Callorhinchus callorynchus | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Chondrichthyes |
Subclass: | Holocephali |
Order: | Chimaeriformes |
Family: | Callorhinchidae |
Genus: | Callorhinchus |
Species: | C. callorynchus |
Binomial name | |
Callorhinchus callorynchus | |
American elephantfish range. [2] |
The American Elephant Fish (Callorhinchus callorynchus), commonly referred to as the cockfish, belongs to the family Callorhinchidae, a unique group of cartilaginous fishes. This species has a striking appearance, characterized by a silver to gray body with prominent brown spots concentrated on the dorsal half of the fish and on the fins. Subtle hues of pink are also present around areas such as the mouth and fins. Its broad pectoral fins play a critical role in stabilization, allowing the fish to maintain balance on the ocean floor, while its heterocercal tail, a feature common among cartilaginous fishes, is highly effective for maneuvering within the water column. The asymmetrical structure is essential for tasks such as ascending, descending, and making sharp turns. [3]
As one of the oldest living groups of jawed cartilaginous fishes, C. callorynchus has adapted to its habitat by benthic foraging. Benthic foraging is a method of seeking prey that entails sifting through the sludge of the ocean floor that bottom feeding fish utilize to forage for prey. Its most notable characteristic is its unique sub-terminal plough-shaped snout that is well-adapted for crushing invertebrate prey including scallops, mollusks, and other benthic invertebrates. Its strong jaws contain tooth plates, which are structures in the mouth designed to crush hard-shelled prey, making it an efficient bottom-dwelling predator. Furthermore,Sexual dimorphism is present in this species, with females reaching lengths of up to 102 centimeters and males growing to about 85 centimeters. Upon birth, juveniles measure approximately 13 centimeters in length. [4]
Callorhinchus callorynchus is a species predominantly found in the coastal waters of southern Brazil, Peru, Chile, Argentina, and Uruguay. This species inhabits the open seas of the southeast Pacific Ocean and southwest Atlantic Ocean, with a preferred depth range of approximately 200 meters. [5] However, during their reproductive cycle, including mating and egg-laying periods, these fish are known to migrate to shallow coastal waters. Although they are closely genetically related, it is important not to confuse them with other chimeras because they differ greatly in their preferred location. Other chimeras include the Callorhinchus milii, which found in the sea floors surrounding Australia in the southwest Pacific Ocean, and Callorhinchus capensis, which inhabits waters off the coast of South Africa.
The mating and egg-laying cycle of Callorhinchus callorynchus happens primarily in the spring and early summer months, typically in shallow murky waters at depths of around 30 meters. C. callorynchus are oviparous, in which their eggs are internally fertilized and layed to mature and hatch outside of the female body. This reproductive process is highly dependent on water temperature, with optimal conditions ranging between 14 °C and 16 °C. This acts as a biological trigger for the onset of egg-laying. Once fertilized, the embryonic development of this species spans a period of six to eight months.
The eggs themselves are distinctively yellowish-brown in color and spindle-shaped, measuring approximately 13 to 18 centimeters in length. They are also asymmetrical, with one side of the egg being flat and covered in a hairy texture, while the other side is round and smooth, providing additional protection for the developing embryo. [6] The odd shape of the egg is vital for its success in remaining buried within the sediments. Adult females of this species typically reach sexual maturity between six and seven years of age, whereas males mature earlier, usually between four and five years. The relatively late sexual maturity is consistent with the species' lifespan, which averages fifteen to twenty years. This longevity allows for extended growth and development before reproduction. [7] The species exhibits selective feeding behavior based on sex, age, and prey availability, often targeting different species of scallops depending on factors such as prey strength, behavior, and size. This dietary flexibility further highlights its adaptability as a bottom-dwelling predator. [8]
The Cockfish is currently listed as vulnerable (VU) on the IUCN Red List, with its population steadily declining due to environmental pressures, particularly overfishing. This species plays a vital role in the Argentine fisheries. It is often caught for its meat and, more concerningly, as bycatch in commercial fishing operations. [9] The pressures from these fisheries are contributing significantly to the decline of this species.
A study conducted by Melisa A. Chierichetti from the National University of Mar del Plata (UNMDP) focused on the reproductive biology of C. callorynchus and revealed important findings. One of the key discoveries was the presence of sexual dimorphism, with females typically being larger and heavier than males within the studied population. [10] The study also highlighted the species' low fecundity rate, a factor that increases its vulnerability. Females were often found in the resting phase of their reproductive cycle, and many of the males had not yet reached sexual maturity, which contributes to the low reproductive output of the population. This information is crucial for the development of conservation strategies, as it emphasizes the need to limit fishing pressures and allow for population recovery.
The vulnerability of C. callorynchus is heightened by several biological and environmental factors. Its tendency to form large aggregations makes it particularly susceptible to overfishing, while its low fecundity rate and late sexual maturity further reduce its ability to recover from population declines. Additionally, global environmental changes pose a significant threat to this species. Rising sea temperatures, driven by climate change, has the potential to disrupt their reproductive cycles. These fish rely on specific water temperatures between 14 °C and 16 °C to trigger their instinctual migration to shallower waters for mating and egg-laying. A recent study indicated that sea surface temperatures have risen by 0.9 °C over the past 37 years, potentially altering the conditions needed for successful reproduction.
Furthermore, the food supply of C. callorynchus is at risk due to coastal pollution, particularly along the Brazilian coastline. Warmer water temperatures have led to an increase in nutrient and bacterial blooms, which negatively impact the populations of scallops, one of the primary prey species for C. callorynchus. [11] As a benthic forager, the elephant fish rely heavily on these invertebrates, and any decline in the benthic population could have negative effects on its food security. This instability in food sources, combined with environmental stresses and fishing pressures, poses a serious threat to the long-term survival of the species.
Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, rat fish, spookfish, or rabbit fish; the last three names are not to be confused with rattails, Opisthoproctidae, or Siganidae, respectively.
The shovelnose guitarfish is a ray in the family Rhinobatidae. The genus is derived from the Greek word rhinos, meaning nose, and the Latin word batis, which means ray. R. productus was first described by ichthyologist William Orville Ayre in 1854. As its common name suggests, this species possesses a pointed shovel-shaped snout and a body similar to that of a guitar with a larger head and long, slender body. The shovelnose is considered to be a primitively developed ray, with many features of both sharks and rays. The shovelnose guitarfish was first considered to be a shark because of its dorsal fins' shape. Fossils of R. productus ancestors have been recovered, dating back over 100 million years.
The whitespotted bamboo shark is a species of carpet shark with an adult size that approaches one metre in length. This small, mostly nocturnal species is harmless to humans. The whitespotted bamboo shark is occasionally kept as a pet in larger home aquaria. It can grow up to 93 centimetres (37 in) long.
The blue stingray is a species of whiptail stingray of the family Dasyatidae often found in the coastal waters of southern Africa.
The cobbler wobbegong is a carpet shark in the family Orectolobidae, the only member of the genus Sutorectus. It is found in the subtropical eastern Indian Ocean around Western Australia between latitudes 26° S and 35° S. It is frequently found in rocky and coral reef areas. Cobbler wobbegongs reach a length of 92 cm. It has unbranched dermal lobes on the head, rows of warty tubercles along the back and black spots on the body and fins.
The shortnose spurdog also known as the piked spurdog is a small shark located primarily off the coast of Southern Australia and South Africa. The shortnose spurdog's size is dependent on the sex of the animal. The female shortnose spurdog is consistently larger than the male shortnose spurdog and will typically measure out to about 56.41 cm (1.85 ft) while the male shortnose spurdog will typically only measure out to about 44.36 cm in length (1.46 ft) which means the female shortnose spurdog is over 10 cm longer than the male shortnose spurdog. Some females can even measure up to 78 cm which is over 2.5 feet long. The life span of spurdog's can be quite long with females typically living longer than males. The average life span of a female shortnose spurdog is 0–29 years old while the male life span is 0-26 though it is estimated that a female can live up to 46 years while a male can only live up to 33. Females also take longer to reach sexual maturity than males and on average are not fertile until they are over 15 years of age. 7 years longer than the 8 years it takes males to reach maturity. The shortnose spurdog's eat a variety of items but primarily favor cephalopods such as squid and octopuses for their meals. Other organisms that have been found in their stomachs include fish, hermit crabs, sponges, brittle stars, the remains of sea lion and even primary producers such as algae.
The dark shyshark or pretty happy is a species of shark belonging to the family Pentanchidae, the deepwater catsharks. This species is endemic to the temperate waters off southern Namibia and western South Africa. It is benthic in nature and inhabits shallow, inshore waters and favors rocky reefs and kelp forests. Growing to 60 cm (24 in) long, this small, stocky shark has a wide, flattened head with a rounded snout and a large flap of skin extending from before the nostrils to the mouth. Its dorsal coloration is extremely variable and may feature black-edged orange to blackish saddles and/or white spots on a light brown to nearly black background.
The small-spotted catshark, also known as the sandy dogfish, lesser-spotted dogfish, rough-hound or morgay, is a catshark of the family Scyliorhinidae. It is found on the continental shelves and the uppermost continental slopes off the coasts of Norway and the British Isles south to Senegal and in the Mediterranean, between latitudes 63° N and 12° N. It can grow up to a length of 1 m, and it can weigh more than 2 kg (4.4 lb). It is found primarily over sandy, gravelly, or muddy bottoms from depths of a few metres down to 400 m (1,300 ft). S. canicula is one of the most abundant elasmobranchs in the northeast Atlantic and Mediterranean Sea. The majority of the populations are stable in most areas.
The blackmouth catshark is a species of deepwater catshark, belonging yo the family Pentanchidae, common in the northeastern Atlantic Ocean from Iceland to Senegal, including the Mediterranean Sea. It is typically found over the continental slope at depths of 150–1,400 m (490–4,590 ft), on or near muddy bottoms. The youngest sharks generally inhabit shallower water than the older juveniles and adults. This slim-bodied species is characterized by the black interior of its mouth, a marbled pattern of pale-edged brownish saddles or blotches along its back and tail, and a prominent saw-toothed crest of enlarged dermal denticles along the upper edge of its caudal fin. It reaches lengths of 50–79 cm (20–31 in), with sharks in the Atlantic growing larger than those in the Mediterranean.
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The Cape elephantfish, also known as josef or St Joseph shark, is a species of fish in the family Callorhinchidae.
Callorhinchus, the plough-nosed chimaeras or elephantfish, are the only living genus in the family Callorhinchidae. A few extinct genera only known from fossil remains are recognized. Callorhinchus spp. are similar in form and habits to other chimaeras, but are distinguished by the presence of an elongated, flexible, fleshy snout, with a vague resemblance to a ploughshare. They are only found in the oceans of the Southern Hemisphere along the ocean bottom on muddy and sandy substrates. They filter feed, with small shellfish making up the bulk of their diet. The plough-nosed chimaera lays eggs on the ocean floor that hatch at around 8 months. They are currently not a target of conservation efforts; however, they may be susceptible to overfishing and trawling.
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