Flow seasonality and fish assemblage in a tropical river, French Guiana, South America

Abstract

The objective of this study is to verify the existence of a seasonal pattern of variation in the fish assemblages of a tropical river using taxonomic and functional descriptors. Fish were sampled using gillnets at two sites on the Comté River, a large-sized river 254.8 km long, flowing entirely through rainforest areas of French Guiana. Samplings were conducted every other month from August 1998 to July 2000. Four types of fish assemblage descriptors were used: the species descriptor (number of individual fish of each species in the sample); the family descriptor (number of individual fish of each family in the sample); the trophic descriptor (distribution of the fish biomass in each feeding guild) and the specific maximum observed size -MOS (number of individual fish in each of four classes of MOS: < 100 mm; 101-200 mm; 201-300 mm; > 300 mm). Results point out that changes in the fish assemblage are related to water level oscillations. The role of migration seems to be weak and is limited to trophic displacements characteristic of few species. In the low-water season, characterized by weak water level oscillation, fish species and families belonging to piscivorous or aquatic invertivorous guilds were predominant, whereas in the high-water season the environment is submitted to strong variations caused by fast and large water level oscillations, and the fish assemblage was characterized by species or families with an opportunistic omnivorous diet.O objetivo deste estudo é verificar a existência de um padrão sazonal da variabilidade das assembleias de peixes de um rio tropical utilizando descritores taxonômicos e funcionais. Os peixes foram amostrados em duas estações localizadas ao longo dos 254,8 km do rio Comté, o qual drena regiões de floresta úmida da Guiana Francesa. As amostragens foram realizadas bimensalmente de agosto de 1998 a julho de 2000 utilizando-se redes de espera. Quatro tipos de descritores da assembleia de peixes foram utilizados: espécies (número de indivíduos de cada espécie na amostra); família (número de indivíduos de cada família na amostra); trófico (distribuição da biomassa de peixes de cada grupo trófico presente na amostra) e o tamanho máximo observado -TMO (número de indivíduos em cada uma das quatro classes de TMO: < 100 mm; 101-200 mm; 201-300 mm; > 300 mm). Os resultados indicam que as mudanças na assembleia de peixes estão relacionadas à oscilação sazonal do nível da água. O papel desempenhado pelas migrações parece fraco e é limitado a deslocamentos tróficos característicos de determinadas espécies. No período da seca, caracterizado por uma fraca oscilação do nível da água, as espécies e famílias predominantes são piscívoras ou invertívoras aquáticas, enquanto que no período da chuva, o ambiente é submetido a fortes mudanças, provocadas por rápidas e amplas oscilações do nível da água, onde as espécies ou famílias características são omnívoras.

Discrimination of hydrologic variations for spatial distribution of fish assemblage in a large subtropical temperate river

“…lateral connectivity variations), which produced changes in ß‐diversity of fish assemblages. These results are in line with Tejerina‐Garro and de Mérona (), Mims and Olden (), Abrial et al (), Górski, Collier, Hamilton, and Hicks (), Rabuffetti et al (), Scarabotti, Demonte, and Pouilly (), Abrial et al (), highlighting the importance of the hydrology in the structuring of fish assemblages.…”

Impoundment effects in the population of <i>Auchenipterus osteomystax</i> (Siluriformes: Auchenipteridae): a Neotropical reservoir case

“…On the other hand, in the population at the floodplain lake, where the variations were less pronounced, the decrease in Chaoboridae was accompanied by a reduction in the values for terrestrial insects and increase in aquatic forms such as Ephemeroptera and microcrustaceans. The predominance of allochthonous resources, especially terrestrial insects, in the diet of Auchenipterus species has been discussed for other reservoirs (Mérona et al 2001(Mérona et al , 2003, rivers (Tejerina-Garro & Mérona 2010), and várzea lakes of the Amazon (Mérona & Rankin-de-Mérona 2004). However, the predominance of aquatic forms of insects in the diets of the same species of Auchenipterus is reported for the Itaipu reservoir (Hahn et al 1998) and lakes of the Upper Paraná River floodplain (Hahn et al 2004).…”

Fish movement in an Atlantic Forest stream

“…In order to increase the offspring survival and to avoid intraspecific competition, some species displace kilometres and occupy specific habitats, with higher productivity and lower predator density (Schulz, Leal, 2012). Long spawning migration can occur in some fish groups, such as salmonids and large migratory fishes from Amazon and Paraná basins (Goulding, 1980;Winemiller, Jepsen, 1998;Antonio et al, 2007;Fernadez et al, 2007;Pesoa, Schulz, 2010;Tejerina-Garro, Mérona, 2010). Fish movements in streams can also be important for the fish community stability (Martin-Smith et al, 1999).…”

“…The available studies for Neotropical region described migratory routes in large rivers of Amazon and Paraná basins (e.g. Goulding, 1980;Alves et al, 2007;Antonio et al, 2007;Fernadez et al, 2007;Tejerina-Garro, Mérona, 2010).…”