Pacific Hagfish

The Pacific hagfish (Eptatretus stoutii) is a jawless marine fish of the class Myxini, found along the eastern Pacific Ocean from Alaska to Baja California, Mexico. Like other hagfish, it has an eel-like, scaleless body supported by cartilage rather than a bony skeleton, and it lacks jaws, relying instead on a barbel-ringed mouth with rasping tooth plates. The species is well known for its ability to secrete copious amounts of slime from specialized glands as a defense mechanism against predators. Pacific hagfish live on the seafloor of the continental shelf and slope, where they act as important scavengers, consuming carrion and helping recycle nutrients in deep marine ecosystems. They belong to one of the most ancient surviving vertebrate lineages.

Pacific hagfish share the classic hagfish body plan and are best distinguished from similar species primarily by range and fine anatomical detail.

Key field marks:

• Elongated, scaleless, eel-like body in pinkish-tan to grey-brown coloration
• Jawless mouth surrounded by short sensory barbels, with rasping tooth plates instead of true jaws
• Small, degenerate eye spots that are not functional for image-forming vision
• Series of external gill pores arranged along the lower sides of the body, rather than a single gill opening
• No paired fins; only a low, continuous fin fold running along the tail
• Adults typically 40-60 cm long

It is distinguished from lampreys, which have a circular sucking disc mouth rather than barbels, and from true eels, which have functional eyes, jaws, and paired fins.

Pacific hagfish inhabit soft, muddy seafloor habitats along the continental shelf and upper slope of the eastern Pacific Ocean, from the Gulf of Alaska south to central Baja California, typically at depths ranging from roughly 20 to over 900 meters. They favor cold, low-light bottom environments and are often found partly buried in fine sediment or resting near rocky crevices. Their distribution closely tracks areas with abundant organic material and carrion availability on the seafloor. As with other hagfish, Pacific hagfish avoid brightly lit, shallow, or high-energy waters, making them primarily encountered through deep trawl surveys, baited traps, or submersible observation.

Pacific hagfish are nocturnal, solitary bottom-dwellers that locate food primarily through smell and touch rather than sight, since their eyes are non-functional. They are opportunistic scavengers, often detected in large numbers converging on carcasses on the seafloor, which they may enter and feed on from within. When disturbed or grasped by a predator, a Pacific hagfish rapidly discharges slime from pores along its flanks, which expands dramatically in seawater and can deter or suffocate an attacker; the hagfish can then tie a knot in its body to wipe away the slime and free itself. Reproduction involves the laying of a small number of large, yolk-rich, tough-cased eggs directly onto the seafloor, with no distinct larval stage. Through their scavenging, Pacific hagfish contribute significantly to nutrient cycling in deep benthic communities.