With a special focus on Mayflies, Caddisflies, and Stoneflies Aquatic Entomology & Benthic...
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Transcript of With a special focus on Mayflies, Caddisflies, and Stoneflies Aquatic Entomology & Benthic...
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