Computer model adds ease, precision to managing Asian carp

A computer model developed by University of Illinois researchers to help predict the spread of Asian carp in rivers is now easier to use and more precise. The latest version of the Fluvial Egg Drift Simulator (FluEgg), first introduced in 2013, is described in a paper recently published in the Journal of Great Lakes Research, for which researchers utilized it in a case study of the St. Joseph River in Michigan. The new version of the model includes features that improve predictions of egg transport in rivers and has a user-friendly interface.

Asian carp are invasive species of fish that eat voraciously and reproduce prolifically, and their spread throughout Great Lakes tributaries is of great concern to resource managers because they could pose substantial environmental risks and economic impacts to the Great Lakes if they become established. The control of their eggs is a critical component to controlling their population, said Tatiana Garcia (PhD 2014, Civil Engineering), a research hydrologist at the U.S. Geological Survey (USGS) and lead author of the paper. Garcia developed FluEgg while working on her PhD in CEE.

“It’s not enough to control already developed fish, because one Asian carp can lay millions of eggs in a year, and then those eggs are going to develop into organisms, which will then reproduce,” Garcia said. “If you don’t also control the early life stages, it’s going to be very difficult to control the population.”

Fortunately for managers, several factors affect the viability of the eggs, including the temperature of the water, which affects how long the eggs need to hatch, and the velocity of the river, which affects the movement of the eggs and whether the eggs float or sink to the bottom. Eggs that settle will die, and eggs that move too fast will not have enough drift distances to develop until hatching.

“Asian carp need the optimal conditions of flow and temperature that will allow them to travel in suspension along the river until hatching,” Garcia said. “They need to go at fast enough velocities that most of the eggs are going to be in suspension with enough travel time to develop.”

The improved FluEgg enables users to input data such as water temperature, flow data and water depth. The model also incorporates the latest knowledge about the biology of Asian carp reproduction; the researchers used the work of Duane Chapman and Amy George, USGS biologist, to inform the model. The output allows users to see whether or not the waterway in question is hospitable for Asian carp reproduction. The FluEgg model helps managers navigate the complexity of the Asian carp reproductive process and make informed decisions about mitigation actions.               

In collaboration with the U.S. Geological Survey, the researchers applied the FluEgg model to study the likelihood of Asian carp eggs being kept in suspension and hatching in the St. Joseph River in Michigan, a tributary of Lake Michigan.

“In this study, the FluEgg model allowed us to examine the complex dependencies between flow, temperature and egg development,” said USGS hydrologist Ryan Jackson, a co-author of the paper. “This information provides resource managers with a range of conditions under which the St. Joseph River is vulnerable to Asian carp reproduction."

In the St. Joseph River study, the FluEgg model was used to evaluate egg movement and the likelihood of successful Asian carp reproduction under different streamflow and temperature conditions representative of historical spawning seasons in the river. Results show that eggs develop faster at warmer water temperatures, therefore requiring less time to drift in the river until hatching. Low streamflows can also be conducive to reproduction when the streamflow is just fast enough to keep most of the eggs in suspension while allowing for the greatest amount of drift time before reaching the lake, thus increasing the likelihood of hatching. The study demonstrated the complexity of the problem where the length of the river, velocity and water temperatures cannot be assessed individually. Rather, a holistic analysis is required, where egg development, water-quality characteristics and the hydrodynamics of the river are interconnected and analyzed together. See a video of FluEgg in action.

“Successful reproduction requires a fine balance between the water temperature, the egg development stage and the flow conditions present in a river required to maintain the eggs in suspension,” Tatiana Garcia said.

The development of the FluEgg model is a major advance in the fight against the Asian carp invasion, said CEE Professor Marcelo H. García, who served as Tatiana’s academic adviser during her time at Illinois.

“Management of invasive species such as the Asian carp requires knowledge about fish biology and stream hydraulics that is not commonly found among biologists and engineers, unless they decide to collaborate and work together,” Marcelo García said. “The product of such collaboration, FluEgg, is the first computational model capable of predicting the transport and fate of many thousands of eggs in any given river system. By bridging the gap between fish biology and environmental modeling, FluEgg provides managers with an innovative tool to estimate whether or not a river will be conducive to Asian carp recruitment years before the invasive fish ever migrates into such river. This is unprecedented in the sense that communities and agencies now have an approach to start acting on ways to manage Asian carp in a proactive way rather than a reactive one.”

The paper, “Application of the FluEgg model to predict transport of Asian carp eggs in the Saint Joseph River (Great Lakes tributary)” by Tatiana Garcia, Elizabeth A. Murphy, Patrick R. Jackson and Marcelo H. Garcia, is available online as is the FluEgg software.
_________________