AUTHORS: Patrick W. Padilla, US Fish & Wildlife Service; Garrett R. Johnson, US Fish & Wildlife Service; Benjamin J. Marcek, US Fish & Wildlife Service
ABSTRACT: Silver Carp is an invasive species found throughout large portions of the Mississippi River Basin that is thought to cause economic and ecological damage to invaded systems. Although Silver Carp use a variety of habitat types throughout this large and heterogeneous river system, they are often found in high densities in areas outside of the main river channel (e.g., tributaries and backwaters). The temporal use (e.g., time of year, duration) of these areas by Silver Carp is, however, poorly understood. To better understand temporal patterns in the tributary residency of Silver Carp and to determine if there is a subset of tributaries that are most frequently inhabited by this species, we examined their temporal occupancy of tributaries in six navigation pools of the Ohio River (J.T. Myers–Meldahl pools). Locations of 935 Silver Carp implanted with acoustic transmitters (Innovasea, V-16H tags) that were detected by 60 receivers in our study area during 2021–2023 were summarized to determine the number of individuals detected within tributaries at monthly intervals. These data were used to estimate the monthly proportional use of tributaries by Silver Carp (i.e., the number of individuals detected in a tributary relative to the total number detected within each pool). Generally, proportional occupancy of tributaries was greatest within each pool during February-April. Further, we identified individual tributaries with the greatest proportional occupancy during these periods of high tributary use. Our results suggest that occupancy of tributaries occurs during cooler months and that certain tributaries within each pool are used by a greater proportion of individuals than others. The reasons behind this relatively high utilization of certain tributaries are unknown and further research is necessary to determine if there are anthropogenic (e.g., harvest) and/or environmental factors (e.g., water temperature) associated with the timing of Silver Carp occupying tributary habitats.
