Small-sized fish: the largest and most threatened portion of the megadiverse neotropical freshwater fish fauna / Peixes de pequeno porte: a porção maior e mais ameaçada da fauna megadiversa de peixes de água doce neotropicais

Abstract: We introduce the work providing a synthetic description of the diversity and phyletic structure of freshwater fish in the Neotropical Region, especially emphasizing that of Brazil. This is accompanied by a discussion about environments of fish from small to medium sized to large, taking into account how it shaped their respective biologies/ecologies, as well as what they imply for their use by humans. We present, as figures, the results of our exploratory analysis of Brazilian Red Book of Threatened Species of Fauna (2018), focusing on the small-sized ones, with up to 15 cm of standard length. We continue to present the main human impacts in small fish environments, along with those suffered by medium to large fish environments, and then follow by their respective deleterious effects. Finally, we present a general synthesis, reinforcing the enormous importance of small fish conservation and their respective preferred environments, followed by our main conclusions, and possible conservation strategies.

Resumo: Iniciamos o trabalho fornecendo uma descrição sintética da diversidade e estrutura filética dos peixes de água doce da Região Neotropical, com ênfase naquela do Brasil, acompanhada de uma exposição sobre onde vivem os peixes de pequeno porte e os de porte médio a grande, levando em conta como isso moldou suas respectivas biologias/ecologias, e o que as mesmas implicam para seu uso pelos seres humanos. São apresentados, sob a forma de figuras, os resultados de uma análise exploratória dos dados sobre as 311 espécies de peixes ósseos de água doce contidos no Livro Vermelho da Fauna Brasileira Ameaçada de Extinção (2018), com ênfase naquelas de pequeno porte, com até 15 cm de comprimento padrão. Continuamos apresentando os principais impactos antrópicos nos ambientes de peixes de pequeno porte, juntamente com aqueles sofridos pelos ambientes de peixes de portes médio a grande, seguidos dos seus respectivos efeitos deletérios. Finalmente, concluímos com uma síntese geral, reforçando a enorme importância da conservação dos peixes de pequeno porte e seus ambientes preferenciais, e estratégias possíveis para conservação dos mesmos.

Identification key for fishes from coastal streams of the Atlantic forest of southeastern Brazil / Chave de identificação para os peixes de riachos costeiros da Mata Atlântica, sudeste do Brasil

Abstract In recent decades, current knowledge about fish from Neotropical streams has greatly increased, but is still deficient. Here we present an identification key for fishes from coastal freshwater streams from a large conservation area of Atlantic rainforest of southeastern Brazil, including 39 species. Considering that most of these species (61.2%) are endemic to the coastal streams, this identification key will be useful not only for the species recognition of the sampled area, but also for the surrounding coastal region.

Resumo Nas últimas décadas, o conhecimento acerca dos peixes de riachos neotropicais aumentou consideravelmente, mas apesar disso ainda é deficiente. Apresentamos aqui uma chave de identificação para as 39 espécies de peixes de uma grande unidade de conservação da Mata Atlântica do sudeste do Brasil. Considerando que a maioria destas espécies (61,2%) são endêmicas dos riachos costeiros, esta chave de identificação será útil não só para o reconhecimento de espécies da área amostrada, mas também da região costeira do entorno.

Fishes and aquatic habitats of the Orinoco River Basin: diversity and conservation.

About 1000 freshwater fishes have been found so far in the Orinoco River Basin of Venezuela and Colombia. This high ichthyological diversity reflects the wide range of landscapes and aquatic ecosystems included in the basin. Mountain streams descend from the high Andes to become rapid-flowing foothill rivers that burst out upon vast savannah flatlands where they slowly make their way to the sea. These white-water rivers are heavily laden with sediments from the geologically young Andes. Because their sediment deposits have formed the richest soils of the basin, they have attracted the highest density of human populations, along with the greatest levels of deforestation, wildfires, agricultural biocides and fertilizers, sewage and all the other impacts associated with urban centres, agriculture and cattle ranching. In the southern portion of the basin, human populations are much smaller, where often the only inhabitants are indigenous peoples. The ancient rocks and sands of the Guiana Shield yield clear and black water streams of very different quality. Here, sediment loads are miniscule, pH is very acid and fish biomass is only a fraction of that observed in the rich Andean tributaries to the north. For each region of the basin, the current state of knowledge about fish diversity is assessed, fish sampling density evaluated, the presence of endemic species and economically important species (for human consumption or ornamental purposes) described and gaps in knowledge are pointed out. Current trends in the fishery for human consumption are analysed, noting that stocks of many species are in steep decline, and that current fishing practices are not sustainable. Finally, the major impacts and threats faced by the fishes and aquatic ecosystems of the Orinoco River Basin are summarized, and the creation of bi-national commissions to promote standardized fishing laws in both countries is recommended.

Morphological variation in vanishing Mexican desert fishes of the genus Characodon (Goodeidae).

This study investigated a rapidly vanishing group of fishes in the genus Characodon (including Characodon lateralis and Characodon audax) from the upper Rio Mezquital drainage in Mexico. Using specimens from museum collections, morphological variation was assessed to quantify body shape differentiation among historic (i.e. extirpated and extant) collection sites. In both sexes, body shape (particularly head shape, the proportion of the caudal peduncle and the position and size of dorsal and anal fins) varied significantly among populations and species. Variation among collection sites could at least partially be attributed to geography, as the presence of distinct hydrographic units and a major waterfall coincided with major body shape differences. These results are discussed in the light of previously published molecular genetic analyses, as they have direct implications for taxonomic problems and the need for conservation measures for these endangered fishes.