Protect the Natives to Combat the Aliens: Could Octopus vulgaris Cuvier, 1797 Be a Natural Agent for the Control of the Lionfish Invasion in the Mediterranean Sea?

Seahorse Predation by Octopuses in the Caribbean and the West Pacific

There is much documentation about seahorses (Hippocampus spp.) being threatened by habitat degradation and overfishing, but relatively few published studies mention their natural predators. The present study documents three cases in which seahorses are being caught by octopuses. In one case, the seahorse was partly consumed. These observations made at Bonaire (Caribbean Netherlands) and New South Wales (Australia) suggest that predation on seahorses by octopuses may be more widespread and common than previously thought.

Reproductive dynamics of the invasive lionfish (Pterois miles) in the Eastern Mediterranean Sea

The lionfish Pterois miles invaded the Mediterranean Sea in 2012 and spread fast to the entire eastern basin. This study provides evidence of successful spawning and the first detailed analysis of P. miles ovarian dynamics in the Mediterranean Sea. The ovarian reproductive phases of mature females collected from Cyprus (eastern Mediterranean) between September 2017 and August 2018 were analysed, both macroscopically and histologically. The results suggested a prolonged oocyte recruitment and development season, and a spawning season that primarily occurred during summertime, even though spawning-capable females were caught also in autumn. A year-round spawning activity may have been inhibited due to seasonal variations in water temperature. Multiple oocyte developmental stages co-occurred in females at different reproductive phases, indicating that more than one oocyte batches were released per spawning season. The analysis of the spawning batch formation enabled the batch fecundity estimation at 3225-63149 oocytes. The oocyte development pattern described in this study shared characteristics with the indeterminate fecundity type, where new oocytes are recruited to the secondary growth phase in parallel with spawning activity. Climate change is likely to extend the spawning season of lionfish in the Mediterranean Sea and further favour its invasion. The information provided in this study is vital for the design of strategic and effective management plans to restrain the expansion of this highly invasive fish.

Improving predictions of invasive fish ranges combining functional and ecological traits with environmental suitability under climate change scenarios

Biological invasions represent one of the main threats to marine biodiversity. From a conservation perspective, especially in the context of increasing sea warming, it is critical to examine the suitability potential of geographical areas for the arrival of Range-Expanding Introduced and Native Species (REINS), and hence anticipate the risk of such species to become invasive in their new distribution areas. Here, we developed an empirical index, based on functional and bio-ecological traits, that estimates the Invasive Potential (IP; i.e. the potential success in transport, introduction and population establishment) for a set of 13 fishes that are expanding their distributional range into the Mediterranean Sea, the most invaded sea in the world. The IP index showed significant correlation with the observed spreading of REINS. For the six species characterized by the highest IP, we calculated contemporary and future projections of their Environmental Suitability Index (ESI). By using an ensemble modelling approach, we estimated the geographical areas that are likely to be the most impacted by REINS spreading under climate change. Our results demonstrated the importance of functional traits related to reproduction for determining high invasion potential. For most species, we found high contemporary ESI values in the South-eastern Mediterranean Sea and low to intermediate contemporary ESI values in the Adriatic Sea and North-western Mediterranean sector. Moreover, we highlighted a major potential future expansion of high ESI values, and thus REINS IP, towards the northern Mediterranean, especially in the northern Adriatic Sea. This potential future northward expansion highlights the risk associated with climate-induced impacts on ecosystem conservation and fish stock management throughout the entire Mediterranean Sea.

Invasive Species Control: Predation on the Alien Crab Percnon gibbesi (H. Milne Edwards, 1853) (Malacostraca: Percnidae) by the Rock Goby, Gobius paganellus Linnaeus, 1758 (Actinopterygii: Gobiidae)

Invasive alien species (IAS) are one of the greatest causes of native species extinction. Indeed, they represent a global threat for biodiversity and can also affect the economy and human health. The colonization success of IAS is presumably not only due to their biological and ecological characteristics, but also to the lack of predators and/or parasites in the invaded new areas. In the present work, we demonstrate evidence of predation of the invasive alien crab Percnon gibbesi (H. Milne Edwards, 1853) by the Rock Goby Gobius paganellus Linnaeus, 1758. The diet of G. paganellus was studied analyzing the stomach content of 162 specimens collected in the central Mediterranean Sea. The results obtained from the calculation of the diet indices, namely, frequency of occurrence (%F), percentage weight (%W), percentage abundance (%N), and the Index of Relative Importance (%IRI), showed that small benthic crustaceans were the main prey types. Additionally, these indices and the Levins’ index (Bi) clearly indicated that the invasive crab P. gibbesi was by far the most abundant prey type in the diet of G. paganellus. The relevance of this predator–prey interaction and the role of native species for the biological control of invasive ones are discussed. We also provide a general view on the diet of G. paganellus and other biological and ecological aspects of specimens studied from the central Mediterranean Sea.

The Case of Lionfish (Pterois miles) in the Mediterranean Sea Demonstrates Limitations in EU Legislation to Address Marine Biological Invasions

The European Regulation (EU) 1143/2014 on Invasive Alien Species entered into force in 2015, with the aim to fulfill regional and international biodiversity goals in a concerted manner. To date, the Regulation listed 66 Invasive Alien Species (IAS) that are subject to legal controls. Only one of these is marine. A recent lionfish (Pterois miles) invasion has been closely monitored in the Mediterranean and a detailed risk assessment was made about the profound impacts that this invasive fish is likely to have on the fisheries and biodiversity of the region. In 2016–21, lionfish rapidly became dominant predators along Eastern Mediterranean coasts, yet the process for their inclusion on the EU IAS list has been lengthy and is ongoing. There is an urgent need to learn from this experience. Here, we recommend improvements to the Regulation 1143/2014 and the risk assessment process to protect marine ecosystems and secure the jobs of people that rely on coastal resources.