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3. Lake Invertebrate ID help

The local lake has a healthy population of both lake trout and landlocked salmon. During the spring smelt run I target both by casting streamers from shore or trolling from a canoe. While lake trout often have smelt in their bellies all the salmon I’ve caught are filled with some caddisfly looking critter. It’s early, mid April in upstate NY and the water temp is between 42-50 degrees. I apologize here there is no scale to the image but I would estimate that each is between 1.5 - 3 cm in length.

Howdy, ADK. I don't think they are caddisflies, as I am seeing some tails on several individuals, also some big heads and jaws. Some might be neuropterans? Perhaps alderfly larvae? I could be wrong, not easy to see details, but the individual closest to the camera has a big head and mandibles.

I'll let the bug nuts on here try to get you a little closer to ID.

Jonathon

Kevin - I'm pretty sure they're a Sialis species. Here are a couple of links.

http://www.troutnut.com/topic/9246/Sialis-sp

https://www.uoguelph.ca/debu/STEVEweb/html/Sialis_larva_NA_lg.htm

They're also known as alderflys, so Jonathan got it right.

Thank you, gentlemen! I would agree, they do look like alderfly larvae. I'm just perplexed how the salmon are feeding on them. I would think they would be picking them off as the larva swims to the surface to emerge but I've never seen much of any insect activity on the lake this early in the year. Do the larvae regularly swim throughout the water column?

Glad to be of help. I'm not highly familiar with the life cycle of the alderflies, though I do know that they lay their eggs on overhanging structures like bridges, the larvae dropping into the water upon hatching. I've seen the egg masses and they're pretty cool looking, like a little black patch of tiny ovoids clinging to the cement.

BTW, pretty fish! I would say tie a big-headed nymph of some sort and perhaps slowly lift it through the water column and see what happens! Good luck and send us more pics of your fishies.

Jonathon

You're unlikely to find Sialis larvae in the water column as it is primarily a bottom feeder. They wouldn't be picking them off as emergers since the larvae crawl onto land and make a chamber under a log or in the soil and pupate there. You can find some info here: http://tolweb.org/Megaloptera
And a photo of an alderfly pupae here:http://joycegross.com/images.php?img=2222_1745