9/3/2024
Laboratory Insights into Invasive Fish Species Transport in Rivers
A blog from the Center for Secure Water (C4SW)
Understanding the response of aquatic ecosystems to a rapidly changing environment is a challenging task that requires the participation of multidisciplinary teams to understand physical and biological processes across a wide range of spatial and temporal scales. Through collaboration between civil engineers, hydrologists, and biologists, we have advanced our knowledge on how fish eggs and larvae are transported in rivers, identifying preferential paths and flow conditions that lead to capture or damage of the drifting organisms. This new knowledge will help us design new monitoring and management strategies to maintain healthy aquatic ecosystems, prevent the spread of invasive species, and develop better process-based strategies for stream restoration and stream naturalization.
Natural water systems in flux
Aquatic ecosystems, whether in rivers, lakes, or oceans, are increasingly affected by human activities and rapid environmental changes, with climate change often exacerbating these impacts. Variations in water temperature, quality, and flow dynamics can lead to the decline of native species and the rise of those better adapted to altered conditions. Additionally, the intentional introduction of certain species to new environments to meet specific societal needs can cause significant harm to local ecosystems.
To mitigate and prevent such damage, it is essential to understand how different species interact with their environments. By analyzing these interactions, we can better manage and modify conditions to either attract or deter organisms from vulnerable areas, ultimately protecting and preserving aquatic ecosystems.
Invasive species outcompete endemic species
A current example of an invasive species in aquatic ecosystems is the so-called Asian Carp, a name associated to four species of carp not native to North America, which includes bighead carp, black carp, grass carp, and silver carp. These fish were brought to the United States in the 1970s to control algal blooms but were able to escape onto small tributaries and large rivers to spread over the Mississippi basin. These species of fish grow and reproduce rapidly, outcompeting native fish populations for resources, altering the local food chain, and affecting recreational and commercial activities where they establish.
Given the challenges of eradicating established carp populations, researchers and engineers are focusing on preventing their spread into the Great Lakes, focusing on stopping the passage of carp during their early life stages, targeting the capture and redirection of eggs and larvae drifting in the current. To achieve this, we need to know how such carp eggs and larvae travel under various flow conditions, and how they interact with the flow and in-stream structures as they travel downstream, to identify the best ways to capture them before they reach areas they can populate.
Collaborative work enhances understanding of invasive species management
Given the challenge of predicting the transport of small eggs and larvae in streams, we collaborated with biologists and hydrologists at the US Geological Survey (USGS) to develop a research plan aimed at identifying the fundamental processes influencing early life stage fish transport. Utilizing the facilities at the Ven Te Chow Hydrosystems Laboratory at the University of Illinois, we first conducted experiments with plastic beads that mimic the size and density of fish eggs. These beads were released into a recirculating channel to observe their dispersion under various discharge conditions and to determine the threshold velocities required to keep them in suspension.
Carp eggs are damaged if they settle or roll around the riverbed, so identifying under which conditions they are brought to the bottom provides useful information for their monitoring. To obtain an accurate characterization of their behavior, we used Grass carp (Ctenopharyngodon idella) live eggs from the USGS Columbia Environmental Research Center (CERC) facilities. These eggs were released into a laboratory flume where cameras tracked their movements until hatching in different types of environments. The experiment continued to monitor the larvae as they developed vertical swimming abilities.
The results showed distinct differences in the travel patterns of eggs, newly hatched larvae, and larvae with vertical swimming capabilities under varying flow velocities. This information is valuable for developing strategies for sampling and capturing these organisms in the field and indicates that larvae actively respond to different flow conditions.
A new tool in invasive species control: Bubble Curtains
Our research, one of the few laboratory studies involving live grass carp eggs and larvae, has revealed crucial information about how to predict the movement of organisms in rivers and identify key flow features that affect their transport. These insights paved the way for a novel approach to controlling early life stage invasive carp in rivers: bubble curtains.
Bubble curtains are created by injecting air through a diffuser placed at the bottom of a stream, forming barriers of rising air bubbles. As the bubbles interact with the flow, they produce distinct flow features. While this technology has been used to capture floating plastics in low-speed streams, it shows promise for capturing or deterring invasive fish species.
In a series of experiments at the Ecohydraulics and Ecomorphodynamics Laboratories (EEL), we tested the effectiveness of bubble curtains on various drifting particles, including plastic beads, preserved eggs, and live eggs and larvae. We experimented with different diffuser configurations, orientations relative to the flow, and airflow discharges, across a range of velocities representing field conditions.
Our findings revealed how specific configurations can be optimized to target species with particular physical characteristics while allowing other organisms and particles to pass freely. These results will guide the design of field-scale systems for deployment in tributaries to the Great Lakes, aiming to prevent the passage of invasive fish during critical spawning periods.
Looking forward: do bubble curtains remain effective in natural environments?
While we have identified responses of eggs and larvae to flow features, and have quantified the efficiency of bubble curtains based on organism and flow conditions in laboratory settings, the more complex conditions in the field call for additional steps to ensure the same response and behaviors will be observed in rivers. Real streams present complex bathymetries, with mobile sediment beds and the presence of benthic communities that can be affected by the flow alterations generated by bubble screens. How a bubble screen changes the sediment transport dynamics on a river, its effect on water quality, and how it affects passage of other species, remain open questions to be investigated.
These initial series of experiments provided a unique and extensive dataset that will help develop, calibrate, and validate numerical models to predict the transport of eggs and larvae in streams at risk. As we move beyond proof of concept for the use of bubble screens for invasive fish species, our next steps will involve seeking the deployment of prototype diffusers in tributaries to the Great Lakes, to test feasibility to scale up bubble screen systems capable to capture invasive fish in rivers, as well as assessing their interaction with other species in the stream.
If you want to know more:
Prasad, V., Suski, C.D., Jackson, P.R., George, A., Chapman, D., Fischer, J.R. and Tinoco, R.O. 2024. "Limiting downstream dispersal of invasive carp egg surrogates using a laboratory-scale oblique bubble screen". Journal of Ecohydraulics, TJOE (2332994). https://doi.org/10.1080/24705357.2024.2332994
Prada, A. F., George, A. E., Stahlschmidt, B. H., Jackson, P. R., Chapman, D. C., & Tinoco, R. O. 2021. "Using turbulence to identify preferential areas for grass carp (Ctenopharyngodon idella) larvae in streams: A laboratory study". Water Resources Research, 57, e2020WR028102. https://doi.org/10.1029/2020WR028102
Tinoco, R.O., Prada, A.F., George, A.E., Stahlschmidt, B.H., Jackson, P.R., Chapman, D.C., 2020. “Identifying turbulence features hindering swimming capabilities of grass carp larvae (Ctenopharyngodon idella) through submerged vegetation”. Journal of Ecohydraulics.. https://doi.org/10.1080/24705357.2020.1835566
Prada, A.F., George, A.E., Stahlschmidt, B.H., Jackson, P.R., Chapman, D.C. and Tinoco, R.O., 2019. Influence of turbulence and in-stream structures on the transport and survival of grass carp eggs and larvae at various developmental stages. Aquatic Sciences, 82(1), p.16. https://doi.org/10.1007/s00027-019-0689-1
Prada, A.F., George, A.E., Stahlschmidt, B.H., Chapman, D.C. and Tinoco, R.O., 2018. Survival and drifting patterns of grass carp eggs and larvae in response to interactions with flow and sediment in a laboratory flume. PloS one, 13(12), p.e0208326. https://doi.org/10.1371/journal.pone.0208326