Ireland's Basking Sharks: a high percentage of a rare species

As a follow up to my post on wobbegong shark behavior: researchers in Ireland are studying their resident populations of basking sharks and, as with the wobbegong studies, are able to draw conclusions on changing environmental conditions based on changes in animal behavior.

At the 14th European Elasmobranch Association conference held in Galway, Ireland, marine biologists and shark experts from across Europe gathered to discuss the state of shark populations and consider new research techniques to better understand the fate and future of sharks and rays worldwide. Irish researchers who have been working with Ireland's National Parks and Wildlife Service, presented their study which indicated that a high percentage of the remaining number of basking sharks move through Ireland's local waters.

Basking sharks are typically a cold water species and the second largest fish on the planet, topped only by the whale shark. Like the whale shark, the basking shark is a filter feeder, opening its cavernous mouth to strain hundreds of gallons of water, searching for zooplankton - a collection of tiny creatures including larval or minute juvenile forms of fish, mollusks, and crustaceans. Zooplankton are sensitive to changes in the aquatic environment, such as temperature changes due to global warming or changes in oxygen levels or pH, which can occur in response to acidification. Where the zooplankton go, so go the basking sharks.

“Tracking basking sharks may be far more effective than tracking zooplankton, and [may] provide one of the best indicators of the health of our seas and thus the planet,” said Dr. Simon Berrow, the study's group leader.

Extensive tracking of basking sharks has taken place off of Ireland, replacing the intense hunting that used to occur as the basking shark was prized for its sizable supply of shark oil. Worldwide estimates of basking shark populations have been placed as low as 20,000. Extrapolating population estimates from the 250 sharks that have been tagged, the study claimed that there are probably several thousand that frequent the cold waters off Ireland's coast, making the island nation a prime location and home for an increasingly rare shark species.

Read about the research in Irishtimes.com.