#sphyrnidae

[uncharismatic-fauna]

Uncharismatic Fact of the Day

Can you guess where the shovelhead shark got its name? It's because its head-- wait for it-- looks like a shovel! This is particularly true of males, which have a distinctive bulge in the center of their foreheads, creating the very distinct impression of a spade, while females have a much flatter head. This distinguishing feature also gives the bonnethead shark the unique position of being the only shark species that exhibits sexual dimorphism through the shape of the head.

(Image: A male bonnethead shark (Sphyrna tiburo) by Gerard Soury

[unofficial-sean]

Eyeauh

[oceansoftheworld]

Photo by Simon Rogerson | Info

The scalloped hammerhead (Sphyrna lewini) is a species of hammerhead shark, and part of the family Sphyrnidae. It is a fairly large hammerhead, but is still smaller than both the great and smooth hammerheads. The scalloped hammerhead is a coastal pelagic species; it occurs over continental and insular shelves and in nearby deeper water. It is found in warm temperate and tropical waters, worldwide and can be found at depths over 500 m (1,600 ft), though is most often above 25 m (82 ft). These sharks are often seen during the night, day, and morning in big schools, sometimes numbering hundreds.

[tranceberry]

X-rayed hammerhead shark

[uncharismatic-fauna]

Uncharismatic Fact of the Day

You wouldn't think fish need to hold their breath, but that's exactly what hammerhead sharks do when they hunt! Scallopped hammerheads cruise near the surface, where the water is about 15-20°C (59-68°F), but they hunt in much deeper water where the average temperature is about 5–11°C (41-51°F). To conserve their body heat, hammerhead sharks close their gills-- effectively holding their breath for up to 7 minutes before they ascend back to warmer waters.

(Photo: A shiver of scalloped hammerhead sharks (Sphyrna lewini) by Doug Perrine)

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[uncharismatic-fauna]

Uncharismatic Fact of the Day

Stop: it's hammer time! Great hammerhead shark time, that is! Great hammerheads are the largest species in the hammerhead shark group, which contains nine species total. These sharks are also great swimmers-- so great, that they can even swim on their sides! Doing so reduces drag, and therefore the amount of energy needed to move through the water.

(Image: A great hammerhead shark (Sphyrna mokarran) by Albert Kok)

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[todropscience]

The reproductive cycle in scalloped hammerhead finally understood

The Scalloped Hammerhead (Sphyrna lewini) is a coastal and semioceanic hammerhead shark found worlwide in warm waters. Although it is wide ranging, there is few info about they reproductive behavior. 

Mating behavior in scalloped hammerheads is not fully understood, affortunately, researchers have detalied the complete sequence of a mating event for scalloped hammerhead shark, recorded at Isla del Coco National Park, Costa Rica, where large schools of hammerhead sharks are frequently encountered.

Based on a rare and single observation, researchers found that only one male appears to be involved in a copulation cycle and that mating took place in a high current zone potentially to favor respiration when both individuals are unable to swim. Basically, sharks meet in open water, then there is pre-copulatory biting, followed by grabbing of pectoral fin and copulation. After the highlight the sharks make a free fall, separate and follow. When the female gives birth, it does in protected coastal waters, as mangroves.

Given the major declines reported in many areas of this species' range, increased targeting for its high value fins, low resilience to exploitation and largely unregulated, continuing fishing pressure from both inshore and offshore fisheries, this species is assessed as Endangered globally. 

Illustration:  Life cycle of  the scalloped hammerhead shark  in the Tropical Eastern Pacific.

Reference: Sálinas de León et al., 2017.  First observation on the mating behaviour of the endangered scalloped hammerhead shark Sphyrna lewini in the Tropical Eastern Pacific. Environmental Biology of Fishes.

[mondaymorgue]

Photos: Pantai Kenangan Bongawan Facebook

Malaysia: Hammerhead Shark carcass gains instant fame in Sabah, and online By Avila Geraldine, 14th January 2017;

A Hammerhead Shark (Sphyrna sp.) carcass washed up on Kenangan beach in Bongawan, about 70km from Kota Kinabalu, and caused a sensation among locals and netizens.

Photos of the shark went viral on Facebook, shortly after villagers made the discovery at about 6.30am today.

As news of the discovery spread, curious villagers flocked to the site to take photos of the unique-looking marine predator.

The Hammerhead Shark has been listed in the International Union for Conservation of Nature Red List of globally-endangered species.

Awang Harun Karim, 50, from Kampung Silat, was the first to spot the Shark as he was preparing to open his grocery store for business. His shop is just about 50 metres away from the beach.

"I thought it was a log, but I took a closer look and discovered that it was actually a Hammerhead Shark. I immediately called my son and we rushed to the beach, but it was already dead when we found it," he said.

The Shark was estimated to be 1.8-metres long and weigh about 60 kilogrammes.

"This was the first time I had seen a Hammerhead Shark on the beach. Two years ago, a Dolphin was stranded here and was rescued by the relevant authority," Awang added.

Source: New Straits Times

Based on the shape of the head and the size of the dorsal fin in proportion to the rest of the body, this is likely a Great Hammerhead (Sphyrna mokarran). It's not mentioned whether the shark carcass was found with a rope already tied behind the head. Could it have been caught by a person previously, and then discarded?