Proactively averting the collapse of Amazon fisheries based on three migratory flagship species.

Migratory species are the most important commercial fishes in the Amazon. They are also now the most threatened directly by some combination of overfishing, floodplain deforestation, and dam construction. Limited governmental monitoring and implemented regulations impede adequate management of the fisheries at adequate scale. We summarize the current stock status of the three most heavily exploited long-distance migratory species, which are two goliath catfishes (Brachyplatystoma rousseauxii and B. vaillantii) and the characiform Colossoma macropomum. In addition, we analyze impacts beyond overfishing on these species. Our results indicate: (i) the overfishing trends for these important species are either ominous or indicate the verge of collapse of the commercial fisheries based on them, and (ii) a dangerous synergy between overfishing, hydroelectric dams, and floodplain deforestation further challenge fisheries management of migratory species in the Amazon. We propose eight direct governmental actions as a proactive approach that addresses the main impacts on the fisheries. We consider that the most practical way to assess and manage overfishing of migratory species in the short run in an area as large as the main commercial fishing area in the Amazon is at market sites where enforced regulations can control fish catch. The management of the three species considered here has implications beyond just their sustainability. Their management would represent a paradigm shift where the governments assume their legal responsibilities in fishery management. These responsibilities include regulation enforcement, data collecting, inter-jurisdictional cooperation to protect migratory species at realistic life history scales, mitigation of the Madeira dams to assure goliath catfish passage to the largest western headwater region, and recognition of monitoring and managing wetland deforestation for the protection of fish and other aquatic and terrestrial biodiversity.

Structure and integrity of fish assemblages in streams associated to conservation units in Central Brazil

This study aims to characterize the spatial and seasonal distribution of the fish assemblage and evaluate the integrity of streams in a sustainable use area that includes integral protection conservation units in Distrito Federal, Central Brazil (Cerrado biome). For the study, 12 stretches of 8 streams were sampled in 2008 (dry season) and 2009 (wet season). For that evaluation was estimated the Physical Habitat Index (PHI), vegetation cover (VC), pH, dissolved oxygen, turbidity, and conductivity. We recorded 22 species, about eight undescribed species, by a total of 2,327 individuals. The most representative families in number of species were Characidae (31.8 percent), Loricariidae (31.8 percent), and Crenuchidae (13.6 percent). Knodus moenkhausii was the most abundant species with 1,476 individuals, added to Astyanax sp., Phalloceros harpagos, and Hasemania sp. they represent over 95 percent of the total abundance. The species Astyanax sp. (occurring in 79.2 percent of the stretches) and K. moenkhausii (50.0 percent) were considered constant in both seasons. The longitudinal gradient (River Continuum) exerts a strong influence on the studied assemblage. According to CCA, the variables that structure the fish assemblage are based on aspects related to water volume and habitat complexity. No seasonal variation in richness, diversity, abundance, and mass were detected. A cluster analysis suggests a separation of species composition between the stretches of higher and lower orders, which was not observed for seasonality. The streams were considered well preserved (mean PHI 82.9±7.5 percent), but in some stretches were observed anthropogenic influence, detected in the water quality and, mainly, on the riparian vegetation integrity. The exotic species Poecilia reticulata was sampled in the two stretches considered most affected by anthropogenic activities by PHI, conductivity, and VC.

Esse estudo teve como objetivo caracterizar a distribuição espacial e sazonal da taxocenose de peixes e avaliar a integridade dos córregos de uma área de uso sustentável que inclui unidades de conservação de proteção integral no Distrito Federal, Brasil Central (bioma Cerrado). Para o estudo, foram amostrados 12 trechos de oito cursos d'água em 2008 (estação seca) e 2009 (estação chuvosa). Para essa avaliação foram utilizados o Índice Físico do Habitat (IFH), cobertura vegetal (CV), pH, oxigênio dissolvido, turbidez e condutividade. Foram coletadas 22 espécies, sendo oito não descritas, em um total de 2.327 indivíduos. As famílias mais representativas em número de espécies foram Characidae (31,8 por cento), Loricariidae (31,8 por cento) e Crenuchidae (13,6 por cento). Knodus moenkhausii foi a espécie mais abundante, com 1.476 indivíduos, que juntamente com Astyanax sp., Phalloceros harpagos e Hasemania sp. representaram mais de 95 por cento da abundância total. As espécies Astyanax sp. (ocorrendo em 79,2 por cento dos trechos) e K. moenkhausii (50,0 por cento) foram consideradas constantes nas duas estações. O gradiente longitudinal (rio Contínuo) exerce forte influência na taxocenose estudada. De acordo com a CCA, as variáveis que estruturam a taxocenose íctica se baseiam em aspectos relacionados ao volume e complexidade dos habitats. Não foi detectada variação sazonal na riqueza, diversidade, abundância e massa. Uma análise de agrupamento sugere uma separação na composição de espécies entre trechos de maiores e menores ordens, o que não foi observado para a sazonalidade. Os córregos da APA encontram-se relativamente bem preservados (IFH médio de 82,9±7,5 por cento), porém em alguns trechos foi observada certa influência antrópica, detectada na qualidade da água e, principalmente, na integridade da vegetação ripária. A espécie exótica Poecilia reticulata foi coletada nos dois trechos considerados mais afetados por atividades antrópicas de acordo com o IFH, condutividade e CV.