What is Seal Fish?

In this post, we will know some aspects and curiosities about the life of the Seal Fish, as well as their general biology and ecology.

What is Seal Fish?

Seals are marine mammals members of the Phocidae family. This family is part of the suborder Pinnipedia, which includes animals adapted to terrestrial and aquatic life, such as sea lions, walruses, and elephant seals. 

Seal Fish or Seals have a paddle-shaped fin and a hydrodynamic body, essential characteristics for swimming. These animals are usually found in regions of cold water and have fur and a thick layer of fat, which help them to maintain their temperature.

The Pinnipeds

Before we get to know more about Seals, let’s better understand the characteristics of representatives of the suborder Pinnipedia, which includes the Seal family. 

Pinnipeds are mammals of the order Carnivora, and the term Pinniped is derived from the Latin, pinna, which means “fins”, and pedis, which means “feet”.

Pinnipeds are a group of mammals that stand out for living part of the time in the water and part on a solid substrate, such as ice or land. Generally, these animals return to the solid environment to rest, mate, and give birth to their offspring. In the aquatic environment, Pinnipeds usually only feed.

Pinnipeds have a hydrodynamic body, which is important for moving in the aquatic environment. In addition, their body is covered with hair, and on the snout are the sensory vibrissae, the famous whiskers. 

These animals have a layer of fat that surrounds their entire body, working as a thermal insulator. It is noteworthy that the hairs also act in the thermoregulation of these animals.

We can divide pinnipeds into three families: Otariidae, Odobenidae, and Phocidae. In the Otariidae family, fur seals and sea lions are included. In the Odobenidae family, the walruses are included. Finally, we have the Phocidae family, which includes Seal Fish and elephant seals. 

Seal Fish characteristics

Seals are aquatic mammals that are characterized by having a rounded spindle-shaped body and a short voluminous neck. They have a body covered with hair, which is changed annually. Seals do not have external ears. Furthermore, males do not have external testicles, these organs are intra-abdominal.

To move around in the aquatic environment, Seals use their posterior fins, which cannot be projected forward. They serve as a way to direct the swim. Seals are excellent divers and can reach great depths and remain underwater for long periods. Common Seals can dive to depths of 427 meters and stay up to 30 minutes underwater.

In the terrestrial environment, they are not very agile, moving through the arching of their bodies. Unlike other pinnipeds, Seal Fish do not use their front fins for support as they are quite short. The Seal’s anterior fins are covered in fur and have five toes with sharp nails.

Seals have been heavily hunted around the world due to the high commercial value of their fat and fur. Many populations were exterminated, hunting being one of the causes that led to the extinction of the Caribbean seal. The hunting of these animals is currently prohibited. 

Seal feeding

Seals are carnivorous animals. Among the animals that are part of their diet, we can mention fish, molluscs, krill, penguins, and even other species of seals.

Mating and pregnancy

Males reach shore before females for reproduction. The males arrive in spring and begin competing for leadership, biting and mooing as they fight.

Females only arrive in the summer. Until the females reach the coast, each male defines his place and is always close to the water to receive the females.

The males that win the fights are the ones that can keep the largest number of females to take to their lair starting the mating season. Puppies are born 8 to 12 months after mating. Females nurse their young with great carehttps://youtu.be/BHZf8fYzDEY

Dive

Seals usually reach 60 metres deep to search for food at sea. Due to their protection mechanism, Seals can stay immersed for up to 30 minutes. Their protection system does not allow the eardrums to rupture or the individual suffocation due to the water pressure in the depth. Seals have a muscle that obstructed the entrance of the auditory crestal.  

Identification

One of the greatest characteristics of Seals is the fact that these animals do not have ears. Additionally, they are well adapted to moving around on the water but have some difficulties moving on land.

The fur of seals is grey tones, from the lightest to the darkest. Seals can range from 1.30 m to 1.95 m in length, reaching up to 100 kilograms. Female seals are generally smaller and lighter than male seals. To help on cold days, Seals have a dense layer of fat under their skin. Their head is big and the nostrils are in a “V” shape. 

Where do Seals live?

Seals generally live in cold water regions such as Arctic and Antarctic waters. However, each species has a specific habitat, with some being found in relatively warm regions. The species Neomonachus schauinslandi, popularly known as the Hawaiian monk seal, is the last species in the world of a tropical seal.

They rest and breed on beaches and low rocks and ice shelves. On land, seals are often extremely cautious and shy, making it nearly impossible to approach them without scaring them and fleeing into the water. 

Seal species

There are different species of Seals. However, the best known and seen in different environments are: 

Crabeater seal

The Crabeater seal (Lobodon carcinophagus) is a species of seal found mainly on the ice and coast of Antarctica. After the summer moult, it has a brown coat on the back and a blonde on the underside and a series of darker patches on the lighter coat. Throughout the year, its coat changes fully to blond. It has a slender body and a long muzzle. In general, adult individuals weigh about 225 kg and measure approximately 2.60 metres. The female is slightly larger than the male.

The Crabeater seal feeds mainly on krill. It stands out for having incredibly angular teeth, which present themselves as if they were a sieve. This species can live for about 20 years, and among its predators, the Killer whale and the Leopard seal stand out. Due to the action of this last predator, it is common to observe the presence of scars on the sides of the Crabeater seal’s body. According to the IUCN, the Crabeater seal is classified as “Least Concern”.

Leopard seal

Leopard seal (Hydrurga leptonyx) is found along the coast of Antarctica and is the largest species in the region. Males can reach up to 3 metres in length and weigh around 300 kg, while females can reach 3.8 metres and weigh up to 500 kg. It has a fur with darker colour on the back than on the belly and light and dark spots spread over the body. It has a large head, well-developed jaws, and its teeth are shaped like saws.

They are well known for feeding on baby Crabeater seals, but they also feed on sea birds (such as penguins), fish, crustaceans, and other seal species. The reproduction of this species is little known. They usually give birth to a single pup, which they nurse for approximately four weeks. The species is currently classified as “Least Concern” by the IUCN. 

The Common seal

Common seal (Phoca vitulina), also known as the Harbour seal, has a wide geographic distribution. It occurs in coastal waters of the Northern Hemisphere, from temperate to polar regions. Males range from 1.6 m to 1.9 m in length and can weigh from 70 kg to 150 kg. Females, in turn, can be between 1.5 m and 1.7 m in length and weigh between 60 kg and 110 kg.

They feed on a variety of prey, including fish, crustaceans, and molluscs. They can live from 30 to 35 years and their predators are sharks and orcas. Mating occurs in aquatic environments and usually, the female gives birth to a single pup. Puppies are usually breastfed for 4 weeks with high-fat milk, which allows for rapid growth. 

Conservation and main threats

The Seals main predators are sharks, orcas, polar bears, and the worst of them, humans.

Seals have been hunted as a food source since prehistory. They were killed to supply the fur and textile industry that supplies from small local businesses to large commercial operations, and under contingents and reward systems as threats to the fisheries sector. 

In addition, more recently, an outbreak of a distemper virus caused the death of an estimated 18,000 individuals who inhabited the European region. They also suffer from the proximity of industrial centres that dump into the ocean high loads of toxic pollutants that affect the animal’s health. 

They also suffer from accidental capture in fishing nets, particularly in trawl nets. The IUCN considers that there are unsatisfactory data on the annual mortality of these animals, the conservation status, and the total number of individuals of the species, but classifies it as vulnerable due to human activities, the melting of glaciers and the detriment of the areas where the species is found. 

Conclusion 

In this post, we learnt some aspects and curiosities about the life of the Seal Fish, as well as their general biology and ecology.

If you have any thoughts or doubts, feel free to drop us in a comment below!

Frequently Asked Questions (FAQs): Seal Fish

Where can Seals be found?

Seals live in flocks and are found in calm, very cold waters such as Antarctica and the Arctic Circle. Their body is surrounded by a large layer of fat, which acts as a thermal insulator. 

What do Seals eat?

They feed on a wide variety of fish, cephalopods, and crustaceans that live close to the surface and in the benthic environment.

How does the Seal reproduce?

Mating usually takes place out of the water and the females usually give birth to a pup, which is born with a size around 82 to 98 cm and weighing between 8 and 12 kg.

How long can a Seal stay underwater?

A Seal is capable of staying underwater for up to 30 minutes without needing fresh air, thanks to the pinnipeds’ incredible oxygen-conserving abilities.

How is the Seal body?

Seals have a rounded spindle-shaped body and a short voluminous neck. They have a body covered with hair, which is changed annually. Seals do not have external ears.

References 

Siniff, D. B. (1981). Seal population dynamics and ecology. Journal of the Royal Society of New Zealand, 11(4), 317-327.

Karamanlidis, A. A., Dendrinos, P., De Larrinoa, P. F., Gücü, A. C., Johnson, W. M., Kiraç, C. O., & Pires, R. (2016). The Mediterranean monk seal Monachus monachus: status, biology, threats, and conservation priorities. Mammal Review, 46(2), 92-105.

Stirling, I. (1969). Ecology of the Weddell seal in McMurdo Sound, Antarctica. Ecology, 50(4), 573-586.

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