MidFish: A Large-Scale Aggregation of State Fisheries Data from the Midwestern United States from 1940 - 2023

Lakes in the Midwestern United States support valuable recreational, subsistence, and tribal fisheries. Fisheries assessments that support management decisions are typically conducted within political boundaries and at intervals that limit their spatial and temporal scope. Data aggregation across lakes and regions facilitates research extending across ecological gradients and jurisdictions; for example, how climate variation across latitudinal ranges influences fish community composition and predicts potential changes. Here, we present a consolidated database of standardized fisheries data containing over 60 million fish records from over 8,000 lakes across eight states in the Upper Midwest. Original data provided by state agencies differed substantially in both content (e.g., species coverage, survey types, temporal ranges, gear descriptions, ancillary notes) and structure (e.g., column definitions, interpretation of rows). Data from each state was aggregated to meet a common format in which each column represents the same information across states, and each row represents one fish record. Additional grouping and flagging columns provide efficient summarizing of data for unique user needs. Our design preserves as much methodological detail as possible while supporting both broad-scale analyses and fine-grained, species-specific research. The database follows open science principles, providing adaptability for diverse research and management applications. This database can be used as a resource to unify fisheries data across the region, facilitate cross-jurisdictional collaboration, and support investigations of ecological and management questions at regional scales into the future.