The importance of accounting for hydraulic and geomorphic complexity in riverine biophysical drift modeling
Abstract
Invasive carp were introduced to the Mississippi River Basin nearly 50 years ago and have become widespread in waterways of the central United States. Invasive carp negatively affect ecosystems, and managers are concerned about continued colonization of lotic and lentic systems in the Great Lakes, Upper Mississippi River, and southeast regions. In rivers, recruitment of invasive carp depends on suitable water temperature and sufficient flow velocity to keep eggs in suspension until hatching. Biophysical drift modeling can predict river reaches that may support the spawning-to-hatching recruitment life stage of invasive carp. We used the Fluvial Egg Drift Simulator (FluEgg), to predict recruitment under contrasting hydraulic regimes. We estimated bighead carp (Hypophthalmichthys nobilis) egg hatching success and larval fish retention during a 2018 high flow event along a 50-kilometer (km) reach of the multi-thread St. Croix River, Minnesota and Wisconsin, USA. We parameterized FluEgg using three hydraulic datasets. The first dataset was generated almost exclusively from field data collected within the main channel. The other datasets were generated from a one-dimensional hydrodynamic model parameterized using steady and unsteady flows. Steady and unsteady hydrodynamic model approaches accounted for hydraulic characteristics and conveyance in side channels of the St. Croix River that were not accounted for in the first dataset. The three approaches produced contrasting estimates of egg hatching success. FluEgg simulations parameterized using field data predicted that no eggs would hatch within the study reach across all simulated water temperatures, while hatch rates were between 0% and 96% for steady-state simulations and 2% and 65% for unsteady simulations. These divergent hatch success rates highlight the importance of including complex hydraulics and morphology in ecohydraulic models. This is especially true in rivers with heterogeneous flow fields, such as the braided St. Croix River, where thalweg field surveys may not capture slower flow velocities across the braidplain that can support invasive carp recruitment and hatching. Study results could be used to improve the efficiency and planning of management efforts designed to monitor, sample, and control invasive carp eggs and larvae.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFMEP45A1516K