Brown Trout (Salmo trutta) Abundance and Biomass in Mediterranean Rivers: Environmental, Genetic, and Management Drivers

This dataset (CSV format) contains environmental, biological, genetic, and management data from 88 sampling sites in Mediterranean river basins of Catalonia (NE Iberian Peninsula) collected between 2016 and 2025, as described in the study “Brown Trout (Salmo trutta) Abundance and Biomass in Mediterranean Rivers: Environmental, Genetic, and Management Drivers”. The dataset includes 352 sampling observations derived from standardized electrofishing surveys conducted during low-flow periods.The data were used to analyse the environmental, biotic, genetic, and fisheries-management drivers of brown trout (Salmo trutta) population density, biomass, and size structure across six river basins (Ter, Llobregat, Cardener, Segre, Noguera Pallaresa, and Noguera Ribagorçana). Population metrics include total density and biomass as well as densities of juvenile and large individuals, together with environmental predictors describing habitat characteristics, hydrological regime, water chemistry, temperature, introduced species pressure, genetic introgression, and fishing regulation.The dataset can be used to investigate drivers of salmonid population dynamics, evaluate climate and biological invasion effects on freshwater fish populations, and support analyses of fisheries management in Mediterranean river systems.Contents: SITE_ID sampling site identifier YEAR sampling year BASIN river basin LATITUDE LONGITUDE DENSITY total brown trout density (ind·ha⁻¹) BIOMASS total brown trout biomass (kg·ha⁻¹) DENS_LT120 density of individuals DENS_GT220 density of individuals >220 mm fork length (ind·ha⁻¹) ELEV elevation of sampling site (m a.s.l.) SLOPE mean channel slope (degrees ×100) ALK alkalinity (mg CaCO₃ L⁻¹) COND electrical conductivity (µS cm⁻¹) NO3 nitrate concentration (mg L⁻¹) PO4 phosphate concentration (mg L⁻¹) Q_MEAN standardized mean annual discharge Q_LOW_DAYS number of low-flow days below the 10th percentile Q_MIN_RATIO relative summer minimum discharge Q_MAX_RATIO relative winter maximum discharge T_SUMMER mean July–August air temperature (°C; proxy for water temperature) T_EXT_DAYS number of extreme summer temperature days (above 95th percentile) DENS_INTROD density of introduced fish species (ind·ha⁻¹) LDH_INTROG genetic introgression (frequency of LDH-C* allele) FISH_REG fishing regulation category (harvest allowed vs catch-and-release)