Individual body mass and length dataset for over 12,000 fish from Iberian streams.

We provide a unique fish individual body size dataset collected from our own sampling and public sources in north-eastern Spain. The dataset includes individual body size measures (fork length and mass) of 12,288 individuals of 24 fish species within 10 families collected at 118 locations in large rivers and small streams. Fish were caught by one-pass electrofishing following European standard protocols. The fish dataset has information on the local instream conditions including climatic variables (i.e., temperature and precipitation), topography (i.e., altitude), nutrient concentration (i.e., total phosphorus and nitrates), and the IMPRESS values (a measure of cumulative human impacts in lotic ecosystems). The potential uses of this new fish dataset are manifold, including developing size-based indices to further estimate the ecological status of freshwater ecosystems, allometric models, and analysis of variation in body size structure along environmental gradients.

TREHS: An open-access software tool for investigating and evaluating temporary river regimes as a first step for their ecological status assessment.

When the regime of a river is not perennial, there are four main difficulties with the use of hydrographs for assessing hydrological alteration: i) the main hydrological features relevant for biological communities are not quantitative (discharges) but qualitative (phases such as flowing water, stagnant pools or lack of surface water), ii) stream flow records do not inform on the temporal occurrence of stagnant pools, iii) as most of the temporary streams are ungauged, their regime has to be evaluated by alternative methods such as remote sensing or citizen science, and iv) the biological quality assessment of the ecological status of a temporary stream must follow a sampling schedule and references adapted to the flow- pool-dry regime. To overcome these challenges within an operational approach, the freely available software tool TREHS has been developed within the EU LIFE TRIVERS project. This software permits the input of information from flow simulations obtained with any rainfall-runoff model (to set an unimpacted reference stream regime) and compares this with the information obtained from flow gauging records (if available) and interviews with local people, as well as instantaneous observations by individuals and interpretation of ground-level or aerial photographs. Up to six metrics defining the permanence of water flow, the presence of stagnant pools and their temporal patterns of occurrence are used to determine natural and observed river regimes and to assess the degree of hydrological alteration. A new regime classification specifically designed for temporary rivers was developed using the metrics that measure the relative permanence of the three main phases: flow, disconnected pools and dry stream bed. Finally, the software characterizes the differences between the natural and actual regimes, diagnoses the hydrological status (degree of hydrological alteration), assesses the significance and robustness of the diagnosis and recommends the best periods for biological quality samplings.