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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 – http://nefsc.noaa.gov/rcb/photogallery/sharks/sharks.html, 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

 

EFSA: dangerous contaminants in palm oil — 31. August 2016

EFSA: dangerous contaminants in palm oil

During food production, contaminants can develop. One example is Acrylamide during the frying of potatoes, but also Esters of 3- and 2-MCPD and glycidyl esters (glycidol) are such harmful substances in our food. They cause tumors and are especially dangerous to children. Generated during the production of vegetable oils, they can be found in these oils and consequently in processed foods containing these oils. Their highest levels are, by far, in palm oil or fat. That is worrying, since it is difficult to evade palm oil in our supermarkets. Difficult, but not impossible, in my opinion. Alarming are the high doses found in baby formula.

Source: ESFA-report

theconversation.com: The oceans are changing too fast for marine life to keep up | Die Meere ändern sich zu schnell, als das ihre Bewohner mithalten können — 19. August 2016

theconversation.com: The oceans are changing too fast for marine life to keep up | Die Meere ändern sich zu schnell, als das ihre Bewohner mithalten können

Regarding those who point out that there where periods with much higher (not human-caused) carbon dioxide levels than today, implying it is only natural and no reason to change anything, I found this article that was originally published on The Conversation on October 13, 2015.

Yes, rising carbon dioxide levels happened in the past, but either so slow that nature could adapt, or as rapidly as now, but then coupled with a mass extinction event (Source). The sharks survived the last times (as below mentioned they wouldn’t now), and I think (and hope) mankind would survive, but: how would we live in the world we would find ourselves in after?


Bezüglich denen, die aufzeigen, dass es Perioden mit viel höheren (nicht vom Menschen verursachten) CO2-Pegeln als heute gab, damit unterstellend, dass es nur natürlich ist und es keinen Grund gibt irgendetwas zu ändern, habe ich diesen Artikel gefunden, der ursprünglich am 13. Oktober 2015 auf The Conversation veröffentlicht wurde.

Ja, in der Vergangenheit passierten steigende CO2-Pegel, aber entweder so langsam dass die Natur sich anpassen konnte, oder so schnell wie heute, aber dann  mit einem Massenaussterben gekoppelt (Quelle). Die Haie überlebten es die letzten Male (wie unten erwähnt würden sie das jetzt nicht mehr), und ich denke (und hoffe) die Menschheit würde überleben, aber: wie würden wir leben in der Welt, in der wir uns danach befinden würden?

The oceans are changing too fast for marine life to keep up

Ivan Nagelkerken, University of Adelaide

Some of the ocean’s top predators, such as tuna and sharks, are likely to feel the effects of rising carbon dioxide levels more heavily compared other marine species.

That’s just one of the results of a study published today in Proceedings of the National Academy of Science.

Over the past five years we’ve seen a significant increase in research on ocean acidification and warming seas, and their effect on marine life. I and my colleague Sean Connell looked at these studies to see if we could find any overarching patterns.

We found that overall, unfortunately, the news is not good for marine life, and if we do nothing to halt climate change we could lose habitats such as coral reefs and see the weakening of food chains which support our fisheries.

Acidifying and warming oceans

Humans have been adding carbon dioxide to the atmosphere largely through burning fossil fuels. Under a worst-case scenario, without doing anything to stop increasing emissions, we’d expect concentrations of carbon dioxide to reach around 1,000 parts per million by the end of the century.

This increase in greenhouse gases is “acidifying” the oceans. It’s happening now. Carbon dioxide concentrations have reached around 400 parts per million, compared with around 270 parts per million before the industrial revolution.

This extra carbon dioxide, when it dissolves into the seas, is reducing the pH of the oceans – that is, making them more acidic.

Many ocean creatures, particularly those that build habitats such as corals and shellfish, make skeletons out of calcium carbonate, which they get from ions dissolved in sea water.

When carbon dioxide dissolves in seawater, it makes these calcium carbonate ions harder for marine life to collect and turn into skeletons. It’s like a person going on a diet without calcium.

At first this results in marine life producing brittle skeletons, but can ultimately lead to the skeletons dissolving.

A calcium-free diet

Many studies have looked at what will happen to these lifeforms that produce skeletons, but we wanted to look at how rising carbon dioxide would affect the ocean at a broader scale.

We analysed more than 600 experiments on ocean acidification and warming seas.

Overall it seems warming temperatures and acidifying oceans will have a negative effect on species and ecosystems. This means reduced growth, abundance, and diversity of marine species.

We also found these results were mostly consistent across latitudes – they weren’t just limited to tropical oceans.

The oceans will warm as they acidify, so it’s important to look at these two changes together. Previous analyses typically looked at specific life stages or different ecosystems.

It’s likely that acidification will interact with warming to have a worse effect. For instance, if you would see a 20% reduction in calcification rates because of rising temperatures, and a 25% reduction in calcification because of acidification, then the combined reduction might be 60%. We see these effects regularly in the studies we looked at.

Of course not every species will show the same response. We expect some species to be able to acclimate or adapt to changes, particularly over longer time periods perhaps like a couple of decades. For example, a recent study on a coral living in a tropical lagoon found it has some capacity to adapt. We found that more generalist species like microorganisms seem to be doing particularly well under climate change, and also some fish species at the bottom of the food chain may show increases in their populations.

Changing whole ecosystems

Most worrying are not only the changes to individual species but also whole ecosystems.

We found that reef habitats are vulnerable: coral reefs, but also temperate reefs built by molluscs such as oysters and mussels. A lot of shallow temperate waters used to have oysters reefs, but there are few natural reefs remaining.

There are also cold-water reefs formed by other species of coral, which grow slowly over thousands of years in the cooler temperatures. In our analysis we found that acidification could cause these habitats to show reduced growth. These habitats are often located in deep waters and are very sensitive to human impacts.

We also found that these changes affect whole ocean food webs.

We found that warmer temperatures mean more phytoplankton – the tiny plant-like lifeforms that form the basis of many ocean food chains. This means more food for grazing species that feed on phytoplankton.

Warmer temperatures also mean faster metabolisms, which require more food. However this didn’t translate into higher growth rates in grazing species. That’s fatal because the next level up in the food chain (the species that eat the grazing animals) would have less food, but still need more food because of faster metabolisms.

This effect is expected to become stronger as you go up the food chain, so predatory species like tuna, sharks, and groupers will be the species that would feel the strongest effects.

These species are also threatened by overfishing, which adds another level of stress. Overfishing alters important food web interactions (e.g. top-down control of prey species) and may also reduce the gene pool of potentially strong individuals or species that could form the next generation of more resilient animals. And this is on top of other threats such as pollution and eutrophication.

Therein lies an opportunity. We cannot change climate change (or ocean acidification) in the short term. But if we can mitigate the effects of overfishing and other human stressors we can potentially buy some time for various species to adapt to climate change.

Species can genetically adapt to changes over geological timescales of thousands of years – as we can see from modern species’ survival over many ups and downs in the climate. But the changes we have wrought on the oceans will take place over decades – not even one generation of a long-lived sea turtle or shark.

With such fast changes, many species in the ocean will likely be unable to adapt.

The Conversation

Ivan Nagelkerken, Associate Professor, Marine Biology, University of Adelaide

Read the original article.

Shark of the week: Dumb shark — 15. August 2016

Shark of the week: Dumb shark

Did you know that there is a dump shark? I don’t know why the Centrophorus harrissoni was named like that, but I find it insulting.

Harrisson’s Dogfish, Centrophorus harrissoni. Source: CSIRO National Fish Collection. License: CC BY Attribution

The Harrisson’s Dogfish is a rare species of gulper sharks with a large mouth and large green eyes. It can live up to 43 in -110 cm- long and up to 46 years old. Maturing late (females at about 39 in -99 cm- and males at about 33 in -84 cm- length), female gives birth to mostly only one living young (ovoviviparous) with about 13 in -35 cm- length every two (or possibly three) years (it seems that only their right-side uterus is working properly).

Living solely along the east coast of Australia and off New Zealand and at a relatively high area for a deepwater shark (at 820 to 1260 ft -250 to 385 m- under water), the Harrison’s Dogfish was considered Critically Endangered in 2003. This was based on a more than 99% decline of the species on upper continental slope grounds off central and southern New South Wales (NSW) and eastern Victoria, compared with the 1970s (when commercial trawling began on the NSW upper slope). The species is now known to occupy a greater geographical range than previously thought and a number of conservation measures have been implemented. Earlier restrictive catch limits (to prevent target fishing for its meat und squalene in its liver oil) have been replaced by a total ban on retaining any Harrisson’s Dogfish for sale. There are protection areas (where all kind of fishing are banned), others where only some fishing methods are banned, and a ban on trawling below 2296 ft -700 m- along the east coast south from Sydney (designed to protect all deepwater sharks). The low reproductive rate, late age of maturity, and long lifespan typical of these sharks means they are likely unable to recover quickly after their depletion, despite the fishing ban. Upper-slope dogfish species are more vulnerable to capture than mid-slope species, because they are targeted throughout their vertical distribution and most of their local geographic distribution (except for the protection areas). But since they are used to light and lower water pressure, a high proportion of those captured accidentally are likely to survive if returned quickly to the sea.

The Harrison’s Dogfish is considered as only Endangered, since now the overall population decline is thought to be only 70% (although it will be most likely declining further). Scientists hope that 500 of them will be enough for a genetically diverse population. To me, these numbers mean that this species is almost extinct (In comparison, there are more than tree times as many giant pandas in the wild, and their numbers are increasing further. But they are cute.).

Sources: here, here and here

about climate change denial | über Klimawandel-Leugnung — 13. August 2016

about climate change denial | über Klimawandel-Leugnung

Since I often stay helpless in the face of climate change denial (or rather human-caused global warming denial), I post some links I found to make sense of their arguments (including their motives and why discussing with facts doesn’t work):

skepticalscience.com

short videos on global warming

Denial 101 – Massive Open Online Course 

for instance

climatecentral

George Monbiot from The Guardian


Weil ich oft hilflos bin angesichts Klimawandel-Leugnung (oder eher Menschen-verursachte-Erderwärmungs-Leugnung), poste ich einige Links die Sinn in ihre Argumente bringen (inklusiver ihrer Motive und warum mit Fakten diskutieren nichts bringt):

übersetzte Seite skepticalscience.com

Erklärungvideo zur Erderwärmung

Denial 101 – Massive Open Online Course 

z.B. 

klimafakten.de

George Monbiot from The Guardian (teilweise Übersetzung hier)