By freedivinguae

Dolphins plan their dives

Underwater recordings reveal the cetaceans delay reaching the surface in order to gather intelligence useful for future hunts. Tanya Loos reports.

A Risso's dolphin, on the surface, preparing its next dive on the basis of intelligence gathered on the previous one.
A Risso’s dolphin, on the surface, preparing its next dive on the basis of intelligence gathered on the previous one.
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Dolphins have been found to ignore the pressing need to breathe in order to plan for their next hunting dive, a behaviour scientists say comprises the first evidence of planning in sea mammals.

Dolphins and other mammal and bird marine predators, such as seals and penguins, forage for food bound by two strict parameters – the need to find enough food at depth, and the need to return to the surface to breathe. Penguinsand seals have been shown to increase their oxygen store before they dive if they anticipate a particularly deep excursion, but direct evidence of future planning has been lacking in cetaceans.

The brainy superstars of the avian kingdom, the ravens, have been shown to plan, with scientists devising complicated puzzles to confirm that the birds can and will delay gratification if it means greater reward in the future. It is somewhat trickier to find evidence of planning in wild populations of animals such as dolphins, even though they are known to be highly intelligent.

Dolphin super hearing at least 26 million years old

Dolphin super hearing at least 26 million years old

Risso’s dolphins (Grampus griseus) dive down several hundred metres to hunt shoals of squid off the coast of the US. A multi-agency group of scientists led by Patricia Arranz and Peter Tyack from St Andrews University in the UK used data loggers and echo-sounders to track the mammals and their prey to determine what strategies the mammals use. The results are published in the Journal of Experimental Biology.

The team attached data-loggers to 33 dolphins to record depth and movement, as well as the sounds they emitted. The locations of the squid shoals were recorded by echo-sounders. Then, back in the lab, information from 37 dives was analysed.

The study revealed that at the start of a dive, the animals selected an echolocation range that targeted the best prey-populated depth encountered on the previous one – “which can be interpreted as dolphins recalling information to plan the next foraging dive,” says Arranz.

The team also found that the dolphins were echolocating throughout their ascent to the surface after feeding at depth, even though at that point they had lower motivation to eat and higher motivation to breathe.

The researchers regard this as evidence that the dolphins are planning their next dive – sampling prey at different depths with their buzzes and clicks to build up a mental map in anticipation of their next hunting sortie.

source: https://cosmosmagazine.com/biology/dolphins-plan-their-dives

By freedivinguae

Scientists seek answers about the biggest fish in sea

A whale shark makes diver Alexandra Watts appear tiny as she observes it in the Galapagos Islands area of Ecuador recently.

A whale shark makes diver Alexandra Watts appear tiny as she observes it in the Galapagos Islands area of Ecuador recently. simonjpierce.com via AP

GALAPAGOS ISLANDS, Ecuador — It’s the biggest shark – and the biggest fish – in the sea, often found roaming in warm waters around the globe with its huge mouth agape in search of dinner.

Yet despite its hulking appearance, the whale shark has only tiny, almost useless teeth and is sometimes so docile that entire boatloads of people can swim alongside the enigmatic, spotted beast.

It’s also one of the least understood animals in the oceans.

Marine biologists have been tagging whale sharks in recent years trying to answer questions about their life and reproductive cycles. Only one pregnant whale shark has ever been found: In 1995, a dead whale shark was found off the coast of Taiwan with 300 embryos inside, all at different stages of development.

“The million-dollar questions are where are they mating, hunting and where do their young live?” said Jonathan Green, director of the Galapagos Whale Shark Project.

In an attempt to solve some of the most enduring mysteries, a group of scientists spent several weeks diving with whale sharks in the Galapagos Islands last summer and fall. They tried some never-before-used techniques on the species in the wild: taking blood samples and doing ultrasound exams, all while swimming furiously beside them underwater.

While they are comparable in size to whales, whale sharks are sharks. They typically grow to be bigger than a double-decker bus: between 20 to 52 feet and more than 20 tons. But as filter feeders, the enormous whale sharks are dangerous only to the plankton, fish eggs and tiny fish they chomp on.

The gentle giants aren’t particularly fast compared to other sharks, but a simple wave of their tail propels them through the water faster than any human could ever swim. They have broad, flat heads and their entire dark-blue bodies are covered in dots that act as camouflage underwater.

After years of being overhunted by fishermen, whale sharks are endangered and at risk of extinction.

In the last 75 years, the vast majority of whale sharks have been hunted by people for food and their numbers are still dropping, said Simon Pierce, chief scientist at the Marine Megafauna Foundation.

Some biologists worry climate change could hurt the sharks by reducing their food supply: rising ocean temperatures could mean less plankton. “If we do the things that are necessary to conserve the whale sharks, we’ll be conserving the ocean itself,” said Simon Thorrold of the Woods Hole Oceanographic Institute in Massachusetts.

SOURCE: https://www.pressherald.com/2018/02/28/scientists-go-after-biggest-fish-in-sea/

By freedivinguae

Ultimate sea turtle hero gets lifetime achievement award

If you love something, let it go.

That’s what Donna Shaver does every season with the tiny sea turtles she cares for.

For more than 30 years, Shaver has dedicated her life to sea turtle conservation and recovery at Padre Island National Seashore. She serves as the chief of sea turtle science and recovery.

On Friday, the International Sea Turtle Society gave Shaver its Lifetime Achievement Award.

Like a mother to the endangered species, Shaver has created a bond with them.

From sleeping in a cot in the turtle lab listening for hatching to placing the little fighters on the sand to watch them make their debut into the ocean, she savors every moment.

“When people have children, they grow up and go away,” Shaver said in an interview with the Caller-Times in 2012. “I have a new batch each year.”

More: 395 cold-stunned sea turtles released back into Gulf of Mexico

Since she began volunteering, Shaver has been focused on saving the Kemp’s ridley species. Sea turtle nesting season is from April to September of each year.

“It’s the most endangered sea turtle species in the world. So if it takes a few extra hours at night, if it’s convenient, it’s worth it,” she said.

More: Padre Island turtle patrol works to save rare species

For Shaver, releasing the sea turtles on the beach is like dropping off children at school for the first time.

“I see grown men with tears in their eyes,” she said. The turtles have no maternal care. Going down the sand, they’re on their own. Only a few of them will make it. The odds of that one little turtle are not very good.”

According to a news release, Shaver began her work with sea turtles as a Student Conservation Association volunteer at Padre Island National Seashore in 1980.

She was a member of the team that conducted the Kemp’s Ridley Head-starting and Imprinting Project from 1978 to 1988.

Shaver joined the National Park Service as a park technician at Padre Island National Seashore during the summers of 1981 to 1984 and became a permanent employee in 1985. By 1986, she was leading the park’s sea turtle conservation efforts.

The National Park Service also will celebrate 40 years with the Kemp’s Ridley Sea Turtle Restoration and Enhancement Program.

More: Turtle finding dog Ridley Ranger — who helped at Padre Island National Seashore — dies

The Lifetime Achievement Award was officially presented at an International Sea Turtle Symposium in Kobe, Japan on Friday. Dr. David Owens, Shaver’s former professor from Texas A&M, accepted the award on her behalf.

SOURCE: http://www.caller.com/story/news/local/2018/02/23/ultimate-sea-turtle-hero-gets-lifetime-achievement-award/367905002/
By freedivinguae

Saving Sea Turtles


OWU Connection Supports Zoology Major’s Effort to Aid Leatherbacks

Name: Ryan Bishop ’17

Major: Zoology

Minor: East Asian Studies

Hometown: Sofia, Bulgaria

Experience: Theory-to-Practice Grant, “Leatherback Conservation in Costa Rica with the Earthwatch Institute”

Before graduating in December, Bishop used an OWU-funded Theory-to-Practice Grant to travel to Costa Rica to support sea turtle conservation efforts.

Lessons learned

“The Pacific Ocean population of leatherback sea turtles is very endangered, and it is the focus of the researchers at the Goldring-Gund Research Station, affiliated with the Leatherback Trust.

“Where decades ago thousands of leatherback sea turtles used to nest on Playa Grande (where the research station is located), in the last few years, only about 20 have come out to lay eggs, which is direly worrying. However, conservation efforts there began about 20-25 years ago, and now is the time to begin seeing their effects.

“In the nine days I was there, teams patrolled the beach every night for six hours, waiting for turtles to come out with the high tide and lay eggs. Eggs are then taken and transported to a safe hatchery. It can be tiring and icky work, especially in the high humidity and temperatures on the beach. In those nine days, we had a remarkable number of leatherback turtles come out—four or five.

Leatherback sea turtles come ashore in the high tide to lay eggs. (Photo by Ryan Bishop)

“Three of them came out in one night; I was there to help with two (one even hit me with its flipper). Considering that my stay there was only a fraction of the nesting season, it was very encouraging to have this many turtles come out in such a short time, and I was also just immensely lucky to see them. They are majestic creatures. Often, their carapaces will be covered in barnacles and bioluminescent creatures, and when you swipe your hand over them in the night, they will glow. …

“This expedition allowed me to see a lot of what I learned about conservation in class applied directly in the field. It showed me the devotion that biologists have to their work, and it basically allowed me to experience my major in practice.

“I previously had amazing experiences on a Theory-to-Practice Grant going to Taiwan to learn about the Taiwanese queer community, and I knew that the TPG program is an amazing way to develop a project of one’s own or embark on a program you usually wouldn’t be able to afford.

“TPGs allow students to craft their own project and research, planning everything from scratch independently or with a professor, which is very empowering for undergraduates and gives them a chance to see what developing a project and applying for a grant is like in academia. … It is an incredible way to take part in field work and The OWU Connection allowed me to experience it, thanks to our generous donors in this case, Andres Duarte ’65.”

Why I chose Ohio Wesleyan

“I was looking for zoology programs in the U.S. and OWU’s stood out. OWU also offered me a great financial aid package, without which I would’ve been unable to attend.” 

My plans after graduation

“I am currently an environmental education intern at Stratford Ecological Center and hope to develop a career in wildlife conservation and social justice activism.”

SOURCE: https://www.owu.edu/news-media/details/saving-sea-turtles/

By freedivinguae

Dorset plays part in annual Whale and Dolphin Watch with three sightings off Portland

A dedicated boat trip, 18 hours of observation and a new regional coordinator helped Dorset notch up three sightings during the most recent National Whale and Dolphin Watch.

The three recorded sightings of bottlenose dolphins all took place in Portlandharbour.

The nationwide event took place between July 29 and August 6 last year, and was the 16th year of the growing citizen-led scheme to record marine mammalian life in the UK’s coastal waters.

The previous year, however, no one from Dorset had volunteered to coordinate the county’s watch. This meant that no data was recorded and no sightings reported. For the 2017 watch, organisers the Sea Watch Foundation put out a plea for Dorset’s nature-lovers to offer their time, and were answered by a large number of volunteers, including Catherine De Bertrand.

Ms De Bertrand, 37, helped to coordinate 18 hours of watches along the Dorset coast over the course of the nine-day event, leading to the three sightings of dolphins in the harbour. She also led a dedicated boat trip.

“I got involved after they put out the appeal. It was about putting Dorset on the map,” said the former lecturer at Kingston Maurward College, who is also involved in the year-round dolphin-watching program at Durlston Country Park.

The Dorset whale- and dolphin-watchers were among 2,500 volunteers across the country, a number that has grown every year since the scheme’s inception. There were all told an astonishing 1,410 sightings, from land and from sea, of cetaceans, the collective term for whales, dolphins and porpoises.

“The wonderful thing about watching for whales and dolphins in the UK is that you don’t necessarily have to get on a boat to see them,” said Kathy James, a sightings officer for Sea Watch. “The Sea Watch Foundation holds hundreds of thousands of records which are used by scientists and governments to inform research and policy.

“By taking part, people are directly contributing to the conservation of these wonderful animals.”

 

The Sea Watch Foundation is seeking volunteers to come forward to take part in the National Whale and Dolphin Watch 2018, which takes place from July 28 to August 5. No experience is necessary, as the team at Sea Watch offers training and advice. The Dorset watch will again be overseen by Ms De Bertrand.

 

SOURCE: http://www.dorsetecho.co.uk/news/16046874.dorset-plays-part-in-annual-whale-and-dolphin-watch-with-three-sightings-off-portland/

By freedivinguae

Mystical Mermaids

A manatee swims with its calf. – Photo by Galen Rathbun (US Fish and Wildlife Service)

 

THERE are four species of sea-cow of the order Sirenia, of which three are types of manatee and the fourth is the dugong. The Sirens were the classical mythological mermaids that tempted sailors to their death when their ships were wrecked on rocks. Sadly, a second species of dugong, Stellar’s sea-cow, was hunted to extinction in the 18th century in Mediterranean waters. These mammals have always mystified me and I just wonder whether they may have in the past strayed into North Atlantic waters.

Hans Christian Anderson’s children’s story is immortalised in the bronze ‘Little Mermaid’ statue in Copenhagen, in his native Denmark. In the remote, windswept, clifftop Cornish village of Zennor, only a stone’s throw from my birthplace, the mermaid of Zennor’s legend still exists. It is said that a mermaid once lured a local village lad, besotted by her beauty, into the sea to disappear forever. There today, in the rugged, roughly-hewn granite built 11th century church, this legendary mermaid is carved on the end of one its oak, church-pews. Not dissimilar tales abound in Southeast Asian folklore.

Dugongs (Dugong dugon)

Found in Indo-Pacific inshore seas, stretching from the Red Sea, along the East coast of Africa and across the Indian Ocean and the Andaman Sea to South East Asia, north to the Philippines and south to the western, northern and eastern shores of Australia, the dugong’s distribution is very wide but sadly its numbers do not reflect this.

I have always wanted to swim with a dugong and observe it at close range but my attempts whilst snorkelling in Kenyan, Northern Madagascan and East Malaysian waters have proven futile. It is thought, but yet to be proved, that Southeast Asian dugongs are a distinct sub-species. I have recently seen manatees at Singapore’s River Safari. Dugongs are quite distinctive from manatees, for the latter have a distinct fish-like notch in their rounded tails.

Structure and development

Almost cylindrical in its shaped body, tapering at both ends, a dugong is up to three metres in length with a thick, smooth skin covered in short hairs. Its lobed lips are covered in sensory bristles, which pass foraging seagrass easily into its mouth. In photographs, a dugong grazing, with its small eyes and tusks, looks exactly like its close land mammal relative, the elephant, but without the latter’s trunk.

A dugong’s vision is limited and to compensate for this, its small ears possess acute hearing. It also has an extraordinary sense of small to locate edible plants. With two breathing holes, covered by skin flaps when submerged, it can easily breathe when breaking the sea-surface as the flaps open.

On average, its weight is about 420kg, with females slightly larger than males. Its paddle-like pair of flippers are used in twisting its body and slowing down while its tail, flashing up and down, provides forward propulsion.

Habitat and food source

Dugongs are the only true strictly herbivorous marine mammal, living off only seagrass meadows (see ‘Seagrass and seahorses’ in thesundaypost – Oct 1, 2017). Preferring warm, shallow coastal bay waters up to a depth of 10 metres and found in brackish waters of river outlets and shallow river channels, they are voracious feeders, each consuming up to 40kg of seagrass per day. They grub up the seagrass rhizomes but prefer softer varieties of seagrass to more fibrous ones.

Today, their largest populations are found in Australia, with over 20,000 seen in the Gulf of Carpentaria as well as 25,000 noted in the Torres Strait and New Guinea. Worldwide however, there are numerous reports of ever shrinking populations.

A manatee’s lungs lie along its back, assisting buoyancy when surfacing for air.

Breeding credentials

Males reach maturity when their testosterone levels allow their tusks to erupt. Part of the reason why these mammals are endangered is that although they may live for 50 years or more, female dugongs only give birth to one calf after a gestation period of 13 to 15 months. The calf’s birth is in shallow waters and, just like a cow licks its afterbirth mucus from a calf’s nose, so a dugong pushes her calf up to the surface to take in its first gulp of fresh air. A newborn calf is 1.2 metres long and weighs 30kg, staying with its mother for nursing from her two teats for up to 18 months, partially for protection.

Threats

Well-preserved cave paintings in the Tambun Cave, Perak, depict these mammals – those paintings are 5,000 plus year’s old. For centuries they were hunted by early man, with their bones used in necklace beads and their tusks gracing dagger and sword handles. Their meat was devoured and various organs taken for traditional medicines. The dugong’s oil was used to preserve the hulls of wooden boats.

The International Union for the Conservation of Nature (IUCN) Red List declares these mammals as vulnerable and conservation areas have been established in which hunting and mesh fishing have been banned.

However, enforcement of such bans is difficult to practise worldwide. The dugongs’ main threat comes from trawler fisheries sweeping their very subsistence, seagrass, away from the sea-beds.

Seawater pollution in the forms of untreated sewerage, agricultural herbicides and detergents together with the excavation of sand for building material have had a major impact on seagrass meadows. The reclamation of land in shallow waters for tourist developments has, too, had an impact on dugong-habitats. Inshore propeller boats, often associated with the tourist trade, have also churned up sand, burying and smothering the eel-grass plants, thus preventing vital sunlight from reaching them. The recovery of these seagrass meadows can take more than 10 years after only one day’s damage.

Manatees (Trichecidae)

Like their Asian counterparts, these marine mammals have been in existence for over 60 million years. Unlike dugongs, they spend some of their lives in fresh water, migrating up rivers. Found mostly in Caribbean and South American tropical waters they are also located along the West African coast. Their tails are rounded and their mouths are without tusks and possess molar and premolar teeth, which are replaced from the back of their gums as the frontal teeth decay with age. If only mankind had such genes.

Like the dugong, a manatee possesses a dense, massive bone structure, helping it to submerge. Its lungs lie along its back thus assisting its buoyancy when surfacing for air. Living in mostly saline, brackish and fresh water environments at a depth of two to three metres, they have smaller snouts than dugongs with many more bristles around their mouths, almost seal-like.

Breeding

Slightly more prolific breeders than dugongs, they reach sexual maturity earlier and with a one-year gestation period again produce one calf.

A newly-born calf is suckled for up to 18 months, always swimming above its mother, and thus is more prone to wounds imposed by overhead boat propellers’ blades. Such propeller cuts have been responsible for 25 per cent of manatee deaths, especially in the booming water-sport industry in Florida, USA. Despite these losses, in the last 26 years, and based on aerial surveillance, there has been a six-fold increase in the population of manatees around peninsular Florida’s coastline.

With relatively limited zoological knowledge, I just wonder whether dugongs can be crossbred with manatees to help build further populations to enchant children and adults for years to come in mermaid legends. Perhaps, and with a bit of luck, I may yet see a dugong.

A dugong swims at the Sydney Aquarium. – Photo by Christian Haugen

 

SOURCE: http://www.theborneopost.com/2018/02/25/mystical-mermaids/

By freedivinguae

A rare glimpse into the world of the Red Sea’s dolphins and whales

 

 

The Red Sea is one of the world’s least studied regions when it comes to whales and dolphins – until now. A report was released recently that brings together historic records and the latest information on a range of the sea’s mammal species. This will supply some of the information needed for science based conservation measures. I interviewed Giuseppe Notarbartolo di Sciara, one of the reports’ authors who is also among the region’s most respected marine mammal specialists, on the findings and their implications.

What is special about the Red Sea and the habitat it provides to whales and dolphins?

While huge progress has been made globally in our ecological knowledge of marine mammals, this hasn’t been the case for the Red Sea. With the exception of dugongs, very little is known about the Red Sea’s mammals. This is one of the main reasons we put this report together, conducting and collating research from 1983 to 2017.

Among the things we learned was that the fertility of the Red Sea’s environment affects marine mammal presence in the region.

Life in any ocean starts from the water’s productivity. This is the ability of phytoplankton (microalgae) to bloom because of the nutrients contained in the water, like phosphates and nitrates. This is triggered by upwelling currents that bring nutrient-rich deeper waters to the surface. This fertilises the phytoplankton, which need sunlight. The phytoplankton bloom gets eaten by zooplankton, which are then eaten by little fish, and so on up the food web.

Such upwellings are rare in the Red Sea. This makes it a hard place to live for the great whales, which need big swarms of krill, small crustaceans, to survive.

This could be why only a few whale species have been able to colonise the Red Sea.

We also found out more about how dolphins – which are known collectively with whales as cetaceans – survive in the Red Sea.

The environment is better for smaller dolphin species like spinner dolphins and pan-tropical spotted dolphins. Spinner dolphins take advantage of a community of smaller critters living in what scientists call the deep scattering layer. It’s mostly made up of small crustaceans, fishes and squid. They live in a narrow layer that rises towards the surface at night to feed, and returns to the depths during the day to shelter. It provides the critical source of food for the dolphins to tap into in an otherwise poor marine environment.

What threats do cetaceans face in the Red Sea?

What worries me most is that the Red Sea is crossed by a huge amount of ship traffic carrying oil. It is a key strategic channel: an estimated 4% of global oil supply passes through it. The proportion sounds small, but it represents a vast amount of oil. A major accident would be disastrous for marine life in the narrow Red Sea.

An immediate and obvious threat today is disturbance by tourists. For example, spinner dolphins enter a reef in an area known as Samadai, on the southern coast of Egypt, to rest. They do this because they’ve been hunting at night and the reef gives them protection from sharks during the day.

The tourism industry discovered this and started to advertise swimming with dolphins in the area. It very quickly became a mess, creating an outcry on social media calling for people to stop bothering the animals. Fortunately, the Egyptian government took action and I helped to explore the situation and draft a plan. There is now a large area of the reef that is completely off limits to tourism, and the dolphins have enough space to rest.

Unfortunately these situations aren’t always so well managed. Another area called Sataya, also in Egypt, has no management plan and the spinner dolphins are very stressed. It’s likely the entire reef area will be taken over by people and the animals will be pushed out.

In terms of fishing, I’m aware of situations in which particularly Yemeni fishermen travel widely across the Red Sea to hunt sharks for the Far East fin trade. I know that they have been using dolphin meat as bait for catching sharks. But we really don’t know how big this practice is or its impact on dolphin populations.

What immediate and longer-term steps should be taken to mitigate the threats

It would be great to have a model in the Red Sea similar to the one applied in the Mediterranean and Black Seas. Since 2002 there’s been an agreementbetween most countries bordering those seas. It commits the coastal countries to protecting those seas’ cetaceans. Something like that would be extremely helpful in the Red Sea, and raise their visibility at the policy level.

It’s also important to protect marine mammal habitats in the Red Sea. This could come partly from the identification of important marine mammal areas, work that’s being done by a task force established within the International Union for Conservation of Nature. The identification of the areas is based on specific criteria, and is modelled on earlier work on birds. The areas are critical for some aspect of a species life, for example feeding, breeding or migrating. Identifying them gives decision makers an easy tool to help select which areas need protection.

The task force is in the process of identifying these mammal areas in large portions of the southern hemisphere, and there are plans to do this in the Red Sea in 2019.

 

SOURCE: https://mg.co.za/article/2018-01-30-a-rare-glimpse-into-the-world-of-the-red-seas-dolphins-and-whales

By freedivinguae

Vaquita Update: Idaho Filmmaker Weighs In On The Sea Mammal’s Plight

The last time we checked in with Boise filmmaker Matthew Podolsky in July, he said time was running out for the vaquita.

For three years, he’s been documenting the plight of the small, dolphin-like sea mammal that is only found in the Gulf of California and is threatened by illegal gill-net fishing.

Podolsky says since then, an unprecedented “Dream Team” of over 60 scientists, researchers and veterinarians from all over the world came together to try and catch some of the vaquita and breed them. It was a desperate attempt to save the handful of animals left alive. Podolsky says it was the animal’s last chance for survival.

“There are almost certainly fewer than 15 individuals out there in the upper Gulf of California but this capture effort was the last-ditch effort to save the species from extinction,” says Podolsky.

Podolsky has come back to Idaho after filming the six-week capture attempt. Two vaquitas were caught. One was let go because it got too stressed. He described to Samantha Wright the harrowing events that happened after biologists managed to catch a second animal.

Podolsky and his company Wild Lens is now collaborating with three other production companies to produce a feature length documentary on the vaquita. He’s planning two more trips to Mexico. The film should be released by the Spring of 2019 and Podolsky says, by then, it’s almost certain the vaquita will be extinct.

SOURCE: http://boisestatepublicradio.org/post/vaquita-update-idaho-filmmaker-weighs-sea-mammals-plight#stream/0
By freedivinguae

Hurricanes: Bad for People, Good for Dolphins

 

Biologist Lance Miller noticed something odd while conducting dolphin surveys in the Gulf of Mexico in 2007: baby dolphins. Lots of them, and lots more than he expected given the results of surveys in 2005 and 2006. The reason? Hurricane Katrina.

Hurricanes like Harvey, the one that devastated Houston and other parts of Texas last week, and like Irma, the one currently threatening Florida, are typically associated with loss of life, loss of property, and other economic losses, the effects of which can be felt for years. That’s not only true for humans. It’s true for wildlife too.

Starting in December 2004—before Katrina struck—and continuing through November 2007, a group of scientists from the University of Southern Mississippi led by Miller (now at the Chicago Zoological Society), motored around the Gulf of Mexico looking for Atlantic bottlenose dolphins (Tursiops truncatus), initially as part of an study about their social organization.

But around two years after the storm passed, they noticed a massive increase in the number of dolphin calves in their study area. Hurricanes and other major storms are usually associated with increased strandings of marine mammals. So why would Katrina have been associated with more dolphins, not fewer?

Miller came up with two possible explanations. One, more baby dolphins were being born. Two, the same number of dolphins were being born each year, but more of them had survived past infancy.

Both were probably true. Here’s why.

In normal circumstances, female dolphins nurse their offspring for three or four years, which means that dolphin siblings are usually born at least five years apart. But Miller explained, writing in the journal Marine Mammal Science in 2010, that after a female bottlenose dolphin loses a calf, she is ready to give birth again the following season.

If Katrina had wiped out many of the baby dolphins born earlier that year, then each of those mothers would have been able to become reproductively active again the following year. That would have explained at least part of the spike in dolphin births.

Indeed, stranding data did show a slight increase in juvenile dolphin mortality after Katrina. And when the researchers surveyed the population in the fall of 2005, after the storm had passed, they found proportionally more adults than juveniles, suggesting that the adults had been more likely to survive.

But these trends alone wouldn’t have been enough to entirely explain the baby boom that Miller’s team observed. To explain the rest he had to look towards human activities.

Massive hurricanes don’t just destroy homes and businesses; they also damage fishing vessels. According to one estimate, Katrina wiped out 87 percent of all the commercial fishing, crabbing, and shrimping vessels in Mississippi. In 2005 and 2006, fishing vessels in that state hauled in nearly one million fewer pounds of seafood.

That means that there were fewer boats in the water and also that there was more food for the dolphins. Commercial fisheries target three quarters of the species that make up the Mississippi dolphins’ diets, and two thirds are fished for sport. More food makes pregnant females more likely to deliver healthy babies, and it also makes them better able to nourish their offspring through their milk.

It’s too early to say how Harvey and Irma will impact marine wildlife communities. But Katrina teaches us that by being forced to reduce our fishing activities, we inadvertently created an environment that allowed young dolphins to flourish. The fisheries disruption following that storm was so significant that it was as if a marine reserve had been created in its path.

 

 

source: https://blogs.scientificamerican.com/observations/hurricanes-bad-for-people-good-for-dolphins/

By freedivinguae

Submit Your Galapagos Whale Shark Photos

Whale Sharks in the Galapagos

For the biggest fish in the sea, whale sharks (Rhincodon typus) are rather elusive. Aside from a few known feeding aggregation sites, which are mostly frequented by juvenile males, baby whale sharks, adults, and females whale sharks are rarely seen.

Whale shark feeding sites have been identified in Isla Mujeres Mexico, Mafia Island in Tanzania, also Madagascar, Tofo Mozambique, the Philippines, Seychelles, and Thailand. But still, only juvenile males have been counted in these sites.

There are some exceptions to this general rule, however, where we find huge pregnant momma whales sharks. These are generally offshore seamounts or volcanic islands. Adult females are typically found in oceanic waters around or outside the 200 m isobath, where the ocean is 200m deep, while juveniles tend to stick to shallower nearshore coastal water.

Few animals are as enigmatic as the whale shark. Globally threatened, almost all of the scientific information available on the species pertains to the juvenile males typically found in coastal waters. To see the real giants, such as this pregnant female, intrepid divers must venture to remote seamounts like Darwin Island in the northern Galapagos. Panasonic GX1 camera, Panasonic 8 mm fisheye lens, Nauticam underwater housing. f/3.5, 1/160 sec, ISO 400.

Whale Shark Conservation

Dr. Simon J. Pierce has the job we all dream of. He is the world’s top whale shark conservation biologist and travels the world studying these gentle giants. Identifying whale sharks populations outside of their familiar aggregation sites is important for the conservation of this globally endangered species.

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One of the best places in the world to see gigantic pregnant female whale sharks is 300km from the nearest town, around Darwin Island, Galapagos. Whale sharks normally spend less than a day at Darwin Island not to feed but most likely to calibrate their built-in GPS.

Historical volcanic eruptions at Darwin have created concentric rings of magnetically polarised rock on the seafloor, providing a detailed relief map for animals.Whale sharks are acutely attuned to the Earth’s magnetic field and they use these oceanic seamounts as a way to calibrate their internal compass.

But here is the problem. Darwin Island is remote, and it’s hard for Simon and his team to visit Darwin for more than a couple of weeks per year. Simon has dedicated his life to photographing, studying, and tracking whale sharks, but that doesn’t mean the average diver help too. Cue Wildbook an online photo-identification library for whale shark.

Whale sharks all have a unique pattern of spots, meaning that each individual is photo-identifiable. The Wildbook uses photographs of the skin patterning behind the gills of each shark, and any scars, to distinguish between individual animals.

Learn more whale shark photo identification.

In 2017 Simon and his team documented 7 new sharks over 36 dives, raising the total number of whale sharks identified from the Galapagos to 180.

However, none of these sharks have ever been re-sighted outside the Galapagos.

Where are the sharks going?

They generally swim right out into the Pacific Ocean, far from any landmass. There’s a long productive zone where cooler waters from the Peruvian coast meet warm tropical waters above the equator and, based on tracking data, the whale sharks are feeding out there. They’re also, most likely, giving birth in that area too.

A pregnant female whale shark. Darwin Island

In a recent newsletter from Simon he put out the call for scuba divers to submit their whale shark photos from the Galapagos to the global Wildbook database at www.whaleshark.org. Photos from visiting divers (from years past, too) are a huge boost to their research efforts.

Where sharks breed, and how often they are breeding is still an unknown. The more photos they receive the faster they can solve the whale shark mystery.


We’re just the messenger! Make sure to sign up for Simon’s newsletterand visit his website for inspiring shark stories and incredible whale shark imagery from around the world. If you want to see sharks with the experts check out Simon’s public trip scheduled for 2018/19. There’s also a Galapagos liveaboard trip for 2019.