Cayman Island Tiger Sharks: tagging data shows possible Caribbean migratory patterns

The Cayman News Service reported that three tiger sharks that were tagged almost a year ago in waters off the Cayman Islands have returned having roamed the wide waters of the Caribbean. The original tagging project was a joint effort between the Department of Environment (DoE), Marine Conservation International (MCI), the Guy Harvey Research Institute (GHRI) at Nova Southeastern University and the Save Our Seas Foundation.

The three sharks were tagged with satellite tags which can provide a variety of data in addition to basic positioning information. One of the three sharks spent a great deal of time cruising the coast of Jamaica; another has been in deep waters off the Cayman Islands; while the third shark spent the summer in the southwest, off Honduras and Nicaragua.

While not necessarily covering the same long "point A to point B" distances that have been reported with sharks like great white sharks and whale sharks, the data does show that the sharks can cover a considerable amount of territory and that these movements might constitute "migrations" if there is a schedule or pattern to their journeys.

Being able to verify that sharks frequent the Cayman Islands via migratory patterns might help give weight to the need to protect them - proving that they are not infrequent or fluke visitors not deserving of specific attention.

The Cayman News Service reported, "Despite their precarious situation, there is no law to protect sharks in Cayman waters but hopes for the species have been raised in the region following the ban on shark fishing by Belize, Mexico, St Maarten, Honduras and the Bahamas. Timothy Austin, Deputy Director of the DoE, welcomed the ban by neighbouring countries. 'This will give a boost to the health of the marine environment for the Caribbean,' he said."

Read about the sharks in the Cayman News Service.

Monarch Migration: butterfly faces challenges along the way north and south

It was over three years ago that I started the RTSea Blog with an inaugural entry about the Monarch butterfly and its annual migration from the United States to Mexico. Not much of an ocean conservation subject but I linked it to the plight of white sharks and their migratory routes.

That was in May of 2008 and now the Monarch butterfly once again appears here, this time regarding how the Monarch butterfly is able to last through its entire journey and how researchers are tracking these butterflies in a manner, once again, similar to sharks: tagging.

The Monarch is an endangered insect due to the ongoing loss of deep forest habitat in Mexico. The trees are being cut down, usually illegally, and this limits the Monarch as it migrates south to the tropical forests in southern Mexico and the Yucatan peninsula.

Amazing as this annual migration seems, it is even more unusual because of the fact that many of the Monarchs do not live to make the entire journey, but their offspring know to continue southward, or northward depending on the time of year. Scientists are not sure as to why the Monarch has this ability to know where to go when born and they have yet to conclusively agree on how these insects are able to migrate from point A to point B and back again. Antennae which are sensitive to the magnetic fields around the planet is one of the more common theories - a concept that is used to explain migratory behavior in birds and even sharks.

As reported in the Kansan.com, a large population of Monarchs passes through Kansas, feeding on some of their primary food sources: nectar from milkweed and the Biden flower. In Kansas, there is an organization named Monarch Watch that monitors the butterflies' migration and conducts "tagging" of the Monarchs so that they can better determine the actual migratory route. Butterflies from across the central to eastern United States head south to a much smaller area in Mexico before heading northward in the early Spring.

Monarch Watch holds a one-day tagging event and this year's event drew 500 people of all ages to come see these butterflies and participate in learning more about the migration. According to Orely Taylor, ecology professor and founder of Monarch Watch, “Everybody needs to get out and experience the wild. We need to get out and enjoy nature, and this is one of the opportunities to not only enjoy and participate in this incredible phenomenon, but also to contribute to science by learning about these butterflies through their tagging.”

Just as there is concern over the Mexican government's ability to effectively police the forests and prevent poaching of the trees that the Monarch butterfly seeks at the end of its migration, so it is in Kansas that conservation groups wish to ensure that there is sufficient food for the butterflies as they pass through. Much of the butterflies' food source in Kansas grows in wetlands and wetlands across the nation are continually threatened by urban development. Monarch Watch makes available Monarch Waystation Seed Kits that allow concerned citizens to grow the various types of plants that the butterflies depend on for growth to sustain them through their journey.

If people can become interested in tagging and feeding an endangered butterfly - something that they can see, that flies right into their own backyard literally and figuratively, geographically speaking, then perhaps they can come to appreciate other animals around the world that migrate as part of an evolutionary pattern of self-preservation. Perhaps, as I mentioned in my very first blog post, the Monarch butterfly and great white sharks still have a lot in common.

India's Whale Sharks: a migrating population may be unique to India

For many years, marine scientists have studied the migration patterns of marine animals, trying to better understand the animal's behavior by unlocking the secrets as to why these long-range movement patterns exist. Spawning grounds, food opportunities, seasonal temperature changes - all have entered into the mix, depending on the species or the location.

In the South Pacific and Indian Ocean Ocean, there was a long held belief that a population of whale sharks migrated from Australia to waters off India's Gujarat coast. In the winter months, whale sharks would disappear from Australian waters and reappear in Gujarat, about 300 to 500 strong. The theory was that the sharks were migrating to warmer waters.

But a new study by Wildlife Trust of India (WTI), wherein genetic samples from Australian and Indian whale sharks, along with identifying photographs, were taken and compared, it appears that the two regions may, in fact harbor two distinct populations. According to Arun Kaul, WTI senior director, there were no corresponding DNA indicators between any of the samples taken.

“The samples collected so far have not found a match anywhere in the world, which means they are unique,” Kaul said.

Whale sharks, like many other sharks, can also be photographically identified because their white-spotted markings - along with any other distinctive scars or deformities - act like a fingerprint. The WTI study did not find photographs that showed a whale shark in both Australian and Indian locales.

WTI pointed out that this was a preliminary study and that more work needed to be done to further identify migration routes for these sharks (after all, the Australian whale sharks were going somewhere during the winter months; just, apparently not to India) and to determine whether any cross-breeding is taking place.

I recall when I first became interested in the white sharks at Isla Guadalupe and learned of the "White Shark Cafe" where it appeared that both sharks populations from Isla Guadalupe and the Farallon Islands were both migrating to. It was a tantalizing thought that these two distinct populations were meeting in the mid-Pacific to cross-breed and maintain a healthy gene pool. However, to date, all DNA samples taken have not yet shown any connection between the two groups. It's also not completely clear as to whether all of the sharks migrate or whether there are some who, for whatever reason, stay back. Some divers, who dive Guadalupe in the summer months before the usual return fall migration of the white sharks, have reported seeing a shark or two at the edge of visibility, hanging out in deep water.

Could this be happening in Gujarat? The seabeds in Gujarat are rich in plankton - a primary whale shark food source - and sea grass which feeds many small fish that end up as whale shark prey. But the whale sharks don't stay all year round, so if not Australia, then where are they going?

A coalition of research groups including WTI, Wildlife Institute of India, Space Applications Centre, National Institute of Oceanography, Australian Institute of Marine Science, University of Illinois and others is being formed to carry on a more intensive study. The prospect of a unique population of whale sharks at Gujaret is not only of scientific interest, it is also a source of national pride. In 2000, as many as 500 whale sharks were landed off Gujaret, but in 2001 whale shark hunting was banned and hunters became protectors, viewing the whale sharks as a valuable natural resource. Fishermen free whale sharks caught in their nets and discussion are underway regarding the economics of ecotourism, as several agencies step up an awareness campaign.

“Perhaps we have discovered a population that could be endemic to Indian territorial waters,” said Satish Trivedi, senior official, community development, Tata Chemicals, Ltd (who funds a "Save the Whale Shark" campaign in India), commenting that such a discovery is significant for India.

Read about Gujarat whale sharks in LiveMint.com.

Wintering White Sharks: possible migrations along U.S. east coast

A possible migration corridor has been identified for great white sharks on the east coast of the U.S. A satellite tagging study was initiated in the fall by the Massachusetts Division of Marine Fisheries and some of the early results are intriguing. It is possible that the great white sharks that appear off the New England coast during the summer months - suspected of feeding on seal populations there - travel south during the winter months based on the results of a tagged shark who has appeared as far south as Jacksonville, Florida.

Satellite tagging has been used on great whites and other shark species to record location, speed, depth, and ambient temperature. Typically, a well-placed tag will record data for 30 to as long as 90 days then release itself, float to the surface, and download its data to satellites overhead. Researchers must wait patiently then sift through a mountain of data when it is downloaded all at once. Satellite tags can provide more long-range data than regional telemetry tags (like those documented in my film, Island of the Great White Shark) but are also subject to being dislodged prematurely. A newer technique, SPOT tagging, bolts the tag to the shark to insure a significantly longer monitoring period, but requires that the shark be caught and brought on board; a technique that has raised considerable controversy because of the physical impact imposed on the shark during the procedure.

In the summer months, several species of shark inhabit the New England coastline, from basking sharks to thresher and blue sharks to the great white white (although not in significant numbers). This new tagging study is the first indication that, like their distant cousins throughout the world who exhibit distinct migratory patterns, white sharks could very well be moving up and down the east coast based on seasonal temperature changes and any changes in prey populations that those seasons impose.

Great whites have already been shown to migrate from the west coast Farallon Islands to the mid-Pacific; same for the white sharks at Isla Guadalupe. White sharks have been monitored moving from South Africa all the way to Australia and back. While there can always be the occasional exception, there is continuing evidence that these sharks and other pelagic species develop critical migratory patterns. Our concern would be, what would happen to these sharks if their migrations were intercepted by commercial fishing fleets? Or what would happen to the overall health of their populations with changes in ocean temperature due to global warming? How ingrained are these patterns and what would happen if external factors were altered - could the sharks successfully adjust?

Humboldt Squid: the "red demon" moves into Southern California

Like something from Disney's Twenty Thousand Leagues Under the Sea, the humboldt squid is a formidable predator typically found in deep Pacific waters off of Mexico and Central America. Reaching up to five feet in length and as much as 100 pounds, it is fast and aggressive with a voracious appetite.

And it is beginning to appear in shallower water off of Southern California. In San Diego, during night dives, scuba divers are encountering groups of humboldt squid, and several have moved too close into the shallows and been washed up on the beach.

According to a recent AP news report,

"Research suggests the squid may have established a year-round population off California at depths of 300 to 650 feet, said Nigella Hillgarth, executive director of the Birch Aquarium at Scripps Institution of Oceanography. Divers this summer have been encountering them at about 60 to 80 feet down, they said. No one knows how many squid are in the shallow waters, but one biologist estimated they could number in the hundreds, or possibly thousands.

'Usually where there's one squid, there's a lot of squid, so I would assume that there's a good number,' said John Hyde, a biologist with the National Marine Fisheries Service in San Diego."

Scientists are not sure why the squid have moved further north or are entering shallower waters. Explanations range from global warming to loss of prey to a reduction of natural predators. On this last point, I have read studies that have explained the bio-dispersion of various species based on the predators that feed upon them. When the predators are gone, then the species in question is no longer "corralled" as it normally would and changes in bio-dispersion or migrations can occur. In the case of humboldt squid, sharks are one of its key predators.

Whatever the explanation for the squid's movement north, there is reason for some concern. They can pose a serious risk to unsuspecting divers and their voracious appetites can severely impact local fisheries. Scott Cassell, CEO of the Undersea Voyager Project, who has spent many years studying and filming humboldt squid, recently told me that in his studies he had predicted the potential for this danger as much as ten years ago.

Another possible example of the ramifications either climate change, overfishing, or loss of apex predators - or all of the above.

Care for a calamari ring the size of your dinner plate?