How to Identify Freshwater Drum

To identify Freshwater Drum (Aplodinotus grunniens), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Silvery-gray to brassy on the sides, often darker dorsally (olive-brown to dark gray), and white ventrally. Fins are typically dusky or translucent. Juveniles may have a faint lateral band.

Scale type

ctenoid

Mouth position

inferior

Distinctive features

Deep, compressed body with an arched back., Large, prominent scales., Long dorsal fin deeply notched, appearing almost as two separate fins., Rounded caudal fin., Large, otoliths (ear stones) with a distinctive 'L' shape, often called 'lucky stones' or 'cross stones'., Produces drumming sounds using specialized muscles vibrating against the swim bladder.

Dorsal fin

Long, continuous dorsal fin deeply notched, with 10-11 spines in the anterior portion and 29-32 soft rays in the posterior portion.

Tail fin

Rounded caudal fin.

Pectoral fin

Moderately sized, rounded pectoral fins.

Distinctive fins

Anal fin with 2 spines and 7-8 soft rays; pelvic fins thoracic, located below the pectoral fins.

Identification Tips

1. 1

   Body Shape

   Look for a deep, compressed body with a distinctly arched or humped back, giving it a somewhat 'football' shape.

2. 2

   Dorsal Fin

   Observe the long dorsal fin, which is deeply notched, making it appear almost like two separate fins. The spiny anterior portion is distinct from the soft-rayed posterior portion.

3. 3

   Mouth Position

   Note the inferior (subterminal) mouth, which is adapted for bottom feeding.

4. 4

   Coloration

   Identify the silvery-gray to brassy sides, darker back, and white belly. Juveniles may have a faint lateral stripe.

5. 5

   Otoliths

   If examining a deceased specimen, the large, 'L'-shaped otoliths (ear stones) are a definitive identifier.

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