Simulation of over‐exploitation of ornamental fish and its consequences for the functional structure of assemblages of Amazonian streams

Abstract

The consequences of over‐exploitation may seriously impair the integrity and functioning of ecosystems. When loss of species is accompanied by the loss of ecological processes, the effects are no longer just taxonomic and may affect the stability of the environments. Ornamental fishing is one of the main economic activities of the middle Negro River. Such activity is directed to a small number of species and has the Cardinal Tetra (Paracheirodon axelrodi) as the main target species. Given the potential effects this pressure and the lack of information on its consequences, the present study analysed, through simulations, the possible effects of depletion of ornamental fish populations on the functional structure of fish assemblages, represented by functional diversity (FD) and functional redundancy (FR) indexes. We sampled 13 streams exploited by the ornamental fishery, where we collected 4,286 specimens of 110 species, of which 22 were targeted as ornamental fishing. We found that the ornamental species corresponded, on average, to 27.8% of the species and 33.3% of the FD of the assemblages. In a scenario of complete exclusion of ornamental species, local communities would lose 24.6% of the FD and reduce up to 12% of the FR. With these results, it is possible to infer that the local extinction of exploited species would cause negative impacts on the multifunctionality and the resilience of the streams ecosystems. In this way, we emphasise the need for proper management of the ornamental fisheries aiming to the sustainability of the activity and to the conservation of ecosystem functionality.

Diversidade Funcional De Comunidades De Peixes De Riacho

“…Do ponto de vista da conservação e manejo de riachos e bacias hidrográficas, a diversidade funcional pode proporcionar informações valiosas. Por exemplo, a diversidade funcional pode ser utilizada como alvo na seleção de áreas prioritárias para a conservação (Strecker et al 2011), ou para avaliar os efeitos da extinção das espécies (Leitão et al 2016, Castanho et al 2020). Os descritores de diversidade funcional também possuem grande potencial para serem utilizados no biomonitoramento (Branquinho et al 2019).…”

“…aspectos específicos da estrutura funcional das comunidades e sua utilização deve ser justificada de acordo com os objetivos do estudo. Por exemplo, a riqueza funcional tem sido utilizada para informar sobre a perda de diversidade com a extinção das espécies (e.g., Leitão et al 2016, Castanho et al 2020. Descrever o quanto as espécies se complementam ou se sobrepõem em termos de papéis funcionais (uniformidade e divergência funcional) pode ser útil para a compreensão de processos envolvidos em padrões de co-ocorrência, das respostas das comunidades a distúrbios e dos efeitos da biodiversidade sobre o funcionamento de ecossistemas.…”

“…Esses índices têm sido amplamente utilizados em estudos de ecologia funcional, incluindo ictiofauna de riacho (e.g., Casatti et al 2015, Castanho et al 2020. Contudo, as dissimilaridades deduzidas pelo dendrograma podem resultar em perda de informação sobre a dissimilaridade real entre as espécies (Maire et al, 2015).…”

Patterns of Pelagic Fish Diversity in Floodplain Lakes of Whitewater and Blackwater Drainage Systems Within the Central Amazon River Basin of Brazil

“…At least 2,716 fish species, including 1,696 of which are endemic to the basin, have been identified so far (Reis et al, 2016;Dagosta and Pinna, 2019). It is also one of the earth's most endangered ecosystems, largely from ongoing anthropogenic stressors to its hydrology and biodiversity such as dam building that reduces connectivity among habitats (Kahn et al, 2014;Hurd et al, 2016;Santos et al, 2018), oil and gas development (Finer et al, 2008), overfishing of both food species and ornamental fish (Campos et al, 2015;Costa-Pereira and Galetti, 2017;Castanho et al, 2019), invasive alien species (Latini and Petrere, 2004), deforestation (Lobón-Cerviá et al, 2015), urbanization (Tregidgo et al, 2017), and droughts caused by deforestation and global warming (Castello et al, 2013;Freitas et al, 2013;Nazareno and Laurance, 2015). These problems have caused growing concern over the question of how to preserve fish species richness and also conserve fishery stocks, which are the most important sources of protein for human communities in the region (Castello et al, 2013).…”