Sunday, August 8, 2010

Basking Sharks in the Bay of Fundy

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Laurie Murison wrote:

 Basking sharks are very common to occasional in the Bay of Fundy every year - I saw three on Monday.  I have seen hundreds over the years, although some may be the same individuals.  They are individually recognizable from their dorsal fins and saddle patch behind their large dorsal fin.  The largest number of basking sharks I have seen in one day was 51 (no repeats since we were travelling in from right whales in the Grand Manan Basin).  I don't have the year at hand at the moment but it was during the 1990s, also the same year basking shark numbers were high in the Gulf of Maine with 200 seen on a survey.  This was also during a time when right whale numbers were very high and sei whales were seen in the Bay regularly and also when zooplankton biomass was lower on the Scotian Shelf.

Basking sharks can be found in all depths of water and have been entrapped in herring weirs.  They are seen occasionally from the Grand Manan ferry and obviously glassy calm days are better for viewing. Their 'basking' nature allows them to be seen at the surface when most other sharks' presence would go unnoticed. I have seen them filtering just below the surface but
sometimes they are just cruising slowly.  Basking sharks are also great breachers, coming clear of the water.  They sometimes have lampreys attached which may be one reason for breaching, although there have been days with right whales that both species are breaching.

We have funding at the GMWSRS this year from the NB Wildlife Trust and Canadian Wildlife Federation to continue a pilot study of basking sharks. Our researcher has already obtained two short dive profiles from two different sharks and will be hopefully attaching archival satellite tags this summer which will collect a longer set of data before releasing from the shark and popping up to the surface and transmitting the data.

There was a Quirks and Quarks article about basking sharks in 2009 - very  fascinating about winter travels including transequatorial movements.  From Quirks and Quarks: "The basking shark is the world's second largest fish, and during summers, it lives a peaceful life sifting plankton from temperate ocean waters. It leads a mysterious double life, however, as during the winter, it simply disappears. Dr. Greg Skomal, a marine biologist with the Massachusetts Division of Marine Fisheries in Oak Bluffs on Martha's Vineyard, used special tags to track the sharks' movements during the winter. He discovered that these huge animals were sneaking off for southern vacations, travelling thousands of kilometers to tropical waters in which they'd never been seen before. He suspects these trips are to the secret nursery where the basking sharks bear and raise their young."

Laurie Murison
Grand Manan, NB
From Nature NB

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