Globally, our knowledge on lake fisheries is still limited despite their importance to food security and livelihoods. Here we show that fish catches can respond either positively or negatively to climate and land-use changes, by analyzing time-series data (1970–2014) for 31 lakes across five continents. We find that effects of a climate or land-use driver (e.g., air temperature) on lake environment could be relatively consistent in directions, but consequential changes in a lake-environmental factor (e.g., water temperature) could result in either increases or decreases in fish catch in a given lake. A subsequent correlation analysis indicates that reductions in fish catch was less likely to occur in response to potential climate and land-use changes if a lake is located in a region with greater access to clean water. This finding suggests that adequate investments for water-quality protection and water-use efficiency can provide additional benefits to lake fisheries and food security.

The narrow-clawed crayfish Pontastacus leptodactylus is a large native European astacid crayfish species distributed in the drainage area of the Azov, Black and Caspian Seas. The species shows immense morphological diversity across its range. Various species and subspecies have been described and, recently, eight species and two subspecies were confirmed in the updated classification of freshwater crayfishes. However, genetic diversity studies of the species are scarce, mostly from limited geographical areas. Therefore, we aimed to analyse the genetic diversity of this species using mtDNA and nuDNA from across their distributional range to verify the presence of described species. Analyses of individuals from 65 populations and 14 countries confirmed the existence of three divergent mtDNA phylogroups corresponding to the geographical area of Central and Southern Europe, Eastern Europe and Asia, and Turkey. Analysis of ancestral ranges revealed the Black Sea basin as the most likely area of origin. The nuDNA analysis showed low diversity partially corresponding to the mtDNA pattern. All analyses showed mitonuclear discordance indicating the existence of a single species. Therefore, we point out the possibility of taxonomic inaccuracy with the current number of valid species within the P. leptodactylus species complex.

The release of ornamental pets and associated pathogens outside their native range might directly or indirectly impact the recipient community. In temperate regions, e.g., central Europe, feral freshwater species of tropical and sub-tropical origins are mainly constrained to thermally polluted waters and thermal springs. However, species with high environmental plasticity and reproduction rates, such as the shrimp Neocaridina davidi, may adapt to colder water regimes over time. A widening thermal niche may eventually overcome thermal barriers, further expanding the range and enhancing transmission opportunities for host generalist parasites. This study assesses the observed (field observations) and theoretical (species distribution models) range expansion of N. davidi and associated parasites in Europe. We report three newly established N. davidi populations from thermally polluted waters in central Europe (Germany, Hungary, and Slovakia) and provide further evidence of its range expansion into colder environments. Species distribution models predict thermally suitable habitats in the Mediterranean and a foreseeable expansion into Western Europe and the Balkans by 2050. We confirm the presence of the microsporidian parasite Ecytonucleospora hepatopenaei in feral N. davidi populations across Europe and expand the list of microsporidians found in this host from two to four. Furthermore, we provide the first evidence of parasite spillover from/to the invasive crayfish Procambarus clarkii, suggesting that parasite exchange with native biota might be possible. Such possibility, coupled with an ongoing range expansion of N. davidi bolstered by human-mediated introductions and climate change, will likely exacerbate the impact on native biota.