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Lake: Blue Mesa Reservoir

Bug identification

Post By: malty falcon      Posted: 5/16/2021 2:04:43 PM     Points: 7586    
Caught a very stuffed laker last week, about 20”. We cut him open to see what was on his buffet. At first glance, we thought tiny crayfish. When I got home, I zoomed in, and couldn’t identify the bugs.
Fish was in 60 FOW, and there was a decent school of lakers under us- we managed 3 doubles in 3 hours, and landed 16 lakers and 3 browns, before we went looking for bigger fish.
 Reply by: SirGreg88      Posted: May. 16, 3:10:26 PM     Points: 89    
Mysis shrimp.
 Reply by: Catdubbing      Posted: May. 17, 7:24:10 AM     Points: 68    
scuds, common in lakes and rivers
 Reply by: yard dogs      Posted: May. 17, 9:13:17 AM     Points: 730    
Yep - mysis. Laker pups LOVE them some mysis
 Reply by: malty falcon      Posted: May. 17, 10:08:34 AM     Points: 7586    
While the photos look like crustaceans, they look NOTHING like mysis shrimp to me. Mysis have slender bodies.

I have fished with scuds extensively at Antero and spinney, and recovered many stomach samples of them, and they are pretty different from the photos above, as well.

Does anybody feel the photos are of sowbugs?
 Reply by: Barnacles      Posted: May. 17, 11:42:39 AM     Points: 972    
My eyes are bad, but looks like 3 different things in that sample to me. I think I'm sold on the scuds, but looks like two insect nymphs in there too. I'm glad I'm not the only one that digs things out of fish stomachs.
 Reply by: not too old to fish      Posted: May. 17, 11:43:19 AM     Points: 6363    
Where are fishseal or brookiefly, they should be able to help.
 Reply by: Catdubbing      Posted: May. 17, 12:52:12 PM     Points: 68    
Mysis are in Taylor Res, Ruedi, and Dillon article on web by Pat Dorsey
 Reply by: Smelly      Posted: May. 17, 4:40:40 PM     Points: 25806    
Malty. Sow bugs are those silver bugs that roll up when touched. Sometimes called armadillo bugs . Those look like mysis shrimp to me also
 Reply by: malty falcon      Posted: May. 17, 5:03:24 PM     Points: 7586    
Since Catdubbing pointed out that Mysis Shrimp are in Reudi, Taylor and Dillon Reservoirs, but NOT in Blue, and they DO NOT look like mysis shrimp
[log in for link]

I'm going with Asellus Aquaticus, or the aquatic sowbug. I've only seen them in Spinney near the inlet. Never seen them in great numbers, but the lakers must have found a BUNCH of 'em.
 Reply by: yard dogs      Posted: May. 18, 9:51:58 AM     Points: 730    
Good post man. And now I am very curious. I am still guessing mysis, but I really don’t know. I also agree that I see a couple different looking bugs.

This guy looks shrimpy to me...
 Reply by: bigbear57      Posted: May. 18, 12:04:33 PM     Points: 996    
i used to find Lakers in Williams fork full of those. The one at the top and the very bottom are sow bugs. To hard to tell on the center but looks like maybe two partially digested sitting together.
 Reply by: FishSeal      Posted: May. 18, 8:33:01 PM     Points: 3169    
Stomach samples... ugh.

First off, I'll say that you have a very clean and good sample, less than 12 hours old. Otherwise, you'd probably have mush.

Second, I have not studied aquatic invertebrates, but have studied aquatic insects. Those are not insects. :)

To me, they do have the appearance of the aquatic sowbugs and scuds (or fairy shrimp). Typically more shallow, so my guess is that they were breakfast before the fish went deep again. It's not uncommon for lakers to display diel vertical migration, coming shallow to feed and going deep again to digest. Walleye do the same thing.

Aquatic invertebrates are typically what produce pink meat. When the meat starts turning white, is an indication that the fish is switching meals to more fish (becoming piscivorous).

It's good to know your quarry... including their last meal. :D

 Reply by: Mud      Posted: May. 20, 1:06:58 PM     Points: 68    
I caught 2 lakers yesterday and both were packed FULL of these guys, like, stomach stretched as far as it could go full. I didn't get a picture, but the front half of the stomach was full of freshly eaten ones and they were pretty clearly aquatic sowbugs.

They were concentrated at the edge of a 60 foot flat overlooking deeper water. There was loads of fish there, and they were tough to get to bite. Considering how fresh some of the ones in the stomach were, I thought they must have been feeding on them down there.
 Reply by: brookieflyfisher      Posted: May. 20, 6:15:00 PM     Points: 6154    
Most of that stomach doesn't look like mysis to me. Mysis are long and thin, and would be dang near transparent by the time you got them out of the stomach.

What I'm seeing are isopods, which is a big, diverse order of crustaceans whose best-known member is the rolly-polly (or pillbug or woodlouse or whatever other name you like) that you see in your backyard. Most isopods are marine, and include those bizarre tongue-eating fish parasites (google *that*, I dare you). Regardless, all isopods pretty much look like rolly-pollies, in that they're flat with hard armor plates on their backs. It's totally reasonable that lake trout would be eating these guys, isopods like to live on any sediment surface they can find, even in deep water.

 Reply by: brookieflyfisher      Posted: May. 20, 6:16:00 PM     Points: 6154    
A note on common names for small freshwater crustaceans:

Most anglers don't have any idea what an "isopod" is and generally lump these dudes in with other small aquatic crustaceans and call them all "scuds", "freshwater shrimp", "fairy shrimp", or some such other local name.

To me, "scuds" mean the amphipods, which are closely related to isopods but totally different in shape and habit. That can be important if you're trying to "match the hatch"! If you hear they're getting fish on "scuds", you better find out if they mean isopoda or amphipoda!

"Freshwater shrimp" is a common term that is typically used interchangably with "scud". I hate the term because "scuds" (amphiods/isopods) are not shrimp, and true freshwater shrimps are a totally different animal with totally different shape, color, and habit.

"Fairy shrimp" is typically a term for a totally different thing, and generally not important to anglers. When most folks say "fairy shrimp", they're referring to brine shrimp (sea monkeys), tadpole shrimp, or other weird crustaceans that live in temporary pools or hypersaline lakes.
 Reply by: Barnacles      Posted: May. 20, 8:49:03 PM     Points: 972    
Darn it. When Brookieflyfisher posts, I end up on google or immersed in textbooks for hours just to translate to redneck. My IQ is about 12, but the Isopoda order is under the subphylum crustacea. Them is some scuds.
 Reply by: yard dogs      Posted: May. 21, 8:38:18 AM     Points: 730    
Lol- translate to redneck ... thats funny

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