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Shark of the week: Pacific smalltail shark — 6. November 2017

Shark of the week: Pacific smalltail shark

The Pacific smalltail shark (Carcharhinus cerdale), sister species of the Smalltail shark from last week, is an example for a misguided believe in authorities, in this case the experts Henry Bryant Bigelow and William Charles Schroeder. What happened? After this species was first described in 1898 by Charles Henry Gilbert, colleague Seth Eugene Meek and his assistant Samuel Frederick Hildebrand discovered between 1910 and 1912 several specimen on a fish market in Colón on the Caribbean side of Panama and reasoned that this species lived on both side of the Isthmus of Panama. Maybe they made an error in identification, or wrongly assumed the fish was also caught there, we will never know. Since the Panama Canal had not opened yet, neither the sharks nor the fishing vessel was able to reach the Atlantic side of Panama from the Pacific side afloat, but a fish transporter ashore sure did. Anyway, in 1948 Bigelow and Schroeder not only repeated the mistake of their colleagues, but insinuated that Meek and Hildebrand considered therefore the Pacific smalltail shark not as an own species but as synonymous with the closely related, on the Atlantic side native Smalltail shark. Only in 2011 this mistake was remedied by José I. Castro, but such important websites like the IUCN or the Florida Museum still don’t feature that fact and need an urgent update.

Carcharhinus cerdale SI.jpg
Carcharhinus cerdale by D Ross Robertson, Public Domain, Link

Just like its sister species,the Pacific smalltail shark is a requiem shark and viviparous. It inhabits coastal waters of the eastern Pacific from the Gulf of California to Peru.

Sources: here, here and here

Shark of the week: Smalltail shark — 30. October 2017

Shark of the week: Smalltail shark

Another example to prove the Plate tectonics, anyone? Well, the Smalltail shark (Carcharhinus porosus – named after really big pores behind its eyes) was considered, until 2011, to live in coastal waters on both sides of the Isthmus of Panama: in the western Atlantic Ocean from the northern Gulf of Mexico to southern Brazil as well as in the eastern Pacific from from the Gulf of California south to Peru. A momentous mistake that seems to continue until now (see IUCN Red list and homepage of the Florida Museum). In fact, its sister species Pacific smalltail shark (Carcharhinus cerdale) can be found in the eastern Pacific, and the Smalltail shark lives only in the western Atlantic part. Both had been separated around 2.8 million years ago and developed into different species (just like the Whitenose shark and the Blacknose shark a proof of evolution, as well).

Carcharhinus porosus SI.jpg
Carcharhinus porosus by D Ross Robertson, Public Domain, Link

This small (generally only up to 3.6 ft -1.1 m- long) requiem shark is slow growing and viviparous with two to nine young every two years after an approximately 12-month gestation period. It can be found near the bottom of coastal waters and estuaries and forms large aggregations segregated by sex.

Along the northern Brazilian coast, where some of its nursery areas are, the Smalltail shark is the most common shark, and in Trinidad the most economically important shark (under the name puppy shark). Fishing pressure as bycatch as well as targeted (for its meat, fins, cartilage and liver oil) caused a significant decline in numbers, resulting in an ICUN-classification as vulnerable in Brazil, where mostly juveniles have been caught, but only data deficient overall. Since its habitat is much more narrow as previously assumed (see above), the IUCN should revise that urgently (in my opinion).

Sources: here and here

National Geographic: study about plastic waste| Studie über Plastik-Abfall — 7. October 2017

National Geographic: study about plastic waste| Studie über Plastik-Abfall

Mass production of plastics, which began just six decades ago, has accelerated so rapidly that it has created 8.3 billion metric tons … 6.3 billion metric tons has become plastic waste. (Half of all plastic manufactured becomes trash in less than a year)… Of that, only nine percent has been recycled.


And this recycling can make matters even worse: In China fleece are made of disposable water bottles from Germany (as part of the recycling quota) and sold back to Germany, where they pollute the waste water and lastly the sea with micro fibers (microbeads) due to cleaning and still end up as waste, but already broken down in small particles (instead of after 450 years like the original water bottle).
Waste minimisation instead of recycling, I say!

Die Massenproduktion von Kunststoff, die erst vor 6 Jahrzehnten begann, hat sich so rasant beschleunigt, dass sie 8,3 Milliarden metrische Tonnen erschaffen hat… 6,3 Milliarden metrische Tonnen davon sind zu Müll geworden (Die Hälfte alles hergestellten Kunststoffs wird innerhalb von weniger als einem Jahr zu Abfall)…Davon sind nur 9 Prozent recycled worden.


Und dieses Recycling kann alles noch schlimmer machen: In China werden aus Einweg-Wasserflaschen aus Deutschland (als Teil der Recycling-Quote) Fleece hergestellt und wieder nach Deutschland zurück verkauft, wo sie das Abwasser und letztlich das Meer mit Mikro-Fasern (Mikroplastik) beim Waschen verschmutzen und doch wieder als Abfall enden, aber schon in kleine Teilchen zersetzt (anstatt nach 450 Jahren wie die originale Wasserflasche).
Müllvermeidung anstelle von Recycling, sage ich!

Shark oft the week: Silvertip shark — 2. October 2017

Shark oft the week: Silvertip shark

The Silvertip shark (Carcharhinus albimarginatus), despite being easily recognized due to its eponymous white margins on all fins (even pectoral fins, unlike all other “whitetip” shark species), it often confused with its smaller brother Grey reef shark. Both are requiem sharks and can be found on or near coral reefs in the tropical Indian and Pacific Oceans. They are known to form mixed-species aggregations and both perform (slightly different) ritual threat displays to chase away threats (like other sharks or divers) and protect their personal space. The mock attack of an up to 10 ft -3 m- long Silvertip shark (as described here) remind me of male gorillas. While it seems aggressive, I consider this as defensive behavior. Remarkable that they rather flee or chase away instead of attack, in which case they would, more often than not, prevail due to their size.

0979 aquaimages.jpg
Silvertip shark, Image taken by Clark Anderson/Aquaimages – Originaly uploaded to the english wikipedia, Image:0979 aquaimages.jpg, CC BY-SA 2.5, Link

Like all other requiem sharks, Silvertip sharks are viviparous. Females bear every other year litters of around five young after a gestation period of about one year. They grow slowly and mature at around 6.6 ft -2 m- with 20 years.

Silvertip sharks are caught in direct shark fisheries, as bycatch and by illegal practices (IUU) mostly for their fins and meat, but also for cartilage, liver, teeth, jaws and skin. This resulted in areas like Scott Reef off northern Australia, where they are now extinct because of Indonesian fishers. Hence the IUCN considers them as “Vulnerable“. However, there are no species-specific management measures in place.

Despite their inquisitive and aggressive behavior (see above) and being able to take on large prey (due to their dentition, size and power), Silvertip sharks are not known to attack humans. The ISAF lists only 4 provoked, none fatal attacks under this species.

Sources: here and here

Shark of the week: Carribean reef shark — 13. March 2017

Shark of the week: Carribean reef shark

Despite being the most common shark in reefs of the Caribbean Sea, the Caribbean reef shark (Carcharhinus perezii) is one of the least-studied large requiem sharks. It looks a lot like its sister species Dusky shark, but lives solely on or near coral reefs in the tropical western Atlantic Ocean from Florida to Brazil.

Carcharhinus perezi bahamas feeding
Caribbean reef sharks by Greg Grimes from Starkville, MS, USA – pic_0655, CC BY-SA 2.0, via Wikimedia Commons
Caribbean reef sharks are nocturnal and can be found resting in caves or on the sea floor by day (once famous in Mexico as “sleeping sharks”). They mature at 5 to 5.5 ft -1.5 to 1.7 m- (males) or around 6.5 ft -2.0 m- (females) and can reach a length of up to 9.7 ft -3 m, making them one of the largest apex predators in the reef ecosystem. Females are ovoviviparous and give birth to 3 to 6 24 to 30 inches -61 to 76 cm- long living pups every 2 years.

Despite their size Caribbean reef sharks are normally unaggressive toward divers, except in the presence of food – spear fishermen can get accidentally bitten (there are 4 registered unprovoked non-fatal attacks by this species), but sometimes also members of baited diving tours. Attracting sharks by feeding is a controversial by-product of ecotourism (and banned in Florida). Associate humans with food by the sharks (like by bears) seems only a problem if the species usually feed on mammals (like White sharks), but the artificial concentration of predators (like in the image above) and the intensified removal of fishes from the environment for use as shark bait (instead of using fish offal) could be a concern. Showing sharks to tourists, but also photographers and filmmakers, is more profitable than killing them – and provides a sustainable livelihood for ex-fishermen in times of overfishing. Unless, of course, their colleagues exploit this changed behavior of sharks to catch them all, not on film but on the thousands of baited hooks of longlines.

Because Caribbean reef sharks have been targeted by longline and gillnet for their meat, skin, jaws, fins and liver oil or taken as bycatch, resulting in its Near Threatened status. It is the most common shark species landed in Colombia, but protected in the U.S., Bahamas and some marine protected areas off Brazil. Illegal fishing and habitat degradation (coral bleaching) are dangers, too. Caribbean reef sharks off the coast of Florida have been found with dangerous levels of methyl mercury – higher than the FDA guidelines, anyway, the European guidelines are different and incomprehensibly (imo) permit higher levels for large predator species.

Sources: herehere and here


integrate compassion, listening and creativity into our actions | mit Mitgefühl, Zuhören und Kreativität handeln – from hundredgivers — 17. February 2017

integrate compassion, listening and creativity into our actions | mit Mitgefühl, Zuhören und Kreativität handeln – from hundredgivers

I think that these thoughts of an US-American, although triggered by recent political changes there, are absolutely true worldwide. Strategies for peaceful solutions of conflicts are more necessary than ever.

With our beloved democracy quickly descending into fear and clashing ideologies, I’ve begun to hunt for survival techniques. Instead of rocks and shouting matches, are there more effective ways to resolve our differences? Now would be a good time to get back to the basics, educate our hearts and minds and begin to integrate compassion, listening and creativity into our actions…

via How to Educate our Hearts and Minds to Bring More Compassion and Peace to the World — Hundredgivers

Ich denke, dass diese Überlegungen einer US-Amerikanerin, wenn auch angestoßen durch die kürzlichen politischen Veränderungen dort, durchaus weltweit gelten. Strategien zur friedlichen Lösung von Konflikten sind nötiger denn je.

Während unsere geliebte Demokratie rasch in Furcht und Ideologiekämpfe herabsinkt habe ich angefangen, nach Überlebensstrategien zu suchen. Gibt es effektivere Wege, anstelle von Steinen und lautstarken Auseinandersetzungen, um unsere Unterschiede zu überwinden? Jetzt wäre eine gute Zeit, um zu den Grundlagen zurückzukehren, unsere Herzen und unseren Verstand in die richtige Richtung zu formen und damit zu beginnen, mit Mitgefühl, Zuhören und Kreativität zu handeln…

siehe How to Educate our Hearts and Minds to Bring More Compassion and Peace to the World — Hundredgivers

Shark of the week: Bull Shark — 5. December 2016

Shark of the week: Bull Shark

It is well-known that sharks live in saltwater. Sure, there is such a strange thing as a river shark (like the Ganges shark) that seems to tolerate only fresh water (but, as has been proved, can migrate through saltwater, too). But all other sharks live solely in the ocean or in brackish nursing grounds to protect their young, right? Sadly this is wrong.

Because there is the Bull shark (Carcharhinus leucas). Even if their nursery habitats are in brackish water, older Bull sharks can tolerate high salinity as well as zero salinity, which enables them to live worldwide in coastal areas of tropical to subtropical oceans as well as in rivers and lakes.

(Video S3 of a pregnant bull shark from Brunnschweiler J, Baensch H (2011). “Seasonal and Long-Term Changes in Relative Abundance of Bull Sharks from a Tourist Shark Feeding Site in Fiji“. PLOS ONE. DOI:10.1371/journal.pone.0016597. PMID 21346792. PMC: 3029404., CC by 2.5 )

Bull sharks are able to retain salt through their kidneys, liver, gills and a special gland near their tail (requiring a greatly increased production of highly dilute urine and is energetically very demanding). That’s the reason they survive and even thrive in fresh water as much upstream as 2,360 miles -3,800 kilometres- up the Mississippi River or 2,610 miles -4,200 kilometres- up the Amazon River. There is even a population of Bull sharks in the Lake Nicaragua in Central America, seemingly separate, but tagging showed that they wander between the lake and the Caribbean Sea back and forth, conquering 8 rapids on the way. Since a flood in the 1990s even a golf course lake in Queensland, Australia is the home to several bull sharks.

The Bull shark is a stout species with small eyes and a blunt snout (thus the name) and an average length of 7.9 ft – 2.4 m- (female) and 7.4 ft -2.25 m- (male), but there is a single record of a pregnant female specimen of 13 ft -4 m- in an African river. Their age of maturity seems to be varying according to geographic location, up to 14-15 years for males and 18 years for females. Bull sharks are ovoviviparous, like other requiem sharks.

Being opportunistic feeders, Bull sharks eat everything from bony fish and other sharks (even young Bull sharks), to turtles, birds, dolphins and terrestrial mammals like dogs and hippos, but also carcasses and (in case of Indian rivers) bodies. They have to (as mentioned above) in order to survive in fresh water with its zero salinity and significantly greater negative buoyancy. In the ocean their metabolism can slow down.

Based on their habitat, Bull sharks come in frequent contact with humans. In the clear waters of the Bahamas, for example, divers regularly interact with crowds of bull sharks without problems. Some researchers speculate that this non-threatening behavior may be because the sharks can clearly see people and recognize that they are not a typical food source. In murkier waters, however, incidents happen, and humans get bitten and sometimes die. Some Bull sharks being territorial and having virtually no tolerance for provocation doesn’t help matters, either.

Due to its habitat, but also its size, strength and teeth, the Bull shark has been considered by many experts to be the most dangerous shark in the world. If there is such a thing as a Man eater shark it would be the Bull shark and not the White shark. The latter may not in fact be responsible for many of the attacks pinned on the species (including the famous 1916 shark attacks in New Jersey that may have served as inspiration for Jaws), but the Bull shark with its nearly identical dentition. It’s amazing that we don’t have more incidents, and it just reconfirms that they really aren’t interested in us and usually an attack is a mistake.

The Bull shark is caught as bycatch in longline-fisheries, but more often targeted in small artisanal fisheries because of its abundance in nearshore environments and rivers for its meat, fins and skin. Additionally, it is a popular game fish. Due to pollution of their habitat in shallow costal waters, rivers and lakes, and overfishing of their nursery grounds, Bull sharks numbers have significantly declined.

Sources: herehere, here and here

Shark of the week: Night Shark — 28. November 2016

Shark of the week: Night Shark

Did you know that the shark fisheries off northeastern Brazil catch nearly solely sharks containing dangerous amounts of mercury? 90% of the caught sharks and rays are Night sharks (Carcharhinus signatus), a deepwater species that migrate vertically from as far down as 1.2 mi -2 km- at day to within 85 ft – 26 m- of the surface at night (thus the name). It lives on the outer continental shelfs and upper continental slopes on both sides of the Atlantic Ocean.

The Night shark is a slender, fast shark and reaches usually a length of 6.6 ft -2 m. It has a long pointed snout and large green eyes. Like all requiem sharks it is ovoviviparous and gives birth to 4–18 living young measuring 20 to 28 in -50 to 72 cm- after a gestation period of 1 year. Each embryo has a separate compartment within one of the two uteruses and is nourished by a yolk sac and later through a placental connection. Males mature at an age of 8 years and females at an age of 10 years.

Carcharhinus signatus nefsc2.jpg
Night shark, NOAA/NEFSC –, Gemeinfrei,

Being a target species for its highly prized fins and meat, but also for liver oil and fish meal, the Night shark is caught commercially and as bycatch. It it is the most abundant elasmobranch species in the seamount fisheries off Brazil, yet. Formerly common in Caribbean, Cuban and U.S. shark fisheries, fishing pressure resulted in a substantial decline there, too. That’s why the IUCN has assessed the Night shark globally as Vulnerable, even if the U.S. fishing ban seems to work there.

Given that the caught Night sharks off Brazil are mostly juvenile (I think that the shallow banks off Brazil are nursery areas for Night sharks), it is all the more alarming that the caught sharks contained mercury levels higher than allowed by the Brazilian laws (and WHO recommendations) – what amount of mercury would adult sharks contain since they have more years to accumulate it?

Sources: here and here

Shark of the week: Small-spotted catshark — 24. October 2016

Shark of the week: Small-spotted catshark

Did you know that there are sharks in the Baltic sea? None of the species living solely in fresh water (like river sharks or Freshwater stingrays), and fortunately not the Bullshark, but emigrants from North sea or Atlantic. Many have probably been dragged along by saltwater floods due to storms, or wander temporarily into the afterwards more saline waters. But one species made itself at home and lives even in areas far away from saltwater passages. The small-spotted catshark (Scyliorhinus canicula) or lesser-spotted dogfish is the most common European shark species and lives in the Mediterranean, the north-east Atlantic and the North sea, for some time incl. Skagerrak and Kattegat. But now it is even native in the German Baltic sea (to be precise off Poel island), as shown in this report.

Scyliorhinus canicula 1 by Line1.jpg
Scyliorhinus canicula, Von Liné1Eigenes Werk, CC BY-SA 3.0, Link

The up to 3 ft 3 in -1 m- long Small-spotted dogfish is used commercially, too: for its meat (its liver is poisonous), its sandpaper-skin, oil or fishmeal. Now and then catsharks (named after their catlike eyes: horizontally oval eyes with elongated pupils and a nictitating membrane) have been caught in the Baltic sea, too. Afterwards they would be discarded (with high chances of survival) or go, as mentioned here, to aquariums (in which small-spotted catsharks are easy to keep and therefore a common species). Sometimes you are able to even touch them there. Together with my family I visited such an aquarium in Denmark and curiously touched sharks, rays and starfish under water – until I learnt this summer in Scotland, that you shouldn’t do that since it may damage the protective layer of slime above the skin. Why didn’t the other aquarium operators know that?

Like all catsharks the small-spotted catshark lays eggs called mermaid’s purses with curly tendrils at each end to cling themselves to underwater structures. Inside the egg case one embryo (seldom two) develops during 5 to 11 month, which can be studied easily (as done in laboratories). After hatching, the 4 in – 10 cm – long pups have to fend for themselves. On them it was observed for the first time, that they anchor their prey on the dermal denticles on their tail and tear bits off – they are really flexible.

This egg cases as well as pups have now been found in the Baltic sea, too – proof that they are not only temporary visitors. It is assumed that the reason is the climate change. How do they cope with the small level of salinity?

Sources: here, here and here

Shark of the week: Gulper shark — 26. September 2016

Shark of the week: Gulper shark

Did you know that a little deep sea shark (classified as “Vulnerable”) is – due to the big portion of high-quality squalene in its liver oil – considered as “the Rolls-Royce of squalene-producing sharks” and targeted purposefully (whether legal or illegal doesn’t seem to matter)? Beside the here mentioned use of squalene in expencive cosmetics and dubious health capsules -where other squalene sources could easily be used instead – is it a (according to GSK without alternative) ingredient to medical products, too, like the flu vaccine adjuvant AS03. I don’t want to discuss the whole purpose of vaccines, or adjuvants, or the in Europe highly controversial pig flu vaccine of 2009, either – but it is to lament that many Gulper sharks (Centrophorus granulosus) were sacrificed pointlessly, since millions of swiftly produced and paid vaccine doses had to be destroyed later. And that in the case of a shark with the probably lowest reproductive rate of all sharks.

A photo of a gulper shark that has been caught.
Centrophorus granulosus, by NEFSC/NOAAPublic Domain

Female gulper sharks reach maturity at 14 and can live between 54 and 70 years long. Since they are pregnant with only one pup for 2 years and take long breaks in between, they typically have only between 2 and 10 pups in their lifetime. They are ovoviviparous and feed the embryo with yolk and unfertilised and also fertilised eggs (oophagy). The egg cell of the gulper shark reaches one of the largest cellular sizes described for any animal, weighing between 143 and 370 grams.

Living in the Atlantic, Pacific and Indian Oceans as well as the Mediterranean Sea, the Gulper shark is caught on longlines and by trawling (together with various other marine animals as bycatch). It is a highly migrating species and forms schools.

Sources: herehere and here