Blue Sharks Are True Globalists, Tagging Data Shows
Blue sharks are among the widest-ranging shark species in the oceans. We know this partly because from 1962 to 2013, 117,962 blue sharks were tagged as part of the ongoing Cooperative Shark Tagging Program.
This partnership between the commercial fishing industry, the U.S. government, recreational fishermen and academic research scientists is the longest-running tagging program in the world. Since its launch in 1962, participants have tagged hundreds of thousands of sharks representing 35 different species.
A dart tag, one type used in the Cooperative Shark Tagging Program. NOAA
More than half (51%) of the animals tagged were blue sharks (Prionace glauca) – a total of 117,962 individual sharks. This is probably because blues are abundant: They are found in all of the world's oceans, as far north as Alaska and as far south as Chile, but rarely venture near shore.
Unlike some other sharks, blues are not a prized commercial species, likely because most people think they taste disgusting. That makes fishermen willing to tag and release them instead of harvesting them.
Each tag attached to a shark carries an identification number and contact information, so that recaptures can be reported and matched to data collected during the initial tagging. The data show that these sharks really move. One traveled a record-breaking 3,997 nautical miles from waters off Long Island, New York, where it was first tagged, to the south Atlantic where it was recaptured – a distance longer than the Great Wall of China.
The sharks were caught in all seasons throughout their range, in tropical waters warmer than 68 degrees Fahrenheit (20 degrees Celsius) and temperate waters, which range from 50°-68°F (10°-20°C). In more tropical climates, blue sharks occupy waters as deep as 1,150 feet (350 meters), which are cooler than water near the surface. Their ability to inhabit a wide range of depths enables them to move around as seasons and water temperatures change.
Tagging data confirm that blue sharks migrate incredibly long distances, with some even crossing the equator from the North Atlantic to the South Atlantic. All of this movement allows them to mix and mingle with individuals throughout their range. This tells scientists that all blue sharks in the Atlantic Ocean are part of one mating pool, and can be considered one big population, rather than smaller separate groups.
The fact that blue sharks range so widely suggests that an event in one part of the Atlantic, such as an oil spill, could potentially affect the number of mating pairs across the population. This could reduce the number of blue sharks in the next generation and lead to a decline in their population throughout the Atlantic. It could also reduce their genetic diversity and make the survivors more prone to mortality from disease.
About 7% of the tagged blue sharks (8,213) were recaptured later, sometimes after more than a decade. One shark was recaptured nearly 16 years after it was first tagged. Scientists estimated that this shark was between 8 and 11 years old at the time it was tagged, based on its size. That original age estimate would have made the shark 24 to 27 years old when it was recaptured, which falls within the current estimated range of maximum age for the species.
Thanks to tagging data, scientists have learned a lot about the ecology of several species, including smooth dogfish and sandbar sharks. As a scientist pursuing a career in marine conservation, I look forward to more wondrous discoveries about these marvelous animals.
Reposted with permission from The Conversation.
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By Victoria Masterson
Using one of the world's problems to solve another is the philosophy behind a Norwegian start-up's mission to develop affordable housing from 100% recycled plastic.
Sustainable Homes<p>UN-Habitat says an <a href="https://unhabitat.org/un-habitat-aims-to-use-plastic-waste-to-support-housing-for-all" target="_blank">estimated 60% of people living in urban areas of Africa are in informal settlements</a>. At the same time, between 1990 and 2017, African countries imported around 230 metric tonnes of plastic, "which mostly ended up in dump sites creating a massive environmental challenge," the agency adds.</p><p>UN-Habitat deputy executive director, Victor Kisob, said the aim of the partnership with Othalo was to "promote adequate, sustainable and affordable housing for all."</p>
Artist's impression of an Othalo community, imagined by architect Julien De Smedt. Othalo<p>Othalo's process involves shredding plastic waste and mixing it with other elements, including non-flammable materials. Components are used to build up to four floors, with a home of 60 square metres using eight tons of recycled plastic. A factory with one production line can produce 2,800 housing units annually.</p><p>Following successful laboratory tests, Othalo's factory in Estonia has started producing components to build three demonstration homes for Kenya's capital, Nairobi; Yaoundé, the capital of Cameroon and Dakar, the capital of Senegal.</p><p>Othalo founder Frank Cato Lahti has been developing and testing the technology since 2016 in partnership with <a href="https://www.sintef.no/en/" target="_blank">SINTEF</a>, a 70-year-old independent research organization in Trondheim, Norway, and experts at Norway's <a href="https://en.uit.no/startsida" target="_blank" rel="noopener noreferrer">University of Tromsø</a>.</p>
Othalo founder Frank Cato Lahti. Othalo<p>Almost <a href="https://www.un.org/development/desa/publications/2018-revision-of-world-urbanization-prospects.html" target="_blank">seven out of every 10 people in the world are expected to live in urban areas by 2050</a>. More than 90% of this growth will take place in Africa, Asia, Latin America, and the Caribbean.</p><p>"In the absence of effective urban planning, the consequences of this rapid urbanization will be dramatic," UN-Habitat warns.</p><p>Lack of proper housing and growth of slums, inadequate and outdated infrastructure, escalating poverty and unemployment, and pollution and health issues, are just some of the effects.</p><p>Mindsets, policies, and approaches towards urbanization need to change for the growth of cities and urban areas to be turned into opportunities that will leave nobody behind, UN-Habitat says.</p>
Pioneers of Change<p>Reimagining cities and communities for greater resilience and sustainability was a key topic at the<a href="https://www.weforum.org/events/pioneers-of-change-summit-2020" target="_blank"> World Economic Forum's Pioneers of Change Summit 2020</a>.</p><p>The digital event brought together innovators and stakeholders from around the world to explore solutions to the challenges facing enterprises, governments and society.</p><p>Opening the summit, <a href="https://www.weforum.org/events/pioneers-of-change-summit-2020/sessions/opening-plenary-8f731cbc65" target="_blank">Stephan Mergenthaler, the Forum's Head of Strategic Intelligence and a member of the Executive Committee</a>, said: "We need to change the way we produce, the way we live and interact in our cities to make this transition to net-zero emissions a reality…</p><p>"And as this year has illustrated so dramatically, we need to make every effort that we keep populations healthy, if we want to avoid jeopardizing all this progress."</p><p><em>Reposted with permission from </em><em><a href="https://www.weforum.org/agenda/2020/11/un-africa-recycled-plastic-housing/" target="_blank">World Economic Forum</a>.</em><a href="https://www.ecowatch.com/r/entryeditor/2649069252#/" target="_self"></a></p>
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