save our blue planet

Let's save our blue planet by saving the ocean. Every little step counts.

Shark of the week: Papuan epaulette shark — 2. July 2018

Shark of the week: Papuan epaulette shark

The last species from the genus Epaulette sharks or Hemiscyllium is the Papuan epaulette shark (Hemiscyllium hallstromi). The whole genus is a great example for plate tectonics and evolution, as shown in this great paper by Gerald Allen et. al.

comparisation of all nine hemiscyllium species
comparisation of all nine hemiscyllium species: A) H. freycineti, B) H. hallstromi, C) H. galei, D) H. trispeculare, E) H. ocellatum, F) H. michaeli, G) H. halmahera, H) H. henryi & I) H. strahani Credit: Allen et al 2016

The little (up to 30 in -77 cm- length ) Papuan epaulette shark (B in the picture) has a limited habitat in shallow tropical waters on seagrass beds and occasional rocks and coral reefs near Port Moresby, the capital of Papua New Guinea. It is considered vulnerable by the IUCN due to overfishing (mostly as bycatch) by industrial and artisanal fisheries in destructive practices like trawling and dynamite fishing, pollution by river-borne pollutants, sewerage effluent from Port Moresby and sedimentation from mining run-off, and habitat destruction by oil exploration and pipeline development.

Sources: here and here

Advertisements
Shark of thee week: Indonesian speckled carpetshark — 11. June 2018

Shark of thee week: Indonesian speckled carpetshark

After the Epaulette shark from 1788, the next new species of the genus Hemiscyllium has been described in 1824. The Indonesian speckled carpetshark (Hemiscyllium freycineti) is another walking shark from around Indonesia and seems to live solely off western New Guinea, whereas the newly discovered Milne Bay Epaulette shark assumed the eastside (and many of the pictures). Despite being common for so long, not much is known about this reef shark of the family Longtail carpet sharks (or bamboo sharks, Hemiscylliidae), not even its length.

Hemiscyllium freycineti, Adult from reeflifesurvey.com
adult Hemiscyllium freycineti, © reeflifesurvey.com

Like all Epaulette sharks, the Indonesian speckled carpetsharks is oviparous (that means the female lays egg cases). This cute little shark is often caught for aquarium trade. Due to habitat destruction and destructive or illegal fishing practices, but above all, its newly discovered restricted distribution, it may very well be considered Vulnerable instead of only Near Threatened in the near future.

Sources: here, here and here

Shark of the week: Milne Bay epaulette shark — 14. May 2018

Shark of the week: Milne Bay epaulette shark

Epaulette sharks are cute, can walk and look all at first glance fairly similar. But if you take your time to look closer on those markings, you can find differences. Just like American marine biologist and author Scott W. Michael did, and he discovered that on some pictures and specimen of the common Indonesian speckled carpetshark the shark should not have those large and defined spots remarkably similar to the spots of a leopard. He informed his colleague Gerald Allen, and so, after genetic tests, in 2010 a new species of the genus Hemiscyllium off (the Milne Bay Province region of) eastern Papua New Guinea was named after him: the Milne Bay epaulette shark or Leopard epaulette shark (Hemiscyllium michaeli).

Milne Bay epaulette shark (Hemiscyllium michaeli) (C) Scott W. Michael 2008

Like the majority of the other 8 species of its genus of the family Hemiscylliidae (Bamboo sharks or longtail carpet sharks), the up to 27.4 in – 69.5 cm – long Milne Bay epaulette shark is considered Near Threatened due to its small home range in shallow inshore coral reef waters with problems from overheating, overfishing and destructive fishing practices like dynamite fishing. Additionally, it suffers greatly from habitat degradation due to pollution and siltation from recent gold mining in the region (cyanide poisoning, river run-off and direct dumping of waste) and from ongoing logging and palm oil plantations. Producing and using palm oil not only endangers our air, our soil, our flora and fauna, out health and our atmosphere, but our oceans, too.

Sources: here, here and here

 

Shark of the week: Graceful catshark — 9. April 2018

Shark of the week: Graceful catshark

The last species of the Genus Proscyllium is the Graceful catshark (Proscyllium habereri). Like its sister species, this species of Finback catsharks (or false catsharks) also lays up to two egg cases (oviparous).

The graceful catshark is up to 26 in -65 cm- long (females bigger than males) and lives on the bottom of continental and insular shelfs of the Western Pacific from southeastern Japan to Viet Nam and northwestern Java and Indonesia at depths between 164 and 328 ft – 50 and 100 m. Due to the high fishing pressure in this areas, especially by bottom trawling, it may be in danger – but there are at present only insufficient information and no catch data available.

Sources: here and here

Shark of the week: Borneo Broadfin shark — 26. February 2018

Shark of the week: Borneo Broadfin shark

As mentioned last week, the Broadfin shark had been categorized as Endangered by the IUCN. But this happened before its sister species, the Borneo Broadfin shark (Lamiopsis tephrodes), has been again considered as separate species due to biomolecular analyses. Discovered in 1905 (instead of 1839, where he wasn’t even alive) by zoologist Henry Fowler, it had soon been equalized with the Broadfin shark.

Lamiopsis tephrodes (FOWLER,1905).jpg
Lamiopsis tephrodes von Henry Weed Fowler – http://shark-references.com/species/view/Lamiopsis-tephrodes, Gemeinfrei, Link

Reaching only 4.3 ft – 1.30 m -, the Borneo Broadfin shark lives solely off Borneo. Due to fishing pressure in this waters and 2 separate species, the IUCN should maybe revise its classification.

Sources: here and here

shark of the week: Broadfin shark — 19. February 2018

shark of the week: Broadfin shark

Another species of requiem sharks is the Broadfin shark (Lamiopsis temminckii). Living solely in shallow waters off India, China and Southeast Asia, it suffers greatly from habitat destruction, overfishing and water pollution. The IUCN considers this species as endangered.

Breitflossenhai (Lamiopsis temminckii) aus der Erstbeschreibung von Müller & Henle
Lamiopsis temminckii by Müller & Henle – Systematische Beschreibung der Plagiostomen pl. 18, Gemeinfrei, Link

Like almost all other requiem sharks, the Broadfin shark is viviparous. 4 to 8 embryos feed at first from yolk and later via a placental connection. After about 8 month they are born at 15 to 23 in -40 to 60 cm- length. Maximal length is 5.5 ft – 1.7 m.

Sources: here and here

Shark of the week: Winghead shark — 15. January 2018

Shark of the week: Winghead shark

Did you know that hammerhead sharks did not gradually develop such a large hammer, as it had been believed for decades? Genetic tests showed the opposite. Sharks with giant cephalofoil (hammer) like the Winghead shark, where it is as wide as up to 50% of the shark’s total length, are the primary species, from with later evolved species with a smaller hammer. The benefits of the hammer have to exceed the hindrance of its deformity by far.

Eusphyra blochii X-ray.jpg
X-ray of Eusphyra blochii by Sandra Raredon/Smithsonian Institution – http://eol.org/collections/14770, Public Domain, Link

The Winghead shark (Eusphyra blochii) forms its own genus within the family hammerhead sharks and has been named after the German naturalist Marcus Elieser Bloch, who described it for the first time in 1785. It is a slender shark (hence the additional name Slender hammerhead shark) and has got not only particularly protruding hammer wings (which are at birth folded back along the body and unfold only later on) but extremely long nostrils, too. After a gestation period of 8 to 11 months, where approximately 11 embryos have got each their own compartment inside the uterus and are nourished by yolk and later by a placental connection (viviparous), they are born at a length of 13 to 19 in – 32 to 47 cm. They are slow growing and reach up to 6.2 ft – 1.9 m – at length and 21 years of age.

The Winghead shark lives in coastal tropical waters of the Indio-West Pacific. Due to the high fishing pressure for its fins and meat and the degradation of its habitat in these areas, the IUCN has been classified it as endangered since 2016 (prior to that it was only considered near threatened, but it is absent from several areas by now).

Sources: here and here

Shark of the week: Scalloped hammerhead — 8. January 2018

Shark of the week: Scalloped hammerhead

Sharks do have special healing abilities. They often get wounds (due to mating rituals, combat, collisions with reef substrate or fishing gear) which, however, heal remarkably quickly. A part in it is the fact that dermal-denticles are teeth and are continually replaced like real teeth. Thus wounds are quickly covered with temporary, larger denticles, and the resulting scar become invisible by normal shaped denticles within 6 month.

An example of this was found in Scalloped hammerhead sharks (Sphyrna lewini). This species of Hammerhead sharks (also known as bronze, kidney-headed, or southern hammerhead sharks) lives all over the  world offshore in warm and tropical waters near the surface, partly in large schools. This and the fact that there are several distinct sub-populations makes this species highly susceptible to fishing pressure. They are caught  commercially for their meat and skin, but manly their fins, often illegally (IUU), as bycatch or as big game fish by recreational fishermen. That’s why they are worldwide considered endangered by the IUCN.

Hammerhead shark, Cocos Island, Costa Rica.jpg
Scalloped hammerhead by Barry PetersFlickr, CC BY 2.0, Link

Scalloped hammerheads are up to 14 ft – 4.3 m – long (but on average only up to 8.2 ft – 2.5 m – as female and 5.9 ft – 1.8 m – as male). They are viviparous (once the yolk sack is depleted it converts into a placental connection) and give birth after 9 to 12 month in specific, shallow nursery areas to up to 40 living young. The pups grow slowly and often fall prey to larger sharks, what explains the relative large litter size.

Sources: here, here and here

Shark of the week: Portuguese shark — 18. December 2017

Shark of the week: Portuguese shark

Sharks of the family sleeper sharks are bad ass: they like it cold (like the Greenland shark) as well as hot (like the Pacific sleeper shark). But one of them also likes it deep: the Portuguese Shark (Centroscymnus coelolepis) is the record holder for greatest depth attained by any shark. It usually inhabits depths below 1,300 ft -400 m-, but has been caught as deep as 12,057 ft -3,675 m. It is special in other aspects, too. It has very large dermal denticles shaped like scales of bony fish, and its eyes are well adapted to deep sea conditions: large and green due to a reflective layer named tapetum lucidum (like cat eyes), its cells are optimized for detecting movement and bioluminescence.

A small, dark brown, heavy-bodied shark with large green eyes and small fins, lying on the ground next to a meterstick
Centroscymnus coelolepis by Jon Moore – Marine Fisheries Review 65(4), Public Domain, Link

The Portuguese shark can be found worldwide, but patchily, in several distinct population in the Atlantic and Mediterranean Sea, Pacific and Indian Ocean. It is on average 3.3 ft – 1.0 m – long and ovoviviparous with an average number of 12 pups after one year of gestation (due to the vast extend of the deep sea, it seems that copulation trigger ovulation).

There is depth segregation by size and sex; since pregnant females are found in shallower water of the deep sea, they are more at risk by fishing pressure. It is targeted for the squalene in its liver (22 to 49% by weight) and its meat, but mostly taken as bycatch by bottom trawlers. Thus the IUCN considers the Portuguese shark as Near Threatened and even Endangered in European waters, despite a zero Total Allowable Catch since 2010, because even if discarded, as deep sea species the survival rate is likely to be low. It seems that a separate sub-population in the Mediterranean Sea is secure because it occurs at depths that are outside of the scope of existing fisheries, additionally there has been a ban on deepwater fisheries operations below depths of 3,300 ft – 1,000 m – since 2005.

Sources: here, here and here

Shark of the week: Prickly shark — 11. December 2017

Shark of the week: Prickly shark

The Prickly shark (Echinorhinus cookei), looking like the big brother of the Ninja lanternshark, is thankfully not as irritable as its name suggests. On the contrary, despite its size of up to  13.1 ft -4 m- it is rather shy around humans.

Echinorhinus cookei head2
head of Echinorhinus cookei by D Ross Robertson [Public domain], via Wikimedia Commons
The Prickly shark, as well as its brother Echinorhinus brucus from the family Bramble sharks or Echinorhinidae, is known for its thorn-like denticles. Thus its scientific name Echinorhinus, which is greek for echinos = hedgehog or sea urchin and rhinos = nose. It inhabits deeper coastal waters of the Pacific ocean from California and Hawaii to Chile and China to New Zealand and stays as a homebody in a rather small home range of 0.85 sq mi  -2.2 km2. It likes it rather cool and stays by day in depths of up to 4900 ft -1500 m-, but migrates at night upwards near the surface.

Prickly sharks are not targeted directly (its meat isn’t tasty), but are often victims of bycatch of deepwater trawl fisheries to sate our increasing need for fish meal (used for aquaculture and pig, chicken and even cow husbandry). Therefore they are considered as near threatened by the IUCN, even though a female has been found with up to 114 embryos (they are ovoviviparous).

Sources: here, here and here