New research shows that some aquatic invasive species help others to live longer
WDFW and Oregon State University publish new scientific paper documenting how some invasive species benefit other invasive predator fish species.
A recently published paper co-authored by Washington Department of Fish and Wildlife (WDFW) staffers Andrew Murdoch, Matt Polacek, and Rochelle Polacek explains that invasive predator fish species benefit from other invasive species as food and that the timing of prey availability may be promoting rapid population growth.
The WDFW scientists teamed up with Dr. Jonathan Armstrong from the Department of Fisheries, Wildlife, and Conservation Sciences at Oregon State University over the course of a year to analyze the monthly stomach contents of walleye in the Lower Snake River, the largest tributary of the Columbia, and found that their diets were dominated by Siberian prawn, American shad, salmonids, and lamprey. There were notable periods of time when the fish ate more of one species than the others in response to that species being readily available.
Until this work, there had not been extensive research into the impact of invasive species on aquatic food webs.
In the Columbia River Basin, the growing population of non-native walleye poses an increasing threat to native species like endangered salmonids and Pacific lamprey. At the same time, populations of other non-native species such as American shad and Siberian prawn have grown significantly over the past several decades.
Results from this study revealed that multiple invasive prey species are providing food for walleye during gaps in time when native salmonids and lamprey are not available. This finding is a real-life example of the invasional meltdown hypothesis or, more simply, how the introduction of one or more non-native species make it easier for other non-native species to establish and thrive, leading to a cascade of invasions and a decline in native biodiversity.
The findings demonstrate that instead of all species co-existing at the same time, the composition of the aquatic food web staggered over time. As a result, management of invasive predators and their impacts on the conservation of native fish populations will depend on better understanding the impact of these multiple species interactions over space and time.
For more information on this research and these concepts, the full paper produced from this research, Complementary prey phenologies enhance invasional meltdown: a case study in the Columbia River Basin, is open access and can be read for free.
