Spatiotemporal and multispecies comparisons between a citizen science platform and recall surveys in recreational fisheries

Smartphone applications for anglers that function as citizen science platforms are an alternative to the traditional survey methods that are used to collect data from recreational fisheries. Comparisons between these two methods are needed to understand the impacts of the biases associated with data generated from smartphone applications. However, such comparisons are uncommon, especially for multiple fisheries over time and across space. In this study, we compared catch and effort data from an electronic citizen science platform for anglers with an offsite web-based recall survey for consecutive (i) 3-month periods in a spatially distinct (i.e., the Danish island of Funen) sea trout (Salmo trutta) fishery (2017–2020), (ii) 6-month periods in coastal sea trout and coastal/offshore cod (Gadus morhua) fisheries across eight ICES management areas (2016–2020), and (iii) 6-month periods in a freshwater pike (Esox lucius) fishery (2016–2020). Catch and effort data from the two surveys were, in most cases, consistently similar over time for the Funen sea trout and Danish freshwater pike fisheries. In contrast, we found that the recall survey estimates were consistently 100–200% larger than the citizen science platform for both sea trout and cod in ICES areas. Our findings suggest that the applicability of electronic citizen science platforms for anglers can be fishery-specific, and that systematic bias may occur.