Oarfish

What it is

The oarfish comprises three species within the family Regalecidae. These animals possess extremely elongated, ribbon-shaped bodies that lack scales. The giant oarfish holds the record for the longest bony fish, reaching eight metres. Their dorsal fin stretches from above the eyes along the entire back, featuring a crest with reddish spots. Pelvic fins are reduced to thin rays, while pectoral fins sit low on the body. The tail tapers to a fine point, often lacking a distinct caudal fin. Skin may bear hard tubercles in some species. They appear silver with dark spots. Despite their size, they have little muscle mass due to living in calm deep waters without strong currents.

Where it lives

These fish live in tropical, subtropical, and warm temperate oceans across the globe. They typically dwell between two hundred fifty and one thousand metres below the surface. Humans rarely encounter them alive because pressure changes kill them when they rise too quickly. Records come mostly from accidental catches or beachings. Sightings occur in the Gulf of Mexico, off Japan, and in New Zealand. Deep-sea vehicles have filmed them swimming vertically or horizontally. Their distribution spans wide oceanic areas, though specific locations remain poorly documented due to their elusive nature.

How it lives

Oarfish move by undulating their long dorsal fin while keeping their bodies straight. This amiiform swimming allows efficient movement in still deep water. They feed on zooplankton, shrimp, small fish, and jellyfish. Predators likely include shortfin mako sharks and sperm whales. Oarfish exhibit slow flight responses to threats, suggesting few natural enemies. They practice autotomy, shedding their tails to escape predators. The wound heals, but the tail does not grow back. Some specimens show hyperossified bones supporting their spines during movement. They lack swim bladders, relying on constant tail motion to regulate depth.

Breeding and life cycle

Spawning occurs in batches over one or two months. Females release bright, buoyant eggs up to six millimetres wide into the water column. Larvae hatch after three weeks and drift near the surface feeding on zooplankton. Young fish resemble adults less than typical fish, possessing long fins and extensible mouths. Artificial insemination experiments produced larvae that died after four days. Adults spawn off Mexico between July and December. Males have disconnected testes, while females have bifurcated ovaries. Each female produces hundreds of thousands of eggs.

Fish and people

Oarfish are occasionally caught as game fish or commercially on a small scale. Their flesh is gelatinous and generally considered poor for eating. Beachings before storms led to beliefs they predict disasters. In Japan, they are called the Messenger from the Sea God's Palace. Folklore links their appearance to earthquakes and tsunamis. A 2019 study described this link as an illusory correlation. Historical sea serpent tales likely originated from sightings of these large, strange creatures. Researchers value them for studying deep-sea adaptation and evolution.

Status and threats

Data on oarfish populations remains scarce. Conservation status is listed as data deficient. Threats include commercial fishing and habitat disturbance. Their rarity makes population assessment difficult. Beachings often result in death due to decompression. Research efforts focus on understanding their biology through rare captures and remote footage. No specific protection programmes are mentioned. Their role in deep-sea ecosystems is not fully understood. Future studies may clarify their vulnerability to environmental changes.

Relatives and look-alikes

The family Regalecidae includes three species: the giant oarfish, Russell's oarfish, and streamer fish. They belong to the order Lampriformes. Close relatives include Trachipterus trachypterus and Zu cristatus. Genetic analysis confirms their placement within this group. Other lampriforms share morphological traits like protrusible mouths. Confusion sometimes arises with eels due to their shape, but oarfish are bony fish. Distinctive features include the dorsal fin crest and lack of scales.

Questions people ask about Oarfish

Good reading and sources

• BBC - Earth News - Giant bizarre deep sea fish filmed in Gulf of MexicoBBC, Article
• Oarfish Offer Chance to Study an Elusive Animal Long Thought a Monster (Published 2013)The New York Times, Article
• Third oarfish, mythical harbinger of doom, found washed up in CaliforniaThe Guardian, Article

• Oarfish on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data