Whale Shark Migration Secrets

The amazing and mysterious whale sharks are the world’s largest fish and referred to as the “gentle giants” of the ocean. Neither the scientists who study this immense fish or other researchers have ever witnessed one of these creatures giving birth. A recent nine-year study has revealed information providing researchers with a greater understanding of the whale shark’s migration patterns. The study also provides new insights into the travel areas of the fish and a probable location where they huge 10-ton fish choose to give birth.

In the summer months, more than 800 whale sharks gather to feed on plankton off the coast of Quintana Roo on Mexico’s Yucatan Peninsula. This trip requires many of the whale sharks to migrate long distances every year to reach the feeding grounds. A whale-tagging program was initiated by Robert Hueter, director of the Center for Shark Research at the Mote Marine Laboratory in Sarasota, Florida. At the completion of the nine-year study, and after tagging hundreds of the whale sharks, the research team determined a great many of the large fish return to the plankton-rich feeding ground annually. They also discovered the whale sharks, after satisfying their plankton cravings, swam away from the area in random directions. When Director Hueter spoke to National Geographic Magazine he explained, “From this one feeding area, these animals spread out over vast parts of the region — throughout the Gulf of Mexico, down into the Caribbean Sea, through the Straits of Florida up into the open Atlantic Ocean,”

Odd Characteristics Discovered

One of the odd characteristics the researchers discovered in their study group of fish was the unusually large number (70%) of males. Also interesting is the fact that other global aggregations of the whale shark show the same gender imbalance. According to Hueter, it is difficult to maintain a stable whale shark population with such a large percentage of male fish, and they believe the females are out there somewhere, but their location remains a mystery.

The team observed a specific female whale shark (nicknamed Rio Lady) as she gorged herself on plankton before swimming out to the middle of the Atlantic Ocean. The female spent a considerable amount of time in the area between Brazil and Africa, leading Hueter to tell Christopher Joyce of National Public Radio, “We think that Rio Lady has led us to the place where this particular species gives birth.” Hueter believes the research indicates mature pregnant females travel long distances to the middle of the ocean to give birth near seamounts or remote islands. Whale shark researchers refer to the discovery of the birthing location of whale sharks as “the holy grail of whale shark biology.” Because the nursery areas for the fish are so close to the coast, the scientists feel the middle of the ocean seems an unusual place for the creatures to give birth.

Researchers find it fascinating that a creature as large as a school bus can disappear for six months at a time and no one is able to locate it, and only a small number of very young whale sharks have been observed in nature. The reason why scientists want to locate the birthing areas is greater than the need to satisfy their curiosity. They believe such a find would offer science a “greater understanding of basic whale biology.” Because the majority of the whale’s lives are lived out if the sight of humans, much of what the researchers want to know remains hidden. Director Hueter stated, “And from the perspective of ecosystem management, we’d want to make sure that area was protected over time so they could continue to pup in an unmolested state.” The study is being used to determine the areas of travel, feeding, and reproduction in order to devise a method to protect the species.

Whale Sharks Migrate Towards Healthy Aquatic Ecosystems

Researchers contend the largest fish in the ocean is a representative of a healthy marine ecosystem and can be the example of how the oceans should be protected in the band stretching around the Equator. Because the whales are spotted in a certain location one year and another year they are spotted in a different area hundreds of miles away, the research group believes it will take international cooperation to conserve and protect the whale shark.

The Mating Mystery

The mating process is still a large mystery, but whale shark genetics indicate the fish swap genes in “far-flung geographic locales” and the researchers content there are only two metapopulations. The firsts exists in the Atlantic and the second in the Indio-Pacific. Each whale shark population must be managed on a broad scale. The species is considered to be “vulnerable” on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. In some Asian seas the whale shark is still being hunted for fins and oil. The government of Mexico has designated a Whale Shark Biosphere Reserve in the feeding aggregation grounds. Director Hueter is pleased with the process now in place for the protection of this species, but believes there is a lot more work to be done.

A Gentle Giant

“This is the largest fish that has ever lived, and it’s charismatic,” Hueter said. “It poses no danger to people who love to see it and swim with it in the wild. It might be the largest animal on the planet that you can be close to in its natural environment and not be in any danger whatsoever.”

Other research groups say the currently used state-of-the-art technology has limitations. Michael Berumen, of the King Abdullah University of Science and Technology in Saudi Arabia said, “The satellite tags used in our study can track movements globally for nearly a year, but they are expensive and still have fairly coarse resolution in terms of spatial accuracy, so identifying potential breeding or birthing grounds is very difficult.”

Encountering and observing a whale shark in the ocean is an amazing experience, and is contributing to the rapidly growing ecotourism industry. According to the Nature Conservancy, ecotourism is “Environmentally responsible travel to natural areas, in order to enjoy and appreciate nature.” Ecotourism is supporting the efforts of science to one day unlock all the mysteries of the secretive whale shark.