Jan H. Mol

The fish fauna of Brokopondo Reservoir, Suriname, during 40 years of impoundment

We investigated long-term changes in the fish fauna of Brokopondo Reservoir, Suriname, the first large reservoir (1560 km2) that was created in tropical rainforest. Before closure of the dam in 1964, the fish fauna of Suriname River had 172 species, high diversity and high evenness. The riverine fauna was dominated by small-sized species, but no single species was dominant in numbers. Large catfishes were dominant in biomass. Species were evenly distributed over riverine habitats: rapids, tributaries and main channel. Four years after closure of the dam, only 62 fish species were collected from Brokopondo Reservoir, but the composition of the fish fauna was still changing. The reservoir fauna in 1978 was very similar to the reservoir fauna in 2005, indicating that a stable equilibrium had been reached 14 years after closure of the dam. The reservoir fauna had 41 species, low diversity and low evenness. Most species of Suriname River and its tributaries with strict habitat requirements did not survive in Brokopondo Reservoir. Fish community structure was different among four habitats of Brokopondo Reservoir. The open-water habitat (10 species) was dominated by the piscivores Serrasalmus rhombeus, Acestrorhynchus microlepis and Cichla ocellaris and their prey Bryconops melanurus and two Hemiodus species. B. melanurus fed on zooplankton, Culicinae pupae and terrestrial invertebrates. Hemiodus fed on fine flocculent detritus, demonstrating that the detritus-based food chain was still important in late stages of reservoir development. Serrasalmus rhombeus also fed on peccaries that drowned when swimming across the large reservoir in rough weather. The shore community (27 species) was dominated by seven cichlids, but early stages and juveniles of the open-water species S. rhombeus and B. melanurus also occurred in the shore habitat. Fish biomass in the shore habitat was 66.5±59.9 kg ha-1. The cichlid Geophagus surinamensis and the characid B. melanurus had a lower biomass in Brokopondo Reservoir than in Suriname River. Serrasalmus rhombeus showed reduced body length in Brokopondo Reservoir as compared to riverine populations.

Phenotypic plasticity in fish life-history traits in two neotropical reservoirs: Petit-Saut Reservoir in French Guiana and Brokopondo Reservoir in Suriname

Fish species are known for their large phenotypic plasticity in life-history traits in relation to environmental characteristics. Plasticity allows species to increase their fitness in a given environment. Here we examined the life-history response of fish species after an abrupt change in their environment caused by the damming of rivers. Two reservoirs of different age, both situated on the Guiana Shield, were investigated: the young Petit-Saut Reservoir in French Guiana (14 years) and the much older Brokopondo Reservoir in Suriname (44 years). Six life-history traits in 14 fish species were studied and compared to their value in the Sinnamary River prior to the completion of Petit-Saut Reservoir. The traits analyzed were maximum length, absolute and relative length at first maturation, proportion of mature oocytes in ripe gonad, batch fecundity and mean size of mature oocytes. The results revealed a general increase of reproductive effort. All species showed a decrease in maximum length. Compared to the values observed before the dam constructions, eight species had larger oocytes and three species showed an increased batch fecundity. These observed changes suggest a trend towards a pioneer strategy. The changes observed in Petit-Saut Reservoir also seemed to apply to the 30 years older Brokopondo Reservoir suggesting that these reservoirs remain in a state of immaturity for a long time. Peixes sao conhecidos pela grande plasticidade fenotipica com que respondem as caracteristicas do meio, o que lhes permite aumentar as chances de sucesso frente a variacoes ambientais. No presente trabalho foram examinadas as respostas biologicas de teleosteos apos uma abrupta modificacao no ambiente provocada pelo represamento dos rios. Dois reservatorios de diferentes idades, situados no norte da America do Sul, foram investigados: um mais jovem (14 anos), Petit-Saut, na Guiana Francesa, e outro mais antigo (44 anos), Brokopondo, no Suriname. Em 14 especies de peixes foram avaliados seis atributos biologicos, os quais foram comparados com a situacao apresentada no rio Sinnamary antes do enchimento do Reservatorio Petit-Saut. Avaliamos o tamanho maximo dos individuos, os comprimentos absoluto e relativo de primeira maturacao, a proporcao de ovocitos maduros em gonadas desovantes, a fecundidade por lote, e o tamanho medio dos ovocitos maduros. Os resultados indicam ter havido aumento do esforco reprodutivo com a formacao dos reservatorios. Todas as especies tiveram reducao de tamanho. Comparados aos valores observados antes da formacao dos reservatorios, oito especies tiveram ovocitos maiores e tres especies mostraram aumento da fecundidade por lote. A constatacao dessas mudancas aponta para a adocao de estrategias de ocupacao pioneira. Aquelas observadas no Reservatorio Petit-Saut parecem tambem aplicar-se ao Reservatorio Brokopondo, 30 anos mais antigo, sugerindo que esses reservatorios mantem-se em condicao imatura por muito tempo.

The fish fauna of Suriname

The ichthyofauna of the Neotropics is still badly known. Ecological studies of fish communities are possible, but many species that will be included in these studies are unnamed and can only be indicated by numbers (see for instance Goulding et al 1988). The Surinamese ichthyofauna has been studied by numerous zoologists since Van der Stigchel (1947). During six years of fish collecting, between 1987 and 1993, we (probably) found no species new to science, and only a few that were not mentioned for Suriname before. This indicates a relatively well-known fish fauna (compared to other South American countries), enabling us to make ichthyofaunal comparisons between rivers and river-sections. This chapter will give an impression of the fish fauna of a selection of rivers and river-sections in different parts of the country and consequently with different environmental conditions. The ichthyofauna of the swamps and swamp forests of the Coastal Plain is not included in this study. However, the lotic environment is very dominant in Suriname, and probably few species are exclusively restricted to the standing waters of the Coastal Plain.

Molecular phylogeny of the highly diversified catfish subfamily Loricariinae (Siluriformes, Loricariidae) reveals incongruences with morphological classification

The Loricariinae belong to the Neotropical mailed catfish family Loricariidae, the most species-rich catfish family. Among loricariids, members of the Loricariinae are united by a long and flattened caudal peduncle and the absence of an adipose fin. Despite numerous studies of the Loricariidae, there is no comprehensive phylogeny of this morphologically highly diversified subfamily. To fill this gap, we present a molecular phylogeny of this group, including 350 representatives, based on the analysis of mitochondrial and nuclear genes (8426 positions). The resulting phylogeny indicates that Loricariinae are distributed into two sister tribes: Harttiini and Loricariini. The Harttiini tribe, as classically defined, constitutes a paraphyletic assemblage and is here restricted to the three genera Harttia, Cteniloricaria, and Harttiella. Two subtribes are distinguished within Loricariini: Farlowellina and Loricariina. Within Farlowellina, the nominal genus formed a paraphyletic group, as did Sturisoma and Sturisomatichthys. Within Loricariina, Loricaria, Crossoloricaria, and Apistoloricaria are also paraphyletic. To solve these issues, and given the lack of clear morphological diagnostic features, we propose here to synonymize several genera (Quiritixys with Harttia; East Andean members of Crossoloricaria, and Apistoloricaria with Rhadinoloricaria; Ixinandria, Hemiloricaria, Fonchiiichthys, and Leliella with Rineloricaria), to restrict others (Crossoloricaria, and Sturisomatichthys to the West Andean members, and Sturisoma to the East Andean species), and to revalidate the genus Proloricaria.

New Arrangement in the Synonymy of Megalechis Reis, 1997 (Siluriformes: Callichthyidae)

Abstract The recent examination of the holotypes of Callichthys thoracatus and Callichthys longifilis led to important modifications in the nomenclature of the two species of Megalechis. Inspection of these holotypes demonstrated that they represent the species that has commonly been referred to in current literature as Megalechis personata. Because C. thoracatus is an older name than C. personatus, it has priority and is considered as the senior synonym. Callichthys pictus is the oldest name applicable to the species commonly referred to in current literature as Megalechis thoracata, and is thus the valid name. Rearranged synonymies, updated diagnoses, and illustrations are provided for both species of Megalechis.