Freshwater fishes of Lower Guinean forest streams: Aquaculture heavily impacts the structure and diversity of communities (original) (raw)
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Freshwater Fish Diversity of a Tropical Rainforest River in Southeast Nigeria
Fish samples were collected at three stations twice per month from January to December 2013 with the help of local fishers using hook and line, gill net, cast net, bagnet and local traps for ecological studies of important fish species and resource management issues of Oramiri-Ukwa River, southeast Nigeria. An estimate of 25 fish species, 15 genera, 21 families and six orders were obtained. Ecological indices indicate a polydiverse community and no single species exhibited true dominance (≥ 50%). Paired group cluster analysis establishes Tilapia zilli and Hemichromis fasciatus as the focal species and identifies the associated species combinations that characterize spatial variability and account for the biodiversity resources and structure of the artisanal fishery. Other important species include Tilapia mariae>Synodontis nigrita while Polypterus senegalus>Parachanna africana and Shilbe mystus were the least in number. Monospecific and rare fish species of ecological and conservation significance identified include Ctenopoma kingsleyae, Clarias gariepinus as well as Erpetoichthys calabaricus and Pantodon buchholzi derived from interconnections with other African rivers. This study presents lower fish diversity compared to earlier reports. This difference may be linked to increased human activities and fluctuating biotic and abiotic factors of the ecosystem, among others. 1. Introduction Ichthyodiversity refers to variety of fish species depending on the context and scale; it could refer to alleles or genotypes within piscian population, to species or life forms across aqua regimes (Burton et al., 1992). Fishes are the important elements in the economy of many nations as they have been a stable item in the diet of many people. According to Ehrlich & Willson, (1991) biodiversity is essential for stabilization of ecosystem, protection of overall environmental quality for understanding intrinsic worth of all species on the earth. Freshwater biodiversity has declined faster than either terrestrial or marine biodiversity over the past 30 years (Jenkins, 2003). Biodiversity is often ambiguously misused or overused to describe population dynamics of a location or community (Lawson & Moduke, 2010). Declining river flow rates (discharge) have been a major cause of species loss and are likely to be further reduced by warming temperatures, reduced precipitation and increased water withdrawal for agriculture and other human uses (Plafkin et al., 1989). Future declines can therefore negatively affect freshwater biodiversity. Inland waters and freshwater biodiversity constitute a valuable natural resource, in economic, cultural, aesthetic, scientific and educational terms. The streams and rivers are facing number of environmental problems throughout the world largely associated with anthropogenic activities in their catchment areas (Young et al., 2004). The adverse effects of human activities have resulted in degradation of stream and reverine ecosystem which ultimately alters the structure and function of stream biota. Their conservation and management are critical to the interests of all human, nations and governments. According to Nwafili & Tianxiang (2007), artisanal fishery continues to dominate fisheries, contributing over 85% of total fish production. The inland water and coastal seas are fully exploited and the increase in fishery production is not likely. Nigerian inland water bodies are primarily utilized for fishing by fisher folks. The greater part of inland fisheries is artisanal in nature supplying families with food and income. Artisanal fishing usually is usually not a full-time activity but rather integrated with farming and other activities. The main aim of this study is to provide multi-gear and multi-species ichthyofaunal composition and spatial distribution of the Oramiri-Ukwa River in comparison with others in order to share, update information, and provide data for future analysis. This study also seeks to identify species of ecological significance in the study area and to promote discussions for the management of the fishery to avoid risk of fish stock collapse and loss of invaluable ecosystem goods. 2. Materials and Methods The Study Area was Orammiri-Ukwa River (Fig. 1) located at Azaraegbulu, Emekuku in Owerri North Local Government Area of Imo State, southeast Nigeria at approximately latitude 5 0 30 ′ N and longitude 7 0 19 ′ E. Oramiri-Ukwa is a typical rain forest River. On both sides of the main River channel are large fringes of heavily forested swamps dominated by the raffia palm. The river flows from a highland in Okigwe and joins the Mbaa River to flow through Okahia Ezihe in Isiala Mbano Local Government Area, through Opara-nadim in Mbaise to
Iranian Journal of Fisheries Sciences
Fish assemblage was investigated during the study of longitudinal profile of the Ehania River Basin in southeastern Côte d'Ivoire. This area is subjected to intense human activities with many plantations (palm tree, banana, pineapple, coffee, rubber and cocoa). Samples were collected, with gillnets of different mesh sizes, through 6 sampling surveys during dry and rainy seasons from February 2010 to December 2010 at 6 sampling sites. A total of 70 fish species belonging to 48 genera, 28 families and 10 orders were recorded. The temporal variation of diversity index is less marked than spatial variation. The upstream, with 35 species, was less rich in species than the medium area and downstream areas (respectively 46 and 68). The upstream and downstream areas gathered 35 species. Thirty three species were common to the upper and middle areas and 46 species appeared both in the lower courses and the middle area. The 21 species restricted to the lower part of the river are mainly estuarine/marine origin. The beta diversity value revealed low similarity between the lower and upper course of Ehania River. The lowest values of Shannon's diversity index and equitability index were observed in the middle part of the River which characterized by high population density and intense agricultural activity with many plantations.
Fish species composition of a tropical lentic freshwater ecosystem (Umudike Water Reservoir, Umuahia, Nigeria) belonging to the National Root Crops Research Institute (NRCRI) was investigated from July 2004 to December 2004. The fishes were sampled twice every week using cast nets, traditional baskets traps (drum type), and hook-and-line of various sizes. A total of 896 fish approximately 500 kilogramme by weight were sampled. The sampled fish species belonged to fifteen (15) families, twenty-four (24) genera and thirty-two (32) species. Family cichlidae topped the list in number and weight with 665 (74.2%) fishes and 400, 900 g (82.8%) respectively; while the families Anabantidae and Hepsetidae had the least number, 7 (0.8%) each; 1,400 g (0.8%) and 1,500 g (0.3%) respectively. There was significant difference among the different species composition. The reservoir, with the fish species composition could be utilized for fisheries.
Fish Species Abundance and Diversity of River Uke, Nasarawa State, Nigeria
Banat's Journal of Biotechnology, 2016
A study was conducted to assess fish species abundance and diversity of River Uke, Uke, Nasarawa State, Nigeria. Fish were sampled from three sites, upper (A), middle (B) and lower (C) courses of the river. The study lasted for ten months from June 2014 to March 2015. A total of two thousand, one hundred and twenty six (2,126) fish comprising of 7 families and 11 species were sampled. Seasonal fish abundance of River Uke revealed that average monthly catch in the wet season was 25 % lower than in the dry season. Cichlidae dominated the sampled fish families accounting for 26.20 % of total catch while Latidae was least abundant with 6.21 %. Monthly fish abundance was dominated by three species, namely, Clarias gariepinus (18.44 %), Tilapia zilli (14.44 %) and Oreochromis niloticus (11.76 %) all accounting for 44.64% of the total catch. The trend of monthly fish abundance also showed a bi-modal peak with the minor peak observed in March (260) and the major peak in November (292). Fish abundance by sites revealed individual catches of 671, 365 and 1090 in Site A, B and C, respectively. Total Shannon-Wiener Diversity index of River Uke in this study was 2.312 and the index values were generally higher in the wet season (except October) than in the dry season. Total Simpson Index calculated for River Uke in this study was 0.892.
Diversity and Distribution of Freshwater Fishes in Oguta Lake, Southeast Nigeria
The ichthyofaunal composition of the largest natural lake in Nigeria-the Oguta Lake, was investigated from January, 2012 to December, 2013. Bimonthly random samples of fish catches of artisanal fishers employing hook and line, gill net, cast net, bagnet and local traps were analysed. A total of 1,989 fishes were sampled comprising 6 orders, 22 genera, and 32 species spread into 18 families. The Perciformes, Cichlidae and Tilapia zill were the most abundant fish order, family and species, respectively. The study reveals that species diversity was highest at station 4 (Osemotor) though no significant spatial differences were detected. The lake is of ecological significance in accommodating some threatened species like Erpetoichthys calabaricus and serving as a source of broodstock of Clarias gariepinus for aquaculture. A seriation analysis of species presence/absence matrix in the lake reveals Tilapia mariae, Synodotis schall, Mormyrus rume, Synodontis nigrita and Petrocephalus banebane are important fish species to ecosystem health of the lake. The fish abundance and diversity values in present study are lower than the findings of previous studies in the same water body, suggesting need for proper and articulated management. 1. Introduction Fisheries resources are on the decline in Nigeria due to over exploitation and inadequate management of inland waters. For sustainability of these resources, an adequate knowledge of species composition, diversity and relative abundance of the fisheries resources of the water bodies must be understood. Increased fishing pressure exerted by artisanal fishermen that are operating in this water body coupled with the downstream migration of fish in search for food, shelter and spawning, industrialization, urbanization and farming activities around the river are factors that contribute variation in fish composition and diversity in Nigeria. External factors affecting populations of freshwater species include; simple habitat loss resulting from withdrawal of water for human use such as irrigation, domestic and industrial use; impact of anthropogenic factors; impoundment, wetland drainage and flood control which cause the load of inorganic and organic pollutants in flowing waters to increase. Available evidence strongly suggests that fish abundance and diversity are in decline at the same time that human population's destructive activities are increasing. The fish supply gap in Nigeria as indicated by Adekoya and Olunuga (1999) is at least 1.0 million metric tons. As a measure to bridge the fish demand gap with its supply, Nigeria resorted to importation of fish thereby causing a considerable drain in the foreign reserve. Despite expenses on fish importation, the gap between supply and fish demand widens the more with population increase. In his contribution, Tobor (1973) advanced effective domestic production rather than fish importation in covering this gap. The contribution of artisanal fisheries is poor due to low output, poor processing mechanism, ineffective distribution and marketing of fishing products, pollution and post-harvest loss. Although freshwater ecosystems such as rivers, lakes and wetlands occupy less than 2% of the earth's total land surface, they provide a wide range of habitats for a significant proportion of the world's plant and animal species. Many are yet to be discovered, but the number of freshwater species worldwide is estimated at between 9,000 and 25,000 (Cosgrove and Rijsberman, 2000). The fish yield of most inland waters in Nigeria are generally on the decline for causes that may range from inadequate management of the fisheries to degradation of water bodies (Odo et al., 2009). Due to a general lack of data, it is difficult to access the status of the inland water biodiversity. Indeed monitoring the status and trends of freshwater biodiversity is essential to quantify impacts of human activities on freshwater systems and to improve freshwater biodiversity conservation. According to Adaka et al. (2014) environmental awareness to educate the fishers and other stakeholders on the danger of extinction of the species and the need for its conservation was necessary. Also future developments on autogenic and anthropogenic threats, and activities and harmful practices which predispose fish species extinction along the floodplain and catchment area of rivers should be subjected to environmental scrutiny to maintain the environmental health and integrity of the ecosystem. Similarly, Ude et al., (2011) stated that detailed knowledge of the function of the river system and the responses of fish species are needed for effective fisheries management planning. The aim of this study therefore is to provide ichthyofaunal composition of Oguta Lake along a spatial gradient to promote discussions for its ecological significance and management of the fishery to
Fish Diversity of Two Lacustrine Wetlands of the Upper Benue Basin, Nigeria
A study was conducted at River Mayo Ranewo and River Lau, Taraba State Nigeria. The two rivers empty into the Upper Benue Basin. A survey of visual encounter was conducted within the two wetlands from June to August, 2014. The fish record was based entirely on landings of fishermen, number of canoes that land fish was counted, types of nets and baits used on each sampling day. Fishes were sorted into taxonomic groups, identified to family/ species level, counted and weighed in groups by species. Other aquatic organisms captured by the fishermen were scallops, turtles and frogs. The relative species abundance was determined by dividing the number of species from a site by the total number of species from all tributaries/sites. The fish were preserved in 2% formaldehyde solution and taken to the laboratory, were identified through keys of identification to African fishes and field guides. Shannon-Wieiner index of species diversity indicated that the diversity was highest at River Mayo Ranewo than River Lau. Results showed that at River Mayo Ranewo, the family Mochokidae recorded the highest (23.15%), followed by Mormyridae (22.64%) and the least was the family Lepidosirenidae (0.04%). While at River Lau, the family Mochokidae recorded the highest occurrence of (24.1%), followed by Bagridae (20.20%), and then Mormyridae, which also was the second highest in River Lau, with 18.46% occurrence. There was no occurrence of Malapteruridae and Osteoglossidae (0%) in River Lau, but the least occurrence was the family Gymnarchidae (0.04%). According to the result from the t-test, the fish composition was not significantly different (p≤0.05).
Fish Assemblage of Amadi Creek, Port Harcourt, Rivers State Nigeria
2018
The Amadi Creek, is a vital inland water body in Port-Harcourt, exploited for numerous reasons, including fishing. However, no information exists on the fin fish assemblage of the creek. This research is aimed at documenting the fish population of the Creek. A twelve week survey was conducted, and landed fish collected from fishers using indiscriminate fishing gears. The Fin fish Composition, Diversity and Abundance were ascertained using standard methods. A total 8,5552 fin fishes composed of 3 families, the Cichlid with two species ( Sarotheredon melanotheron and Coptodon zilli ), the Mugilidae and Clupeidae with one species each ( Mugil cephalus and Sardinella maderensis, respectively) .The Sarotheredon melanotheron . Generally, diversity was low with only 4 species in the creek. Quantitatively, the family diversity of the Cichlids were high (50%), the Mugilidae and Clupeidae were low (25%) each. Species diversity revealed Sarotheredon melanotheron was higher (97.7%), Sa...
The ichthyofauna of Hana basin (Taï National Park, Côte d'Ivoire) was studied during two seasons (rainy and dry seasons) at January 2012 and November 2012. The distribution of fish species was recorded at 7 stations on the Hana basin. Fourty one fish species were collected from 28 genera and 16 families: 4 marine and/or brackish water species (Pellonula leonensis, Pellonula vorax, Sarotherodon galilaeus, Sarotherodon melanotheron). As regards the families and species number, the Siluriform order was contained the most important families and species (31.25% of families and 21.95% of species). They are followed by Characiform (18.75% of families; 19.51% of species), Osteoglossiform (12.50% of families and 14.63% of species) and Cyprinodontiform (12.50% of families and 4.88% of species).The spatial distribution of fish species indicated a more diversified settlement in the main channel of Hana basin. The high value for taxonomic richness was obtained in the dry season. The diversity index varied significantly in both seasons. The quantitative analysis indicated that Schilbeidae, Alestidae and Mormyridae were the main families which dominated Hana basin. In the main channel, Spatio-Temporal Patterns of Fish Assemblages and Influential Environmental Gradients in a West African Basin (Tai National Park, Côte D'ivoire) 146 Schilbeidae was the abundant family while Alestidae and Clariidae were respectively abundant families of Moumo and Meno tributaries. The main environmental factors determining the patterns of fish distribution and assemblage structure in Hana basin were canopy closure, width, sand, depth, mud, temperature, mixed clay-mud, gravel and leaves-wood.
Ruhuna Journal of Science, 2022
Globally, we are experiencing higher species extinction rates than ever before which can critically affect food and nutrition security. The ecological classification of fish species was assessed in Owalla reservoir, Okinni, Osun State, Nigeria. Fish landings of fishermen were sampled for 12 months from September 2019 to August 2020). The species were identified and grouped into herbivores, carnivores, and omnivores, and the fish abundance was recorded. The Forage-Carnivore ratio (F/C ratio) was calculated to express the ecological structure of the reservoir. A total of 15 fish species (n=1035 fish) were identified. In the dry and wet seasons, 15 species (692 fish) and 11 species (343 fish) were recorded, respectively, and herbivores were more abundant than carnivores. Chrysichthys nigrodigitatus (25.9%) was the most abundant species and Cichlidae (55.5%) was the most abundant family. The overall F/C ratio during the combined, dry and wet seasons were 1.35, 1.01 and 2.57, respectively. The ecological structure as indicated by the F/C ratio was unbalanced, but in the wet season, it was close to being balanced. We proposed management measures such as fishing across the trophic levels, efficient monitoring and surveillance, regulation of mesh sizes, and registration of fishermen in addition to routine data collection.
The ichthyofaunal composition of the floodplains of the Lower Cross River was investigated and compared in order to promote its management. A total of 5211 fish were sampled for 12 consecutive months from commercial landings of artisanal fishers from three sampling stations. We estimate 77 species distributed into 52 genera, 29 families and 9 orders, both of freshwater (88.66%) and euryhaline (marine intrusive) fishes (11.34%), with averagely 1-3 species per genus. The fishes composed mainly Perciformes, the least being Polypteriformes and Clupeiformes.. The five most abundant fish families are the Bagridae > Cichlidae > Mormyridae > Mugilidae and Cyprinidae. Study suggests growth and recruitment overfishing with populations generally bigger upstream than their counterparts downstream and elucidates contributions of floodplains as nursing and spawning grounds in river fisheries and productivity.