Azzurro, E., Ballerini, T., Antoniadou, C., Aversa, G.D., Souissi, J.B., Blašković, A., Cappanera, V., Chiappi, M., Cinti, M-F, Colloca, F., Cvitković, I., D’Amen, M., Despalatović, M., Di Franco, A., Dimitriadis, C., Dragičević, B., Fanelli, E., Figuerola, L., Fortibuoni, T., Franzitta, G., Garrabou, J., Geloso, T., Ghanem, R., Gori, A., Hervat, M., Izquierdo-Muñoz, A., Linares, C., La Mesa, G., Merotto, L., Micallef, R., Miliou, A., Minelli, A., Moschella, P., Pannacciulli, F., Panzalis, P., Pavičić, M., Petrou, A., Ramos-Esplá, A.A., Saponari, L., Scarcella, G., Spoto, M., Stagličić, N., Vrdoljak, D., Weitzmann, B., Schembri, P.J. ClimateFish: A Collaborative Database to Track the Abundance of Selected Coastal Fish Species as Candidate Indicators of Climate Change in the Mediterranean Sea. Frontiers in Marine Science 2022.

Background:

Under the effects of global warming, many animals and plants are undergoing rapid distribution shifts. These changes can be particularly rapid in marine fishes, and many species have responded markedly to recent increases in sea temperature. ClimateFish is an open-access database, which collates abundance data for 7 Mediterranean indigenous and 8 nonindigenous fishes, proposed as candidate indicators of climate change. These species have been selected by a network of Mediterranean scientists based on their wide distribution, responsiveness to temperature conditions and easy identification. Data are periodically collected according to a standard visual census protocol in four different depth layers. At present, the database collates data on a total number of 101’771 observed individuals belonging to the 15 target species. Counts were realized along 3142 transects carried out in 7 Mediterranean countries between 2009 and 2021. This database, associated with climate data, offers new opportunities to investigate spatiotemporal effects of climate change and to test the effectiveness of each selected indicator. Data are available at https://doi.org/10.17882/86784.

The Mediterranean Sea is warming faster than any other marine region in the world (Pastor et al., 2020; Pisano et al., 2020), with increasingly drastic consequences on marine ecosystems (Albano et al., 2021; Garrabou et al., 2021) and on the services they provide to our societies. These changes can be particularly rapid in fish species, which are globally responding withmarked shifts in latitude or depth or both (Perry et al., 2005; Chaikin et al., 2022). Climate change is indeed driving species ranges toward the poles and increasing the risks of extinction when dispersal capabilities are limited, such as in the semi-enclosed Mediterranean basin (Ben Rais Lasram et al., 2010). During the last decades, several warm water species have expanded their geographical distribution and increased their abundance in theMediterranean Sea. This phenomenon, often indicated as “meridionalization” – i.e., meridional, or southern, species moving northward – (Bianchi and Morri, 1993; Riera et al., 1995) involves several warm-adapted coastal fishes (Azzurro, 2008; Azzurro et al., 2019), such as Sparisoma cretense (Ventura et al., 2019), and Thalassoma pavo (Vacchi et al., 2001), that have been recorded northward with respect to their original geographical distribution. Other visible changes are related to nonindigenous fishes of tropical origin, which are predicted to become increasingly successful and widely distributed under warming conditions (D’Amen and Azzurro, 2020; Golani et al., 2021). This phenomenon is often cited under the name of “tropicalization” (Bianchi and Morri, 2003).

At the same time, cold adapted and temperate native species, such as Sarpa salpa are rapidly losing their preferred climatic habitats and shrinking their distribution and abundance (Marras et al., 2015). Documenting climate-related changes is a key task to support current adaptation policies (O’Regan et al., 2021) and to evaluate the impact of such policies toward international biodiversity goals. However, in marine ecosystems, this goal is often challenged by the complexity of ecological transformation along with the pragmatic challenge of performing large scale studies with limited financial resources (Tiralongo et al., 2020). This stimulates efforts to identify and test essential biodiversity components and appropriate indicators (Jetz et al., 2019) to enable effective biodiversity monitoring, under a common and unified framework. Thus, the aim of this database is to collate information on a selected number of coastal fish species, which could serve as effective indicators of climate change effects in the Mediterranean Sea.