The How, the Why, and the What of a New Freshwater Fish Dataset of Individual Body Size in the Iberian Peninsula ^†

Never before have there been so many ecological datasets available. The organization, accessibility, and collection of ecological datasets create more opportunities among researchers to find new and original questions, perform strong analytical analyses, and gain reliability among the results obtained through alternative methodologies. In addition, increasing the number of ecological datasets in ecoregions and organisms more susceptible to global change may be particularly useful, in order to improve the understanding of ecological processes and mechanisms. Freshwater fish communities in the Iberian Peninsula show unique biological characteristics and high levels of endemicity, but they are sadly impaired by human impacts, including nutrient pollution, landscape changes, and climate warming. Despite previous efforts in creating publicly archived datasets of Iberian fish, most of them are based on specific geographical areas or species-centric approaches, including species occurrences and relative abundances. The individual body size of fish is the simplest metric to collect from the field but it has strong implications on the most physiological, ecological, and evolutionary processes of fish. Thus, a complete raw dataset covering broad spatial and temporal gradients of freshwater fish in the Iberian Peninsula, with information on the fish length and weight, would be a key step if we want to synthesize our current knowledge of Iberian fish trends in space and time. In this talk, we reflect on our own opinion on the how, the why, and the what of having such a dataset. We point out that a new open fish dataset of individual body size would fulfill its potential to advance the knowledge of freshwater fish in the Iberian Peninsula, and develop efficient management plans using size-based approaches, such as the community size spectrum or functional size diversity. We also emphasize that environmental factors (e.g., altitude, ecosystem size) that need to be integrated with the information of the biotic communities. Finally, we provide several suggestions to build this dataset by searching for synergies among researchers and practitioners to create a single unifying standard dataset of fish individual body size across freshwater habitats in the Iberian Peninsula.