Decade-scale stream morphology and stream fish community structure in headwater streams draining Mississippi's National Forests

Decade-scale ecological datasets provide critical insights into long-term ecosystem properties, and long-term ecosystem response to human driven landscape alterations. In the state of Mississippi, USA, a history of intensive deforestation between 1830 and 1920 was followed by intensive sediment mitigation measures including intentional channel straightening and dredging and widespread reforestation. These corrective actions led to widespread and sometimes catastrophic channel incision and the potential for decoupling of floodplain and channel aquatic ecosystems. In this dataset we document a quantitative multi-decadal fish community and fish habitat dataset for 762 samples from streams draining National Forests in Mississippi. These data are used in a companion manuscript to test the hypothesis that increased channel incision relates to decreased prevalence of species with ecologies indicating floodplain, backwater, or off-channel habitat use. We provide data for associated landscape-level covariates (land use, stream network topology) derived from remote sensing data sources. We further provide a literature-based database of resource use for each species encountered in the survey. Scripts which document analyses of channel-floodplain ecological decoupling in an associated manuscript (Stearman et al. 2025) and code required to run these scripts are also provided. 

Methods
Quantitative fish and habitat data were collected at 369 sites in headwater streams draining five national forests in Mississippi (Bienville, DeSoto, Holly Springs, Homochitto, and Tombigbee National Forests). Collections occured from 1999-2003, 2008-2009, and 2015-2022, with 40-50 sites sampled yearly. Sampling at each site encompassed a stream reach 30x the mean wetted width, bounded between 120 and 240m. Fishes were collected with a combination of single-pass backpack electrofishing and single-pass seining. Habitat data were collected using a standardized point-transect method, with points taken at 1m intervals on 12 transects perpendicular to the channel width. Habitat data quantification included metrics of channel morphology and meter-scale habitat characteristics. 

Watershed-scale topology metrics and land use/land cover metrics were calculated for each site and each sampling event. Topology metrics (metrics of stream size and watershed network position of the sample site) were derived from the NHD+ V2 dataset. Land use data for watersheds upstream of sites were drawn from the National Land Use/Land Cover database (MRLC), using data from the closest time period for each sample event. 

A resource use database was constructed for each of the 117 species in the dataset. This database records known resource utilization on five gradients documented to be important for resource partitioning by stream fishes: gross microhabitat type on a fluvial in-channel to lacustrine off-channel gradient, foraging depth, foraging diel periodicity, cover utilization, and gross trophic categories. Species were scored 0 (no use) or 1 (use) for ranked ordinal categories within each gradient by consulting regional literature reviews as well as observations during field sampling events.