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about 8 years ago
Manta Ray hot lunch Marianas Variety (Press Release) — The Manta Ray Band will be having a hot lunch this Saturday, Feb. 6, 2016, to raise funds for their trip to the Tumon Bay Music Festival on Guam next month. The lunches are $5 each and include fried chicken, lumpia (fried spring roll ...
about 8 years ago
gulfnews.com Whale shark sightings along UAE coast not alarming: experts gulfnews.com Dr. Elsayed Ahmad Mohammed, Regional Director, Middle East and North Africa, of International Fund for Animal Welfare (IFAW), told Gulf News that the recent appearances of the fish make sense given the whale shark feeds close to the surface and often ... and more »
about 8 years ago
KHON2 Whale shark surprises tour group off Haleiwa KHON2 A group led by North Shore Shark Adventures was visited by a whale shark Friday morning, the intimate experience captured on video. They were about three miles off Haleiwa when the shark slowly emerged. “It swam right up to the boat, really slow ... and more »
about 8 years ago
Thanh Nien Daily Carcass of beached whale shark to be preserved by Vietnamese scientists Thanh Nien Daily The Nha Trang Oceanography Institute in central Vietnam has decided to preserve the carcass of a whale shark that died after it got caught in a fishing net last week. Fishermen and local authorities on Thursday handed over the dead fish to the institute. Giant whale shark to be embalmed for scientific researchVietNamNet Bridge all 2 news articles ...
about 8 years ago
National Geographic Manta Rays Get Crittercams for First Time Ever National Geographic We didn't think suction cups would work because manta ray skin is really rough like sand paper. We knew suction cups worked well on the smooth skin of whales. The cups were originally designed to move pieces of glass. But we gave it a try, and with a ... Scripps Grad Student Receives Prestigious Environmental FellowshipScripps Oceanography News all 4 news articles » ...
about 8 years ago
Video From a Whale Shark's Point of View National Geographic Their goal was to deploy Crittercams on whale sharks to get a glimpse of the sharks' underwater world and to better understand their behavior along the reef. Like most people, Wilhelm had never seen a whale shark. He worked on the Crittercams for about ... and more »
about 8 years ago
Zap2It Dominic Monaghan on meeting the Whale Shark: 'I had this sort of out of body experience' Zap2It “Wild Things With Dominic Monaghan” returned to Travel Channel with its third season on Wednesday (Jan. 27). The premiere, aptly titled, “Majestic Mozambique,” finds our host on the hunt for the elusive — and quite massive — Whale Shark. Early on in ... Monaghan knows where the 'Wild Things' areVirgin Islands Daily News all 9 news articles ...
about 8 years ago
CBC.ca Brian Keating swims alongside La Paz's mysterious whale sharks CBC.ca They're such huge animals," said Keating, who saw his first whale shark less than 15 minutes out of the bay. By the day's end, Keating had met at least a dozen whale sharks. He even managed to snap a few underwater photos from their tail end as proof.
about 8 years ago
FIS Fishing ban for giant manta ray FIS The Ministry of Production (Produce) has banned the capture of the giant manta ray (Manta birostris) in the Peruvian marine waters, in order to preserve this species on the coast of the country. The measure, established by a ministerial decree, is in ... and more »
about 8 years ago
The National Whale shark seen swimming in Abu Dhabi marina The National ABU DHABI // A whale shark between three and four metres long has been seen swimming in the marina at the InterContinental Abu Dhabi. Employees at the hotel first noticed the fish at 1.45pm on Friday and quickly took a video and photos to capture the ...
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Friday
Jul022010

Implications of the first sighting of whale sharks in the gulf oil slick

I recently experienced a moment of genuine dread regarding the oil spill in the Gulf of Mexico, and it was neither a familiar nor comfortable feeling. What is it that invoked such a powerful feeling after a disaster that has been underway for the last 80-odd days, now? Something that struck a little close to home, of course: the first direct impact to whale sharks. You may have seen this story coming across the wires over the past two days about NOAA scientists who, while on an aerial survey of the impacted area, observed 3 whale sharks swimming among ribbons of surface oil, not 4 miles from the epicenter of the Deepwater Horizon spill. This observation has serious implications; let me explain.

Whale sharks are widely-ranging tropical migratory sharks that are unusual among their more toothy relatives in that they eat plankton. Two of the adaptations they use to pursue this lifestyle – surface filter feeding and an exquisite sense of smell – make them especially susceptible to the impacts of the oil spill. I had all but convinced myself (perhaps wishfully thinking) that whale sharks would be able to sense the altered chemistry of the affected water bodies and avoid the area. It now seems that this is not the case; the observation by the NOAA scientists suggest that either whale sharks cannot tell the difference between polluted and unpolluted water, or they can tell the difference but do not alter their behaviour in such a way as to avoid the ribbons and plumes. As USM researcher Eric Hoffmayer states in the article, this is the realization of the worst fears of whale shark scientists, and I count myself among those.

How can it be that whale sharks are unable to tell the difference if their sense of smell is so good? One simple explanation is that the olfactory abilities may be extremely selective. Scientists don’t know exactly what sort of chemicals whale sharks are homing in on when they seek out patches of food in the ocean – indeed, addressing this question is one of the goals of this year’s whale shark research program at Georgia Aquarium – but we have some good candidate molecules. If the whale shark sense of smell is highly tuned to these compounds and relatively insensitive to other families of chemicals, like hydrocarbons (oil and gas), then it’s certainly possible that whale sharks simply cannot detect the problem.

That’s when the second adaptation, surface filter feeding, becomes a liability for whale sharks trying to negotiate the deadly emulsions and surface slicks in the Gulf. To fully appreciate why this is such a problem, we need to look a little more closely at the filtration apparatus whale sharks use to feed.

Like most plankton-feeding fishes, whale sharks use filters in the mouth/gill cavity to sift food particles from the water (see the exellent illustration by Emily Damstra at right). And like most plankton-feeding fishes, these filters develop from structures associated with the gills and gill rakers (cartilaginous rods that come off the leading edge of the gills and protect the gills from fouling and shape the current of water across the breathing surface). Where whale sharks differ radically from other planktivores like, say, anchovies, is that they do not have feathery interlocking gill rakers that serve to filter the plankton but can be disengaged from each other to allow bulk water flow out through the gill opening. Rather, their filters are so derived and so heavily branched that they form a single continuous pad that occupies the space between gill arches; it looks a lot like a black scouring pad. The gill arches cannot be disengaged from each other; thus, anything that goes in the mouth must be small enough to pass through the filters (less than 2mm, or about 1/12th of an inch), or it must be swallowed, or be spat back out through the mouth (something they are surprisingly good at!). In a paper currently in the review process, comparative anatomist Phil Motta from USF is describing the full functional anatomy of these structures; he took the photo of the filter pad surface shown hereabouts based on material samples from Georgia Aquarium.

The implication here is that oil that finds its way into the mouth, if it is not to be swallowed or to foul the filters, must be continually spat back. OK, I hear you say, perhaps if the whale sharks avoid feeding, there won’t be a problem. If only it were that easy. Whale sharks do not only use their mouths for feeding, they use them for breathing. They need to be passing water continually across the filters and thence across the gills, in order to keep the body supplied with oxygen. For the whale shark swimming in oil-affected waters, therefore, the animal’s breathing needs and the susceptibility of their feeding filters to fouling are in complete opposition.

If whale sharks are swimming into oil-polluted waters and fouling their filters with oil, what does that mean? In my best estimation, it means that the oil spill represents an extremely serious threat to whale shark health. I am by no means the first person to suggest this. Nature identified whale sharks as one of the 5 species most likely to be affected by the oil spill, and other scientists like Bob Hueter from Mote Marine Laboratory have also highlighted the risks. The true toll that the spill exacts on the Gulf of Mexico whale shark population will not be known for some time, but the thought of dead or dying whale sharks sinking silently into the depths (dead sharks generally sink, not float) is yet more motivation to put an end to the spill and to undertake immediate and extensive research and conservation programs to assess the damage and plan a road to recovery for the whale sharks – and all the other affected wildlife – in the Gulf of Mexico.

Reader Comments (1)

This is sad, sad news. Whale sharks and all of these animals in the ocean are magnificent. Not enough people realize or care. For days after this disaster I wondered if the animals would leave the area. It is apparent now that they aren't. Almost seems some are being attracted to it. Is there any possible way to distract them from the area, safely?

July 3, 2010 | Unregistered CommenterAnonymous

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