RESEARCH PAPER How a multidisciplinary approach involving ethnoecology, biology and fisheries can help explain the spatio-temporal changes in marine fish abundance resulting from climate change Josep Lloret 1 *, Ana Sabatés 2 , Marta Muñoz 1 , Montserrat Demestre 2 , Ignasi Solé 3 , Toni Font 1 , Margarida Casadevall 1 , Paloma Martín 2 and Sílvia Gómez 4 1 Faculty of Sciences, University of Girona, Campus Montilivi, 17071 Girona, Spain, 2 Institut de Ciències del Mar, CSIC, Pg. Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain, 3 Escola Superior d’Enginyers Industrials, Polytechnic University of Catalonia, Diagonal 647, Barcelona, Spain, 4 Dept of Social Anthropology, University of Barcelona, Montalegre 6, 08001 Barcelona, Spain ABSTRACT Aim Predicting the impact of climate change on marine ecosystems or how fish and other species are adapting to rising sea temperatures is still subject to much uncertainty, despite considerable progress in recent years. In this study we assess whether our understanding of the impact of sea warming on marine fish can be enhanced with an interdisciplinary approach that collates data from fisheries, fishermen and scientific research. By doing this, we aim to shed light on the major changes in the abundance and diversity of warm and cold water fish in recent decades in relation to sea warming. Location This study was conducted in the north-western Mediterranean, where the impacts of global warming are particularly critical because range shifts are physically constrained. Methods We collected and combined statistical data from fisheries, the tradi- tional ecological knowledge of fishermen (TEK), reproductive data (histological gonad analyses and ichthyoplankton surveys) and extensive research into the rel- evant literature (including systematic catalogues and museum collections and their databases). Results We have found that changes in the abundance of fish have followed a particular spatio-temporal sequence, with three different phases of coloniza- tion in the case of warm-water species (occasional occurrence, common presence and establishment), and three phases of regression (abundance reduction, range contraction and disappearance from the catch) in the case of cold-water species. Main conclusions Overall, the results show that this multidisciplinary approach, combining qualitative and quantitative information from different sources, pro- vides new insight into the observed changes in fish diversity and abundance in relation to climate change. Keywords Ethnoecology, fisheries, ichthyoplankton, reproduction, sea warming, time-series analysis. *Correspondence: Josep Lloret, University of Girona, Faculty of Sciences, Campus Montilivi, 17071 Girona, Spain. E-mail: josep.lloret@udg.edu Global Ecology and Biogeography, (Global Ecol. Biogeogr.) (2014) © 2014 John Wiley & Sons Ltd DOI: 10.1111/geb.12276 http://wileyonlinelibrary.com/journal/geb 1