Fin Whale (Balaenoptera physalus)

The fin whale (Balaenoptera physalus) is the second largest marine mammal after its close relative the blue whale (Balaenoptera musculus) and belongs to the family Balaenopteridae. A long-lived and migratory species the fin whale is classified as “Vulnerable” by the IUCN and is under international protection against various environmental threats.

The fin whale (Balaenoptera physalus) is distinguished by its long cylindrical and streamlined body. Its coloration is markedly asymmetrical: the left side is dark while the right lower jaw area is visibly white. This color contrast is believed to serve a functional role in orientation and confusion during feeding.

Adult individuals range in length from an average of 18 to 22 metres with some reaching up to 25 metres. Their weight varies between 40 and 80 tonnes. The head is broad and flat. Between 50 and 100 longitudinal grooves extend from the lower jaw to the belly allowing the mouth to expand during feeding. The upper jaw contains 260 to 480 baleen plates each made of keratin which filter seawater to capture plankton and small fish. The paired blowhole on the top of the head produces a vertical spout of water vapor up to 5 to 6 metres high during exhalation.

^{Fin Whale (}pixabay⁾

The fin whale is a widely distributed species found throughout all major oceans and some seas worldwide. It is particularly abundant in temperate and cold waters of the northern and southern hemispheres. It prefers open ocean habitats over shallow coastal areas. Seasonally migratory fin whales travel to polar waters during summer months to exploit high levels of food productivity and return to warmer waters in winter for breeding and calving. Fin whales have been documented along the coasts of Türkiye with observations concentrated in the Aegean Sea and the eastern Mediterranean. Since the 1990s beachings (stranding events) have also been reported along Turkish coasts.

Fin whales are microphagous feeders whose diet varies by region and season but primarily consists of krill planktonic crustaceans and small schooling fish such as herring and mackerel. During feeding they open their mouths widely to engulf large volumes of water and prey. By expanding the pleats of the lower jaw and pushing the water out with their tongues against the baleen plates they retain the trapped organisms. Daily food consumption is approximately two tonnes.

Female fin whales give birth every two to three years on average. Gestation lasts about eleven months and typically results in a single calf. A newborn calf is approximately six metres long and weighs about two tonnes. Nursing lasts for six to seven months. Females reach sexual maturity between six and twelve years of age while males mature between six and ten years. The average lifespan of fin whales ranges from 80 to 90 years.

This species generally travels alone or in pairs but larger groups have been observed in feeding areas. When surfacing they move rapidly in a straight line. Fin whales are highly agile underwater and can reach speeds of 35 to 40 kilometres per hour. Average dive durations are between six and ten minutes though dives lasting up to 20 minutes have been recorded.

Fin whales are among the most powerful and lowest frequency sound producers among marine mammals. Males especially produce calls between 16 and 40 Hz reaching up to 188 decibels during the breeding season. These sounds can travel thousands of kilometres underwater. Sound production is also used for navigation (echolocation) and social communication.

During the first half of the 20th century fin whale populations declined sharply due to commercial whaling. Protected since 1976 by the International Whaling Commission (IWC) the species still faces numerous threats today. Classified as “Vulnerable” by the IUCN and listed on Appendix I of CITES the fin whale is subject to a ban on international trade. Major threats include ship strikes noise pollution microplastic and chemical contamination entanglement in fishing gear and the negative impacts of climate change on the food chain.

Fin whales play a vital role in marine ecosystem nutrient cycles. By diving to deep waters and releasing nutrients through fecal plumes they enhance surface water productivity supporting phytoplankton growth. This process directly influences the ocean’s carbon cycle.