in which Lake Ahémé and its Benin, constitute an ecosystem that plays an channels are included: maritime, lagoon, lacustrine important role in the economy of the region. The local and fluvial. Lake Ahémé is a major water body located population exerts all kinds of pressure to secure most in southwestern Benin. It is part of a fluvial-lacustrine of their food for survival. But this previously identified and lagoon complex with a significant biodiversity human pressure on aquatic ecosystems is neglected and fragile and valuable ecosystem. It covers an (Gourene et al., 1999; Villanueva, 2004). In fact, in the average area of 85km2 and is located between area covered by Lake Ahémé and its channels, socio- latitudes 6°20’ and 6°40’ N and longitudes 1°55’ and economic development requirements have led to 2°00’ E (Viaho, 2014). Trapped between the activities with recursive threats to aquatic ecosystems Kpomassè and Comé plateaus, it is fed by waters from (Oyédé, 1983; Paugy et al., 2003; ADELAC, 2018). The the Couffo and Mono rivers and flows into the ocean construction of hydroelectric dams in Nangbeto, the through the Ahô channel, the coastal lagoons of discharge of industrial and domestic waste, the Grand-Popo., and the mouth of the "Bouche du Roy". leaching of cultivated land and the overexploitation of The study area covers municipalities bordering Lake resources, further weaken these already confined Ahémé and its channels, namely: Bopa, Comé, Grand- environments characterized by overpollution and low Popo, Houéyogbé, Kpomassè, and Ouidah (Fig. 1). renewal of the water (Adandédjan, 2012). According to ADELAC (2018), the study area benefits In order to tackle this situation, the national from a subequatorial Beninian climate characterized government of Benin has decided to rehabilitate by the two rainy seasons and two dry seasons Ahémé Lake and its channels. Thus, the distributed as follows: intercommunal program for the rehabilitation of ➢ Major rainy season: mid-March to mid-July; Ahémé Lake and its channels was conceived. This ➢ Small rainy season: mid-September to November; 122 | Viaho et al. J. Bio. & Env. Sci. 2020 ➢ Long dry season: December to mid-March; ➢ Short dry season: mid-July to mid-August. Fig. 1. Geographical location of Ahémé Lake and its channels. Rainfall amounts are higher on the one hand in May, meadow, sacred forest, etc.) and anthropogenic June and July when they exceed 120mm with a peak in (mosaic culture, coconut plantation, private plantation, June (196.9mm in the Comè municipality in 2017) and communal planting) vegetation. In there can be found 296.5mm in the Ouidah municipality in 2017) and are Acacia auriculiformis, Tectona grandis, Eucalyptus higher elsewhere in September and October. In camaldulensis, Terminalia sp. Adansonia digitata, December, January and February (dry months), Ceiba pentandra, Milicia excelsa, Triplochyton recorded rainfall amounts are less than 40mm. The scleroxylon, Antiaris toxicaria, etc. It is worthy to note first rainy season concentrates 40 to 60% of the rainfall the presence of wetlands along the water bodies where compared to 18 to 30% for the second. The average aquatic vegetation consists of Raphia gigantea, number of rainy days is higher in June during the Rhizophora racemosa, Avicennia africana and major rainy season and is higher in October for the Acrostichum aureum. In addition to marshy meadows small rainy season. Temperatures in the study and mangroves, there are relics of fruit plantations in environment vary depending on weather conditions, some places (including mango, orange, etc.). A few rare the season (dry or wet), the month of year. signs of wet or semi-humid natural forests survive in Temperatures are relatively high throughout the year the form of sacred forest. with an annual average of 27.4°C and 21.1°C is minimum observable especially in the months of Sampling stations August and December. As for maxima, they are of the The study area forms a hydrological complex order of 36.6°C in the month of February, which is one composed of Lake Ahémé which flows into the Ahô of the hottest months. The study area is characterized channel. Then the Ahô channel feeds into the Tihimey by the presence of several types of natural (mangrove, channel and ends in the Ouidah and Grand-Popo 123 | Viaho et al. J. Bio. & Env. Sci. 2020 lagoons. The Grand-Popo Lagoon is home to the observation stations. These stations were set in the mouth of Mono River delta in the Avlo village, which general direction in which the water flows: upstream, connects the whole thing to the Atlantic Ocean. As middle, downstream, taking into the lake and channels. part of this study, each water body was considered as In sum, the study environment has been subdivided a separate entity, for a better understanding of each into five areas within which we have nineteen sampling environment. Each area has been subdivided into stations presented on a map of the area (Fig. 2). Fig. 2. Sampling stations. Sampling fish species account the tides, and were set in descending order of The collection of fish species was made each month mesh sizes (45mm, 40mm, 35mm, 30mm ... 10mm). from fishermen catches, from May 2016 to April 2017. Identification of fish species This collection was supplemented by monthly Specimens collected were first stored in a 10% formalin experimental fishing. Thus, gill nets have been made solution for 10 days and then in a 70% alcohol solution with different mesh sizes, namely: 10mm, 12mm, after identification in the appropriate jars (suitable for 15mm, 20mm, 25mm, 30mm, 35mm, 40mm and specimen size). Fish identification was made on the 45mm. Experimental fishing was conducted for 2 basis of morphometric and meristic characteristics days at each station every month. The nets were set at using the key according to Paugy et al. (2003). 5:00 pm and surveyed every 4 hours to observe and collect data on the species caught. The nets were Category of fish species arranged perpendicular to water current, taking into 124 | Viaho et al. J. Bio. & Env. Sci. 2020 In this study, the fish species were grouped according to possible to establish the accumulation curves of the the classification by Albert (1999). They are species in randomized species resulting from 100 simulations at a marine (ME + Ma + Mo), estuaries (E + Ec + Em) and 95% confidence interval.