The Sei whale gets its name from the Norwegian word for pollack as their presence is known to coincide with plentiful pollack in the water. They are a member of the rorqual family of whales which includes blue, fin and minke whales, however, unlike other rorquals, Sei whales do not gulp feed, instead skimming the surface open-mouthed feeding on a variety of fish species, squid and plankton.
The Sei whale can reach up to almost 20 metres in length but is a fast swimmer, reaching speeds in excess of 30mph. They were once heavily targeted by whalers seeing Sei whale numbers plummet and they are now classed as an endangered species. Around the world they are divided into three subpopulations – North Atlantic, North Pacific and Southern Hemisphere. There are thought to be around 12,000 individuals in the North Atlantic population and in excess of 50,000 worldwide with their numbers on the increase.
They can be identified by their long backs with a tall dorsal fin two thirds of the way along their back. They are around twice the size of a minke whale so noticeably larger and with a much taller dorsal fin than that of a fin whale. Although they do not raise their tail flukes when they dive, they can often leave distinctive “fluke prints” at the surface as they flick their tail flukes up, creating a large flat circle at the surface of the water – a whale footprint!
The Fin whale is the second largest species of whale in the world (second only to the Blue whale), growing up to 27 metres long. They are fast swimmers and deep divers, reaching speeds of nearly 30mph and diving over 200 metres deep – deeper than other rorqual whales like Blue and Sei whales can dive. Their diet consists mainly of krill, small fish and crustaceans, but due to their enormous size, they have to consume up to 2000kg of food each day!
Fin whales are unusual cetaceans in that their appearance is asymmetrical with its jaw being black on the left side and white on the right side. Scientists theorise that this could be useful in hunting but nobody really knows exactly why it has evolved this way. Fin whales are very long lived, living over 100 years old! However, despite their vulnerable conservation status, sadly, they are still today targeted by whalers in Iceland.
Humpback whales are incredibly distinctive with their knobbly faces and huge 17 metre bodies flanked by long, white pectoral fins which are around a third of their body length. The “knobbles” on their faces are known as tubercles and are enlarged hair follicles which can be used as sensory receptors. Humpbacks are arguably one of the most charismatic whale species, known for their energetic displays, breaching out of the water, lobtailing and slapping their pectoral fins on the water.
They can dive for up to 40 minutes at a time and when they dive they raise their tail flukes out of the water. Each whale’s pattern on the underside of their flukes is unique, so can be used by researchers to identify individuals. Like many other baleen whales, humpbacks gulp feed on their prey which mainly consists of krill and schooling fish. Unlike other whales, however, humpbacks have evolved a unique feeding technique of “bubble netting”. Swimming in circles around their prey, the whales will blow bubbles to create a curtain or net of bubbles that confuse and trap their prey, allowing them to gulp huge quantities of fish at once.
Another special trait of the humpback whale is their renowned signing voice! All whales make vocalisations, however, humpbacks make longer and more complex songs than any other marine species, particularly during the mating season where it is thought that the males may use their song to serenade and attract a female (although nobody knows for sure).
Atlantic Blufin Tuna
The Atlantic bluefin tuna is a large, fast, predatory fish. They average in length between 2 – 2.5 metres but can grow over 4 metres in length (the size of a large dolphin), and can weigh over 600kg. They are one of the fastest fish in the world, reaching speeds in excess of 40mph and can dive down to 1000 metres deep. They are a vulnerable, slow growing and long lived species that can live for 40 years. They are heavily exploited across their range, mainly due to demand from the Japanese sashimi markets. The Atlantic bluefin is listed by the IUCN as an endangered species and due to their slow growth rate, the average weight has halved since the 1970’s. They are also slow to reproduce, taking up to 5 years to reach reproductive age and only spawning once a year, so even when conservation efforts are enforced, the species takes a long time to bounce back. Bluefin tuna almost disappeared from the UK around 40 years ago, however in recent years, warm water currents have been carrying the fish back into UK waters and sightings of these fish have been increasing. It would be easy to assume that more sightings mean more tuna, however, it seems as though they are merely being displaced by the movement of warm currents, than significantly increasing in number. Bluefin tuna are protected in British waters and it is illegal to catch and land a tuna in the UK.