The ones that didn’t get away: assessing recreational fisheries and biological impacts in coastal ecosystems

Recreational fisheries constitute a substantial yet often poorly quantified component of global fisheries, with the potential to influence stock dynamics, ecosystem structure, and management outcomes. However, their disperse nature, heterogenous participants, and incomplete sampling frames make them difficult to monitor and integrate into fisheries science. The aim of this thesis is to improve the understanding of recreational fisheries and their biological implications in coastal ecosystems by addressing key methodological and biological challenges.This thesis combines empirical studies and methodological development across four research papers. I) A probabilistic on-site survey based on an indirect spatial sampling frame, which provided the first unbiased estimates of Swedish recreational catches of Western Baltic cod. II) A structured decision framework based on Total Survey Quality, which enabled transparent comparison and selection of survey designs aligned with management objectives. III) A participatory monitoring program for European lobster on the Swedish west coast, that demonstrated how volunteers can generate spatially expanded, fisheries-independent data comparable to scientific surveys. IV) Long term data on Western Baltic cod, which revealed pronounced changes in life-history traits, including reduced size structure, declining length-at-age, lower body condition, and earlier maturation, with both commercial and recreational fisheries selectively removing larger individuals, with additional selectivity for fish in better condition observed in recreational catches.Together, these results highlight that recreational fisheries contribute to fishing mortality and selective pressures, while uncertainty remains a defining feature of their assessment. Reliable, management-relevant knowledge depends on integrating complementary data sources and approaches. Improving monitoring is not only a technical challenge, but a prerequisite for understanding biological change and supporting precautionary management. Recreational fisheries should be considered not only a source of pressure, but also a potential contributor to data, knowledge, and more inclusive governance of coastal fisheries.