Many studies demonstrated that there is a correlation among water temperatures, species distribution and other global drivers, such as biological invasions and pollution. These changes are particularly evident in the Mediterranean Sea, which is warming faster than any other marine region in the world. However, despite the relevance of these changes for conservation and adaptation measures, observational studies are often fragmented and lacking a homogeneous methodology. This fragmentation is an obstacle to the availability of reliable information to stakeholders and decision-makers.

This explains the growing need of integrated monitoring and assessment systems to capture the ongoing transformations of marine ecosystems and to bring them into the policy agendas. To achieve this, the use of standardized and cost-effective procedures are key principles for collecting and integrating information from stakeholders across national boundaries. A pilot study focused on the Mediterranean Sea, a hotspot for climate change and biological invasions, to assess changes in fish abundance and distribution. In order to achieve this purpose, the researchers accessed the local ecological knowledge (LEK) of small-scale and recreational fishers. In fact, fishers are a particularly interesting group of stakeholders, as they spend a considerable proportion of their lives in close contact with the marine environment and they become familiar with local species. Therefore, their personal experience and expert knowledge can provide precious complementary information and can be used to set effective monitoring practices. Knowledgeable fishers with more than 10 years of experience were identified and selected and individual face-to-face interviews were realised according to a standard protocol. Respondents were asked to mention the species perceived as “new” or increasing in different fishing areas.

Over 500 fishers across 9 different countries were interviewed and 75 species were mentioned by the respondents, mostly warm-adapted species of both native and exotic origin. Fishers belonging to the same bio-geographic sectors described coherent spatial and temporal patterns. This information demonstrates that the LEK methodology might be applied successfully beyond the local scale, across national borders and jurisdictions, and could reinforce the potential for adaptive ecosystem-based management. In fact, this methodology, which has demonstrated to provide tangible results at regional scale, could be extended to assessments at global scale, if properly designed and organised. It could be instrumental to help local communities to better understand, manage and adapt to the ongoing changes driven by climate change and biological transformations. The LEK protocol is currently applied across different Mediterranean countries and adopted by five Mediterranean marine protected areas generating new data.