You know that most sharks travel to bear their young in a special area (nursery) to protect them. Mostly it is a shallow bay or estuary, sometimes even a river, but the Pacific Angelshark (Squatina californica) does the very reverse: normally living on sandy flats or rocky reefs as shallow as 10 ft -3 m-, female Pacific Angelsharks wander as deep as 180 to 300 ft -55 to 90 m – to give birth to 1 to 13 living young (their number is independent from the size of their mother, unlike in other sharks). But that is not the only peculiarity of this species.

Squatina californica.jpg
Squatina californica by Tony Chess/NOAA SWFSC (Public Domain)

Pacific Angelsharks are up to 5 ft – 1.5 m – long sharks living in coastal Pacific waters from Alaska to Chile in a number of genetically discrete subpopulations (or possible even different species like the Chilean Angel Shark (Squatina armata) off Chile). Like all other angel sharks, they have a flattened body with greatly enlarged pectoral and pelvic fins and are ovoviviparous (young hatch inside the womb). The embryo has at first an external yolk sac, but that begins to shrink as the yolk is transferred to an internal yolk sac. The embryo feeds from this yolk until it is fully resorbed (if the pup is born prematurely, it does not feed until everything is gone). Born after a 10 month gestation at 9 in – 23 cm- length, Pacific Angels mature at 35 to 39 in – 90 to 100 cm – (both sexes, unlike in other sharks). At what age is unknown, since, unlike in other sharks, their vertebral growth rings (analog to annual growth rings in trees) don’t indicate age but only size (and therefore feeding success). That makes age verification difficult. But tagging and recapturing indicates a relatively slow growth (adults around 0.79 in -2 cm- per year) with maturity occurring relatively late in life, and therefore a moderate fecundity.

As ambush predators, Pacific Angel Sharks bury themselves in the sand near rocky reefs, facing up-slope to better see the silhouette of prey against the sunlight, and lie quietly on the bottom. They appear sluggish, but high-speed videography has revealed that their “predatory strikes are sudden and dramatic: in about a tenth of a second, the front half of the shark’s body snaps upward about 90 degrees from the bottom, the bear trap-like jaws protrude a remarkable distance from the head, and snap shut with audible authority”. During the strike, the eyes roll backward into the head for protection. After a strike they bury themselves again. But, since prey animals often learn quickly where local predators tend to lie-in-wait, ten days later they move under cover of darkness to a new site up to 4.5 mi – 7.3 km – away.

To detect prey, Pacific Angel Shark nearly entirely depend on vision. Experiments showed that they caught fish models every time on vision alone, without scent, electrical or vibratory cues. Even at night, they detect prey indirectly by the faint greenish sparkle of bioluminescent plankton agitated in its wake (their retinal pigments suggest that this species’ peak visual sensitivity occurs at wavelengths almost identical to that produced by local bioluminescent plankton).

A fascinating shark, isn’t it? But humans nearly wiped out this species. Why? Due to fear for their lives? Hardly, since no human has been attacked by a Pacific Angelshark without provocation – they do snap when provoked, but even then don’t leave much damage. No, only for profit. The promotion campaign of a seafood processor in California named Michael Wagner in 1976 and later changed the former “junk fish” almost single-handedly to a tasty seafood, resulting in an annual caught of up to 1.2 million pounds -544,311 kilograms- of Pacific Angelsharks (in 1985) and making this species the number one shark fished off California. The eradication of this species was averted, as in the 90th the central Californian halibut and angel shark fishery (caught with the same gillnets with medium-sized mesh) was closed completely. Pacific angelshark numbers off California appear to be increasing, resulting in an assessment of Least Concern in the United States. Globally however, it is considered as Near Threatened, because the largely unregulated Mexican fisheries took over. This species is now absent from regions in Baja California Sur where it was historically found.

Sources: here, here, here and here

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