Imminent threat of the predator fish invasion Salminus brasiliensis in a Neotropical ecoregion: eco-vandalism masked as an environmental project

A classification framework for interspecific trade-offs in aquatic ecology

In some cases, wildlife management objectives directed at multiple species can conflict with one another, creating species trade-offs. For managers to effectively identify trade-offs and avoid their undesirable outcomes, they must understand the agents involved and their corresponding interactions. A literature review of interspecific trade-offs within freshwater and marine ecosystems was conducted to illustrate the scope of potential interspecific trade-offs that may occur. We identified common pitfalls that lead to failed recognition of interspecific trade-offs, including, single-species management and limited consideration of the spatial and temporal scale of ecosystems and their management regimes. We devised a classification framework of common interspecific trade-offs within aquatic systems. The classification can help managers determine whether the conflict is species based through direct relationships (i.e., predator-prey, competition, other antagonistic relationships) or indirect relationships involving intermediate species (i.e., conflict-generating species) or whether the conflict is driven by opposing management objectives for species that would otherwise not interact (i.e., nontarget management effects). Once the nature and scope of trade-offs are understood, existing decision-making tools, such as structured decision-making and real-options analysis, can be incorporated to improve the management of aquatic ecosystems. Article Impact Statement: A synthesis of interspecific trade-offs in aquatic ecosystems supports their identification and resolution.

Invasive species trait-based risk assessment for non-native freshwater fishes in a tropical city basin in Southeast Asia

Biological invasions have created detrimental impacts in freshwater ecosystems. As non-native freshwater species include economically beneficial, but also harmful, species, trait-based risk assessments can be used to identify and prevent the import of potentially invasive species. Freshwater fishes are one of the most evaluated freshwater taxa to date. However, such assessments have mostly been done in sub-temperate to temperate regions, with a general lack of such research in the tropics. In view of this knowledge gap, this study aims to determine if a different set of traits are associated with successful establishment of non-native fishes within the tropics. In tropical Southeast Asia, Singapore represents a suitable model site to perform an invasive species trait-based risk assessment for the tropical region given its susceptibility to the introduction and establishment of non-native freshwater fishes and lack of stringent fish import regulation. A quantitative trait-based risk assessment was performed using random forest to determine the relative importance of species attributes associated with the successful establishment of introduced freshwater fishes in Singapore. Species having a match in climate, prior invasion success, lower absolute fecundity, higher trophic level, and involvement in the aquarium trade were found to have higher establishment likelihood (as opposed to native distributional range and maximum size being among the commonly identified predictors in subtropical/temperate trait-based risk assessments). To minimize invasive risk, incoming freshwater fishes could be screened in future for such traits, allowing lists of prohibited or regulated species to be updated. The findings could also potentially benefit the development of invasive species action plans and inform management decisions in the Southeast Asian region. Considering a geographical bias in terms of having relatively less documentation of biological invasions in the tropics, particularly Asia, this study highlights the need to perform more of such risk assessments in other parts of the tropics.

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 Oreochromisniloticus (Linnaeus, 1758) and Coptodonrendalli (Boulenger, 1897) (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.

Update on the ichthyofauna of the Piquiri River basin, Paraná, Brazil: a conservation priority area

Abstract: Knowledge of the fish species in river basins is among the minimum requirements for the management of water and fish resources. Therefore, the aim of this study was to update the fish species composition of the Piquiri River basin, upper Paraná River basin. Data were gathered from recent information published in specialized literature and records for ichthyology collections. This update reports the occurrence of 152 fish species distributed in 8 orders, 31 families, and 89 genera. Non-native species accounted for 20% of all species, and the construction of the Itaipu Power Plant and its fish ladder were the main vectors of introduction. Three percent of the species were endangered, and 11% were classified as migratory. The Piquiri River basin harbors a large number of species, some of which are rare, endangered, migratory, endemic, and even unknown by science. Because of this, maintaining the integrity of this river basin will support the persistence of regional biodiversity.