With a special focus on Mayflies, Caddisflies, and Stoneflies

Aquatic Entomology & Benthic Macroinvertebrates

Why are there so many insects around streams, rivers, and lakes? Aquatic insects spend the majority of their

lives in water. Hatch in/under water Live for a large percentage of their life under

water getting bigger. When they are ready for adulthood they

rise/crawl to the surface to molt and begin the adult portion of their life above the surface

At this point their primary goal is to reproduce

Why look at invertebrates?

An immediate indication of water quality can be seen just by observing what is living in in it.

Invertebrates are broken down into 3 taxons:

1) Pollution sensitive 2) Somewhat- sensitive 3) Tolerant What if you find no sensitive

organisms in a stream? ** Diversity is key! When fishing they help you

understand what insects are present and therefore what the fish may feed on.

Benthic Macroinvertebrates

Benthic- Bottom dwelling Macro- large Invertebrate- spineless

organism ** Large bottom-dwelling

spineless organism Most are found in the

substrate or on the bottom of rocks. Scrapers, Shredders

Some are climbers- climb up on plant and stems

For fishing we will look at when they are below and above water.

Invertebrate Classification

Taxonomy- science of naming and classifying organisms

Each organism is given a two part name consisting of a Genus(noun) and a species(adjective)

Kingdom Phylum Class Order Family Genus Species

Insect Identification Insect identification begins with

the Class- Insecta Then is divided into more specific

orders. Three important examples

are: Mayfly = ephemeroptera Caddisfly = Trichoptera Stonefly = plecoptera

A dichotomous key is often used for insect identification

This tool uses a list of identifiable characteristics to group organisms into related taxons

Taxa one on the S.O.S. sheet is insects and one mollusk that are sensitive to pollution. Several orders are represented.

Adult Mayfly

Note the Sailboat wings

Adult Caddisfly

Note the tent wings

Adult Stonefly

Note the size and flat wings

Insect Life Cycles

Most insect invertebrates found in a stream are in some stage of metamorphosis

All insects undergo some type of Metamorphosis (series of life changes from the egg to the adult)

Two types- 1) complete 2) incomplete

Complete Metamorphosis

Four stages: 1) egg 2) Larva- all insects

have the post embryonic larval stage

3) pupal- transitional stage, stationary cocoon or mobile

4) Adult- above water Ex. Butterfly

Incomplete Metamorphosis

Has no Pupal stage Larval stage is

characterized by a series of molts

Periods between molts are called instars

Insect is sometimes referred to as a nymph or naiad during the larval stage

Metamorphosis for the beginning fly fisher (Caddis example) Caddis “nymph”

Adult Caddis

Mayfly Life Cycle

How do most fly fishers refer to insect life cycles? “Nymph” = Bottom dwelling version “Pupae” = Worm-like stage “Emerger” = Making it’s way to the surface “Adult” = Normal flying version “Spinner” = Laying eggs

What “life cycle stage” should I fish with? It depends on quite a few things

What are the fish feeding on Do you like fishing a dry fly or nymph? What is your fly selection?

Trout get 90% of their food underneath the surface. Nymphing is more productive!

Invertebrate Sampling

Kick net- large net used to sample a 3’x3’ area in a riffle(current in a stream)

1) Place the net in a riffle, weight down the bottom to prevent escaping underneath

2) pick up and rub large rocks, place aside

3) Stir the substrate by kicking thoroughly with your feet

Grab net- lower right Most fishers will turn over

rocks or run their hands through the bushes to try to locate bugs