An important method in the management of Asian carps is research. Research is on-going in this field to find more ways to prevent the arrival of, control, and eradicate these species. Scientists are focusing on a few key areas:
- Biology and behaviour of Asian carps in environments where they have already established (e.g. U.S. waters excluding the Great Lakes) or are predicted to arrive
- Social, economic, and environmental impacts of an establishment
- Methods of prevention, monitoring, and detection
- Methods of control
Biology and Behaviour
To understand the impacts of Asian carps, it is important to understand their biology and behaviour. Currently, there are no established populations in Canadian waters of the Great Lakes. A recent study has found that Grass Carp have spawned in the Sandusky River which flows into Lake Erie (Embke et al. 2016). To get a better understanding of the reproductive dynamics of Grass Carp, some were captured from western Lake Erie over a three-year period. Of the 60 captured, 86.7% were reproductively viable (Wieringa et al. 2016). Based on the bigheaded carps (Bighead Carp and Silver Carp) Risk Assessment of the Great Lakes conducted by Fisheries and Oceans Canada in 2011, we know that these species could survive in the Great Lakes and a single event that accidentally introduces a few adults has a high probability of leading to an established population (Cudmore et al. 2012, Cuddington et al. 2013).
Establishment of Asian carps in the Great Lakes could have devastating effects ecologically and socio-economically. In areas where they have already become established, they have negatively impacted not only the ecosystem but the commercial and recreational fishing industries as well (Kolar et al. 2007). It is expected that Asian carps could successfully establish in Lake Erie and reach biomass greater than native species with a similar function in the ecosystem (Wittmann et al. 2014).
To what extent do Asian carps impact native fish species?
Current research suggests that Bighead and Silver carp abundance is negatively impacting the body condition of native planktivores, such as bigmouth buffalo and gizzard shad, due to diet overlap (Irons et al. 2007). A Grass Carp invasion would lead to a reduction in biomass of aquatic vegetation, negatively impacting native species like largemouth bass and bluegill (Wittmann et al. 2014).
Prevention, Monitoring and Detection
There are methods for preventing, monitoring, and detecting Asian carps such as the electric barrier in Chicago, surveillance with traditional gears (i.e. electrofishing, netting) and the environmental DNA (eDNA) program. Currently, eDNA is used as an early detection method. It can detect genetic material that has been shed by organisms into their environment. New methods look to develop species specific markers to better detect Asian carps (Farrington et al. 2015). Many aquatic invasive species in the Great Lakes have used the Welland Canal as a pathway between Lake Erie and Lake Ontario, however; specific movement of fish between this canal is unknown (Kim and Mandrak 2016). It was determined using acoustic telemetry that 7 of 139 tagged fish (3.9%) moved between lakes Ontario and Erie through the canal, demonstrating that fish can move through the canal, but locks limit dispersal (Kim and Mandrak 2016).
How can we prevent Asian carps from entering the Great Lakes?
New research is being done to investigate more options for prevention. Bubble curtains are a tool that can be used to deter the movement of Asian carps. Bubble curtains use air bubbles to produce loud noises and movement within the water. This technique was found to deter 73-83% of Bighead and Silver carps in an experimental study (Zielinski and Sorensen 2016).
The use of carbon dioxide as a deterrent is also being studied. Bigheaded carps were found to avoid areas of higher carbon dioxide concentrations, and as the carbon dioxide spread throughout the study area they moved farther away from the source (Donaldson et al. 2016). Acoustic deterrents have been found to be effective in Asian carp management. Silver Carp exhibited a habitual behaviour to acoustic deterrents (Vetter et al. 2015). They reacted and moved away from the source a couple of times but eventually ignored it, suggesting that a complex sound stimulus would be effective in prevention and management of Asian carps (Vetter et al. 2015).
What is the most effective way to detect Asian carps?
Understanding how to detect Asian carps is essential in their control and management. Early detection of Asian carps provides the opportunity to respond quickly and control the situation. To better understand where we should be looking for Asian carps in case of arrival, Canadian scientists have modeled their habitat requirements and overlapped them with habitats in Canada to identify locations that are highly suitable for these species (DFO unpublished data). These results continue to be refined with new tools as new information becomes available to continuously identify at risk habitats. Studying the movement of Asian carps provides information on where and when to implement control and management efforts.
Using acoustic telemetry to monitor the direction, distance and timing of carp movement, recent research suggests that specific seasons (spring and early fall) and locations (backwater) are good target areas for control in the Wabash River in Indiana (Coulter et al. 2015). This research provides useful information that can assist with pre-existing detection methods.
It is important to study control methods that can effectively eliminate populations of Asian carps or prevent their movement, and ensure that any resulting damage is minimal. These methods should also work to ensure that native species are not negatively impacted.
Do native predators of Asian carps exist in North America?
A common issue with invasive species is that they have no predators in their new ecosystems. This is an issue for Asian carps as well. Juvenile carps are prey for native predatory fishes right after a spawning event, but as they grow bigger quickly, predation decreases (Anderson 2016).
Recent research has found Asian carps in the diet of River Otters in Illinois (Feltrop et al. 2016). If River Otters develop an affinity for Asian carps, perhaps they could be an effective biological control.
Other uses for Asian carps?
Since predation is not always effective on its own, other options need to be considered. Use of Asian carps as fertilizer, pet food, and for human consumption is being explored in the U.S.A.. In a blind test conducted by the Missouri Department of Conservation, Silver Carp was preferred 2-1 over tilapia and catfish (Phelps 2016).
Can pheromones aid in Asian carp control?
The use of pheromones has been studied in Sea Lamprey control, and is being studied for Asian carps as well. Asian carps were found to avoid alarm pheromone cues (i.e. pheromones of a predator) and be attracted to chemical cues of schooling and sex pheromones (Little et al. 2014). These results have implications for capturing and deterring Asian carp populations.
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