Rising temperatures, falling fisheries: causes and consequences of crossing the tipping point in a small-pelagic community

Global change has profound effects on marine species, communities, and ecosystems. Among these impacts, small pelagics have emerged as valuable indicators for detecting regime shifts in fish stocks. They exhibit swift responses to changes in ocean variables, including decreased abundances, accelerated juvenile growth rates, early maturation, and reduced adult sizes in warm waters. However, each pelagic species occupies a unique local ecological niche, that reflects the sum of all environmental conditions. Consequently, their responses to environmental changes manifest in distinct ways. We explore here how global change affects small pelagics in the Madeira Archipelago (NE Atlantic Ocean) at (i) community level, by studying the effects of climate change over a 40-year (1980-2019) period on small pelagic landings, and (ii) population level, by studying the effects on the life-history traits of the two most abundant species, Scomber colias and Trachurus picturatus. Our study demonstrated that anomalies in the Sea Surface Temperature and the North Atlantic Oscillation caused a regime shift within the small pelagic community. Both environmental predictors explained 88.9% of the community landings oscillations. S. colias appears to exhibit a relatively more favorable adaptive response to climate change compared to T. picturatus. Understanding the species-specific ecological responses of small pelagic fish to global change is crucial for effective management and conservation efforts in the face of ongoing environmental scenarios.