Individuals tagged off of Newfoundland have been recovered in Iceland years later. There have also been records of transatlantic crossings. However the bulk of the population migrates seasonally along the northeastern coast of North America. The spiny dogfish is an opportunistic feeder eating whatever prey is abundant. In general their diet is comprised of small fishes such as capelin, cod, haddock, hake, herring, menhaden and ratfish.
They also eat invertebrates such as krill, crabs, polychaete worms, jellyfish, ctenophores, amphipods, squid and octopus. Development in this shark is ovoviviparous. The gestation length is the longest known for sharks at an estimated 22 months.
Young are born in the warmer waters off of North Carolina or New England during the winter months. The number of young born in a litter is dependant on the size of the female, larger females bearing more pups.
However most litters are between 2 and 16 individuals that are approximately 20 to 30 cm 8 to 12 inches in length. Sexual maturity in males is reached at a size of 80 to cm 31 to 39 inches at which time they are usually 11 years of age. Females reach sexual maturity at a later age, between 18 and 21 years at which time they are between and cm 39 to 49 inches long.
The spiny dogfish is found in cold and warm temperate oceans at temperatures between 6 and 15 degrees Celsius. However on the Scotian Shelf this shark has been caught in water temperature between 3 and 11 degrees Celsius. The spiny dogfish is tolerant of a wide range of salinities and can be found in estuaries.
The Portuguese dogfish has a fragmented worldwide distribution. It is found on both sides of the Atlantic, from Greenland to the west African coast with a separate population around South Africa and along the coastline of the USA and Canada with a much smaller South American population.
The Portuguese dogfish is only found in Britain in the Rockall Trough, Faroe-Shetland Channel and a few other locations on the west coast of the British Isles which are deep enough to hold populations of this species. The Portuguese dogfish is primarily a predator. It will scour around the seabed hunting fish and squid. However, at times they will also scour the seabed for any other sources of food they can find, and will take any crustaceans and prawns they come across, and will also feed on dead and rotting fish.
Portuguese dogfish have been targeted by fishermen since the earliest years of the twentieth century as their flesh is edible and the liver contains valuable oil. This means that fisheries across the world but particularly in Japan, Portugal and several Mediterranean countries have targeted this species. In addition to this deep-sea trawls which are targeting other species also catch Portuguese dogfish as bycatch.
A picture from showing Portuguese dogfish caught on a long line which had been set at metres. This has caused populations of this species to plummet, with the IUCN International Union for the Conservation of Nature stating that Portuguese dogfish numbers in the north east Atlantic have declined by eight per cent over the last one hundred years.
The European Union has imposed catch limits, but with Portuguese dogfish still being caught as bycatch the long term outlook for this species, especially in European waters, is uncertain.
Velvet Belly Lanternshark. The velvet belly lanternshark is a small species which lives in very deep water. While it can be found at depths of several hundred metres it is much more common at around metres, and can be found substantially deeper than this.
This species has little commercial value but high levels of bycatch have seen its numbers reduced in European waters. Worldwide distribution of the velvet belly lanternshark. The velvet belly lanternshark is found throughout the north east Atlantic from the waters of Iceland and Norway although it is absent from much of the Baltic Sea all of the way through European waters and along the west coast of Africa down to South Africa.
It is also found in the Mediterranean Sea, although only in limited numbers in the Black Sea. Its name comes from the fact that its belly is a dark colour whereas most other species have a paler underside and that this species displays a trait known as bioluminescence — the ability to produce light from cells in the skin. Light producing cells are located in the lower half of its body and along the ridges of its dorsal fins.
The velvet belly lanternshark is thought to use this ability to light up cells on its body to deter predators and confuse prey. There is a BBC article on the light-producing abilities of the lanternshark available by clicking here.
The velvet belly lanternshark is not valuable commercially and is not targeted by commercial fishing vessels. However, it may be inadvertently caught as bycatch by deep sea trawlers or caught on long-lines which have been set for other species. While a small proportion of velvet belly lanternshark bycatch may be retained to be processed into fishmeal the vast majority will be thrown back into the sea dead.
Velvet belly lanternsharks have had their numbers reduced by commercial fishing such as long-lines which are set for other species.
While the IUCN International Union for the Conservation of Nature classes the velvet belly lanternshark as a species of Least Concern overall a separate regional assessment has classed this species as one which is Near Threatened in European waters. Due to its deep-sea habitat and the fact it is of little commercial value it has been poorly studied by the scientific community and many aspects of its life cycle are unknown.
This species is classed as a deep-sea fish, being found at depths of several thousand metres. They have a wide distribution, being found across the temperate and subtropical seas and oceans of the world. In terms of their distribution around the British Isles they are found in the deep areas of the Atlantic along the west coast of the British Isles. They are believed to be predators which use their sharp, fanglike teeth to prey on smaller fish.
The teeth are so large relative to the body size that the mouth of this species cannot fully close. They are calculated to have a lifespan of twenty to thirty years. He was an Anglo-Irish naturalist and medical doctor who left his vast collection of preserved animals, human and animal skeletons, books, manuscripts and illustrations to the nation on his death. This collection formed the basis of the British Museum and also part of the British Library.
Several other species of plants and animals are also named after him, as is Sloane Square in London. He is also credited with introducing drinking chocolate to England, although his legacy became controversial in due to his connections with slavery. Spiny Eel Species. There are two spiny eel species found in the deep water environments around the British Isles — the shortfin spiny eel Notacanthus bonaparte and the snub-nose spiny eel Notacanthus chemnitzii.
There are four other species of spiny eel found elsewhere in the world. Despite being commonly named as eels, and having an eel-like appearance, spiny eels are not true eels at all but are in fact fish species. While shortfin spiny eels are not common around the British Isles they can be found the in and around the deep-water areas of the Rockall Trough to the west of Ireland and the Faroe-Shetland Channel to the north of Scotland. They are a deep sea species, occasionally found in depths of metres but generally being found in waters at least to metres deep, and can be found at depths greater than metres.
Shortfin spiny eels are thought to shoal in large numbers and are believed to feed by swimming with their head pointing downwards allowing them to scavenge and forage as they travel across the seabed.
They are thought to feed predominantly on the small invertebrate creatures which are found at great depths such as deep-sea prawns, brittle stars, sea anemones and comb jellies. The spiny eel species found in British waters are of no importance to commercial fisheries, although they may be caught as bycatch in commercial deep-sea trawls and discarded at sea. The other species of spiny eel found in the waters of the British Isles is the snubnose spiny eel, which is distinguished from its shortfin relative by its upturned, pointed snout, smaller mouth and eyes, more rounded body and larger pectoral fins.
The shark meat is dried or salted for storage, and used to make fishmeal. Another reason for the active pursuit of this species is the high squalene content of the liver. Squalene is an organic compound found in plants and animals, but particularly in shark livers. It is used as an additive to foods, cosmetics, medication and health supplements, and in vaccines to help boost immune responses.
Information about the current status of Portuguese dogfish populations is sketchy, because it is difficult to separate data about this species from other dogfish sharks in fisheries records. However there is evidence that numbers are declining, and some stocks are considered to be depleted. The ongoing removal of this species is worrisome to begin with — having such a low rate of reproduction, it cannot logically withstand such fishing pressure.
At the very least, available scientific information indicates that commercial exploitation of the Portuguese dogfish should proceed with caution. Page Created By: Mike Rogers. Diets and bathymetric distributions of two bathyal sharks of the Catalan deep sea western Mediterranean. Marine Ecology Progress Series CRC Press.
Castro JI The Sharks of North America. Oxford University Press. Aspects of reproduction of the deep water sharks Centroscymnus coelolepis and Centrophorus squamosus from west of Ireland and Scotland.
Crawford D Reaktion Books.
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