Gestão de populações de truta-de-rio (Salmo trutta, L.) em rios do nordeste de Portugal: Será possível compatibilizar a conservação com a exploração de recursos piscícolas?

Abstract

Browntrout (Salmotrutta, L.) is a bioindicator species of the ecological quality of mountain rivers in the north and center of Portugal. The ecological requirements, high sensitivity to disturbances and their interest for recreational fishing, justify the sustain able management, balancing adequately the conservation and exploitation of these fish populations. In this context, the objectives of the present study were to assess the status and management of wild brown trout population sin the Montesinho Natural Park (MNP) and neighboring areas, supported by aprevious bioecological characterization. Thus, in the spring/summer of 2020,water quality, hydromorphology and macroinvertebrate and fish communities were characterized in 41 sampling sites (rivers Mente, Rabaçal, Tuela, Baceiro, Sabor, Igrejas, Onor, Maçãs and ribeira da Aveleda). The growth and population parameters of S. trutta for the Sabor and Baceiro rivers were determined and the success and dispersion of stocked brown trout, after their release, was monitored in four distinctriver reaches. The results obtained showed the excellent ecological integrity of the sites sampled in the sampling sites of headwater streams. On the other hand, in the downstream zones were detected signs of disturbance, such as water pollution, fragmentation of aquatic and riparian habitats, the introduction of non-native species and overfishing. These negative pressures contribute to low fish abundance and differences in growth and physica lcondition of wild brown trout populations. For these reasons, the use of stocking with brown trout rear edincaptivity is the main fishing management technique commonly used by the fish manager sin the NE of Portugal. However, the success rate has never exceeded 30% and the mobility of the released stocked fish is predominantly stationary orin downstream way. Taking into consideration the status of the study area (e.g.,the protected area of Montesinho Natural Park, Montesinho/Nogueira Special Conservation Area and the Meseta Ibérica Biosphere Reserve) and human andnatural pressures, specific conservation measures oriented towards the mitigation of impacts and the preservation of natural values will allow, within a framework of sustainability, the conservation and exploitation of river resources in the mountainous rivers of northeasternPortugal.