— Start adding red to your shrimp flies

The bloody red shrimp (Hemimysis anomala), an invasive species from the Ponto-Caspian region, has just rounded all the bases in the Great Lakes with an individual found in Lake Superior.  What does the invasion of the bloody red shrimp mean for the Great Lakes Basin? Ricciardia, Avlijas and Marty (2012) provide a pretty good synthesis of what we might expect.

The bloody red shrimp, along with an ominous name, has the potential to shake up the Great Lakes ecosystem. While they appear very similar to the native opossum shrimp, they do not act the same. The opossum shrimp is generally limited to the deep water zones of Boreal lakes below the thermocline. In contrast, the bloody red shrimp is able to handle higher temperatures so they can access basically any part of the environment including rivers which do not currently have any mysid shrimp species.

The main predicted effect of the introduction of bloody red shrimp is a disruption of the zooplankton food web. Reaching up to ½” in length, the bloody red shrimp eat mainly zooplankton; they compete with fish and affect the diversity and abundance of zooplankton communities. They can also be fish food.

The bloody red shrimp has already made it’s way into fish diets in the Great Lakes.The bloody red shrimp is a better source of calories than zooplankton, but less than the native opossum shrimp. There are mixed results for salmonids when mysid shrimp species have been introduced. In some cases fish to respond positively with increased growth, other cases they have switched their diets to mysids from fish prey resulting in declines in growth. An extreme response is also possible, as some fish populations have collapsed.

That being said, they were noticed in the Great Lakes in 2006 and we really haven’t heard that much about them. It is hard to say if that if due to a lack of an effect on the system or a lack of interest. It is possible that the worse is yet to come, or maybe we simply need to add a new twist to an old pattern in our fly box when heading out on the water.

Ricciardi, A., S. Avlijas, and J. Marty (2012) Forecasting the ecological impacts of the Hemimysis anomala invasion in North America: Lessons from other freshwater mysid introductions. Journal of Great Lakes Research. 38: 7-13

Featured image microphotograph by S. Pothoven, GLERL, December 2006.

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