Recreational fishers consistently inform about different meridionalization dynamics of two Mediterranean subregions

Marine recreational fishers accumulate a vast amount of local ecological knowledge (LEK) during their fishing activity that can be of paramount importance for monitoring how climate change affects fish assemblages. We assessed LEK of recreational fishers to investigate the increase in the abundance of 5 northward-expanding indigenous thermophilic fish species in 2 Mediterranean subregions. We accessed LEK through an online survey completed by 794 re- creational fishers (386 from the Adriatic/Ionian subregion and 408 from the Tyrrhenian/Ligurian subregion). The species perceived to have increased most in abundance were Pomatomus salta- trix (71% of replies) followed by Sphyraena viridensis (58%). The remaining species (Sparisoma cretense, Balistes capriscus and Coryphaena hippurus) ranged between 17 and 25%. Recreational fishers have a stable system of beliefs about meridionalization, which is perceived homogeneously between recreational anglers and recreational spearfishers. Our results indicate that latitude is negatively correlated with meridionalization in the Adriatic/Ionian, but not in the Tyrrhenian/ Ligurian Seas, suggesting that meridionalization of the Adriatic/Ionian Seas could be a process that has temporally lagged with respect to the Tyrrhenian/Ligurian Seas. Our study demonstrates that LEK of recreational fishers can be easily accessed on a large geographical scale and can be useful to monitor changes in the distributions of data-limited species such as those studied here.