Sei Whales: Are They Still Roaming The Sea? (By: Gabriella Orta)

The Sei Whale

*Reffered to in the scientific community as: Balaenoptera borealis

This species of baleen whale is classified as a rorqual. It's slender body enables it to be one of the fastest swimming whales in our oceans today--reaching speeds up to 30 mph; however, the sei whale isn't known for diving great depths down beneath the ocean despite it's
incredible speed. Sei whales are a molten gray color, with their undersides being a slightly lighter shade. This particular species of whale is a baleen whale, meaning they catch their various prey of zooplankton, krill, squid, and small fish and gather masses of it in their baleen plates, eating up to 900 kg of food each day (that's about 1 ton!).

See a sei whale hunt in the wild: https://www.youtube.com/watch?v=fOMzFFh3rEA

Geographic & Population Changes

Sei whales sightings in the wild are a very rare occurrence. This is mostly due to the fact that sei whales are highly mobile cetaceans. They enjoy temperate waters and the open ocean and aren't usually found in coastal waters. The global population is currently estimated between 57,000 and 65,000 individuals. This population estimation is broad because of the sei whale's highly mobile activity and favoritism of open ocean, two factors that make it hard to even spot these creatures in the first place. The only ocean basins where sei whales have not been found is tropical and polar waters (the two extremes).    

Listing Date & Type

The sei whale is globally listed as endangered under the IUCN Red List since the creation of the International Whaling Commission in 1986, along with most all whale species due to the vast amount of overexploitation and commercial whaling that occurred from the 1800s up until the mid/late 20th century. 

The Final Recovery Plan for the sei whale was drafted by the National Marine Fisheries Service and established in December 2011.

Cause of Listing & Main Threats

There are a few main threats the current population of sei whales, all having different ranks of severity. The main cause of initial depletion was unregulated commercial whaling during the second half of 20th century, where technological advancements made it possible to catch sei whales and other similar species. Although commercial whaling is completely banned for all whale species today, courtesy of the International Whaling Commission, "scientific whaling" (or so they say) is still being conducted by Japan, Iceland, and Norway. According to the NMFS's final plan for sei whale recovery, “between 1988 and 2009, Japan, once again under opposition from many IWC member nations, took 592 sei whales in the northwestern Pacific Ocean (International Whaling Commission 2010)”.

(below) A Japanese whaling ship, hunting for "scientific purpsoes"

The illegal trade of baleen whale meat also became a problem in the 1990s with numerous species being found in Japanese markets. 

Another large contribution to the depletion of the sei whale population is the negative impact of humans, both directly and indirectly. Human development and the problem of climate change has had negative effects on global sei whale populations because climate change can cause disturbances in prey abundance, therefore negatively affecting the sei whales.
Increasing ocean noise can also have negative affects on sei whales because they rely on vocalization, or calls, to find one another and mate. Ocean noise at the same low frequency at which sei whales communicate could have detrimental effects. However, the majority of direct human impacts are from vessel strikes on sei whales in open waters.

Recovery Plan

According to the sei whale recovery plan, it's main purpose is to "provide a research strategy to obtain data necessary to estimate population abundance, trends, and structure and to identify factors that may be limiting sei whale recovery." This plan is very extensive and is divided up into three tiers:

Tier 1- Continued international regulation of whaling

Tier 2- Determine population size, trends, and structure & monitor acoustics 

Tier 3- Continued stranding response and associated data collection 

The overall goal of this plan is to down-list sei whales from being endangered to being threatened and ultimately de-list sei whales altogether. Certain criteria has to be met for this goal to be achieved. For the global sei whale population to become down-listed from endangered to threatened, there has to be a less than 1% chance of extinction in 100 years. For the species to be taken off the list completely, there has to be less than a 10% chance of sei whales becoming endangered within 20 years. 

Of course, if criteria are met, a monitoring plan will have to be established to ensure the prosperity of the global sei whale population.

Definitions

*rorqual: a baleen whale of streamlined appearance with pleated skin on the underside
*baleen whale: a whale that has plates of whale bone in the mouth for straining plankton from the water. Baleen whales include rorquals, humpback, right whales, and gray whale 

*cetacean: a marine mammal of the order Cetacea; a whale, dolphin, or porpoise
*IUCN: International Union for the Conservation of Nature and Natural Resources  

*commercial whaling: hunting whales to make a profit from selling whale parts
*NMFS: (acronym) for the National Marine Fisheries Service
*endangered: any species which is in danger of extinction throughout all or a significant portion of its range
*threatened: any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range

Sources

Borealis, Balaenoptera. (n.d.): n. pag. Fws.gov. U.S. Fish and Wildlife Service, Dec. 2011. Web. 8 Mar. 2015.

"Sei Whale." WorldWildlife.org. World Wildlife Fund, n.d. Web. 13 Mar. 2015.

"Sei Whales, Balaenoptera Borealis." MarineBio.org. N.p., n.d. Web. 13 Mar. 2015.