LWR parameters can also be an important tool for supporting fish biology studies, fisheries management plans, fish diversity conservation actions and maintenance of ecosystem services (Oliveira, Loverde-Oliveira, Mateus, & Teixeira-de Mello, 2014). Campos Gerais National Park (CGNP) is a protected area located in the state of Paraná, southern Brazil. It is a remnant of the Atlantic rainforest, a biodiversity hotspot. The park is in an ecoregion characterized by the predominance of Araucaria angustifolia (Bertol.) Gunze, popularly known as Parana Pine, this tree is a critically endangered species (Thomas, 2013). CGNP was created in 2006 and aims to preserve native, endemic and endangered species. However, the park has been economically exploited by landowners, with negative impacts such as pollution, erosion, riparian vegetation degradation and introduction of non-native species (Oliveira, 2014). In addition, the CGNP does not have a management plan and studies of continental water fishes in the region are scarce, which makes local preservation difficult. In this context, this study is the first investigation of LWR parameters of seven fish species from the CGNP. We hope to contribute to the database needed to develop the park's management plan and conservation actions for the investigated species. 2 | MATERIAL S AND ME THODS Fishes used for the Length-Weight Relationship parameters were collected in nine streams of the Ribeira of Iguape River basin, inside the CGNP, near Ponta Grossa city, in Paraná, Brazil (Figure 1).