Claws in front, tail fan behind, bottom underneath.
First checkAre there pincers much larger than the walking legs? Then it is a crayfish.
Nothing else you are likely to meet in fresh water carries a pair of pincers that size. The claws settle the identification on their own; everything after that is about which crayfish and what condition it is in.MDC-CRAYFISH, UMW-AQUATIC-INVERTSEvidence from: Missouri statement; shrimp comparison from the Upper Midwest guideDispute
Two things about the animal matter more than its name. It lives on and in the bottom, and it walks forward slowly but escapes backwards in a hard flick of the tail fan. Those are two entirely different movements from the same animal.Dispute
The third is moult. A newly moulted crayfish is soft for two to four days and is the same animal, not a different one. Young crayfish moult six to fourteen times in a first year, so size within a season is not fixed.VT-EXT-CRAYFISHDispute
The tell
What settles it, and what settles against it.
Read off this record's own diagnostic weights, heaviest first. A structure near the top of the left column does most of the work on its own; one near the bottom only leans.
Argues for Crayfish
Pincers or claws on the front legs+6
Fan-shaped tail; escapes by flicking rapidly backwards+5
Aquatic insect crawling on rock or debris+3
Two long antennae+3
Argues against it
A shell with no claws or pincers on it at all-6
Fish-shaped forage silhouette (minnow / shiner / fry) — not an insect-5
Moving as a school or tight bait cluster, not as a single insect-4
Body flattened side to side, often lying or swimming on its side-4
No hardened head capsule and no legs — soft and segmented throughout-4
Backs into wet sand rear end first-3
A pair of feathery antennae fanned out into the water-3
Back legs flattened into paddles-3
Body translucent — light passes through it, and the backbone or gut shows-3
A toothed blade projecting forward between the eyes-1
A structure at −4 or below is treated as a hard exclusion by the comparison tool rather than as a penalty: if you saw it, this group is ruled out and no amount of matching elsewhere brings it back. Run a comparison →
Pincers. A crayfish has large claws, far bigger than its walking legs, and a tail fan it flicks backwards with. A sowbug's front legs are small, at most claw-like.
Where in the column it mattersNear the bottom. A bottom animal that is under a rock by day and walking on the bottom at night. Burrowing species spend most of their lives in the substrate itself.
Read from the record's own position notes: on and in the bottom; under rocks and logs by day; burrowed into the substrate; rarely far from the bottom.
What eats it
Which fish the dossiers actually name.
No reviewed dossier names this group. That is an absence in the dossier layer rather than a finding about the animal — four dossiers exist and only one of them names any forage group at all.
The pattern layer ties this group in Nymph. That is a correspondence between an imitation and an animal, worked out when the patterns were written. Whether a fish is on it today is a question this page cannot reach.
Near Nuff Crayfish
Nymph
Hook4–10
A crayfish backing under a rock — claws in front, tail fan behind.
Hopped along the bottom. The flick backwards is the behaviour.
11 of them. The limits are part of what was reviewed rather than a disclaimer bolted on afterwards. An entry that hid them would be claiming more than it checked.
Written by the reviewer
Declared by the reviewerSources disagree on basic counts — four pairs of walking legs plus chelipeds or five pairs with the first enlarged, and six or seven abdominal segments. Neither is offered as a field character.MDC-CRAYFISH, VT-EXT-CRAYFISH, UMW-AQUATIC-INVERTSDispute
Declared by the reviewerSize varies with moult stage: six to fourteen moults in the first year, one to three a year after that.VT-EXT-CRAYFISHDispute
Declared by the reviewerNo source consulted states that crayfish enter the invertebrate drift, so this reference makes no such claim.Dispute
Declared by the reviewerSources disagree on basic counts: whether crayfish have four pairs of walking legs plus chelipeds or five pairs with the first enlarged, and whether the abdomen has six or seven segments. Neither count is offered as a field character.MDC-CRAYFISH, VT-EXT-CRAYFISH, UMW-AQUATIC-INVERTS, EPA-MACROINVERT-FIELD-GUIDEDispute
Declared by the reviewerSize varies with moult stage. Young crayfish moult six to fourteen times in the first year and older crayfish one to three times a year.VT-EXT-CRAYFISHDispute
Declared by the reviewerNo source consulted gives a size for first-year crayfish; newly hatched young are about 8 mm (a third of an inch).VT-EXT-CRAYFISHDispute
Sources disagreeLeg counts are worded two ways. Missouri and Virginia Tech give four pairs of walking legs plus one pair of pincers; the Upper Midwest guide and EPA's Pacific Northwest guide give five pairs of walking legs with the first enlarged.
Sources disagreeAbdominal segments differ by source: six in the Upper Midwest guide, seven in Virginia Tech's.
Read off the record
Nobody typed these. They are fields that are empty, said out loud rather than left for you to notice from a section that simply is not there.
SeasonalityNo reference window is published for this group, so this entry says nothing about when it is available. That is an absence in the calendar layer, not a claim that the animal has no season.
What eats itNo reviewed species dossier names this group. Some dossiers describe forage in class terms — small forage, insects, bait — and those are shown below, but a class description is not a reviewed link to this group and none is claimed.
Sources
Everything above rests on 6 published pages.
These are every page behind this entry. Where a reviewer traced a line above to the pages that carry it, that line names them itself, with where the evidence comes from when it is narrower than the whole entry. A line with no names beside it rests on this list as a whole: nobody has yet checked which page carried it, and naming one would be a mapping nobody made.
A plate shows shape. It cannot show a gill beating, a mask firing, or an animal reversing into sand — so where motion is the field mark, the entry points at motion. These are demonstrations, selected by hand and by publisher. Nothing here is a source: it changes no score, no window and no reviewed claim.
Leaf Pack Network. Walking forward on its legs, then the backward tail-flick retreat. Two locomotion modes, one of them this entry's cue.
Research institute · external video · title read back from the publisher 2026-09-09
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Take the group to the next step.
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Which fish in this kind of water are documented eating this class of forage, and how they behave when they are.
What this forage class asks of the setup — the weight it wants, and where the chain gives first.
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