Changes in biogeographic patterns of coastal fishes: Indicators of tropicalization in the Canary Islands over the last 40 years

The Canary Islands are a key marine biodiversity hotspot in the eastern-central Atlantic. Coastal fishes, characterized by extensive taxonomic and functional diversity, serve as a highly representative group in nearshore environments, occupying a wide range of ecosystems. This study focuses on three significant milestones in the publication of comprehensive checklists for the Canary Islands' ichthyofauna during 1985-1991, 2002, and 2019-2024. Coastal fish species (0-200 m depth) were reviewed and updated, revealing biogeographic patterns and vertical distribution ranges for the region. The primary aim is to evaluate potential indicators of tropicalization by examining changes in the percentage of fish species with warm-water affinities, thereby identifying shifts in the composition of the Canarian marine ichthyofauna. This approach provides a distinct and complementary perspective on the tropicalization process, particularly its initial phase. Special emphasis is placed on the increasing proportion of warm-water species compared to those with Atlanto-Mediterranean (temperatewater) affinities. Additionally, an inventory was compiled documenting historical records of primarily exotic and non-native species, including their biogeographic patterns, dispersal mechanisms, observed bathymetric ranges, year of first record, current status, and criteria used to classify them as established in the Canary Islands.