Abstract
Prey availability is among the most influential and highly variable determinants of fish growth and freshwater habitat carrying capacity, yet it remains understudied compared to physical habitat variables (Rosenfeld et al. 2014; Weber et al. 2017; Ouellet et al. 2025). We often lack a clear understanding of how much food is available to fishes, how it varies among habitats, and how it influences responses to restoration (Wipfli et al. 2010; Ouellet et al. 2025; Rossi et al. 2024). Drift invertebrates—the primary food source for juvenile salmonids and other drift-foraging fishes—play a pivotal role in these dynamics.
To better understand the spatial and temporal variability of drift invertebrate abundance and biomass across the freshwater range of juvenile salmonids in western North America, we compiled the DRIFteRS dataset (DRift Invertebrates For salmonids in River Systems). The dataset encompasses 6,160 samples of drift invertebrates collected from 1,360 reaches on 456 unique rivers and streams spanning 55 river basins considered hydrologically independent (i.e., not nested within the same larger watershed), including iconic systems like the Columbia, Fraser, and Colorado rivers, across Alaska, British Columbia, Washington, Idaho, Oregon, California, Wyoming, Utah, Nevada, Colorado, New Mexico, and Arizona. Sample sites represent a diverse array of river and stream habitats (e.g., headwater, mainstem, side channel), in watersheds with diverse land uses (e.g., urban, wilderness, agricultural), and disturbance histories (e.g., fire, restoration). Collected between 1997 and 2024, the data span the full calendar year and capture daily and seasonal patterns in drift abundance and biomass densities.
When paired with remotely sensed environmental landscape data, such as land use / land cover, climate, and disturbance history, and other relevant reach-scale covariates, such as water temperature, canopy cover, riparian vegetation composition, and channel and valley type, the DRIFteRS dataset can aid in identifying key drivers of drift invertebrate densities and support predictive modeling in unsampled locations and times. In addition to its primary relevance for salmonid conservation, the dataset may also inform broader investigations of food web connectivity, cross-ecosystem energy transfer, and ecosystem responses to landscape-scale environmental change. For salmonid-focused applications, the dataset can be integrated into habitat evaluation models, including bioenergetic (e.g., Naman et al. 2019) and life cycle models (e.g., Beechie et al. 2023), to improve estimates of habitat capacity for juvenile salmonids. Understanding the dynamics of prey availability will become increasingly important since metabolic rates and thus food requirements of juvenile salmonids are likely to increase with projected rising water temperatures (Crozier et al. 2010). Flow regime transitions (i.e., snow or glacier dominated to rain dominated; Beechie et al. 2013), wildfire frequency and intensity (Hessburg et al 2021), as well as plant community and phenology shifts (Cleland et al. 2007; Franklin et al. 2016) are all predicted to change with rising temperatures and are potential drivers of aquatic prey quality and availability. These insights can ultimately inform restoration prioritization and design, helping managers consider food resource implications when evaluating restoration priorities and match habitat improvement to food supply.