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Sydney's Endangered Seahorses Find Protection in Underwater Hotels
By Manuela Callari
It can grow to a maximum of six inches (16 centimeters), change color depending on mood and habitat, and, like all seahorses, the White's seahorse male gestates its young. But this tiny snouted fish is under threat.
White's seahorse, also called the Sydney seahorse, is native to the Pacific waters off Australia's east coast. In recent years, populations have decreased drastically. It and the South African Knysna seahorse are the only two out of around 50 seahorse species to be listed as endangered.
A wild storm season from 2010 to 2013 left the Sydney seahorses' habitat in tatters, wiping out 90% of the population in the area. Several large storms shifted huge volumes of sand, smothering the soft corals, sponges and seagrass they call home.
That's why researchers in Sydney Harbor have built special seahorse hotels to help restore their habitat and encourage would-be White's seahorse dads to fall pregnant.
"There are two things that we're trying to gain from this project," said Robbie McCracken, an aquarist at Sydney Sea Life Aquarium, who's working with researchers from University of Technology Sydney and the New South Wales DPI Fisheries on the program.
"Number one is that we can breed these animals in an aquarium to release them into the wild. And number two is that the seahorse hotels provide a suitable environment for them to live on."
Building an Ocean Seahorse Destination
Seahorses are found in tropical and temperate coastal water worldwide, but are most abundant around Australia, China and the Philippines.
Trade in the tiny creatures is strictly regulated because of their use in traditional medicine, aquariums and their sale as dried curios. But because they are poor swimmers and cannot easily move elsewhere, habitat loss is a particular threat for these curious animals.
Seahorses wrap their tails around seagrass and corals to avoid being carried away on currents. They use the habitat to spawn and hide from predators such as crabs, while also feeding on riches of plankton and small crustaceans living in the reef.
Where corals aren't available, scientists found seahorses taking up residence in fishing nets and old crab traps abandoned at the bottom of the ocean.
This inspired the Sydney team to increase available habitat in the famous Australian harbor by building cages of net and steel. Over time, algae, sponges and corals colonize the structures, creating a safe, welcoming environment for the seahorses, say the researchers. The hotel frame will eventually corrode, leaving behind the coral mounds that have grown around them.
The researchers trialed the first hotels in 2018. Within two months, seahorses had begun to move in and soon a few males fell pregnant. Knowing that the hotels were a hit, the next step was to boost seahorse numbers.
In 2019, the team caught eight pairs of White's seahorses — the creatures are monogamous and, so, mate with one partner for life. The babies were born in September and October of last year.
"We were able to watch them court with each other, and mate with each other, and then we were able to watch the dads deliver," said McCracken, "so, it was always quite exciting."
Mixing With the Locals
Baby seahorse mortality is high in the wild because they are easily caught, so those bred in the protected environment of the aquarium weren't ready to be released into the wild until early May.
The team released 90 new arrivals into Sydney Harbor, placing some directly into the purpose-built hotels, and others onto a net that wild seahorses had already settled on.
Before setting them free, the researchers marked each young seahorse with a fluorescent tag with unique IDs inserted just beneath the skin to track how they get on in the different environments.
"The most exciting part was being able to put these animals into the wild and then go back a month later and still see them surviving and growing," said McCracken.
The seahorses will be old enough to mate and reproduce around October or November 2020. And researchers hope that by then, they will be able to breed with the wild population.
Building a Global Seahorse Hotel Chain
With seahorses everywhere facing the loss of their coral reef homes, similar projects have sprung up in places like Greece and South Africa, home to the world's most endangered seahorse, the Knysna seahorse.
"The endangered South African seahorse is benefiting from something quite similar, even though it wasn't intentional," said Peter Teske, professor at the Department of Zoology, University of Johannesburg.
In the South African case, seahorses have bedded down in "Reno mattresses" — wire cages filled with rocks — that were used to build a new marina. Researchers from NGO Knysna Basin Project found the structures acted as a refuge for the animals.
While Teske describes the seahorse hotels as "a positive news story" and a great way to create public awareness of conservation, he added that establishing artificial habitats in some areas will only prevent the extinction of local populations.
"For a complete recovery, it is necessary to give the natural habitat a chance to regenerate," said the seahorse expert.
In Australia, the researchers hope the project could provide an opportunity to raise awareness not only of the plight of the Sydney seahorses but the other animals with which it shares its ocean habitat.
The waters around Sydney and the east coast are rich in biodiversity and include several threatened species like the weedy seadragon — a relative of the seahorse — and the grey nurse shark. Like the seahorse, they're also under pressure from pollution, ocean traffic and habitat loss through storms and coastal construction.
"It's a good thing to get people's support and interest. The seahorses are a useful vehicle to get people concerned if the harbor is in trouble," said David Booth, professor of marine ecology at the University of Technology Sydney who is also working on the project.
The hotels have become an attraction for divers hoping to catch a glimpse of these small but near mythical creatures.
"Everyone loves seahorses," added Booth, "they are so popular."
Reposted with permission from Deutsche Welle.
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As Biden Embraces More Ambitious Climate Plan, Fossil Fuel Execs Donate to Trump 'With Greater Zeal' Than in 2016
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By Gavin Naylor
Sharks elicit outsized fear, even though the risk of a shark bite is infinitesimally small. As a marine biologist and director of the Florida Program for Shark Research, I oversee the International Shark Attack File – a global record of reported shark bites that has been maintained continuously since 1958.
A Big, Diverse Family<p>Not all sharks are the same. Only a dozen or so of the roughly 520 shark species pose any risk to people. Even the three species that account for almost all shark bite fatalities – the <a href="https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/carcharodon-carcharias/" target="_blank">white shark</a> (<em>Carcharodon carcharias</em>), <a href="https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/galeocerdo-cuvier/" target="_blank">tiger shark</a> (<em>Galeocerdo cuvier</em>) and <a href="https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/carcharhinus-leucas/" target="_blank">bull shark</a> (<em>Carcharhinus leucas</em>) – are behaviorally and evolutionarily very different from one another.</p><p>The tiger shark and bull shark are genetically as different from each other as a dog is from a rabbit. And both of these species are about as different from a white shark as a dog is from a kangaroo. The evolutionary lineages leading to the two groups split 170 million years ago, during the age of dinosaurs and before the origin of birds, and <a href="https://www.ck12.org/book/CK-12-Human-Biology/section/7.2/" target="_blank">110 million years before the origin of primates</a>.</p>
White, tiger and bull sharks are distinct species that diverged genetically tens of millions of years ago. Gavin Naylor / CC BY-ND<p>Yet many people assume all sharks are alike and equally likely to bite humans. Consider the term "shark attack," which is scientifically equivalent to "mammal attack." Nobody would equate dog bites with hamster bites, but this is exactly what we do when it comes to sharks.</p><p>So, when a reporter calls me about a fatality caused by a white shark off Cape Cod and asks my advice for beachgoers in North Carolina, it's essentially like asking, "A man was killed by a dog on Cape Cod. What precautions should people take when dealing with kangaroos in North Carolina?"</p>
Know Your Species<p>Understanding local species' behavior and life habits is one of the best ways to stay safe. For example, almost all shark bites that occur off Cape Cod are by white sharks, which are a large, primarily cold-water species that spend most of their time in isolation feeding on fishes. But they also aggregate near seal colonies that provide a reliable food source at certain times of the year.</p><p>Shark bites in the Carolinas are by warm-water species like bull sharks, tiger sharks and <a href="https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/carcharhinus-limbatus/" target="_blank">blacktips</a> (<em>Carcharhinus limbatus</em>). Each species is associated with particular habitats and dietary preferences.</p><p>Blacktips, which we suspect are responsible for most relatively minor bites on humans in the southeastern United States, feed on schooling bait fishes like menhaden. In contrast, bull sharks are equally at home in fresh water and salt water, and are often found near estuaries. Their bites are more severe than those of blacktips, as they are larger, more powerful, bolder and more tenacious. Several fatalities have been ascribed to bull sharks.</p><p>Tiger sharks are also large, and are responsible for a significant fraction of fatalities, particularly off the coast of volcanic islands like Hawaii and Reunion. They are tropical animals that often venture into shallow water frequented by swimmers and surfers.</p>
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="1cfa1c9590e386ecc9455b4762b87518"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/yDqzGOa-adc?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
Humans Are Not Targets<p>Sharks do not "hunt" humans. Data from the International Shark Attack File compiled over the past 60 years show a tight association between shark bites and the number of people in the water. In other words, shark bites are a simple function of the probability of encountering a shark.</p><p>This underscores the fact that shark bites are almost always cases of mistaken identity. If sharks actively hunted people, there would be many more bites, since humans make very easy targets when they swim in sharks' natural habitats.</p><p>Local conditions can also affect the risk of an attack. Encounters are more likely when sharks venture closer to shore, into areas where people are swimming. They may do this because they are following bait fishes or seals upon which they prey.</p><p>This means we can use environmental variables such as temperature, tide or weather conditions to better predict movement of bait fish toward the shoreline, which in turn will predict the presence of sharks. Over the next few years, the Florida Program for Shark Research will work with colleagues at other universities to monitor onshore and offshore movements of tagged sharks and their association with environmental variables so that we can improve our understanding of what conditions bring sharks close to shore.</p>
More to Know<p>There still is much to learn about sharks, especially the 500 or so species that have never been implicated in a bite on humans. One example is the tiny <a href="https://www.newsweek.com/one-worlds-rarest-sharks-also-one-most-adorable-325280" target="_blank">deep sea pocket shark</a>, which has a strange pouch behind its pectoral fins.</p><p>Only two specimens of this type of shark have ever been caught – one off the coast of Chile 30 years ago, and another more recently in the Gulf of Mexico. We're not sure about the function of the pouch, but suspect it stores luminous fluid that is released to distract would-be predators – much as its close relative, the <a href="https://sharkdevocean.wordpress.com/2015/04/23/second-ever-pocket-shark-discovered-in-gulf-of-mexico/" target="_blank">tail light shark</a>, releases luminous fluid from a gland on its underside near its vent.</p>
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="5783b39d0838d6e410344a852ed0dcc3"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/UTO5debfmsg?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>Sharks range in form from the bizarre <a href="https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/mitsukurina-owstoni/" target="_blank">goblin shark</a> (<em>Mitsukurina owstoni</em>), most commonly encountered in Japan, to the gentle filter-feeding <a href="https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/rhincodon-typus/" target="_blank">whale shark</a> (<em>Rhincodon typus</em>). Although whale sharks are the largest fishes in the world, we have yet to locate their nursery grounds, which are likely teeming with thousands of <a href="https://www.earthtouchnews.com/oceans/sharks/baby-whale-shark-rescued-from-gillnet-in-india-video/" target="_blank">foot-long pups</a>. Some deepwater sharks are primarily known from submersibles, such as the giant <a href="https://twitter.com/gavinnaylor/status/1146144452681113601" target="_blank">sixgill shark</a>, which feeds mainly on carrion but probably also preys on other animals in the deep sea.</p><p>Sharks seem familiar to almost all of us, but we know precious little about them. Our current understanding of their biology barely scratches the surface. The little we do know suggests they are profoundly different from other vertebrate animals. They've had 400 million years of independent evolution to adapt to their environments, and it's reasonable to expect they may be hiding more than a few tricks up their gills.</p>
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