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Fish bones These bones of a freshwater drum (Aplodinotus grunniens) are being prepared at MVAC’s Lab for use in identifying drum fish bones commonly found at local archaeological sites. Drum, also called sheepshead, are common in larger lakes and rivers of Wisconsin and can grow to over 30 pounds. Their distinctive cranial bones are easy to identify–especially the pharyngeal arches and the otoliths. The two pairs of robust arches in the upper and lower portion of the fish’s throat are used to crush snails, freshwater mussels, and other macro-invertebrate foods. The nickel-sized, paired otoliths, or ear stones, are located in the fish’s cranial vault behind the brain. They assist in hearing and balance. The otoliths, sometimes called “lucky stones,” are composed of a hard calcium carbonate material. When sectioned, they show incremental growth rings that can be used to age the fish.

(Entry by Dr. James Theler)