Aerobic scope mapping of an invasive fish species in a global warming scenario

The aerobic metabolic scope (AMS) of marine ectotherms, a measure of their energetic potential in relation to environmental conditions, can be adopted as a metric to support the prediction of their habitat distribution through time and space. Considering that climate change will exacerbate the negative effects associated with the introduction of non-indigenous species in marine ecosystems, the prediction of their thermal habitat suitability is a central task in ecology and conservation. In this context we proposed a methodology to (i) infer the suboptimal AMS of an invader and (ii) to map its suitable thermal habitat during the past decades and in a global warming scenario. Specifically, we combined sightings records, known physiological models of aerobic performance and sea surface temperatures to determining their effects on the AMS of the fish. The methodology has been tested in the Baltic Sea that is currently displaying the highest increase in sea surface temperature of the world’s large marine ecosystems and that hosts the invasive round goby (Neogobius melanostomus), a fish of Ponto-Caspian origin. As the most widely dispersed invasive fish in the world this species has produced vast ecological impacts in colonized environments including the alteration of benthic invertebrate composition through predation and competition with native fish for food, shelter, and spawning grounds. Round goby, introduced to the Baltic Sea about 30 years ago, is well established in the southern and central parts of the basin but is still absent, aside from sporadic observations, from the north and coldest areas of this region. Its distribution is likely to expand beyond the current cold boundaries due to predicted climate change. However, the proportion of the currently uninvaded areas of the Baltic Sea that will become suitable thermal habitat for round goby, and how fast it can be expected to occur, remain uncertain. Via AMS mapping, we described changes in the round goby thermal 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 considering the current climate models predictions. Notably, although the predicted new thermal conditions do not cause any reduction in the AMS of round goby populations, the wintertime cold ranges are likely expected to preserve substantial areas from invasion. The results of this research are intended to guide future monitoring programs, increasing the chance to detect this invader in novel areas, and to enhance the reliability of the projected changes in ecological models that incorporate the thermal safety margins of native and non-indigenous species.