Callorhinchus callorynchus | |
---|---|
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 elephantfish (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 Australian ghostshark (C. milii), which found in the sea floors surrounding Australia in the southwest Pacific Ocean, and the Cape elephantfish (C. capensis), which inhabits waters off the coast of South Africa.
The mating and egg-laying cycle of C. 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's 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. [4] 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. [4] 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. [9] 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 pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word pelagic is derived from Ancient Greek πέλαγος (pélagos) 'open sea'. The pelagic zone can be thought of as an imaginary cylinder or water column between the surface of the sea and the bottom. Conditions in the water column change with depth: pressure increases; temperature and light decrease; salinity, oxygen, micronutrients all change. In a manner analogous to stratification in the Earth's atmosphere, the water column can be divided vertically into up to five different layers, with the number of layers depending on the depth of the water.
Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that live on or near the bottom, and reef fish that are associated with coral reefs.
The chain catshark or chain dogfish is a small, reticulated catshark that is biofluorescent. The species is common in the Northwest Atlantic, Gulf of Mexico, and Caribbean. It is harmless and rarely encountered by humans. It has very similar reproductive traits to the small-spotted catshark.
The slimy sculpin is a freshwater species of fish belonging to the family Cottidae, which is the largest sculpin family. They usually inhabit cold rocky streams or lakes across North America, ranging from the Great Lakes, southeast Minnesota, northeast Iowa, southwest Wisconsin and northeast Canada. Slimy sculpins have also been found roaming the cold streams of eastern Siberia. They are commonly confused with their closely related relatives, Mottled sculpin, and with tubenose gobies who are both freshwater fishes as well. The slimy sculpin is a nocturnal fish that usually spends most of its time on the stream bottom and seeks shelter under rocks and logs, especially during spawning season. When it swims, it sometimes appears to be "hopping" along the bottom because of its inefficient ability to swim. This is partly due to the absence of a swim bladder, which normally gives buoyancy to a fish.
The Australian ghostshark is a cartilaginous fish (Chondrichthyes) belonging to the subclass Holocephali (chimaera). Sharks, rays and skates are the other members of the cartilaginous fish group and are grouped under the subclass Elasmobranchii. Alternative names include elephant shark, makorepe, whitefish, plough-nose chimaera, or elephant fish. It is found off southern Australia, including Tasmania, and south of East Cape and Kaipara Harbour in New Zealand, at depths of 0–200 m (0–656 ft). Despite several of its names, it is not a shark, but a member of a closely related group.
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 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 scalloped hammerhead is a species of hammerhead shark in the family Sphyrnidae. It was originally known as Zygaena lewini. The Greek word sphyrna translates into "hammer" in English, referring to the shape of this shark's head, which is its most distinguishing characteristic. The shark's eyes and nostrils are at the tips of the extensions. It is a fairly large hammerhead, but is still smaller than both the great and smooth hammerheads.
The spotback skate is a species of fish in the family Arhynchobatidae. It is found off the Atlantic coasts of Argentina, Brazil, and Uruguay where its natural habitat is over the continental shelf in the open sea. It is a large fish, growing to over a metre in length. It feeds mainly on other fish according to availability, with shrimps, octopuses and other invertebrates also being eaten. Reproduction takes place throughout most of the year, with the eggs being laid in capsules that adhere to the seabed. The spotback skate is the subject of a fishery and is thought to be overfished, resulting in Greenpeace adding the fish to its red list of fish to be avoided, and the International Union for Conservation of Nature listing it as an "endangered species".
The Cape elephantfish, also known as the St Joseph shark or josef, 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.
Chimaera monstrosa, also known as the rabbit fish or rat fish, is a northeast Atlantic and Mediterranean species of cartilaginous fish in the family Chimaeridae. The rabbit fish is known for its characteristically large head and small, tapering body. With large eyes, nostrils, and tooth plates, the head gives them a rabbit-like appearance, hence the nickname "Rabbit fish". They can grow to 1.5 metres (5 ft) and live for up to 30 years.
The eastern shovelnose ray is a species of guitarfish in the family Rhinobatidae of order Rhinopristiformes. The species is endemic to the east coast of Australia and inhabits subtropical and temperate waters from southern Queensland to southern New South Wales.
The great northern tilefish or golden tile, is the largest species in the family Malacanthidae (tilefishes). It grows to a length of between 38 and 44 inches. The great northern tilefish is a slow-growing and long-lived species that has four stages of life. After hatching from eggs, the larvae are found in plankton. As they grow into juveniles, the individuals seek shelter until finding or making their own burrows. As adults, the tilefish continue to expand their burrows in the sediment throughout their lives. The diet of the larvae is unknown, but presumed to consist of zooplankton; juveniles and adults feed upon various benthic invertebrates, crustaceans, and fish. After reaching sexual maturity between 5 and 7 years of age, females lay eggs throughout the mating season for the male to fertilize, with each female laying an average of 2.3 million eggs.
The emerald rockcod, also known as the emerald notothen is a species of marine ray-finned fish belonging to the family Nototheniidae, the notothens or cod icefishes. It is native to the Southern Ocean
The Pacific spiny dogfish is a common species of the Squalidae (dogfish) family of sharks and are among the most abundant species of sharks in the world. This species is closely related to the Spiny dogfish and for many years they were treated as a single species. Recent research, using meristic, morphological and molecular data led to the resurrection of the Pacific spiny dogfish as a separate species. The American Fisheries Society recommends the common name "Pacific spiny dogfish" for Squalus suckleyi over alternatives such as "spotted spiny dogfish" and "North Pacific spiny dogfish" and "spiny dogfish" for Squalus acanthias.
Octopus bimaculatus, commonly referred to as Verrill's two-spot octopus, is a similar species to the California two-spot octopus, which it is often mistaken for. The two can be distinguished by the difference in the blue and black chain-like pattern of the ocelli. O. bimaculatus hunt and feed on a diverse number of benthic organisms that also reside off the coast of Southern California. Once the octopus reaches sexual maturity, it shortly dies after mating, which is approximately 12–18 months after hatching. Embryonic development tends to be rapid due to this short lifespan of these organisms.
The winter skate is a globally endangered species of skate found in the surrounding waters of northeastern North America. They inhabit shallow shelf waters and are prone to bycatch during commercial fishing. There are three populations or Designable Units (DU) including the Gulf of St. Lawrence population (GSL), the Eastern Scotian Shelf and Newfoundland population (ESSN), and the Western Scotian Shelf population.