Coelacanth Behavior, Swimming, Mating, Feeding and Threats | Sea Life, Islands and Oceania

COELACANTH BEHAVIOR

Coelacanth are very slow moving creatures. Those observed have tended to be nocturnal animals that hide in underwater caves by day, then venture out at night, feeding on small fish, squid, and octopus. Coelacanth are very passive, hardly showing any response, when approached by an intruder or another coelacanth.

According to Animal Diversity Web: Coelacanths have shown a tendency to aggregate in their daytime cave habitats. However, there has been no observation of social interactions of any kind among coelacanths in their aggregations. Any physical contact appears to be accidental and non-aggressive. No pattern has been discerned in cave selection in coelacanths beyond temperature and depth requirements. Individual coelacanths have been observed staying in different caves from night to night, but also will sporadically revisit the same cave over many years. /=\

John E. McCosker (1979) in his paper "Inferred Natural History of the Living Coelacanth" writes: "An hypothetical life history of Latimeria chalumnae can be constructed on the basis of its anatomy, diet, catch records, and Comoran oceanographic and meteorological data. On that basis, it appears that Latimeria behaves like a large, reef-associated piscivorous grouper.”

Coelacanth are move within a well-defined range. At night, they drift hunt individually. From the few observations made so far of their feeding, it appears that coelacanths do not pursue prey, but will simply snap up any prey of suitable size which passes within 20 centimeters of the front of their mouths. During the course of their nightly hunting, coelacanths may range over several kilometers. The definitive home range of coelacanths is not known. Individuals tagged with a tracking device have traveled between two and eight kilometers in a day. /=\

Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Woods Hole Oceanographic Institute whoi.edu ; Cousteau Society cousteau.org ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures

Coelacanth Swimming

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Coelacanths have strange way of swimming. Sometimes backwards or belly up. "At first glance the ungainly movements of the coelacanth suggest total discordance with al fins flailing helter skelter," The German biologist and coelacanth expert Hans Fricke wrote. "But careful analysis of our motion-picture films of coelacanths persuades me that in fact the fish is well coordinated. The fish's forward, or pectoral, fins and rear pelvic fins are synchronized." [Source: National Geographic]

The coelacanth's slow, graceful stroke is like no other fish's. It moves left pectoral and right pelvic fins, then right pectoral and left pelvic fins — akin to the cross-step of tetrapods (land animals). Because of their specialized fin anatomy, coelacanths possess remarkable agility in the water. They can swim in any direction, and have been witnessed swimming inverted, or in a vertical, face-down posture.

Lobed fins, found on coelacanth and lungfishes, can swivel, allowing the fish to maneuver precisely. Susan L. Jewett wrote in the Washington Post: The coelacanth swims unlike any other fishes. While in the passive drift posture, its body is fairly rigid, with snout pointing slightly down, spinous dorsal fin fully spread like an inverted keel and lobed fins moving in gentle sculling motions. Rapid acceleration can be achieved by strong undulations of the body and tail but probably is of brief duration and used only to capture prey or escape harm. [Source: Susan L. Jewett, Washington Post November 11, 1998]

The two sets of paired lobed fins, pectorals and pelvics — lying to the side and beneath the belly — move in a synchronized pattern typical of tetrapods, four-footed vertebrates — the right pectoral fin or forelimb is coordinated with and moves in the same direction as the left pelvic fin or rear limb. When swimming: 1) The caudal fin sways left as the second dorsal fin and anal fin sway right. The right pelvic fin moves down as the right pectoral fin rises. The left pelvic and pectoral fins do the opposite. 2) The caudal fin sways right as the second dorsal fin and anal fin sway left. The right pelvc fin rises as the right pectoral fin moves down. The left pelvic and pectoral fins do the opposite.”

Coelacanth, Perception and Head Standing

Coelacanths sense using vision, detecting vibrations and using electric signals. They have a rostral organ in their snouts that is believed to have an electroperceptive function. They also possess color vision that is strongly adapted to a deep water environment. Most visible light at that depth has a wavelength around 480 nm, and the visual pigments of coelacanths are most sensitive to wavelengths of 478 nm and 485 nm, which is a blue shift of roughly 20 nm relative to corresponding orthologous pigments. [Source: Animal Diversity Web (ADW)]

Sometimes coelacanths float head down for several minutes perhaps to detect moving prey. Fricke observed the coelacanths resting on stalklike fins and doing headstands on the ocean floor. The fish held the handstand position for up to two minutes. Frick was unable to come up with a plausible explanation for the behavior although he noted that they performed headstands when exposed to an electrical field.

Susan L. Jewett wrote in the Washington Post: One theory proposes that headstanding behavior has to do with an electrosensory system, a nerve apparatus that is shared by many types of fishes and makes it possible to detect even very faint electrical fields, for determining motion of other fish. If the "rostral organ" in the coelacanth's snout is part of the electrosensory system, as many scientists believe, the fish may use head-standing to put that organ closer to the bottom to detect subtle movement of possible prey. No one knows for sure. [Source: Susan L. Jewett, Washington Post November 11, 1998]

Food and Eating Behavior

Coelacanths feed at night on or near the sea floor, drifting with the current. They are categorized as slow drift-hunters and eat a variety of benthic and epi-benthic prey, such as cephalopods, eels, cuttlefish, and deepwater fish. It feeds mostly on fishes but also consumes relatively large amounts of squid and octopus, a diet that is similar to that of a large grouper except that it presumably eats less food as a grouper is much more active and uses more energy than a coelacanth. [Source: NOAA]

Coelacanths are opportunistic in their feeding. Fish species they prey on include Coranthus polyacanthus ( a species of cardinalfish native to the Indian Ocean and the western Pacific Ocean), the The splendid alfonsino (Beryx splendens), bronze whiptail (Lucigadus ori), and goatsbeard brotula (Brotula multibarbata). These fish ten to be 20 to 100 centimeters in length and live at depths of 100 to 650 meters.

The coelacanth intracranial joint and associated basicranial muscle likely play an important but unresolved role in feeding. Aside from their role as large predators, nothing is known about the ecosystem role of coelacanths. Humans are the only known predator of coelacanths. They are considered unfit for eating, and are usually caught by accident by fishermen angling for oilfish (Ruvettus pretiosus). /=\

Coelacanth Mating, Reproduction and Offspring

Female coelacanths reach maturity between 16 and 19 years. They give birth to live young after a very lengthy gestation period up to three years — the longest gestation period of any vertebrate species. They also have the largest eggs of any known fish and give birth to a litter of 26 live and fully developed pups. The growing young live off a large yolk sac until birth at which time they are about a 30 centimeters (a foot) long and look like miniature versions of their parents.

Coelacanths are ovoviviparous, meaning that eggs are hatched within the body of the female, parent, with females bearing their offspring internally for 13 months to three years in the mother's oviduct. Embryo development is supported by yolk provisioned by the female. A gestation period of 13 months was originally determined by Hureau and Ozouf in the 1970s. Once it was established that coelacanths are ovoviviparous, Froese and Palomares (2000) argued that the von Bertalanffy growth function can apply to coelacanth embryos, and found their gestation period to be roughly three years, with supporting evidence based on scale rings. [Source: Animal Diversity Web (ADW) /=]

Coelacanth egg

Susan L. Jewett wrote in the Washington Post: The embryonic coelacanth develops from the fertilized egg and is nourished by an attached "yolk sac" that it sheds at or before birth. Only two mature females with well-developed young have been documented. One had five pups. The other, the heaviest known coelacanth at 98 kilograms (216 pounds) and nearly 182 centimeters (six feet) long, contained 26 young in an advanced stage of development. The largest, presumed to be near birth, was 35.5 centimeters (14 inches) long and weighed half a kilograms (1.1 pounds). Few juvenile specimens have ever been caught following birth, and none have been witnessed in the presence of adults. /=[Source: Susan L. Jewett, Washington Post November 11, 1998]

There is little information available for the life history of coelacanth but is believed that they are monogamous (having one mate at a time). It is likely that fertilization is internal and it has been suggested that males possess a modified cloaca for this purpose due to the absence of an intromittent organ, the equivalent of a penis in land animals, that normally delivers sperm when internal fertilization occurs in fishes. Genetic studies have found evidence of single-male paternity but direct observations of mating behavior are lacking. /=\

During the pre-birth stage provisioning and protecting is done by females. During the lengthy gestation period there is a large energy investment by females in the bearing and nourishment of live young There is no known investment by males in raising young. While gravid females have been found to bear up to 26 fully developed young at a time, the number of eggs at earlier developmental stages can be 60 or more which suggests a decline of brood size during gestation. The long gestation time suggests that females may reproduce at intervals of two or more years. /=\

Threats on Coelacanth Population

Coelacanth is not fished because its flesh is “dense, oily and foul with urea” so few people eat it. However the coelacanth population is in decline. Their total number is believed to be in the hundreds, and it takes years for a female to reach sexual maturity. The greatest source of coelacanth mortality appears to be as bycatch from gill nets or near-shore, deep water fishing. /=\

Fricke (1997) discusses black-market trade of coelacanths. He dismisses as rumor the widely reported use of coelacanth oil in eastern medicine for longevity. However, despite their protected status, Fricke notes that there does exist some low-value, illegal local trade in dead coelacanths, and that the amount private organizations would be willing to pay for a live coelacanth could exceed seven figures. /=\

International Union for Conservation of Nature (IUCN) Red List: Critically Endangered. Convention on International Trade in Endangered Species (CITES): Appendix I, which lists species that are the most endangered among CITES-listed animals and plants. Because the habitat tolerance range of the coelacanth is still poorly defined, major organizations involved in its conservation are emphasizing the importance of a greater understanding of their environmental requirements. /=\

The Tanzanian distinct population segment (DPS) of African coelacanth in particular is subject to bycatch in the Tanzanian shark gillnet fishery, which has been expanding over the last decade. The Tanzanian DPS may experience direct habitat loss due to deep-water port construction, including submarine blasting and channel dredging known to occur in coelacanth habitat.[Source: NOAA]

Efforts to Catch Coelacanths

Coelacanth embryo

Coelacanths are accidentally caught by fishermen in search of commercial species. Fricke wants the World Bank to finance a project in which a fish-attracting devise is used to lure commercial species so local fishermen leave the caves of the coelacanth undisturbed.

In the 1980s fishermen who caught coelacanths were paid about $200 for dead fish and $1,000 for a live one. At that time Comoran fishermen began using heavier lines in a concerted effort to catch the fish live and get a big reward.

No coelacanth has survived more 20 hours in captivity. Coelacanth are poor at absorbing oxygen and live at great depths, reasons why they don't survive long in captivity. The shock of decompression after being brought to the surface after being caught is usually seals their doom. Decompression interferes with their ability ro absorb oxygen.

Japanese and American aquariums have tried to acquire live coelacanths to display. The Japanese have even given free fishing line to fisherman in an effort to get a hold of the rare fish. The New York Explorers Club and New York Aquarium have tried to recruit volunteers, paying $400 a head, to join an expedition to search for the fish.

Some scientists who are seeking life fish for their aquariums say they doing so to set a captive breeding program to ensure the survival of the fish, but critics say they are doing it for the publicity and money that can be made by displaying the rare fish.

Image Sources: Wikimedia Commons; YouTube, Animal Diversity Web, NOAA

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated March 2023