The Pacific angelshark (''Squatina californica'') is a species of
angelshark
The angelsharks are a group of sharks in the genus ''Squatina'' of the family Squatinidae. They commonly inhabit sandy seabeds close to in depth. Many species are now classified as critically endangered by the International Union for Conservat ...
, family Squatinidae, found in the eastern
Pacific Ocean
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...
from
Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S. ...
to the
Gulf of California
The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja C ...
, and from
Ecuador
Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ' ...
to
Chile
Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
, although those in the Gulf of California and southeastern Pacific may in fact be separate species. The Pacific angelshark inhabits shallow, coastal waters on sandy flats, usually near rocky
reef
A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock o ...
s,
kelp forest
Kelp forests are underwater areas with a high density of kelp, which covers a large part of the world's coastlines. Smaller areas of anchored kelp are called kelp beds. They are recognized as one of the most productive and dynamic ecosystems on Ea ...
s, or other underwater features. This species resembles other angel sharks in appearance, with a flattened body and greatly enlarged
pectoral
Pectoral may refer to:
* The chest region and anything relating to it.
* Pectoral cross, a cross worn on the chest
* a decorative, usually jeweled version of a gorget
* Pectoral (Ancient Egypt), a type of jewelry worn in ancient Egypt
* Pectorali ...
and
pelvic fins. Characteristic features of this shark include a pair of cone-shaped
barbel Barbel may refer to:
*Barbel (anatomy), a whisker-like organ near the mouth found in some fish (notably catfish, loaches and cyprinids) and turtles
*Barbel (fish), a common name for certain species of fish
**''Barbus barbus'', a species of cyprinid ...
s on its snout, angular pectoral fins, and a brown or gray dorsal coloration with many small dark markings. It attains a maximum length of .
An
ambush predator
Ambush predators or sit-and-wait predators are carnivorous animals that capture or trap prey via stealth, luring or by (typically instinctive) strategies utilizing an element of surprise. Unlike pursuit predators, who chase to capture prey ...
, the Pacific angelshark conceals itself on the sea floor and waits for approaching prey, primarily
bony fishes and
squid. Prey are targeted visually and, with a quick upward thrust of the head, snatched in protrusible jaws. Individual sharks actively choose ideal ambush sites, where they stay for several days before moving on to a new one. This species is more active at night than during the day, when it stays buried in sediment and seldom moves. Reproduction is
ovoviviparous
Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...
, with the
embryos hatching inside the mother's
uterus
The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The ...
and being sustained by a
yolk sac
The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac'' is ...
until birth. Females give birth to an average of six young every spring.
Pacific angelsharks are not dangerous to humans unless provoked, in which case their bite can cause a painful injury. They are valued for their meat and are captured by
commercial
Commercial may refer to:
* a dose of advertising conveyed through media (such as - for example - radio or television)
** Radio advertisement
** Television advertisement
* (adjective for:) commerce, a system of voluntary exchange of products and s ...
and
recreational fishers across their range. A targeted
gillnet fishery for this species began off
Santa Barbara, California
Santa Barbara ( es, Santa Bárbara, meaning "Saint Barbara") is a coastal city in Santa Barbara County, California, of which it is also the county seat. Situated on a south-facing section of coastline, the longest such section on the West Co ...
in 1976 and ended in 1994, after
overfishing and new regulations led to its near-collapse. This species is now mainly fished in
Mexican waters. The
International Union for Conservation of Nature
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of nat ...
(IUCN) has assessed this species as
Near Threatened
A near-threatened species is a species which has been categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature as that may be vulnerable to endangerment in the near future, but it does not currently qualify f ...
, as the Californian population is largely protected and recovering, while the impact of Mexican fisheries is unknown.
Taxonomy and phylogeny
The Pacific angelshark was first scientifically described in 1859 by
William Orville Ayres
William Orville Ayres (September 11, 1817 – April 30, 1887) was an American physician and ichthyologist. Born in Connecticut, he studied to become a Physician, doctor at Yale University School of Medicine.
Life and career
Ayers, the son of J ...
, the first Curator of
Ichthyology at the
California Academy of Sciences
The California Academy of Sciences is a research institute and natural history museum in San Francisco, California, that is among the largest museums of natural history in the world, housing over 46 million specimens. The Academy began in 1853 ...
.
He gave it the
specific epithet ''californica'', as the originally-described specimen was caught off
San Francisco
San Francisco (; Spanish for " Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the fourth most populous in California and 17th ...
. Locally, this species may also be referred to as angel shark, California angel shark, or monkfish.
The
Chilean angelshark (''Squatina armata'') of the southeastern Pacific was
synonymized with this species by Kato, Springer and Wagner in 1967, but was later tentatively recognized as a separate species again by
Leonard Compagno Leonard Joseph Victor Compagno is an international authority on shark taxonomy and the author of many scientific papers and books on the subject, best known of which is his 1984 catalogue of shark species produced for the Food and Agriculture Organ ...
.
The taxonomic status of angel sharks in the southeastern Pacific – whether they are ''S. californica'', ''S. armata'', or if there is more than one ''Squatina'' species in the region – remains unresolved. The angel sharks inhabiting the Gulf of California may also represent a different species, as they mature at a much smaller size than those from the rest of their range.
A
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
study based on
mitochondrial DNA, published by Björn Stelbrink and colleagues in 2010, reported that the
sister species
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A and ...
of the Pacific angelshark is the
sand devil (''S. dumeril'') of the western
North Atlantic. The two species are estimated to have diverged approximately 6.1
Ma, close to when the
Isthmus of Panama first began to form. The authors also found that Pacific angelsharks from the Gulf of California differed genetically from those elsewhere, though they were equivocal as to whether this represented a species-level distinction.
Distribution and habitat
Pacific angelsharks are found in cold to warm-temperate waters from the southeastern corner of Alaska to the Gulf of California, including the entire
Baja peninsula, and are most common off central and southern
California
California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
. It may also occur from Ecuador to the southern tip of Chile (see taxonomic uncertainty above). This bottom-dwelling shark prefers habitats with soft, flat bottoms close to shore, such as
estuaries
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environmen ...
and
bays, and are often found near rocky
reef
A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock o ...
s,
submarine canyon
A submarine canyon is a steep-sided valley cut into the seabed of the continental slope, sometimes extending well onto the continental shelf, having nearly vertical walls, and occasionally having canyon wall heights of up to 5 km, from c ...
s, and
kelp forest
Kelp forests are underwater areas with a high density of kelp, which covers a large part of the world's coastlines. Smaller areas of anchored kelp are called kelp beds. They are recognized as one of the most productive and dynamic ecosystems on Ea ...
s. On occasion, they have been seen swimming above the sea floor.
Off California, the Pacific angelshark is most common at a depth of , but has been reported from as deep as .
A number of
genetically discrete subpopulations have been identified across the northern range of the Pacific angelshark. Several subpopulations exist along the coast from
Point Conception
Point Conception (Chumash: ''Humqaq'') is a headland along the Gaviota Coast in southwestern Santa Barbara County, California. It is the point where the Santa Barbara Channel meets the Pacific Ocean, and as the corner between the mostly north ...
northward to Alaska. In the
Southern California Bight
The Southern California Bight is a 692-kilometer-long (430 mi) stretch of curved coastline that runs along the west coast of the United States and Mexico, from Point Conception in California to Punta Colonet in Baja California, plus the area o ...
, there are at least three separate subpopulations off the mainland and northern and southern
Channel Islands
The Channel Islands ( nrf, Îles d'la Manche; french: îles Anglo-Normandes or ''îles de la Manche'') are an archipelago in the English Channel, off the French coast of Normandy. They include two Crown Dependencies: the Bailiwick of Jersey, ...
. The subpopulation along the Pacific coast of
Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
are distinct from those in the Gulf of California.
These subpopulations have diverged from one another over time because Pacific angelsharks do not undertake long
migratory movements outside of their preferred home areas, and deep waters serve as effective geographical barriers to population mixing.
Heterozygosity
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.
Mo ...
, a measure of
genetic diversity, is higher in the Pacific angelshark than in other shark species that have been examined.
Description
![Squatina californica jaws](https://upload.wikimedia.org/wikipedia/commons/6/6d/Squatina_californica_jaws.jpg)
With its flattened body and wing-like pectoral fins, the Pacific angelshark superficially resembles a
ray. Unlike in rays, its five pairs of
gill slit
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of cartilaginous fish such as sharks and rays, as well as deep-branching vertebrates such as lampreys. In con ...
s are located on the sides of the head rather than underneath, and the expanded anterior lobes of its pectoral fins are separate rather than fused to the head. The eyes are located on top of the head, with the
spiracles behind. There are folds of skin without triangular lobes on the sides of head. The mouth is very wide and placed terminally (at the front of the snout); a pair of cone-shaped
barbels
In fish anatomy and turtle anatomy, a barbel is a slender, whiskerlike sensory organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the zebrafish, the black dragonfish and some s ...
with spoon-like tips are located above.
There are 9 tooth rows on either side of the upper jaw and 10 tooth rows on either side of the lower jaw, with toothless gaps at the middle of both jaws. Each tooth has a broad base and a single narrow, smooth-edged cusp.
Pacific angelsharks are founded in Clover Point, Vancouver Island to southern Baja California and Gulf of California and Peru. Although, there are unverifiable records from southeastern Alaska and Chile. Common from Tomales Bay, northern California southward. Pacific angelsharks grow to be 175 cm (68.9 in) long, and at birth about 25 cm (9.8 in). Depth: surf zone to 205 m (672 ft).
The pectoral and pelvic fins are broad and angular with pointed tips. The two
dorsal fin
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through c ...
s are located far back on the body, and there is no
anal fin. The lower lobe of the
caudal fin
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...
is larger than the upper. A row of small thorns runs down the middle of the back and tail; thorns are also present on the snout and over the eyes.
As the shark ages, the thorns decrease in size and may disappear. The dorsal coloration is gray, brown, or reddish brown with scattered dark markings: large blotches surrounded by a ring of tiny spots in adults, and pairs of
ocelli
A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...
in juveniles. The underside is white, extending to the margins of the pectoral and pelvic fins.
This species measures up to long and weighs up to .
Biology and ecology
During the day, Pacific angelsharks are almost never seen in the open, instead resting motionless on the sea floor buried under a thin layer of sediment that disguises their outlines. At night some individuals remain motionless, waiting for prey, while others may be encountered on the bottom unburied or actively swimming.
Large sharks, including the
great white shark
The great white shark (''Carcharodon carcharias''), also known as the white shark, white pointer, or simply great white, is a species of large Lamniformes, mackerel shark which can be found in the coastal surface waters of all the major ocean ...
(''Carcharodon carcharias'') and the
broadnose sevengill shark
The broadnose sevengill shark (''Notorynchus cepedianus'') is the only extant member of the genus ''Notorynchus'', in the family Hexanchidae. It is recognizable because of its seven gill slits, while most shark species have five gill slits, with ...
(''Notorynchus cepedianus''), and the
northern elephant seal
The northern elephant seal (''Mirounga angustirostris'') is one of two species of elephant seal (the other is the southern elephant seal). It is a member of the family Phocidae (true seals). Elephant seals derive their name from their great siz ...
(''Mirounga angustirostris'') are known to consume Pacific angelsharks.
Known
parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
s of this species include the
copepod ''Trebius latifurcatus'', which infests the skin, the
myxosporidian
Myxosporea is a class of microscopic parasites, belonging to the Myxozoa clade within Cnidaria. They have a complex life cycle which comprises vegetative forms in two hosts, an aquatic invertebrate (generally an annelid but sometimes a bryozoan ...
''Chloromyxum levigatum'', which infests the
gall bladder
In vertebrates, the gallbladder, also known as the cholecyst, is a small hollow organ where bile is stored and concentrated before it is released into the small intestine. In humans, the pear-shaped gallbladder lies beneath the liver, although ...
, and the
tapeworm
Eucestoda, commonly referred to as tapeworms, is the larger of the two subclasses of flatworms in the class Cestoda (the other subclass is Cestodaria). Larvae have six posterior hooks on the scolex (head), in contrast to the ten-hooked Cesto ...
''Paraberrapex manifestus'', which infests the
spiral valve
A spiral valve or scroll valve is the corkscrew-shaped lower portion of the intestine of some sharks, Acipenseriformes (sturgeon and paddlefish), rays, skates, bichirs, Lepisosteiformes (gars), and lungfishes. A modification of the ileum, the s ...
intestine. The
leech ''Branchellion lobata'' may be attached around this shark's
cloaca, inside the intestine, and even inside the
uterus
The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The ...
and on developing embryos.
Feeding
![Squatina squatina](https://upload.wikimedia.org/wikipedia/commons/5/5c/Squatina_aculeata.001_-_Aquarium_Finisterrae.jpg)
A sedentary ambush predator, the Pacific angelshark feeds mainly on bony fishes, including
kelp bass
''Paralabrax clathratus'', the kelp bass, bull bass or calico bass, is a species of marine ray-finned fish, a sea bass from the subfamily Serraninae, classified as part of the family Serranidae which includes the groupers and anthias. It is foun ...
,
croakers
Sciaenidae are a family of fish in the order Acanthuriformes. They are commonly called drums or croakers in reference to the repetitive throbbing or drumming sounds they make. The family consists of about 286 to 298 species in about 66 to 70 gene ...
,
flatfishes,
damselfish
Damselfish are those within the subfamilies Abudefdufinae, Chrominae, Lepidozyginae, Pomacentrinae, and Stegastenae within the family Pomacentridae. Most species within this group are relatively small, with the largest species being about ...
es,
mackerels, and
sardine
"Sardine" and "pilchard" are common names for various species of small, oily forage fish in the herring family Clupeidae. The term "sardine" was first used in English during the early 15th century, a folk etymology says it comes from the It ...
s. During the winter and early spring, spawning squid are abundant and become the primary source of food.
In the southern Gulf of California, the most important prey species are, in descending order, the mackerel ''
Decapterus macrosoma
''Decapterus'' is a genus of marine fishes of jack family, Carangidae, commonly known as mackerel scads, round scads, or horse mackerel. They are found throughout the world.
Species
Currently, 10 or 12 recognized species are found in this genus: ...
'', the
toadfish
Toadfish is the common name for a variety of species from several different families of fish, usually because of their toad-like appearance. "Dogfish" is a name for certain species along the gulf coast.
Dolphin-Toadfish relationship
Toadfish mak ...
''
Porichthys analis'', the
lizardfish
The Synodontidae or lizardfishes(or typical lizardfish to distinguish them from the Bathysauridae and Pseudotrichonotidae) are benthic (bottom-dwelling) marine and estuarine bony fishes that belong to the aulopiform fish order, a diverse group ...
''
Synodus evermann'', the
soldierfish
Myripristinae is a subfamily
In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus
Genus ( plural genera ) is a taxonomic rank us ...
''
Myripristis leiognathus'', and the shrimp ''
Sicyonia penicillata''.
At
Catalina Island, this species feeds mainly on the
blacksmith
A blacksmith is a metalsmith who creates objects primarily from wrought iron or steel, but sometimes from other metals, by forging the metal, using tools to hammer, bend, and cut (cf. tinsmith). Blacksmiths produce objects such as gates, gr ...
(''Chromis punctipinnis'') and the
queenfish
The queenfish (''Seriphus politus'') is a species of fish in the family Sciaenidae, the drums and croakers. It is native to the eastern Pacific Ocean, where it occurs along the North American coastline from Oregon to Baja California; it has been ...
(''Seriphus politus'').
Adults and juveniles have similar diets.
Individual sharks choose sites giving them the best ambush success. They prefer junctions of sandy and rocky substrates near reefs (used by many fishes for shelter) usually orienting themselves either toward or parallel to nearby vertical structures. They tend to face upslope, which may facilitate burying via falling sediment, bring more fish swimming downstream from the reef, or ease targeting by silhouetting prey against the sunlight.
Once settled at a successful site, an angelshark may remain there for ten days, re-burying itself on or near the same spot after every strike. As the local prey eventually learn to avoid the stationary predator, the shark periodically shifts at night to a new site several kilometers away. One study off Santa Catalina Island found that over 13–25 hours, nine sharks together used only 1.5 km
2 (0.6 mi
2). A later, longer-term study found that the sharks' sporadic position changes covered as much as over three months, almost circling the island. Single individuals swam up to in a night.
[Martin, R.A]
Sandy Plains: Pacific Angel Shark
ReefQuest Centre for Shark Research. Retrieved on June 22, 2009.
The Pacific angelshark is primarily a visual hunter; experiments in nature show that they strike at fish-shaped targets without any electrical, chemical, vibrational, or behavioral cues. At night, they are guided by the
bioluminescence of
plankton
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
ic
dinoflagellates and
ostracod
Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typi ...
s disturbed by moving prey.
This species' visual system is attuned to the
wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats.
It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, t ...
s of light emitted by these
plankton
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
ic organisms, showing the importance of night hunting. Pacific angelsharks are more likely to strike at prey approaching from the front.
It usually waits until the prey approaches to , as its attack is less accurate beyond this distance.
The strike is a
stereotyped behavior in which the shark presses the forward lobes of its pectoral fins against the bottom and thrusts its head upwards at up to a 90° angle. Its mouth forms a tube when opened, creating a suction force, while its jaws protrude forward to secure the prey between sharp teeth. During the strike, the eyes roll backward into the head for protection. The strike is often completed in under a tenth of a second.
Life cycle
The Pacific angelshark is
aplacental viviparous
Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop ins ...
with the unborn young nourished by a yolk sac; reproduction occurs on an annual cycle. Most females have a single functional
ovary (on the left side), though some have two; the
oviduct
The oviduct in mammals, is the passageway from an ovary. In human females this is more usually known as the Fallopian tube or uterine tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, o ...
s are often filled with
yolk
Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example ...
, which is speculated to be from the resorption of unfertilized eggs. At long, the young embryos have translucent skin, protruding eyes, and exposed
gill filament
A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...
s. Spots of
pigment
A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...
have developed when the embryo is long, and the first row of teeth has appeared when the embryo is long. By the time the embryo is long, the mouth has migrated to a terminal position and the color pattern has fully developed; the external yolk sac begins to shrink as the yolk is transferred to an internal yolk sac, where it is held until it can be transferred to the intestine for
digestion
Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these smaller substances are absorbed through the small intest ...
. The internal yolk sac is fully resorbed before birth; if the pup is released prematurely, it does not feed until this process is complete.
Off Santa Barbara, birthing takes place from March to June after a
gestation period of ten months, and the females
mate again shortly afterward. The average litter size is six, with a range of 1–11 (rarely 13); there is no correlation between female size and number of offspring.
The young are born in water deep, probably to protect them from predators.
Pacific angelshark embryos grow at per month when young, slowing down to per month just before birth, and are born at a length of . Newborn pups in captivity grow at a rate of around per year, while adults in the wild grow at around per year. Both sexes
mature at long, corresponding to an age of 8–13 years.
Gulf of California sharks, which may be another species, mature at long for males and long for females.
About 20% of newborns survive to maturity.
The maximum lifespan has been estimated at 25–35 years.
Unlike other sharks, the growth rings on the
vertebra
The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...
e of this species are deposited in proportion to the shark's size rather than yearly, making age determination difficult.
Human interactions
Although usually sedate and approachable underwater, Pacific angelsharks are quick to bite if touched, captured, or otherwise provoked, and can inflict severe lacerations.
Commercial fisheries for this species exist off
Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
and to a lesser extent off California (see below); the meat is considered excellent and is sold fresh or frozen. This species is captured in limited numbers by
recreational fishers using hook-and-line,
spears, or even by hand, particularly off southern California. It is also taken as
bycatch in
shrimp trawl
Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch different speci ...
s operating in the Gulf of California, and processed into
fishmeal
Fish meal is a commercial product made from whole wild-caught fish, bycatch and fish by-products to feed farm animals, e.g., pigs, poultry, and farmed fish.R. D. Miles and F. A. Chapman.FA122: The Benefits of Fish Meal in Aquaculture DietsFisheri ...
.
The capacity of this species to withstand a focused fishing effort is limited, due to its low rates of reproduction and movement.
In 1976, the commercial
gillnet fishery for the
California halibut
The California halibut or California flounder (''Paralichthys californicus'') is a large-tooth flounder native to the waters of the Pacific Coast of North America from the Quillayute River in Washington to Magdalena Bay in Baja California. It f ...
(''Paralichthys californicus''), operating off Santa Barbara, expanded to include the Pacific angelshark as well. The sharks had become valuable due to their promotion as a substitute for the seasonally available
common thresher shark (''Alopias vulpinus''), and the development of new processing techniques. Around 50% of the shark was used, while the
skin
Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.
Other animal coverings, such as the arthropod exoskeleton, have different de ...
,
cartilage, and
offal
Offal (), also called variety meats, pluck or organ meats, is the organs of a butchered animal. The word does not refer to a particular list of edible organs, which varies by culture and region, but usually excludes muscle. Offal may also refe ...
were discarded. In the 1980s, rising demand led to the introduction of gillnets with a medium-sized mesh, designed specifically for this species. Fishery landings increased from a dressed (post-processing) weight of in 1977, to in 1983, to in 1984. The fishery peaked in 1985 and 1986, when 550,000 kg (1.2 million lbs) were taken annually, making this species the number one shark fished off California. This level of exploitation was unsustainable, and despite a minimum size limit imposed in 1986, catches fell to in 1990.
In 1991, the use of gillnets in nearshore Californian waters was banned by a voter initiative (Proposition 132); the restricted area included much of the Pacific angelshark's habitat and reduced fishing pressure on the species. As a result, Pacific angelshark landings dropped further to dressed in 1994, when the central Californian halibut/angel shark fishery was closed completely, and have remained low since. The decline of the Californian fishery led to the industry shifting to Mexico, where gillnet ''pangas'' (
artisanal fishing vessels) targeting this species now meet most of the angel shark demand in California.
The
International Union for Conservation of Nature
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of nat ...
(IUCN) has assessed this species as
Near Threatened
A near-threatened species is a species which has been categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature as that may be vulnerable to endangerment in the near future, but it does not currently qualify f ...
; Pacific angelshark numbers off California appear to be increasing and demographic modeling suggests the stock is healthy.
However, the impact of the intense, unregulated Mexican fishery on the global population is yet undetermined. There is continuing interest in California for a resumption of the commercial fishery, though conservation concerns have thus far taken precedence.
References
{{Good article
Pacific angelshark
Western American coastal fauna
Fish of the Pacific Ocean
Pacific angelshark