The Sei Whale
Peter Stevick
The Sei Whale or Balaenoptera borealis , is a whale that has a coloration of
dark steely grey on its back, flanks andrear part of the belly. Its throat grooves are white
or pale grey on anterior portion of belly. It may have white scars overits body caused by
lamprey bits. Sei whales tend to weigh 30 tons with an average length for males being between
12.0 to 17.5 meters and females being between slightly larger between 12.7 to 21.0 meters.
They have grey-black plates fringed with white and a relatively slim long body. They have
a slender head with a slight arched forehead, though it is not as rounded as
the blue whale's. Sei whales tend to have a single prominent ridge along the middle of
the top of their head. They have many longitudinal throat grooves that extent to the navel
and many small bleen plates, of which they have 300 to 410 on their upper jaw. They have
slender, pointed unitorm grey flippers and a moderately tall blow which can reach heights of 3
meters. These blows are shaped like inverted cones, with almost the same simultaheous showing
as the fin whale's. Both of these whales remain in view for relatively long periods before
typically doing a shallow dive. They may blow 2 to 3 times at 20 second intervals following a
short dive of 5 to 6 minutes, or 5 to 6 times at 30 to 40 secound intervals before longer
dive of 15 to 30 minutes. They have nearly erect strongly sickle-shaped dorsal fin,
which is placed slightly less than two thirds the way down the back. Sei whales have relatively
broad, triangular shaped tail flukes that has a slight median notch. Sei whales can be found
mainly offshore with seasonal migrations from polar and cold temperature feeding grounds
to tropical to warm temperature breeding grounds that are not very well known. Their estimated
population size is 54,000 with 17,000 located in the northern hemisphere mainly in North Pacific
and 37,000 or less in southern oceans.
Andrea-Vanessa-Erica @ the Advanced Technologies Academy