Adaptive life history strategies of the Adriatic commercial Gadiformes facing fishing pressure and climate change

Understanding the biology, ecological interactions, and population trends of key marine species is essential for achieving sustainable marine resource management. This is particularly true for those basins characterised by high levels of anthropogenic impacts and high susceptibility to climate change, whose negative effects can be interactive and unpredictable. The Adriatic Sea represents the paradigmatic example, showing the highest level of fishing pressure and warming trend in the Mediterranean area. For its unique hydrographic and environmental features, this basin is considered one of the last cold refugia and it hosts several species with affinity to relatively cold waters, such as the Gadiformes. Despite most of them having been commercially exploited, there is a lack of knowledge about their life cycles and the effects of climate on their populations. This thesis focuses on some gadiform species, investigating their biological responses to increasing sea temperatures and high fishing exploitation. I used an experimental approach to investigate the life history traits of whiting, blue whiting, and poor cod and compare their current growth performances with samples collected between 1985 and 1991. Then, I complemented the experimental part by applying a joint species distribution model to explore the influence of some environmental factors on the abundance of five Adriatic gadiforms (whiting, blue whiting, poor cod, silvery pout, and European hake), using data from the MEDITS surveys carried out between 1998 and 2020. The integration of different methodologies allowed me to highlight both common and species-specific variation patterns. On the one hand, the experimental approach allowed me to observe a common pattern of size reduction in the three gadid species, on the other hand, the modelling approach revealed species-specific levels of sensitivity to sea warming. The results of the present study underscore the importance of using more complex and comprehensive approaches to effectively inform management policies.