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| Biomass measurements of "Bloaters" in Lake Michigan. Line added to show "zero". Source |
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| Biomass Alewives in Lake Michigan. You can see that as the alewife biomass dropped the bloater population grew. |
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| Sampling plan. Trawls were pulled through the water at various depths to get a representative sample of the column of water. |
Alewives and bloaters are both "prey" species and are near the base of the food pyramid. "No prey fish" means collapsing populations of glamor fish like salmon and steelheads.
Other important prey species in Lake Michigan include smelt, sticklebacks, round gobies and sculpin. In terms of mass, they are dwarfed by alewives and bloaters.
Notable fact, bloaters averaged 40 kg/ha between 1985 and 1998. That is about 40 pounds per acre or 25,000 pounds per square-mile or half a billion pounds for all of Lake Michigan.
To quote directly from the document linked in the first image:
In 2019, this survey estimated a total biomass density of (all species of) prey fish equal to 1.77 kg/ha
That is a 95% decline from the 1980s and 1990s.
And it was not just a one-year decline. The biomass of prey species flat-lined in 2006 and have not recovered.
Less directly, those mussels sequester or "sink" the phosphorous that plankton needs to grow and that prey species need for their bones and brains. A small fish like a smelt or sardine is approximately 0.5% phosphorous by fresh body-weight.
The amount of phosphorous represented by the missing prey species in Lake Michigan is about 1500 tons. Presumably, a similar amount was carried by the plankton they ate.
Ironically, the EPA has been all over reducing phosphorous and nitrogen releases to the Great Lakes. That was probably appropriate before the zebra and quagga mussels invaded Lake Michigan, but circumstances changed and it might be appropriate to reconsider that position.
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| "Smoked chubs" as they are known in the trade. Apparently, people outside of Wisconsin and Michigan have negative association with eating something called a bloater. |
After all, we are talking about a half-billion pounds of human quality food for just Lake Michigan.
Ugh ERJ. That is alarming.
ReplyDeleteI wonder if that Chub is the same fish we have here in the river running through my valley ? They look rather like that and about the size of a large Sardine . We seine them for bait for the Bass .
ReplyDeleteYou are talking about creek-chubs. I, too wondered.
DeleteCreek-chubs are in the minnow family and the bloater is a whitefish in the salmon family.
I remember the great alewives die-offs in Lake Michigan. They had to use bulldozers to clear the beaches in Chicago.
ReplyDeleteI've attended invasive species meetings about zebra mussels in pueblo colorado. The small clam can have population density measured at 100,000 per sq meter. They are able to filter all the near by water so effectively that there no microscopic food left for bottom food chain with in several days. Originally from Caspian sea. In area's with the mussels water intake systems have to have redundant systems that can be shut off and cleaned out. The Hoover dam has to have divers routinely clean out systems there. Bad, bad news. Colorado has discovered it's first infestation at Highline lake Grand Junction last month.
ReplyDeleteEcosystems are devastated by invasive species. No natural predators to keep them in check leads to bad outcomes. Now substitute your aquatic species with illegal aliens, entry level jobs, skilled trades etc... What is the outcome for a nation?
ReplyDeletehold a big contest among the country's best chefs to create several killer recipes for the mussels. Then we all can be their natural predators.
ReplyDeleteThe government making a bad decision?!? Color me shocked!
ReplyDeleteHaha
Grew up on the shores of the Niagara River. Fishes lakes Erie and Ontario many a time. The mussles hit when I was still a kid, the river _had_ gotten pretty bad. Couldn't see 3 feet in to see what you caught, suckers and catfish all had tumors, and there was a light brown colored foam that inhabited parts of the river...
ReplyDeleteLast time I was there the mussles had cleaned up the water you could see 8+ feet in. There are these little gobyy fish, too, that are invasive Ive been told, that are competing at the bottom of the food chain. Allegedly the bass have figured out the gobies are edible, so that should be the end of that!
"Apparently, people outside of Wisconsin and Michigan have negative association with eating something called a bloater.
ReplyDeleteBloater? What's in a name? Call it a "Chubby" and be done with it.