A Little Bit More
It may come as a surprise to learn that there are shrimp living in many of the large, northern lakes of North America – I know it did for me. After all, we tend to think of shrimp and warm Gulf waters as going together. Although Opossum Shrimp aren’t “true” shrimp – the differences are rather technical - they’re closely related and do look very similar. The interesting habit of this animal spending its daylight hours in the depths makes it almost invisible to people so we rarely see this abundant animal when we’re active on or near the waters in which they live.
Opossum Shrimp are so named because, like an Opossum mammal, the female has a brood pouch between her legs where she keeps the eggs as they’re developing. These animals are found all around the poles (circumpolar) in North America, northern Europe and northern Asia. In North America, Opossum Shrimp can be found in the Great Lakes; Green Lake, Trout Lake, and Lake Geneva in Wisconsin; the Finger Lakes in central New York; Waterton Lake in Alberta/Montana plus several other deep lakes of the U.S. and Canada.
Opossum Shrimp are excellent forage for fish and this fact encouraged state agencies in the past to introduce this species into deep lakes where they had never been present before. At first, there was a marked increase in the size of gamefish being caught and sportsmen were pleased. But then there was a marked decline in the fish population. Only after careful examination of the situation did researchers realize that the introduced shrimp were competing for the very same foods that the baby gamefish were eating thus they reduced the overall fish population with their presence. Once again, researchers learned the hard lesson that nature is all interrelated, changing one aspect usually affects another in unpredictable ways.
Activities
Science, Social Studies & Math – Deepest Lakes
Objectives: Research a specific question
Materials: Library or access to internet
The Opossum Shrimp are only found in especially deep lakes and this got me to wondering what are the deepest lakes in the world and what are their depths. This information should be readily available in a library or on the internet and be worthwhile for students to find out for themselves. I think they’ll be surprised at how deep some are; I know I was. You may want to have the students provide their information in both metric and English equivalents.
If you would like to check out the top 13 deepest lakes in the world, check out the websites I’ve provided.
Key Concepts
Adaptations and Diversity, Behavior and Regulation, Food Webs /Food Pyramids, Identification
Questions
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