Sei Whales are always on always on the move...But for how long? by Hannah Stone

Description of Organism

The sei whale is a type of baleen whale. Baleen whales do not have teeth, so instead they have what is known as a baleen plate that filters their food from water. Within the category of baleen whales, sei whales are categorized in the largest group of baleen whales, known as rorquals. Out of the nine species of rorquals, the sei whale is the fourth largest behind the blue whale, the fin whale and the humpback whale.

SOURCE: http://news.bbc.co.uk/2/shared/spl/hi/pop_ups/03/sci_nat_whaling_debate_-_key_species/html/3.stm

It is difficult to distinguish sei whales from their close relatives when at sea. Sei whales are highly mobile, prefer deeper waters and do not reside in one specific location. They are dispersed throughout most of the world’s oceans including the North Atlantic Ocean, the North Pacific Ocean and the Southern Hemisphere.

Geographic and Population Changes

Due to their mobility, natural populations of sei whales are historically considered unpredictable and irregular. In certain feeding areas, specifically in the eastern North Atlantic Ocean, the occurrence of sei whales is sometimes referred to as an invasion. However, their migration patterns are somewhat traceable. They can be found at low latitudes in the winter and move to higher latitudes in the summer.

SOURCE:http://www.whales.org.au/discover/sei/seid.html

 In recent decades, sei whale population and movements recorded in the North Atlantic have indicated change. Although there is not enough data to officially calculate trends in the amount of sei whales, the population began to quickly decrease from overexploitation in the 19th century. There is reason to believe the population has decreased because of the large-scale commercial whaling back then that took the lives of over 250,000 whales.

Endangered or Threatened Species Listing

The sei whale is listed as endangered and is protected in the United States under the Endangered Species Act. It is also listed on the Convention on International Trade in Endangered Species (CITIES) list, to protect species against international commercial trade. 

SOURCE: http://e2nz.org/2010/03/09/nz-gives-support-to-resumption-of-commercial-whaling/

The current main threats to the species, not including low-level threats, are directed hunting and the loss of their prey base due to climate and ecosystem change. Whale hunting, although rare today, is the main reason for the sei whale endangered status. This is still listed as a medium level threat because a scientific whaling program in Japan still actively hunts sei whales and there is still a possibility that hunting could again become a more serious threat. In addition, despite the immeasurable risk of climate change, it is speculated that oceanographic changes likely threaten the habitat and food availability for sei whales.

Recovery Plan

The reality is that there is very little known about the current sei whale population structure. One of the biggest priorities of the recovery plan is to gather more data in order to find patterns between the observed changes and outside factors. The first out of the three tiers outlines a few different data collection methods. The second tier’s goal is to estimate the population size of the species. And the third tier is dependant upon the data and estimations to conduct risk analyses. The last tier aims to use the information gathered to ultimately promote action steps.

SOURCES:

Recovery Plan: http://ecos.fws.gov/docs/recovery_plan/FINAL%20Sei%20Whale%20Recovery%20Plan.24July.pdf