Travis Brenden | Search USGS

USGS2024

Predicting the response of fish populations to changes in river connectivity using individual-based models

Barrier removal restores physical stream processes and improves accessibility of critical habitats to migratory fishes. Although increasing connectivity benefits stream systems and migratory fishes, barrier removals may also lead to increased production of undesirable or invasive migratory species, as well as myriad other concerns (e.g., reduced recreational opportunities). Few studies have predicted how migratory fish populations will respond to enhanced fish passage, despite being a critical step in the decision-making process. We developed an individual-based model framework to forecast the response of migratory fishes to changes in connectivity and applied the framework to six species under multiple fish passage scenarios for the FishPass project on the Boardman River, MI, which outlets into Lake Michigan. Population response to barrier removal was species-specific and varied based on initial population size and distribution within the watershed, number of fish passed upstream, and species life history traits. Species restricted to below the barrier prior to removal benefitted most; non-native species were found to have greater production potential under full passage scenarios than native Great Lakes species. With increasing passage of non-native Pacific salmonids, steelhead Oncorhynchus mykiss surpassed brook trout Salvelinus fontinalis as the system’s dominant species. Our results will inform decision-makers on management alternatives for fish passage on the Boardman River and our model framework can be modified, updated, and applied to additional river systems as more barrier removal projects are conducted in the future.

Michigan↗

USGS2023

Seasonal spatial ecology of Lake Trout in Lake Erie

Objective Lake Trout Salvelinus namaycush are native coldwater apex predators that play an important role in maintaining ecosystem functionality and diversity in the Laurentian Great Lakes. Following population collapses, rehabilitation efforts were widely initiated in the Great Lakes to reestablish self‐sustaining Lake Trout populations. Lake Erie may pose a challenge to these rehabilitation efforts due to limited availability of appropriate oxythermal habitat. Our goal was to investigate seasonal habitat use of adult Lake Trout in Lake Erie to inform management and rehabilitation efforts. Methods We used acoustic telemetry in Lake Erie, which was equipepd with a lake‐wide acoustic receiver grid, to quantify Lake Trout seasonal region occupancy, dispersal distances, bottom depth occupancy, space use extent, and space use overlap. Result We found that 32% of fish tagged in the eastern basin and all fish from the western basin dispersed more than 100 km from their tagging location, which represents a greater proportion of the population moving long distances than what has been previously documented in the Great Lakes. During stratification, Lake Trout were detected almost exclusively in the offshore eastern basin in areas where water depth exceeded 25 m. During nonstratified seasons, fish used other regions of the lake, occupying areas of highly variable depths. During fall, most fish tagged in the eastern basin occupied habitat along the southern shore of the eastern basin. Fish tagged in the western basin returned to this region in the fall of subsequent years despite occupying the offshore eastern basin during stratification and having depth occupancy, home range size, and overlap similar to that of eastern basin‐tagged fish. Fish size was positively correlated with receiver depth during winter and spring, and with home range overlap during spring and summer. Conclusion The results of this study can begin to inform management decisions regarding stocking locations, harvest regulations, and habitat restoration to facilitate the continued rehabilitation of this important native species.

Lake Erie↗