| Family overview: The freshwater drum (Aplodinotus grunniens) is Pennsylvania’s only freshwater representative of a large group of 210 marine species found in temperate and tropical coastal waters around the world. The lower pharyngeal (throat) arches are heavy and fused, and they bear flat, molar-like teeth. The spiny and soft-rayed portions of the dorsal fin are narrowly joined. The spiny-rayed portion is shorter that the spinous section. The lateral line continues to the end of the tail fin. In Pennsylvania, the freshwater drum occurs in Lake Erie, and in the Allegheny, Ohio and Monongahela rivers.
Identification: The freshwater drum is dark-green to olive-brown on the upper part of the head, back and sides, shading to silvery on the sides. The belly is white. The anal fin has two spines, the first, very small and the second, quite large. The body is sharply arched.
Life history: Some of the marine members of this family are called “croakers” because of the sounds they produce. As in the marine species, Pennsylvania’s freshwater drum produces a drumming sound by using muscles attached to the air bladder. These sounds are produced most often during the summer breeding season. Spawning takes place in relatively shallow portions of lakes or in the backwaters of streams. The eggs are very small. Freshwater drum are unique among freshwater fishes because their eggs are so buoyant, they float.
The young grow rapidly at first, but most Pennsylvania freshwater drum do not reach 20 inches even after more than 10 years of growth. The pharyngeal teeth allow it to feed on mollusks, but it also feeds on insects and other invertebrates. |
