High-resolution app data reveal sustained increases in recreational fishing effort in Europe during and after COVID-19 lockdowns

It is manifest that COVID-19 lockdowns extensively impacted human interactions with natural ecosystems. One example is recreational fishing, an activity which involves nearly 1 in 10 people in developed countries. Fishing licence sales and direct observations at popular angling locations suggest that recreational fishing effort increased substantially during lockdowns. However, the extent and duration of this increase remain largely unknown due to a lack of objective data. We used four years (2018 to 2021) of anonymous, high-resolution data from a personal fish-finder device to explore the impact of COVID-19 lockdowns on recreational fishing effort in four European countries (Lithuania, the Czech Republic, Denmark, and Germany). We show that device use and, by extension, angling effort increased 1.2-3.8 fold during March-May 2020 and remained elevated even at the end of 2021 in all countries except Denmark. Fishing during the first lockdown also became more frequent during weekdays. Statistical models with the full set of fixed (weekdays, lockdown, population) and random (season, year, administrative unit) factors typically explained 50-70% of the variation, suggesting that device use and angling effort were relatively consistent and predictable through space and time. Our study demonstrates that recreational fishing behaviour can change substantially and rapidly in response to societal shifts, with profound ecological, human well-being and economic implications. We also show the potential of angler devices and smartphone applications to supply data for high-resolution fishing effort analysis and encourage more extensive science and industry collaborations to take advantage of this information. Significance statement Recreational fishing is a popular and widespread activity with ecological, social and economic impacts, though problematic to assess and manage due to a paucity of information regarding effort and catch. Here, we use high-resolution data from a personal angler sonar device to show how the COVID-19 pandemic changed angler behaviour and fishing effort across Europe. We demonstrate that angling effort doubled and remained higher at the end of 2021 than before the first lockdowns. Such rapid and profound changes could have significant consequences for aquatic ecosystems, possibly requiring new management approaches. We encourage the adoption of novel data from angler devices, citizen science, and more active science-industry collaborations to improve recreational fishing assessment and management. ### Competing Interest Statement Competing interest statement: VV is an employee and data manager at the company Deeper Sonar, who provided the anonymous data used in this study. The data were obtained through a data sharing agreement between Nature Research Centre (Lithuania) and Deeper Sonar. Due to a substantial intellectual contribution to the study, VV was invited to be a co-author. All other authors declare no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.