Partial migration: new findings suggest management opportunities for common carp
The phenomenon of partial migration – when some individual animals migrate seasonally while others of the same species remain in place – is relatively common in the natural world and generally has positive impacts on the stability and abundance of native populations. However, many invasive animals employ this tactic as well, leading MAISRC researcher Przemek Bajer to ask how partial migration may be leading to the success of the ubiquitous and detrimental common carp.
Newly published research from MAISRC now suggests that common carp engaging in partial migration to exploit outlying marshes for better spawning areas may be an important factor that leads to their enhanced abundance.
To conduct this research, MAISRC partnered with computer programmers and fish biologists to develop an individual-based, age-structured population dynamics model of carp in Minnesota lakes. They modelled carp movement through numerous scenarios including varying ages, migration patterns, and winterkill frequencies. Ultimately, results showed that common carp are unlikely to become excessively abundant in lakes in central Minnesota unless they conduct partial migrations to marshes that experience winterkill.
Lakes and marshes that experience winterkill (a natural occurrence in which many fish die due to a lack of oxygen) will then lack the egg and larval predators – such as bluegills – which would normally act as a control for common carp populations. Without these native predators, common carp populations can continue to grow unchecked, leading to increased population success.
Interestingly, carp were found to be most abundant if marshes winterkilled with low frequency (roughly every 3 – 20 years). More frequent winterkills ultimately led to population declines, because some adults (and most juveniles) became stranded in the winterkill habitat.
These findings suggest specific management opportunities: whereas some marshes could be aerated to eliminate winterkills, others could be mixed during winters to promote winterkills to control juveniles and adults that decide to overwinter in marshes. Behavioral deterrents (such as acoustic barriers) that slow down the movement of juveniles from marshes into lakes could also be beneficial. The carp population dynamics model developed in this study could be used to determine exactly which strategies might be most beneficial for a particular system of lakes.
Common carp are one of the world’s most invasive species and have long been a problem in Minnesota lakes. Ultimately, having a better understanding of how they are able to become successful helps inform control strategies. Learning about the role of partial migration into winterkill-prone areas adds another piece to the puzzle.
Read the full paper, “Partial migration to seasonally-unstable habitat facilitates biological invasions in a predator-dominated system,” online here.
This project was funded by the Minnesota Environmental and Natural Resources Trust Fund and the Riley Purgatory Bluff Creek Watershed District and was conducted in partnership with the Minnesota Department of Natural Resources.