Sei Whales
by Lindsay Mitchell
The Sei Whale
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| Photo found on: http://www.whalematch.org/whales.php |
The sei whale is a part of the largest whale species, as it is a part of the
baleen whale family, and is the third largest whale. However, there are not many significant distinguishing
factors that visually set the sei whale apart from other whales of the baleen
family; specifically from the fin whales or Bryde’s whale. This often leads to problems
identifying the population size and diversity, but there’s more information on
that later.
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| Picture of baleen in whale mouth. Photo found on: http://cimioutdoored.org/whale-teeth-vs-baleen/ |
The sei whale is a member of the baleen whale species, which falls under the classification of cetaceans, which are marine mammals like whales, dolphins and porpoises. Specifically, the sei whale is a rorqual, which is the largest group of baleen whales, and falls under the baleanopterinae subfamily – precisely in the baleanoptera genus (which houses mammals such as the sei whale, Bryde’s whale, blue whale, fin whale and Omura’s whale). The exact scientific name for the sei whale is balaenoptera borealis (National Marine Fisheries Service).
Baleen whales are different from other whale species due to their size, and lack of teeth. They have baleen plates in place of teeth. Baleen is a substance made of keratin, and the baleen whales have many plates that hang down from their upper jaws, one after another (ecokids.ca).
Home of the sei whale
Sei whales live in all oceans,
but are commonly found in the North Atlantic and North Pacific Oceans. They are
highly mobile, and there is no indication that any population remains in a
particular area year round (National Marine Fisheries Service). The sei whales
tend to avoid coastal waters and prefer to be offshore in subtropical,
temperate, and subpolar waters.
There is debate as to whether or not more than one species of sei whale exist. Some scientists believe there to be two different species divided by longitudes, and some believe there to be 3 different species of sei whale (National Marine Fisheries Service). However, there is not enough effort being put toward the discovery of new sei whale species, as they are hard to distinguish and generally swim across all the oceans.
The current population status of sei whales is unknown. Some efforts that were made included transect surveys, and photographic identification, but these actions did not produce very high results with sufficient data (National Marine Fisheries Service). The big purpose of the recovery plan is to provide a strategy to gather data to give information on the population, the genetic diversity and the trends that may be limiting the number of whales.
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| Photo found on http://www.north-atlantic-society.com/education/sei-whale.html |
One of the biggest problems in noting the population size of sei whales is identifying them. Their close resemblance to Bryde’s and fin whales create problems in distinguishing the numbers of sei whales from the oceans surface. Mead cited that the very fine bristles of their baleen (comb-like teeth) are the most reliable distinguishing factors for discerning them from other balaenoptera species (National Marine Fisheries Service).
Starting to Save the Sei Whale
The sei whale was listed as an endangered species since
the Endangered Species Act was passed in 1973, but there was not a recovery
plan made until December of 2011.Whats Harming the Sei Whale?
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| Picture by: Halldor Kolbeins/Getty Images – found on http://www.takepart.com/article/ 2014/09/10/why-world-ignoring-icelands-growing-whale-hunt |
The legal protection of sei whales was passed in 1970, however, Japanese and Icelandic whalers have continued to diminish the numbers of the population. Beyond that, just recently, there was a recorded case of sei whale being used for sushi right here in California (Sei Whale Found in Sushi).
Although the International Whaling Commission has put a halt on commercial whaling, these sei whales continue to face threats. Collisions with vessels, entrapment in active or abandoned fishing gear, reduced food source due to climate change, possible reoccurrence of legal whaling, and increased anthropogenic ocean noise pollution all still threaten the population of the sei whales (National Marine Fisheries Service). Click here to listen to the sounds a sei whale uses to communicate. (Sei Whale Call)
Unfortunately, there was a recorded case of a sei whale being killed by a bottom trawl in India in 2012. Click here to read more (Trawlers entangle sei whale).
Plan of Action!
Without much data on the sei
whale, forming a recovery plan was proven to be difficult. The purpose of this
plan was to “provide a research strategy to obtain the data necessary to estimate
population abundance, trends, and structure, and to identify factors that may
be limiting sei whale recovery” (National Marine Fisheries Service).
Due to the close resemblance to the Bryde’s and fin whales, high mobility of the sei whale, and general deep water occurrences by individual whales or small groups, common survey approaches have not been able to produce enough data that provides population structure, abundance or trends, making it very hard to incorporate a plan of action in helping the sei whale (National Marine Fisheries Service).
The recovery plan is essentially a three-part plan to help get the sei whales off the endangered species list. Step one: continue to regulate international whaling. Step two: determine population size, trends, and structure using data collection and passive acoustic monitoring. Step three: continued stranding response and associated data collection (National Marine Fisheries Service). The ultimate goal will be to move the sei whale from endangered to threatened, and then remove it from the endangered species list entirely.
National
Marine Fisheries Service recovery plan found at: http://ecos.fws.gov/docs/recovery_plan/FINAL%20Sei%20Whale%20Recovery%20Plan.24July.pdf
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