Trout Releases & Macroinvertebrate Sampling

Last Thursday and today I volunteered with the Croton Watershed chapter of Trout Unlimited to assist with a trout release and macroinvertebrate sampling at Cross River as part of the Trout in the Classroom program.

In the fall, the New York State Department of Conservation sends trout eggs to schools. The students watch them hatch, learn about them, and care for them until spring, when they take a field trip to release the fingerlings into the wild.

Last Thursday they released brown trout. Today (and the photo above) they released brook trout.

During the field trip, the students also learn about the local watershed, test the water quality, and do some macroinvertebrate (bugs!) identification.

That is where our TU chapter comes in. Before the students arrive, we put on our waders and go out into the river with a kick net and collect samples of bugs in the stream, and set up identification stations for the students to check out. Then we give a short introduction and float from group to group to answer questions and help them identify the bugs.

It was a lot of fun. Cross River is an incredible stream, running through a protected area (Ward Pound Ridge Reservation), and the water quality is excellent. It only took us 10 minutes each day to collect more than the amount of macroinvertebrates we needed for the stations.

We found:

Stoneflies

Rock caddis

Stick caddis

Free living caddis (green)

Net spinning caddis

Scuds

Cranefly larvae

Crayfish (lots!)

Mayflies (multiple species)

Hellgrammites (Dobsonfly larvae)

Water Pennies

Nematodes

We even had an adult early stonefly land on the table so we could point out an adult stage of one of the nymphs.

A mixed sample container

Upper left: Stick cased caddis. Two mayflies, a stonefly, and a hellgrammite.

Nematode, Crane fly larvae, hellgrammite, rock cased caddis, and lots of tiny mayflies

Stonefly, Mayfly, nemotode, rock cased caddis, and net spinning caddis.

Crane fly larvae

Water Penny

Some different kinds of caddisflies:

Net spinning caddis

Rock cased caddis

Stick cased caddis and a rock cased caddis together

Cased caddis outside of its case

Crawfish and some mayflies

I liked the charts we used for identification, so I found the PDFs online when I got home. I printed and laminated copies for myself to keep in my fishing bag!

TIC Dichotomous Key

dnr_bugsheet

I was taken aback at how big the stoneflies were. At least size 8 hooks. The hellgrammites and craneflies were huge, too. I need to tie some bigger flies.

I’ll no longer give the side eye to folks who tie mop flies, because I’ll be damned if they don’t look just like the crane fly larvae. The killer bugs look just like them, too.

Afterward everything goes right back to the river.

Of course, after the students leave we have a bit of free time to head upstream and fish for a bit! Last week I caught an early black stonefly hatch on the stream. All around great day!