Freshwater Drum, Aplodinotus grunniens

Freshwater Drum, Aplodinotus grunniens, Juvenile. Fish caught from the Niagara River, Fort Erie, Ontario, Ontario, Canada, July 2017. Length: 21 cm (8.3 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

Freshwater Drum, Aplodinotus grunniens. Fish caught from the Gatineau River, Gatineau, Quebec, Canada, June 2014. Length: 33 cm (13 inches). Catch, photograph, and identification courtesy of Kenneth Tse, Toronto, Canada.

Freshwater Drum, Aplodinotus grunniens.  Fish caught in the St. Francis River in Wappapello, Missouri, June 2016. Length 41 cm (16 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

Freshwater Drum, Aplodinotus grunniens.  Fish caught from a stream in St. Paul, Minnesota, June 2016. Length 41 cm (16 inches). Catch, photograph, and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.

Freshwater Drum, Aplodinotus grunniens. Fish caught from the Niagara River, Fort Erie, Ontario, Ontario, Canada, July 2017. Length: 61 cm (2 feet 0 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

The Freshwater Drum, Aplodinotus grunniens, is a member of the Croaker or Sciaenidae Family, that is also known as the Sheephead and in Mexico as roncador de agua dulce. It is the only global member in the genus Aplodinotus and is found throughout the freshwater systems of mainland Mexico.

The Freshwater Drum is a large fish with laterally compressed deep body and high arched back. Larger fish have a significantly greater body depth anterior of the first dorsal fin. They vary in color being gray or silvery in turbid waters and bronze-brown in clearer waters. Their anal fin has 2 spines with a posterior straight margin and the second spine is significantly larger than the first, and 6 or 7 rays; their caudal fin is rounded or triangularly-shaped; their first dorsal fin has 9 or 10 spines, their second dorsal fin has 28 to 31 rays; their pectoral fins have 15 or 16 rays; and, their pelvic fins have 1 spine and 5 rays. Their head has a rounded snout and a sub-terminal blunt mouth equipped with numerous small sharp teeth on each jaw and small round teeth on the pharynx used for crushing and grinding prey. They are covered with scales and their lateral line is prominent and continuous into the caudal fin.

The Freshwater Drum inhabits freshwater their entire life, making them the only North American member of the Sciaenidae Family to do so. They are a demersal species found in clear water over sand and gravel substrates but can also tolerate turbid and murky waters. They are found in deep pools in medium to large rivers and at varying depths up to 18 m (60 feet) in large lakes. They are dimorphic with females growing faster and become larger than males. They reach a maximum of 1.22 m (4 feet 0 inches) in length and 27 kg (60 lbs) in weight. They are known to congregate in large schools for feeding and breeding. They are nocturnal predators consuming aquatic insect larvae, bivalve mussels, crayfish, and small fish. They are believed to help control minimally the invasive Zebra Mussel in northern lakes and rivers. In the northern part of their range they associate with the Walleye, Sander vitreus. Juveniles are preyed upon by numerous predatory fish including Smallmouth Bass, Walleye, and birds. They migrate to warmer shallower waters for spawning during the summer as they require water temperatures in excess of 18^oC (65^oF) for reproduction to commence. Reproduction is oviparous with females broadcasting 34,000 to 67,000 eggs into the water column which float to the surface and are then fertilized randomly by males. Eggs and larvae are pelagic without parental care and subject to significant predation. Mature males emit sounds which are believed to be linked to the spawning process. They are long-lived with lifespans of seventy-four years based on extensive otolith measurements. The Freshwater Drum is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

The Freshwater Drum is one of the most wide-ranging species in North America being found from the Hudson Bay, Canada in the north to Guatemala in the south. In Mexican waters they are residents of all freshwater systems that drain into the Atlantic Ocean.

The Freshwater Drum is straightforward to identify and not easily confused with any other species due to its two anal spines, the second of which is large, and its prominent lateral line that extends into the caudal fin base.

From a conservation perspective the Freshwater Drum is currently considered to be of Least Concern with stable, widely distributed populations. They are an important commercial fish that are caught from the Mississippi River with the majority being taken as a by-catch of targeted higher value fisheries. They are harvested at a level of 1,000,000 lbs per year in North America and considered a popular food fish in some areas. Current adult population levels are estimated to exceed 100,000 individuals. At present they are without any form of protection. They are of modest interest to traditional recreational anglers and are known for their great fighting ability and large size. Due to their abundance they are also a target of bowfishermen. They are also used on a limited basis as live bait for other fish. They have exceptionally large inner ear bones or otoliths which are called “lucky stones” and collected for good luck. The otoliths have been found in old Indian settlements and used in trade and as jewelry.