Cette étude a pour objectif principal dinventorier les espèces de poissons de la partie congolaise de lInkisi et de contribuer à la connaissance de leur structure de peuplements. A partir des pêches expérimentales et artisanales effectuées entre octobre 2005 et octobre 2008 et des spécimens déposés antérieurement dans les musées, 61 espèces appartenant à 38 genres et 15 familles ont été répertoriées. Trente-sept de ces espèces nétaient pas encore connues du bassin de lInkisi ; huit espèces sont endémiques et sont localisées en amont de la chute de Zongo : Barbus vanderysti, Labeobarbus sp. inkisi, Varicorhinus robertsi (Cyprinidae), Nannopetersius mutambuei (Alestidae), Schilbe zairensis (Schilbeidae) Aphyosemion labarrei (Nothobranchiidae) et Haplochromis sp. snoeksi et Chetia sp. inkisi (Cichlidae). Deux nouvelles espèces ont été décrites, Nannopetersius mutambuei et Haplochromis sp. snoeksi et les descriptions de deux autres sont en préparation. En ce qui concerne les proportions, la famille des Cyprinidae est la plus diversifiée (15 espèces soit 24,6 %); puis viennent les Mormyridae (11 espèces soit 18,0 %), les Cichlidae (9 espèces soit 7,1 %), les Clariidae (7 espèces soit 11,5 %), les Schilbeidae (4 espèces soit 6,6 %), les Mochokidae et les Amphilidae (3 espèces chacune soit 4,9 %) et les Nothobranchiidae (2 espèces soit 3,3 %). La somme des autres familles, représentées par une seule espèce, vaut 6,4 %. Les peuplements des poissons ont été échantillonnés aux filets maillants dans dix stations en prenant en compte 21 variables environnementales. Des analyses canoniques de redondance ont permis de mettre en évidence cinq variables environnementales (la couverture de la canopée, la présence de gros blocs de roches, la largeur de la rivière, le plancher rocheux et le substrat vaseux) qui influent sur la distribution des poissons et un plan spatial de peuplement de cinq types dhabitats : trois sur les affluents (Nsoni, Ngeba et Nua-Luidi-Bongolo-Wungu) et deux sur le cours principal (amont de la chute de Zongo et aval de la chute de Zongo). Les espèces qui caractérisent Nsoni, habitat à canopée sont Parauchenoglanis balayi, en terme dabondance et Barbus vanderysti, en terme de présence. Dans Ngeba, habitat à substrat boueux, les espèces caractéristiques en terme de présence sont Parachanna obscura et Ctenopoma nigropannosum. Dans le complexe Nua-Luidi-Bongolo-Wungu il y a, en terme dabondance, Varicorhinus latirostris, Raiamas kheeli et Garra congensis. Sur le cours principal, en amont de chute Zongo, habitats larges à fond rocheux, on retrouve, en terme dabondance Varicorhinus macrolepidotus, Labeo macrostomus, Doumea alula, Barbus cf. argenteus, et Chetia sp. inkisi. Finalement, en aval de la chute Zongo, habitat à gros blocs de roches, il y a 14 espèces caractéristiques en terme de présence dont les plus abondantes sont Labeo nasus, Steatocranus casuarius, Labeo greeni, Campylomormyrus rhynchophorus et Schilbe grenfelli. Dans la partie congolaise de lInkisi le gradient longitudinal de peuplement nest pas perceptible : laugmentation de la richesse spécifique amont-aval napparaît pas mais la composition spécifique amont-aval est différente. Les indices de diversités (richesse spécifique et équitabilité) variées en fonction des stations ; les plus élevés sont dans la station aval de la chute Zongo et les plus faibles dans la station Nsoni (pour la richesse spécifique) et la station Nua (pour léquitabilité). Les peuplements ichtyologiques semblent équilibrés dans la partie située en aval de la chute Zongo. Des affluents tel que Wungu ont été perturbés suite à lutilisation des techniques destructives (ichtyotoxique). Une planification et une gestion rationnelle des ressources halieutiques dans ce bassin doivent sopérer et être effectives pour préserver sa biodiversité. The present study aimed making a species inventory and contributing to the knowledge of the fish community structure of the Congolese part of Inkisi basin. Based on fishes collected between October 2005 and October 2008 using gill nets and local fishing gear, and specimens previously deposited in musea, a total of 61 species belonging to 38 genera and 15 families have been surveyed. Thirty seven of these species are new citations for the Inkisi basin; eight species are endemic and are only found upstream from the Zongo fall: Barbus vanderysti, Labeobarbus sp. inkisi, Varicorhinus robertsi (Cyprinidae), Nannopetersius mutambuei (Alestidae), Schilbe zairensis (Schilbeidae) Aphyosemion labarrei (Nothobranchiidae) and Haplochromis sp. snoeksi, Chetia sp. inkisi (Cichlidae). Two new species were described, Nannopetersius mutambuei and Haplochromis sp. snoeksi and two others are currently under preparation. The family Cyprinidae is the most diversified (15 species, 24.6 %), followed by Mormyridae (11 species, 18.0 %), Cichlidae (9 species, 7.1 %), Clariidae (7 species, 11.5 %), Schilbeidae (4 species, 6.6 %), Mochokidae and Amphilidae (with 3 species each one), and Nothobranchiidae (2 species, 3.3 %). The remaining families have only one species each and constitute 6.4 %. The fish communities were sampled using gill nets in ten stations taking into account 21 environmental variables. The canonical redundancy analysis retained five important environmental variables (canopy cover, presence of big rock blocs, river width, rocky bottom and muddy bottom) explaining the distribution of the fish species and revealed a spatial plan of five habitat types: three patterns for the affluents (i.e. Nsoni, Ngeba and Nua-Luid-Bongolo-Wungu) and two for the main channel (i.e. upstream of the Zongo fall and downstream of the Zongo fall). For the Nsoni, station with canopy, the typical species are Parauchenoglanis balayi and Barbus vanderysti, respectively, in abundance, and presence. In the Ngeba, station with muddy bottom, the typical species, in abundance, are Parachanna obscura and Ctenopoma nigropannosum. For the Nua-Luidi-Bongolo-Wungu complex, the typical species, in abundance, are Varicorhinus latirostris, Raiamas kheeli and Garra congensis. For the main channel of the Inkisi course upstream of the Zongo fall, wide habitats with rocky bottom, the typical species, in abundance, are Varicorhinus macrolepidotus, Labeo macrostomus, Doumea alula, Barbus cf. argenteus, and Chetia sp. inkisi. Finally, for the Inkisi main channel downstream of the Zongo fall, the station with big rock blocs, 14 species are typical in term of presence, among them the most common are Labeo nasus, Steatocranus casuarius, Labeo greeni, Campylomormyrus rhynchophorus, and Schilbe grenfelli. For the Congolese part of Inkisi no longitudinal gradient of the fish community assemblages was observed along the river. Species richness did not increase from upstream to downstream although the species composition between both is certainly different. Diversity index (species richness and equitability) vary according to station with the highest indexes observed downstream of the Zongo fall and the lower ones at Nua (for the equitability) and Nsoni (for the species richness). Fish communities seem equilibrated downstream of the Zongo fall. On the contrary affluents like the Wungu are being disturbed mainly by bad fishing practice (use of ichthyotoxin). A planification and sustainable use of the natural resources of the Inkisi River must be applied and executed to protect its fish diversity.

No description available.

Following the construction of the Pongolapoort Dam in 1974, the potential impacts on the lower Phongolo River and floodplain due to alterations in the natural flow regime have caused concerns. Fish communities and population structures are directly influenced by these alterations. The only protected section of the Phongolo River is a 15 km reach and its associated pans that flow through the Ndumo Game Reserve. Historic data shows that the community and population structure of the fish in the Phongolo Floodplain has changed as a result of irregular flood releases. The Ndumo Game Reserve plays an important role in the conservation of many ecologically and economically important species as the pans inside the reserve serve as a refuge area in which these species can breed to replenish the fish numbers in the Phongolo River. The fish diversity inside the Ndumo Game Reserve is also higher when compared to outside. During the high flow period fish move into the floodplain pans as a result of the higher water level. Oreochromis mossambicus, the most common species found in this area, utilize Nyamiti Pan for breeding but the health of this species is under pressure due to severe infestations of Lernaea cyprinacaea and nematode parasites. Lernaea cyprinacaea is a parasitic copepod associated with the introduced exotic fish species Cyprinus carpio which is found in large numbers in various pans inside Ndumo Game Reserve. The presence of this alien species in the refuge area raises concerns as it competes for the same resources as the economically important native fish species. Nyamiti Pan is largely populated by adult cichlid species between the ages of six and ten years old. The importance of flood releases which simulate natural flow regime is emphasised by the negative impacts irregular floods have on fish health, community and population structure. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Following the construction of the Pongolapoort Dam in 1974, the potential impacts on the lower Phongolo River and floodplain due to alterations in the natural flow regime have caused concerns. Fish communities and population structures are directly influenced by these alterations. The only protected section of the Phongolo River is a 15 km reach and its associated pans that flow through the Ndumo Game Reserve. Historic data shows that the community and population structure of the fish in the Phongolo Floodplain has changed as a result of irregular flood releases. The Ndumo Game Reserve plays an important role in the conservation of many ecologically and economically important species as the pans inside the reserve serve as a refuge area in which these species can breed to replenish the fish numbers in the Phongolo River. The fish diversity inside the Ndumo Game Reserve is also higher when compared to outside. During the high flow period fish move into the floodplain pans as a result of the higher water level. Oreochromis mossambicus, the most common species found in this area, utilize Nyamiti Pan for breeding but the health of this species is under pressure due to severe infestations of Lernaea cyprinacaea and nematode parasites. Lernaea cyprinacaea is a parasitic copepod associated with the introduced exotic fish species Cyprinus carpio which is found in large numbers in various pans inside Ndumo Game Reserve. The presence of this alien species in the refuge area raises concerns as it competes for the same resources as the economically important native fish species. Nyamiti Pan is largely populated by adult cichlid species between the ages of six and ten years old. The importance of flood releases which simulate natural flow regime is emphasised by the negative impacts irregular floods have on fish health, community and population structure. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

This study compared traditional community analysis with stable-isotope trophic analysis to define process-based trophic elements of community structure in the eastern Gulf of Mexico, and developed a predictive capability regarding changes to fish community structure that would be expected from increasing eutrophication. Specifically, it used an existing trawl survey program (SEAMAP) to compare invertebrate herbivore (sponge and sea urchin) isotopes with groundfish isotopes, and then compared the resulting spatial patterns with spatial variation in community structure, as identified by cluster analysis. The comparison was applied to seven NMFS survey zones that extended offshore from the Caloosahatchee River, FL northwest to Mobile Bay, AL. Isotopic patterns were consistent with the presence of an oligotrophic-eutrophic spatial gradient in this region. δ15N values increased in the northwestward direction in herbivores and in each of the 17 fish species examined. In the southern NMFS survey zones, δ13C was elevated in shallow depths for individual fish species, but not in herbivores, indicating a higher proportion of benthically derived biomass contributed to the biomass of fish in the shallow parts of the southern NMFS zones. Fish community analysis using SIMPROF created a similar pattern, with distinct nearshore and offshore communities and also a northwesterly community transition. Among the 17 fish species, five appeared to have obligate dependence on either benthic or planktonic basal resources, while twelve species appeared to be have facultative relationships. Impairment of current water-quality (nutrients, turbidity, light transmission, chlorophyll a) is expected to lead to reductions in the abundance of both obligate and facultative benthic-dependent fishes.

Novel ecosystems emerge from alterations to historic abiotic regimes and contain new species combinations. Everglades canals offer an opportunity to understand the function of novel habitat for native and non-native fishes and how novel conditions in turn influence distribution, abundance and assembly patterns. I examined native and non-native fish assemblages collected across a gradient in novelty, defined by the loss of wetland connectivity and habitat complexity. As novelty increased, native species richness and abundance strongly declined, and the contribution of non-natives increased. Community structure vastly differed among canals and was strongly influenced by spatial factors and secondarily by hydrological factors. Natives and non-natives had opposing responses to key hydrologic and habitat parameters. This study represents the first comprehensive assessment of Everglades canal fishes, providing insight into the factors influencing native and non-native abundance and assembly patterns and contributing to our understanding of this novel but permanent habitat.

Le lac de Tonlé Sap (TSL), Cambodge, est un écosystème lac-rivière de forêt alluviale au régime d'écoulement alternatif. Le lac est un déversoir lors de l'inondation saisonnière du Mékong et sert de réservoir en période de basses eaux. La superficie du lac pendant la saison sèche (février à mai), est d'environ 2 700 km2 pour une profondeur d'environ 1 mètre. Cette superficie est pratiquement multipliée par six quand arrive la saison des pluies, pour atteindre près de 16 000 km2 et une profondeur de 9 mètres, noyant rizières et forêts. C'est le plus grand lac d'eau douce d'Asie du Sud-Est. C'est aussi l'une des zones de pêche d'eau douce les plus importantes et productives du monde avec près de 75% du volume annuel de pêche en eau douce du Cambodge, ce qui permet la survie de près de 2,5 millions de personnes. Les changements saisonniers du cycle hydrologique ont une influence sur la structuration des communautés de poissons à l'échelle temporelle et spatiale, mais aussi sur les comportements trophiques des principales espèces qui n'exploitent alors pas les mêmes habitats. Toutefois, le bassin versant du Mékong est en changement constant avec un développement important des infrastructures en lien avec l'eau : production d'hydro-électricité, besoins important en irrigation, maitrise des inondations, eau potable, ... Les changements climatiques accélèrent les modifications du cycle hydrologique annuel. Il est alors supposé que ces modifications ont des effets forts sur les habitats et les proies disponibles et finalement sur la biodiversité, notamment de l'ichtyofaune et sur l'abondance des poissons disponibles pour les pêcheries.Dans un premier temps, nous avons caractérisé les variations spatio-temporelles de la composition taxonomique des poissons et mis en lumière quels sont les déterminants de ces variations. À cette fin, nous avons estimé la diversité bêta comme la variance totale de la matrice site par communauté d'espèce et l'avons divisée en contribution locale à la diversité bêta (LCBD) et contribution des espèces à la diversité bêta (SCBD). Nous avons ensuite effectué plusieurs régressions linéaires pour déterminer si la richesse taxonomique, l'abondance des espèces et le niveau de l'eau expliquaient la variation temporelle de la contribution du site et de l'espèce à la diversité bêta. Nos résultats indiquent une forte variation temporelle de la diversité bêta due aux contributions différentielles des sites et des espèces à la variation spatiale de la composition taxonomique des poissons. Nous avons également constaté que la direction, la forme et l'effet relatif de la richesse spécifique, de l'abondance et du niveau de l'eau sur la variation temporelle des valeurs LCBD et SCBD varient grandement selon les sites. Ces résultats suggèrent ainsi une variation spatiale des processus conduisant à une variation temporelle de la composition de la communauté. Dans l'ensemble, nos résultats suggèrent que la composition taxonomique des poissons n'est pas distribuée de manière homogène dans l'espace et dans le temps et risque d'être affectée à l'avenir si la dynamique saisonnière d'écoulement du système est altérée par les activités humaines et/ou les changements climatiques. Dans un second temps, nous avons cherché à étudier le modèle d'évolution temporel des principales espèces en terme d'occurrence et d'abondance à travers le cycle saisonnier hydrologique. / The Tonle Sap Lake (TSL), Cambodia, is a flood-pulse system. It is the largest natural lake in South- East Asia and constitutes one of the largest fisheries over the world, supporting the livelihood 2.5 million peoples. Seasonal change in annual hydrological cycle appears to have influence on fish community structure, both spatial and temporal variation, particularly on feeding behavior of TSL's fishes. Nonetheless, the Mekong River Basin is changing rapidly due to accelerating water infrastructure development (hydropower, irrigation, flood control, and water supply) and climate change, bringing considerable modifications to the annual flood-pulse of the TSL. Such modifications are expected to have strong impacts on fish biodiversity, abundance, reduced habitat and food availability within the lake. To invest how TSL's fish community structure responds to the seasonal change, how they shift their diet across hydrological cycles and feeding competing for food resource: First, we aim to characterize the spatio-temporal variations of fish taxonomic composition and to highlights the underlying determinants of these variations. For this purpose, we estimated beta diversity as the total variance of the site-by-species community matrix and partitioned it into Local Contribution to Beta Diversity (LCBD) and Species Contribution to Beta Diversity (SCBD). We then performed multiple linear regressions to determine whether species richness, species abundances and water level explained the temporal variation in the contribution of site and species to beta diversity. Our results indicate strong temporal variation of beta diversity due to differential contributions of sites and species to the spatial variation of fish taxonomic composition. We further found that the direction, the shape and the relative effect of species richness, abundances and water level on temporal variation in LCBD and SCBD values greatly varied among sites, thus suggesting spatial variation in the processes leading to temporal variation in community composition. Overall, our results suggest that fish taxonomic composition is not homogeneously distributed over space and time and is likely to be impacted in the future if the flood-pulse dynamic of the system is altered by human activities. Second, we aim to investigate the temporal pattern of the most occurrence and abundance species and how their co-occurrence pattern across hydrological cycles. We found that occurrence and abundance patterns were temporally varied at all water level seasons. Strong temporal variation in species occurrence was occurred with visiting species such as Labiobarbus leptocheilus and Poropuntius deauratus while water level starts to fill into the TSL. We further observed that the abundance of 17 species was strongly varied while other 22 species (mainly TSL's residential species) were stable within the year. Positive species co-occurrence pattern was generally higher than negative species co-occurrence at all water level seasons. Highest positive co-occurrence patterns were found during the period of decrease and low water level seasons while fishes are migrating from flooded areas, competing for resource and habitats during low water season. Study on temporal distribution and species co-occurrence of fish and how community responds to the seasonal change in hydrological cycles provides critical information for fisheries management and conservation in the Tonle Sap Lake (TSL) as well as maintaining fish biodiversity in the Mekong system. Third, the implications of seasonality on food web structure have been notoriously understudied in empirical ecology, particularly in TSL's system. The current study, we focus on seasonal changes in one key attribute of a food web, vertical trophic position of consumers.