Using a 2010 review of non-indigenous species (NIS) reported in the Mediterranean Sea as a baseline, this study undertakes a paramount revision of the non-indigenous species list in the region up to December 2021, re-evaluating the established, casual and failed introduction events of over 1366 taxa. In the light of new data and expert judgement, 14 species have been removed from the “established list” of the Mediterranean Sea inventory. The total number of validated NIS is close to 1000—751 established taxa and 242 casual taxa—while 23 species are considered as failed introduction. The rest are tagged as cryptogenic (58 taxa), questionable (70 taxa) or excluded (223 taxa). Mollusca have the highest diversity among established and casual NIS (230 taxa), followed by Pisces and Crustacea with 173 and 170 NIS respectively. The changes in establishment status reveal an accelerated rate of establishment (13%) between January 2020 and December 2021 (>6% yearly), compared to an establishment rate of 27% in the period 2011–2021 (<3% yearly). This increased establishment success is more pronounced in Crustacea (47%) and Pisces (43%) than in Polychaeta (27%) and phytobenthos (30%). In the period 2011–2021, 42% of the newly reported species were established (149 out of 352). On a shorter timescale, out of 79 new species reported in the period 2020–2021, 17 NIS (21.5%) have already established, a figure well above the 10% prediction of invasion theory on establishment success for Mediterranean marine NIS.

The lionfish, Pterois miles, is one of the most recent Lessepsian immigrants into the Mediterranean Sea, and it poses a serious threat to marine ecosystems in the region. This study assesses the basic biology and ecology of lionfish in the Mediterranean, examining morphometrics, reproduction and diet as well as population structure and distribution. The population density of lionfish has increased dramatically in Cyprus since the first sighting in late 2012; by 2018 aggregations of up to 70 lionfish were found on rocky grounds with complex reefs and artificial reefs in depths of 0-50 m. Lionfish in Cyprus become mature within a year, and adults are capable of spawning year-round, with peak spawning in summer when the sea-surface temperature reaches 28.4 C. The Cypriot lionfish grow faster and bigger than in their native range, and females are more common than males. Lionfish are generalist predators in these waters, as also found in their native range, consuming a range of teleost and crustacean prey, some of which are of high economic value (e.g., Spicara smaris and Sparisoma cretense) or have an important role in local trophic webs (e.g., Chromis chromis). Overall, the reproductive patterns, the presence of juveniles and adults throughout the year, the rapid growth rates and the generalist diet indicate that lionfish are thriving and are now already well established in the region and could potentially become the serious nuisance that they are in their temperate and tropical western Atlantic-invasive range.

Marine biota are redistributing at a rapid pace in response to climate change and shifting seascapes. While changes in fish populations and community structure threaten the sustainability of fisheries, our capacity to adapt by tracking and projecting marine species remains a challenge due to data discontinuities in biological observations, lack of data availability, and mismatch between data and real species distributions. To assess the extent of this challenge, we review the global status and accessibility of ongoing scientific bottom trawl surveys. In total, we gathered metadata for 283,925 samples from 95 surveys conducted regularly from 2001 to 2019. We identified that 59% of the metadata collected are not publicly available, highlighting that the availability of data is the most important challenge to assess species redistributions under global climate change. Given that the primary purpose of surveys is to provide independent data to inform stock assessment of commercially important populations, we further highlight that single surveys do not cover the full range of the main commercial demersal fish species. An average of 18 surveys is needed to cover at least 50% of species ranges, demonstrating the importance of combining multiple surveys to evaluate species range shifts. We assess the potential for combining surveys to track transboundary species redistributions and show that differences in sampling schemes and inconsistency in sampling can be overcome with spatio‐temporal modeling to follow species density redistributions. In light of our global assessment, we establish a framework for improving the management and conservation of transboundary and migrating marine demersal species. We provide directions to improve data availability and encourage countries to share survey data, to assess species vulnerabilities, and to support management adaptation in a time of climate‐driven ocean changes.

To deal with the difficulties of species differentiation and delimitation among the commercially important sardines from the genus Sardinella, an integrative approach was adopted, incorporating traditional taxonomy with four DNA markers (coI, cytb, 16s and nuclear rag2). Combining these methodologies has enabled a thorough re-description of three of the most common species of Sardinella of the Indo-west Pacific Ocean: white sardinella Sardinella albella, fringescale sardinella Sardinella fimbriata and the goldstripe sardinella Sardinella gibbosa, as well as a description of a new species, Gon's sardinella Sardinella goni, from the island of Boracay, Philippines. In addition, extensive widespread sampling of S. gibbosa reveals a significant genetic separation between the populations from the western Indian Ocean and the west Pacific Ocean, despite no supporting morphological differentiation. An updated morphological key of the species of Sardinella of the Indo-west Pacific Ocean is also provided in order to minimize future misidentifications within these economically important taxa. Finally, the genetic and morphological variabilities within and between the investigated species are used to discuss their biogeographical distribution and possible processes of speciation.