The newest invader of the Great Lakes is the Hemimysis anomala, more commonly known as the bloody red shrimp. This newcomer is the 183rd invasive species to call the Great Lakes home.
Since its discovery in all Great Lakes except Superior, researchers from various government agencies and universities, including the University of Waterloo, have been trying to determine if the bloody red shrimp will pose a significant ecological threat.
The Great Lakes fishing industry is a $7 billion per year business,” says former Biology master’s student Jessica Ives who studied Hemimysis for her thesis project. “Anything affecting this sector affects everyone living in the region.”
Europe’s tiny hitchhiker
The nocturnal shrimp hides from its predators during the day and comes out at night to feed. This behaviour helps the bloody red shrimp avoid becoming a food source itself.
The invasive species travelled from the Caspian and Black seas via commercial shipping ballast water. Hemimysis has also invaded rivers in Western Europe where it has affected aquatic food webs.
In Europe, the species has disrupted food webs and altered nutrient and contaminant cycles of the environments it has invaded. It has been known to reduce zooplankton biomass and biodiversity – an important food source for young fish and a critical part of the ecosystem.
At less than 15 millimetres in length, the bloody red shrimp can travel in large, dense swarms towards the surface. This vertical migration through the water column may result in increased cycling of pollutants, such as heavy metals, that would otherwise be confined to the bottom of the lake.
Ecologists use new tools to track invasives
Ives and her advisor Michael Power, a professor of Biology in the Faculty of Science used stable isotopes to track the food sources of the bloody red shrimp to determine its overlap in the food web with existing species. The greater the overlap, the greater the competition between invader and native species for limited food resources.
Measuring the stable carbon and nitrogen isotopes in whole animals is a convenient way for ecologists to tell if the shrimp are eating from the water column or the bottom of the lake. Using stable isotopes facilitates a whole food web and ecosystem approach to understanding how Hemimysis are integrating themselves into their new habitats.
Ives' results showed that the bloody red shrimp is an opportunistic feeder and lives on what’s available. At every site, they fill the easiest niche competing very little with other species already present.
Unlike some other invaders such as zebra mussels, sea lamprey and Phragmites australis (marsh grass), researchers are finding the bloody red shrimp is having less of an impact than originally feared. Researchers are continuing to track Hemimysis and are encouraging boaters traveling between water bodies to take measures to prevent Hemimysis’ further spread.
Ives graduated with her Master of Science from Waterloo's Biology department in 2013 and continues to be involved with invasive species as a Fishery Research Program Associate at the Great Lakes Fishery Commission.