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 Anchovies from Menhaden (bunker, pogy) cleanly, and every pair of groups still in play differs on it and you can check it at a glance.
What to look at
Anchovies
Menhaden (bunker, pogy)
Rows of small spots behind the shoulder spotdecisiveClose look
No
Yes
Sawtooth belly keel you can feeldecisiveIn hand
No
Yes
Body see-through, backbone or gut visibledecisiveAt a glance
Yes
No
Which way the mouth pointsdecisiveClose look
Snout overhangs the mouth
Mouth angled up, lower jaw leading
Deep, slab-sided bodydecisiveAt a glance
No
Yes
Eye wider than the snout is longdecisiveClose look
Yes
Not diagnostic
Rounded, cigar-shaped bodydecisiveAt a glance
Yes
No
Dark spot behind the gill coverdecisiveAt a glance
No
Yes
Reported size
20–178 mm
30–500 mm
How it moves
dense schools; spawning takes place in the evening
dense schools that ripple or splash at the water surface; young fish corralled at the surface or tight to the shoreline in a feeding blitz
Reference seasonality
Warm-season spawn: May, Jun, Jul, Aug, Sep
Inshore season: May, Jun, Jul, Aug, Sep, Oct
The same for both: water, 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
Engraulidae
Anchovies
You can see through it. That is the character.
First check
Can you see light through the body? One dorsal fin, a large mouth and a narrow faint stripe with it, and you are on an anchovy.
What it is
Hold a bay anchovy up against the sky and light comes through it. The body is described as slender, silvery-green and translucent, grey-shaded over the back, with a narrow silver line down the middle of the side and a large mouth.
Stages
First year (No consulted source gives a first-year length; bay anchovy can mature at about 37 mm within a few months of hatching) · Full-grown (51–102 mm typically; the Pacific northern anchovy to about 178 mm)
Water
surf, inshore, nearshore
Separates from Menhaden (bunker, pogy)
Menhaden are deep-bodied, opaque, keeled along the belly and spotted at the shoulder. An anchovy is none of those things.
Typical windows
Warm-season spawn (adult)
Patterns (correspondence)
None mapped yet.
Limits
The pronounced overhanging snout belongs to the Pacific northern anchovy in the sources, not to the bay anchovy, whose overhang is explicitly described as slight.
Everyone knows the shoulder spot. The shoulder spot is not the answer.
First check
Find the shoulder spot, then look BEHIND it. Rows of smaller spots trailing back is menhaden. A single spot on its own settles nothing.
What it is
A menhaden is a deep, slab-sided, oily fish with a head about a third of its body, swimming with its mouth open and straining plankton through a basket of gill rakers. In a school they ripple and splash at the surface, and when something is under them the young ones get corralled tight to the shoreline in what Massachusetts calls, in an official publication, a blitz. That is the animal most of the coast is actually fishing over.
Stages
First year (30–150 mm; the NOAA staging runs larva under 30, prejuvenile 30–38, juvenile above 38) · Full-grown (152–500 mm depending which source you read — see the limitations)
Water
surf, inshore, nearshore
Separates from Anchovies
An anchovy is translucent with a narrow stripe. A menhaden is opaque, deep-bodied and keeled.
Typical windows
Inshore season (adult)
Patterns (correspondence)
None mapped yet.
Limits
Adult size is stated five incompatible ways across five agencies, one of them exceeding another's stated maximum.