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Large dead fish surface on Mystic River

Dead fish in the Mystic River

UPDATE: Probably natural causes, river advocacy group says.

Michael Marshall went out for his usual afternoon jog in the Mystic River Reservation just upriver from Assembly Row - and was struck by the sight of "dozens, if not hundreds, of these large fish. All dead."

He says he reported the fish kill to DCR, adds: "There was also this strange orange boat with wheels churning the water. I wondered if that had anything to do with it."

Strange boat in Mystic River

Ed. note: The original headline for this post mentioned a "mysterious" boat churning through the water. As you'll see in the comments, it's a weed chopper and harvester.

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Menhaden die off?

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Interesting, I saw these fish on the Mystic during the Eversource Walk as well, and assumed it was due to low oxygen levels in the water. But it might be more complex than that:

http://www.theday.com/article/20150528/NWS01/150529229

http://newyork.cbslocal.com/2015/06/01/peconic-bay-fish-die-off/

Thanks for identifying the fish species, it was very interesting to learn of them!

I also saw the orange scooper boats docked on Sunday. Right behind them on land was a pile of seaweed or other aquatic vegetation. Looks like these boats scoop up the vegetation. The vegetation could be messy and spoil the water for boating, fishing, etc, or they could also contribute to the low oxygen in the Mystic. Only the DCR knows for sure! EDIT: Thanks for the info, Hokey.

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Those look like common carp (world's largest minnow) to me. Definitely not menhaden--the body is the wrong shape.

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They don't look as flat as menhaden, the bottom one looks kind of like one. I figured they were bloated if you will, from floating in the water.

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Menhaden.

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They do look like carp, but carp also handle low-oxygen environments pretty well.

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Yeah, if it was a low oxygen situation there would be a bunch of other fish species belly up before the carp. So I'd be looking for another explanation.

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Lot's to chew on here: http://mysticriver.org/
This is the tail end of the season when Alewife run on the Mystic Lakes and their tributaries. From MWRA: "When plants die and decompose, aerobic bacteria feed on them. The metabolic processes of the bacteria use available oxygen. When a water body receives excess nutrients (like nitrogen or phosphorus), plant growth is stimulated, which eventually leads to greater bacterial growth and higher BOD. This leaves less oxygen available for other organisms like fish and aquatic invertebrates...Chlorophyll a is one of the types of chlorophyll used by aquatic plants, including algae, to conduct photosynthesis. It is the dominant chlorophyll found in true algae and blue-green algae (Cyanobacteria), and is used as an estimate of algal biomass. Although these important organisms form the base of the food chain, high levels of chlorophyll a can indicate excess nutrient input to a water body. When massive quantities of algae die off, toxins can be released and decomposition can lead to reduced oxygen levels, causing fish kills. "

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A weed-cutting boat. Maybe the one pictured here:

http://aquaticcontroltech.com/spring-2009/

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That's a weed-cutter.

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The spinning wheel chops up the weeds and algae. It can only cut as deep as the spinning wheel. No idea how non bottom-dwelling fish are impacted.

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Are used for propulsion. The machine is known as a harvester.

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Those look like carp. I used to fish the river as a kid and we caught them all the time.

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It was in Longfellow Pond in Swellesley.

https://youtu.be/qlpBKhmLIko

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did any of you see Jeepers Creepers? because that boat looks like the aquatic version of the nightmare truck in Jeepers Creepers.

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The weed harvester is in the Mystic as part of an ongoing effort to remove the invasive water chestnut that was choking the river a few years ago. The plant in the photo with the dead fish isn't water chestnut --- that's water lily I think.

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These are carp which sometimes are very close to the surface. They are generally very tolerant of poor water quality. My first thought was the harvester that has been operating in front of Assembly Square for the first time, cleaning out a lot of water lillies and water chestnuts. The harvester operated only upriver of Route 28 last year. However the number of floating dead fish is prodigious. Never seen anything like it in fifteen plus years of walking along the Mystic at Assembly.

Regards, Wig

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I've been seeing these upriver, too, where the harvester has not been.

Makes me wonder if they didn't tolerate the extremely hard freeze.

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Is there any way we can blame the bunny explosion for this?

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Debone the fish, put the little skeletons out there (strewn about a bunny), and say to King Arthur:

"Look at the bones, man!"

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