Aerobic metabolic scope mapping of an invasive fish species with global warming.

Climate change will exacerbate the negative effects associated with the introduction of non-indigenous species in marine ecosystems. Predicting the spread of invasive species in relation to environmental warming is therefore a fundamental task in ecology and conservation. The Baltic Sea is currently threatened by several local stressors and the highest increase in sea surface temperature of the world's large marine ecosystems. These new thermal conditions can further favour the spreading of the invasive round goby (Neogobius melanostomus), a fish of Ponto-Caspian origin, currently well established in the southern and central parts of the Baltic Sea. This study aims to assess the thermal habitat suitability of the round goby in the Baltic Sea considering the past and future conditions. The study combines sightings records with known physiological models of aerobic performance and sea surface temperatures. Physiological models read these temperatures, at sighting times and locations, to determine their effects on the aerobic metabolic scope (AMS) of the fish, a measure of its energetic potential in relation to environmental conditions. The geographical mapping of the AMS was used to describe the changes in habitat suitability during the past 3 decades and for climatic predictions (until 2100) showing that the favourable thermal habitat in the Baltic Sea has increased during the past 32 years and will continue to do so in all the applied climate model predictions. Particularly, the predicted new thermal conditions do not cause any reduction in the AMS of round goby populations, while the wintertime cold ranges are likely expected to preserve substantial areas from invasion. The results of this research can guide future monitoring programs increasing the chance to detect this invader in novel areas.

Conservation physiology of marine fishes: advancing the predictive capacity of models.

At the end of May, 17 scientists involved in an EU COST Action on Conservation Physiology of Marine Fishes met in Oristano, Sardinia, to discuss how physiology can be better used in modelling tools to aid in management of marine ecosystems. Current modelling approaches incorporate physiology to different extents, ranging from no explicit consideration to detailed physiological mechanisms, and across scales from a single fish to global fishery resources. Biologists from different sub-disciplines are collaborating to rise to the challenge of projecting future changes in distribution and productivity, assessing risks for local populations, or predicting and mitigating the spread of invasive species.

Hydrodynamic controls on connectivity of the high commercial value shrimp Parapenaeus longirostris (Lucas, 1846) in the Mediterranean Sea.

In the Strait of Sicily (SoS), a wide passage of the Mediterranean Sea, Parapenaeus longirostris, (Lucas, 1846; DPS hereafter) is the main target species of trawl fisheries, with an estimated annual market value of about 80 million euro. The exploitation of this resource is shared between Italian, Tunisian and Maltese bottom trawlers and its management raises social, economic and environmental interests. Recent stock assessment revealed high fishing mortalities and low size at first capture, thus promoting the adoption of a strategic plan for a sustainable management. However, the current knowledge of the geographical boundaries of the stock, supporting  the implementation of such management plan is still poor. In this respect, under different hydrodynamic regimes, particle-tracking modelling was used to explore connectivity between both, known and unexplored, spawning and nursery areas of DPS in the SoS. Ensembles scenarios derived by model outcomes displayed decadal changes in connectivity between spawning and nursery areas in the north side of the SoS, hence confirming the presence of a single stock in this area. Expanding the area of investigation, the model results showed weak connectivity between spawning ground in the north side of SoS and nurseries on the African shelf-break. This method could support the spatial management of the stock, such as the protection of the nursery and spawning areas, by providing estimates of how connectivity is influenced by hydrodynamic regimes at different temporal and spatial scales.

Predicting future thermal habitat suitability of competing native and invasive fish species: from metabolic scope to oceanographic modelling.

Global increase in sea temperatures has been suggested to facilitate the incoming and spread of tropical invaders. The increasing success of these species may be related to their higher physiological performance compared with indigenous ones. Here, we determined the effect of temperature on the aerobic metabolic scope (MS) of two herbivorous fish species that occupy a similar ecological niche in the Mediterranean Sea: the native salema (Sarpa salpa) and the invasive marbled spinefoot (Siganus rivulatus). Our results demonstrate a large difference in the optimal temperature for aerobic scope between the salema (21.8°C) and the marbled spinefoot (29.1°C), highlighting the importance of temperature in determining the energy availability and, potentially, the distribution patterns of the two species. A modelling approach based on a present-day projection and a future scenario for oceanographic conditions was used to make predictions about the thermal habitat suitability (THS, an index based on the relationship between MS and temperature) of the two species, both at the basin level (the whole Mediterranean Sea) and at the regional level (the Sicilian Channel, a key area for the inflow of invasive species from the Eastern to the Western Mediterranean Sea). For the present-day projection, our basin-scale model shows higher THS of the marbled spinefoot than the salema in the Eastern compared with the Western Mediterranean Sea. However, by 2050, the THS of the marbled spinefoot is predicted to increase throughout the whole Mediterranean Sea, causing its westward expansion. Nevertheless, the regional-scale model suggests that the future thermal conditions of Western Sicily will remain relatively unsuitable for the invasive species and could act as a barrier for its spread westward. We suggest that metabolic scope can be used as a tool to evaluate the potential invasiveness of alien species and the resilience to global warming of native species.