How to Identify Alewife

To identify Alewife (Alosa pseudoharengus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Silvery sides, darker blue-green to olive-brown back. A distinct dark spot is often present behind the upper operculum (gill cover).

Scale type

cycloid

Mouth position

terminal

Distinctive features

Deep, compressed body, Large eyes relative to head size, Ventral keel (saw-toothed belly) formed by sharp, bony scutes, Single, short dorsal fin, Absence of a lateral line (or very faint), Small, pointed teeth in both jaws

Dorsal fin

Single, short, located mid-body, typically with 15-19 soft rays.

Tail fin

Deeply forked, symmetrical lobes.

Pectoral fin

Relatively small, low on the body, with 13-16 rays.

Distinctive fins

Pelvic fins are small and located abdominally, with 9 rays. Anal fin is short, located far back on the body, with 17-21 rays.

Identification Tips

1. 1

   Body Shape

   Look for a deep, laterally compressed body, typical of herring species.

2. 2

   Coloration

   Silvery sides with a darker back (blue-green to olive). A key identifier is the single, often indistinct, dark spot behind the upper operculum.

3. 3

   Ventral Keel

   Feel the belly; it will have a sharp, saw-toothed edge formed by bony scutes, characteristic of Alosa species.

4. 4

   Eye Size

   Alewives generally have larger eyes relative to their head size compared to some similar species like Blueback Herring.

5. 5

   Peritoneum Color

   Internally, the peritoneum (lining of the body cavity) is typically pale or silvery in Alewives, which can distinguish them from Blueback Herring (Alosa aestivalis) which usually have a dark peritoneum.

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