The Death and Life of the Great Lakes -- Zoo 101
Are sea lampreys r-selected or K-selected? or both?
sea lampreys are more r-selected because the live short lives (6-20 years) and have many offspring
The Great Lakes have how much coastline?
10,000 miles
Salmon are anadromous. How did researchers deal with this issue while stocking the lakes with salmon?
Coho salmon usually spend the first year and a half in the rivers in streams before descending into the ocean for about 18 months before returning. The great lakes turned out to be a great place for the salmon to live. They planted these fish into Strawberry Creek for several weeks so that the scent of "home waters" would be imprinted on their senses. The fish then followed this scent and came back to the creek where they could be harvested.
Sea lampreys are anadromous. What does this mean? Describe the life phases of sea lampreys.
Anadromous= spend first portion of life in freshwater rivers and streams and then descend to the ocean to live until returning to spawn and die. Born in freshwater, move to ocean's saltwater, migrate back to freshwater, breed, and die.
What is an ecological niche and what led to the demise of lake trout in the Great Lakes?
Ecological niche= how an organism responds to the environment around it... Lake trout filled a large number of ecological niches, meaning that they were adapted to many different conditions and filled the space where other species may have lived. Their demise was met when sea lampreys were introduced to the great lakes. These salt water natives made their way up the canal system and into the great lakes where they multiplied and began to kill off the lake trout.
Briefly describe Vernon Applegate's study on killing sea lamprey and why his lampricide is still being used today
He stalked the lampreys and watched their migration, life, and breeding patterns in order to find their weaknesses -- a way to kill them off. He found they are weakest when they are in the stream (larva, young migrant, or old spawner). The initial plan created traps to catch spawning adults traveling upstream, but Applegate needed something more efficient -- a poison that would kill the lampreys, but not the other species in the lakes. They did this by testing different poisons until they found one (bottle 5,209) that killed the lampreys and not the other fish like bluegills and trout.
How did scientists explain/ hypothesize the cause the great fish die-off of 1967? What was determined to be the cause?
The herring breed very quickly, but the great lakes were not the saltwater environment they needed, and so their bodies were working overtime by trying to expel the freshwater and retain the salt in the water. They reproduce rapidly, but they are ill-suited for the environment.
Lake herons made their way into the Great lakes and this led to an ecological meltdown. What does this mean and why was their population able to grow relatively unchecked? How did they dominate native fish species?
The lake's largest predators, the Atlantic salmon and lake trout, could have kept the herring in check, but due to the over-harvesting of these populations, the herring's populations have skyrocketed. The outcompeted with the native fish for food by feasting on their young.
What impact did introducing the coho salmon do? Why did they eventually die off?
The lampricide took care of the lampreys and the coho salmon took care of the herrings that were overpopulating the waters. The salmon were also "sexy" to the fishermen that wanted a more challenging fish to catch (lake trout were boring and too easy to catch). But they overdid it and the salmon began to populate the great lakes at rates that were unsustainable.
In 1535, the Great Lakes were "ecologically naive." What does this mean?
They had not yet been exposed to change. They had not been able to built an immune system because they were isolated, and thus, naive.
Lake Erie, Huron, Michigan, and Superior are described as the "upper lakes." What does this mean?
They're 600 feet above the level of the ocean
