Introductions of non-native fishes into a heavily modified river: rates, patterns and management issues in the Paranapanema River (Upper Paraná Ecoregion, Brazil)

Understanding the pathways and impacts of non-native species is important for helping prevent new introductions and invasions. This is frequently challenging in regions where human activities continue to promote new introductions, such as in Brazil, where aquaculture and sport fishing are mainly dependent on non-native fishes. Here, the non-native fish diversity of the Paranapanema River basin of the Upper Paraná River Ecoregion, Brazil was quantified fully for the first time. This river has been subject to considerable habitat alteration through hydroelectric dam construction and concomitant development of aquaculture and sport fishing. Through compilation of a non-native fish inventory by literature review, with complementary records from recent field studies, analyses were completed on the timings of introduction, and the taxonomy, origin and introduction vectors of the fishes. A total of 47 non-native fish are now present across the basin. Of these, 24 invaded from the Lower Paraná River following construction of Itaipu Dam that connected previously unconnected fish assemblages. Activities including fish stocking, aquaculture and sport angling continue to result in new introductions. Discounting Itaipu invasions, the introduction rate between 1950 and 2014 was approximately one new introduction every three years. Introduced fish were mainly of the Cichlidae and Characidae families; most species were from other South American ecoregions, but fishes of African, Asian, North American and Central American origin were also present. These introductions have substantially modified the river’s fish fauna; when coupled with altered lentic conditions caused by impoundment, this suggests that the river’s native fishes are increasingly threatened

Escapes of non-native fish from flooded aquaculture facilities: the case of Paranapanema River, southern Brazil

Non-native species are a major driver of biodiversity loss. Aquaculture activities play a key role in introductions, including the escape of fishes from fish farm facilities. Here, the impact of flooding due to El Niño rains in 2015/2016 in the Lower and Middle Paranapanema River basin, southern Brazil, was investigated by evaluating fish escapes from 12 fish farms. The flooding resulted in the escape of approximately 1.14 million fishes into the river, encompassing 21 species and three hybrids. Non-native species were the most abundant escapees, especially Oreochormis niloticus and Coptodon rendalli (96% of all fish). Only seven native fishes were in the escapee fauna, comprising 1% of all fish. Large floods, coupled with inadequate biosecurity, thus resulted in considerable inputs of non-native fish into this already invaded system

Influence of cage fish farming on the diet of dominant fish species of a Brazilian reservoir (Tiete River, High Parana River basin)

The cage farming of aquatic organisms was initiated 50 years ago, and was introduced to Brazil in the 1990's. In these systems, there is an input of organic matter from ration that is not totally used by the cage fishes, becoming available for the organisms of adjacent biota, including fish fauna. The aim of this work is to evaluate the interference in the diet of three dominant fish species (Plagioscion squamosissimus Heckel, 1840, Astyanax altiparanae Garutti and Britski, 2000 and Metynnis maculatus Kner, 1858) associated with ish cage farming. For determination of the diet, the Alimentary Index (AI) was used. In both stretches (around cage farm and control), P. squamosissimus selected aquatic insects, while A. altiparanae preferred terrestrial insects and M. maculatus eats ration remains. Diferences in abundance of these feeding resources found of the stomach content were observed among the two stretches. Thus, the small alterations in the diets of P. squamosissimus and A. altiparanae, indicate that cage farming can change the diet of resident species in reservoirs. This practice also influences the population structure of fish species, since higher middle standard lengths were found in A. altiparanae and P. squamosissimus populations resident around cage farms, in relation to the control stretch.A utilização de sistemas de criação em tanques-rede iniciou-se há mais de 50 anos, sendo implantada no Brasil em meados de 1990. Nesses sistemas, há uma entrada de matéria orgânica decorrente do manejo, que se torna disponível para os demais organismos da biota adjacente, incluindo a fauna de peixes residentes. O objetivo deste trabalho é avaliar a influência da atividade de piscicultura em tanquesrede na composição da dieta das três espécies de peixes mais abundantes (Plagioscion squamosissimus Heckel, 1840, Astyanax altiparanae Garutti and Britski, 2000 and Metynnis maculatus Kner, 1858) atraídas por essa atividade. Para determinação da dieta utilizou-se o Índice Alimentar (IAi). Em ambos os trechos (tanquesrede e controle), P. squamosissimus apresentou preferência por insetos aquáticos, enquanto A. altiparanae por insetos terrestres e M. maculatus por restos de ração. Constata-se que há diferenças quanto à abundância desses itens alimentares encontrados no conteúdo estomacal entre os trechos estudados. Assim, infere-se que as pequenas alterações na dieta de P. squamosissimus e A. altiparanae, aliadas a dieta caracterizada para as três espécies alvo, quando comparadas com a literatura, indicam que os empreendimentos de piscicultura em tanques-rede alteram a dieta das espécies de peixes residentes nos reservatórios. Também, influenciam na estrutura populacional, visto que já foram evidenciados maiores comprimentos padrões médios nas populações de A. altiparanae e P. squamosissimus residentes no entorno dos tanques-rede em relação ao trecho controle

Assessment of the ichthyofauna in stretches under the influence of Salto Grande Reservoir (Middle Paranapanema River, SP/PR, Brazil).

Aim: To analyze the composition, species richness and spatial distribution of the fish fauna in the area under influence of the Salto Grande Reservoir; Methods: Fish were caught every two months from November/05 to October/06, using gill nets, seining nets and sieve; Results: It was registered 67 fish species, 1,964 individuals and 146.2 kg, representing CPUEn of 1,964 and CPUEb of 278 kg. The most representative orders were Characiformes, with 29 species, Siluriformes (21 species) and Perciformes (11 species) Nine non-native species were registered. The most abundant species in the reservoir were Astyanax altiparanae, Steindachnerina insculpta and Acestrorhynchus lacustris, indicating the predominance of medium and small fishes in this reservoir. The dendrogram of similarity separated the Dam and Pedra Branca stretches from Pardo River Mouth, indicating differences in the assemblages. The species turnover among the stretches was demonstrated by the beta diversity, which may be related to the diversity of habitat; Conclusions: Although being a small reservoir, it displays great habitat diversity, reflecting in the composition and structure of fish assemblages.Objetivo: analisar a composição, a riqueza e a distribuição espacial da fauna de peixes dos diversos trechos sob a área de influência do reservatório de Salto Grande; Métodos: Foram realizadas coletas bimestrais no período de novembro/05 a outubro/06, utilizando-se de redes de espera, arrasto e peneirão; Resultados: Foram registradas 67 espécies, 1.964 indivíduos e 146,2 kg, representando CPUEn de 3.804 indivíduos e CPUEb de 278 kg. As ordens mais representativas foram Characiformes, com 29 espécies, Siluriformes (21 espécies) e Perciformes (11 espécies). Cabe ressaltar que nove espécies são não-nativas. As espécies mais abundantes no reservatório como um todo foram Astyanax altiparanae, Steindachnerina insculpta e Acestrorhyncus lacustris, indicando o predomínio de peixes de médio e pequeno porte neste reservatório. O dendograma de similaridade distanciou os trechos Barragem e Pedra Branca do trecho Foz do rio Pardo, indicando diferenças nas assembleias. A análise da diversidade mostrou que ocorre substituição de espécies entre os trechos o que pode estar relacionado com a diversidade de habitats; Conclusões: Embora o reservatório seja pequeno, apresenta grande diversidade de habitats, o que reflete na composição e estrutura das assembléias de peixes