Data and R code in support of: Fish tissue mercury concentrations increase following the invasion of zebra mussels

Aquatic invasive species pose threat to human consumption of fish by altering mercury cycling in lake systems. This dataset supports an analysis of the impact of zebra mussels (Dreissena polymorpha) on mercury concentrations in fish tissue across six sport fish species: northern pike (Esox lucius), walleye (Sander vitreus), largemouth bass (Micropterus salmoides), black crappie (Pomoxis nigromaculatus), yellow perch (Perca flavescens), and bluegill (Lepomis macrochirus). It includes mercury observations from 18,011 fish collected in 523 unique lakes across Minnesota between 2000 and 2023. Data were filtered from the Minnesota statewide fish contaminant database to enable robust statistical analysis across zebra mussel invasion in the same lake. For each species, lakes were included if they had at least one year of data both before and after the assigned year of zebra mussel invasion ("impact"), or during an equivalent time span for reference (uninvaded) lakes. Recognizing that ecological responses to invasion may be delayed, we constructed six species-specific subsets reflecting different lag times (0 to 5 years) after the reported invasion year. Each species-lag specific subset contains a unique set of lakes and fish, with some overlap across lag years. As such, fish records may repeat across species-lag year subsets. These data enable robust analysis of mercury concentration trends before and after zebra mussel invasion while accounting for background changes experienced in reference systems.