  Citation: Lipej, L.; Kovaˇ ci´ c, M.; Dulˇ ci´ c, J. An Analysis of Adriatic Ichthyofauna—Ecology, Zoogeography, and Conservation Status. Fishes 2022, 7, 58. https:// doi.org/10.3390/fishes7020058 Academic Editor: Reinhold Hanel Received: 11 February 2022 Accepted: 2 March 2022 Published: 4 March 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). fishes Article An Analysis of Adriatic Ichthyofauna—Ecology, Zoogeography, and Conservation Status Lovrenc Lipej 1, *, Marcelo Kovaˇ ci´ c 2 and Jakov Dulˇ ci´ c 3 1 Marine Biology Station, National Institute of Biology, Fornaˇ ce 41, 6330 Piran, Slovenia 2 Natural History Museum Rijeka, Lorenzov Prolaz 1, 51000 Rijeka, Croatia; marcelo@prirodoslovni.com 3 Institute of Oceanography and Fisheries, Šet. I. Meštrovi´ ca 63, 21000 Split, Croatia; dulcic@izor.hr * Correspondence: lipej@nib.si Abstract: The paper presents an analysis of biogeographic and habitat distribution patterns, and the conservation status data of Adriatic fishes, based on the last published checklist and evidence-based critical analyses of species presence. The total number of species recorded in the Adriatic is 449. The Adriatic has 58.8% of Mediterranean species richness, 76.1% of its families, and 87.8% of its orders. Among species discovered in the Adriatic after 2010, twelve species were attributed to biological invasion, mostly Atlantic immigrants or alien species, and ten species were attributed to improved research on the native ichthyofauna of the Adriatic area. About 58% of species are native species of Atlanto-Mediterranean origin, 21% are native species of wider global occurrence, 15% are Mediterranean or Mediterranean and Black Sea endemics and 5% originated outside Mediterranean Sea. The majority of species inhabit the benthic environment (71.9%), while others occur in the pelagic environment (20.7%) or are euryhaline (7.3%). The benthic littoral species are the most numerous Adriatic fishes, representing 40% of all species richness, whereas pelagic fishes are mainly eurybathic or epipelagic; only 3.6% of species are deep pelagic species. A Red Book of marine fishes of the Adriatic Sea is urgently needed to assess their conservation status, covering the entire Adriatic Sea and reviewing all fish species to assess their conservation status. Keywords: Adriatic ichthyofauna; evidence-based approach; zoogeography; habitat distribution; biological invasion; meridionalisation 1. Introduction Marine biodiversity in the Adriatic is attributed to its geological history, limited by its present bathymetric, hydrographic, and climatic characteristics, and influenced by present geographical connectivity and anthropogenic processes [1]. These characteristics have been crucial in shaping the peculiarities of Adriatic ichthyofauna. Although the Adriatic Sea is a part of the Mediterranean, it is an independent biogeographical and ecological subunit, which is evident in the composition and properties of its biological communities [2]. The marine biodiversity of the Mediterranean Sea is currently facing substantial changes in its flora and fauna [3]. It is rapidly changing due to the increasing arrival of non-indigenous fishes and other taxa [4–7]. Such changes have also been recorded in the Adriatic Sea. During the last few decades, various factors including climate change, anthropogenic activity, and “Lessepsian migration” have changed the composition of Adriatic ichthyofauna [5–10]. While “Lessepsian migration” is responsible for the arrival of non-indigenous species through the Suez Canal, climate change has caused northward spreading of southern, thermophilous species, a process known as meridionalisation [7–10]. Furthermore, extensive investigations carried out in recent decades have recognized species that have not been recorded in this area previously or led to the description of new species [2,5,7,11]. The only existing analysis of the zoogeographic distribution of Adriatic fishes was published about forty years ago by Jardas [12]. In addition to this time span, the number Fishes 2022, 7, 58. https://doi.org/10.3390/fishes7020058 https://www.mdpi.com/journal/fishes