Butterfish

The Butterfish (Peprilus triacanthus), also known as the Atlantic butterfish or dollarfish, is a small, deep-bodied schooling fish in the family Stromateidae, found over the continental shelf of the northwestern Atlantic from Newfoundland to Florida. Unlike many of the rocky-shore species it shares its range with, Butterfish is a pelagic, open-water schooler that seasonally migrates between inshore summer waters and deeper offshore wintering grounds. Its smooth, slippery skin and disc-like body shape give rise to its common name. It is abundant and not of conservation concern, and forms an important prey source for larger predatory fish, seabirds, and marine mammals within shelf ecosystems.

Identify the Butterfish by:

• Deep, oval, strongly laterally compressed body, giving a disc-like silhouette
• Silvery-blue, iridescent sides, sometimes with faint irregular dark spots
• Small, terminal mouth and a short, blunt snout
• No pelvic fins in adults
• Deeply forked tail fin and a short-based dorsal fin mirrored by a similar anal fin
• Smooth, slippery skin with small, easily shed scales, typically 15-23 cm long

Its flattened, coin-like body shape and lack of pelvic fins readily separate it from similarly sized schooling fish such as herring or scad, which have a more elongated, rounded profile and obvious pelvic fins.

Butterfish occurs over the continental shelf of the northwestern Atlantic, from the Gulf of St. Lawrence and Newfoundland south to Florida, most abundant between Cape Cod and Cape Hatteras. It is a pelagic, open-water species associated with the mid- and upper water column rather than the bottom, though it can occur near the seafloor over the shelf. Seasonally, it moves inshore into bays, sounds, and shallow shelf waters during warmer months, then migrates offshore to deeper, warmer water along the shelf edge in autumn and winter to avoid cold inshore temperatures.

Butterfish is a highly gregarious species, forming large, loose schools that move through open shelf waters, often associating loosely with drifting jellyfish, under which juveniles sometimes shelter for protection. It feeds on zooplankton, small crustaceans, and other small invertebrates filtered or picked from the water column. Seasonal migration is a defining behavior, with schools moving inshore in spring and summer to feed and spawn in warmer surface waters, then retreating to deeper, more thermally stable offshore water as temperatures drop in fall. Spawning occurs over an extended season, with pelagic eggs and larvae drifting in open water. As an abundant schooling forage fish, Butterfish is a key link between plankton and larger shelf predators.