The comparison scores every group at once. This page is for the moment you already have a pair of names in mind — mayfly or stonefly, scud or sowbug, shad or alewife — and want the structures that keep them apart, in one look. Nothing here is a current hatch.
The differences, and nothing else
Best separating check: Deep, slab-sided bodyAt a glance It separates Shiners and minnows from Shad (gizzard and threadfin) cleanly, and every pair of groups still in play differs on it and you can check it at a glance.
What to look at
Shiners and minnows
Shad (gizzard and threadfin)
Long thread trailing from the back findecisiveIn hand
No
Yes
Sawtooth belly keel you can feeldecisiveIn hand
No
Yes
Deep, slab-sided bodydecisiveAt a glance
Not diagnostic
Yes
Dark spot behind the gill coverAt a glance
Not diagnostic
Yes
Rounded, cigar-shaped bodyAt a glance
Not diagnostic
No
Dark vertical bars down the flankAt a glance
Not diagnostic
No
Which way the mouth pointsClose look
Varies
Snout overhangs the mouth
Reported size
38–230 mm
30–520 mm
Water it is recorded in
lake margin, lake open, river, stream, reservoir
reservoir, lake open, river, lake margin
How it moves
schooling; emerald shiners spawn at night in shallow water over sand or mud
constantly moving schools; leaping or skittering across the surface when pressed
Reference seasonality
No family-level window
Spring spawning: Apr, May
The same for both: life stages.
Rows come from the reviewed diagnostic weights the comparison scores with. “Decisive” means one answer puts them at least four points apart — the carrier's own rule for a structure that separates a pair.
The two entries, side by side
no reviewed plateNo plate is drawn for this group, and that is a decision rather than a backlog item. This family is identified by what is missing — no belly keel, no spines, no adipose fin, no thread off the back fin — so a drawing of one shiner would be asserting a shape the record does not claim for the family. Read the four absences below instead. A plate becomes possible here the day this entry narrows to a named species.
Cyprinidae
Shiners and minnows
One soft fin, no saw on the belly, nothing else to it.
First check
Run a finger along the belly, look at the front of the back fin, and check behind it. No saw-edged belly, no spines and no adipose fin is a minnow.
What it is
In forage terms the plainest family: a small fish with one soft dorsal fin, no spines anywhere, no saw-edged belly and no adipose fin. Almost every identification here is made by what is absent.
Stages
Adult (38–230 mm across four common baitfish species)
Water
lake-margin, lake-open, river, stream, reservoir
Separates from Shad (gizzard and threadfin)
A sawtooth belly, or a thread off the back fin, means a young shad rather than a shiner.
Typical windows
No family-level window in this layer.
Patterns (correspondence)
None mapped yet.
Limits
Family-level only. Species separation within Cyprinidae is not supported here.
Is there a long thread trailing off the back fin? That is the one character in this group that nothing else shares.
What it is
A deep, slab-sided, silver fish in a school near the surface is a common big-water forage sight. Two animals here fit that description before you look closer: shad and alewife. Cisco, the other silver schooling fish, is long and slender instead.
Stages
Young of year (About 30 mm when the adult shape forms; 100–180 mm by the end of the first year)
Water
reservoir, lake-open, river, lake-margin
Separates from Shiners and minnows
No saw-edged keel and no dorsal thread on a small silver fish means a shiner, not a young shad. A golden shiner's belly keel is soft and scaleless.
Typical windows
Spring spawning (adult)
Patterns (correspondence)
None mapped yet.
Limits
This entry covers gizzard and threadfin shad together. Anal-ray and scale counts on a fish in hand separate them reliably; yellow fins and a black-speckled chin on a live threadfin are field hints.