Shark: Characteristics, Feeding, Habitat, Reproduction

The shortfin mako or shark ( Isurus oxyrinchus ) is an elasmobranch that is part of the Lamnidae family. This shark has a metallic blue tone in the dorsal area, while ventrally it is white. In particular, the lower part of the muzzle and around the mouth are white.

Regarding its distribution, it is a pelagic and oceanic fish. Thus, it is located in tropical and temperate waters of all oceans, between 50 ° N and 50 ° S. The mako shark can inhabit the high seas, but it could enter the coastal coast, where the platform is narrow.

This species is highly migratory, whose movement is limited to the hemisphere where it lives or to nearby regions. In this way, research indicates that Isurus oxyrinchus does not carry out trans-equatorial migrations.

In the North Atlantic, the shortfin mako makes large-scale movements of more than 4,542 kilometers, averaging 50 to 55 kilometers per day.

In relation to diet, it includes bony fish, cephalopods, sea turtles, birds, small mammals and other elasmobranchs. Generally, almost all prey are smaller than shark. However, experts suggest that large ones prefer large prey, such as swordfish ( Xiphias gladius ).

 The swim

The mako shark is a fast swimmer with great strength. Experts point out that it is capable of reaching speeds of up to 70 km / h. Also, it can take big jumps out of the water.

Its speed is related to various factors, such as its aerodynamic shape, strong musculature and the tail fin, which is shaped similar to a crescent. In addition, the fact that porbeagle is homeothermic, increases its muscle power .

On the other hand, the speed when swimming is also associated with the characteristics of the skin, which is composed of dermal denticles. The size and shape of these help to reduce the turbulence of the water around the body.

According to research, the rounded morphology of the dermal denticles on the dorsal fin greatly contributes to the efficiency of swimming in this species.

General characteristics

Size

In this species, the female is larger than the male. This can measure from 200 to 215 centimeters, while the length of the female’s body varies between 275 and 290 centimeters. In terms of weight, it ranges between 60 and 135 kilograms. However, the female can weigh 150 kilograms.

Body

The mako shark has a cylindrical body. This streamlined shape makes it easy to move quickly through the water. In relation to the fins, the pectorals are narrow and small, less than the length of the head. The dorsal fins are large and the tail is elongated, thick and vertical.

Coloration

The Isurus oxyrinchus dorsally exhibits coloring bright metallic blue, which contrasts with the white belly area. The area around the mouth and the underside of the muzzle are white. As for the young, it has a coloration similar to that of the adult, but it differs from it by a black spot on the tip of the snout.

On the other hand, the tones vary with the age and size of the shark. Thus, those white areas that are present in small species, become dark in larger ones.

Head

The shortfin mako has a long, pointed snout. Its gill slits are wide, allowing the animal to obtain large amounts of oxygen.

The teeth of this shark are unique. The teeth of both jaws are similar in size, but those of the upper jaw are wider than those of the lower jaw. In general, teeth are large, tapered, and sharp. In addition, they are hook-shaped and lack serrations.

Large mako sharks, which are over ten feet tall, have wider and flatter teeth than their smaller conspecifics. This allows them to more effectively hunt swordfish, dolphins, and other sharks.

Dermal denticles

The mako shark, like other cartilaginous fish, possess dermal denticles. These replace the function of the scales, by creating a protective barrier against water. They also allow the shark to swim silently, thus avoiding being detected by predators or their prey.

In this species, the dermal denticles are small in size and overlapping. In addition, they have 3 marginal teeth and 3 to 5 ridges. The middle marginal tooth is the longest and is more worn than the others.

State of conservation

Porbeagle populations are in a progressive and excessive decline. This is due to the action of various factors, among which are poaching and accidental hunting of the animal.

This situation has caused the IUCN to include this species within the group of animals in danger of extinction.

Threats

The Isurus oxyrinchus is hunted to market their meat and fins. In addition, this shark is highly valued in sport fishing. Despite the fact that many of the people who practice this activity release the shark, the mortality after this is close to 10%.

Likewise, the mako shark is caught worldwide in commercial pelagic fisheries and gillnet, seine and longline fisheries. The vast majority of these accidents occur in offshore waters, in industrial pelagic fleets.

In addition, it is caught incidentally in those areas with narrow continental shelves, by entangling its body with trammel nets, trawl nets and coastal longlines. In some cases, the animal is released, but the researchers note that the mortality after this is between 30 and 33%.

Conservation actions

Since 2008, the Isurus oxyrinchus has been included in Appendix II of the Convention on Migratory Species. In this treaty, the parties involved reflect their commitment to work regionally for the conservation of the species.

In 2019, the shortfin mako entered the list of animals that make up Appendix II of CITES. In this way, exports of said species must include the corresponding permits where it is proven that they come from sustainable and legal fisheries.

Globally, there are few regulations on their capture. Furthermore, the implementation of international agreements has been ineffective.

The success of all agreements, which are part of the international fisheries and wildlife treaties, depends fundamentally on their implementation at the national level. In the particular case of the mako shark, experts consider that it is necessary to strengthen the follow-up actions of the established protectionist agreements.

Habitat and distribution

The Isurus oxyrinchus is an oceanic coastal species. Its habitat extends from the surface to approximately 500 meters deep. Thus, it is distributed in tropical and temperate waters, from 50 ° N and 60 ° N in the northeast Atlantic, up to 50 ° S.

Occasionally it may be found in areas near the coast, where the continental shelf is somewhat narrow. On the other hand, it is not usually located in those waters that have temperatures below 16 ° C.

Western Atlantic

The habitat of this shark covers the Grand Banks, in Canada, to Uruguay and northern Argentina, including the Caribbean, the Gulf of Mexico and Bermuda.

Eastern Atlantic

In this region of the ocean, the shortfin mako is found from Norway, the Mediterranean and the British Isles to the Azores, Morocco, Western Sahara, Senegal, Mauritania, Ivory Coast, Angola and Ghana.

Western Indo-Pacific

It is distributed in South Africa, Mozambique, Kenya, Madagascar, and Mauritius up to the Red Sea. To the east, it is found in the Maldives, Oman, Iran, Pakistan, Indonesia, India, China, Vietnam, Taiwan, Japan, North Korea, Russia, South Korea, Australia, New Zealand, Fiji, and New Caledonia.

Central pacific

The Isurus oxyrinchus is from the south of the Aleutian Islands to the archipelago of the Society Islands, including the Hawaiian Islands.

Eastern pacific

In the eastern Pacific, the mako shark inhabits southern California and has occasionally been sighted in Washington. It is also found in Costa Rica, southern Mexico, Ecuador, Chile, and Peru.

Atlantic

Experts indicate that in the western North Atlantic, it lives between 20 ° and 40 ° N, bordered to the west by the Gulf Stream and to the east by the mid-Atlantic. The margins of the distribution are in the waters of the Canadian Atlantic. In relation to the North Atlantic, this species lives in the Strait of Gibraltar.

Mediterranean

As for this region, the highest population density is found in the western Mediterranean. Occasionally it can be seen in eastern waters, such as the Sea of ​​Marmara and the Aegean Sea.

Eastern north pacific

Research indicates that this area is a breeding ground. This is based on the fact that, during the spring, there are abundant juvenile populations in Southern California Bight.

Feeding

The mako shark is a fast and powerful predator. In general, the diet includes swordfish ( Xiphias gladius ), Atlantic mackerel ( Scomber scombrus ), albacore ( Thunnus alalunga ) and Atlantic herring ( Clupea harengus ).

Also, eat squid ( Illex illecebrosus or Loligo pealeii ), green turtles ( Chelonia mydas ), dolphins ( Delphinus capensis ) and small cetaceans.

The diet can vary, depending on the geographic region where they live. According to research, 92% of their diet in the Northwest Atlantic is based on bluefish ( Pomatomus saltatrix ).

Regarding the diet in the Southeast Pacific, Isurus oxyrinchus shows a clear preference for bony fish, relegating cephalopods to second place. As for seabirds, mammals and crustaceans are occasionally eaten.

Feeding Habits

The Isurus oxyrinchus consumes daily the equivalent of 3% of its weight. To hunt, it can locate the prey and swim quickly upwards, tearing its fins or pieces of the flanks from it.

Also, the shortfin mako moves under its prey, in order to be able to specify its movements and attack it in a surprising way. In the case that the animal consumed is large, the digestive process could last between 1.5 and 2 days.

Regarding feeding strategies, it is of a general nature. However, the diet of the mako shark is conditioned by the abundance or scarcity of prey. Thus, this fish can make long migratory movements, changing its habitat relatively frequently.

Experts indicate that there are no differences between the eating habits between the female and the male. However, they show a more heterogeneous diet.

On the other hand, this species presents temporal-spatial nutritional variations. These are associated with the prey-predator dynamic, where there is the influence of predation, competition, reproduction, and migrations.

Reproduction

Sexual maturity in this species varies between different populations. In this sense, the females that inhabit New Zealand can reproduce between 19 and 21 years, while the males do it from 7 to 9 years. Males living in the western Atlantic mate at 8 years old and females can procreate at 18 years old.

According to research, courtship and the reproductive process occur in late summer or early fall. Experts point out that, during this stage, the male assumes somewhat violent behaviors.

These observations are based on the scars on the female, both on the belly, as well as on the gills, flanks and pectoral fins.

The Isurus oxyrinchus is ovovivíparo, so the embryos develop in utero. Because there is no placental connection, the growth of the fertilized ovum occurs because they feed on the yolk, contained in egg sacs.

The babies

The gestation period lasts between 15 and 18 days. As for hatching, it takes place in the uterine cavity, and newborns exhibit oophagia. In this way, they can feed on the unfertilized eggs or the young that are less developed.

The litter can vary from 4 to 25 young. At birth, they measure between 68 and 70 centimeters and are completely independent of their mother.

Behavior

The mako shark is solitary. During the mating period they do not form a couple and when the young are born, neither parent exhibits parental care behaviors.

This species has a highly developed sense of smell. As the water enters the nostrils, it comes into contact with the olfactory sheets, which are made up of neurosensory cells. In this way, the shark can detect the existence of few drops of blood in the water.

On the other hand, the Isurus oxyrinchus has the ability to detect the electromagnetic field, typical of some of its prey. This can be done due to the existence of Lorenzini blisters. These sensory organs are formed by a wide network of channels, which contain electroreceptors.

These structures are scattered throughout the body, concentrating especially on some areas of the shark’s head. In this way, the shortfin mako can find its prey while detecting the direction of the water current, in order to swim in its favor.

References 

  1. Bridge, M .; R. Knighten, S. Tullgren (2013). Isurus oxyrinchus. Animal Diversity Web. Recovered from animaldiversity.org.
  2. MARINEBIO (2020). Shortfin Mako Sharks, Isurus oxyrinchus. Recovered from marinebio.org.
  3. Rigby, CL, Barreto, R., Carlson, J., Fernando, D., Fordham, S., Francis, MP, Jabado, RW, Liu, KM, Marshall, A., Pacoureau, N., Romanov, E. , Sherley, RB, Winker, H. (2019). Isurus oxyrinchus. The IUCN Red List of Threatened Species 2019. Recovered from iucnredlist.org.
  4. Cailliet, GM, Cavanagh, RD, Kulka, DW, Stevens, JD, Soldo, A., Clo, S., Macias, D., Baum, J., Kohin, S., Duarte, A., Holtzhausen, JA, Acuña, E., Amorim, A., Domingo, A. (2009). Isurus oxyrinchus. The IUCN Red List of Threatened Species 2009. Recovered from iucnredlist.org.
  5. FAO (2020). Isurus oxyrinchus (Rafinesque, 1809). Recovered from fao.org.
  6. EDGE (2020). Shortfin Mako. Isurus oxyrinchus. Recovered from edgeofexistence.org.
  7. Nancy Passarelli, Craig Knickle, Kristy DiVittorio (2020). Isurus oxyrinchus. Recovered from floridamuseum.ufl.edu.
  8. Sebastián Lopez, Roberto Meléndez, Patricio Barría (2009). Feeding of the shortfin mako shark Isurus oxyrinchus Rafinesque, 1810 (Lamniformes: Lamnidae) in the Southeastern Pacific. Recovered from scielo.conicyt.cl.
  9. Valeiras and E. Abad. (2009). Toothless shark. ICCAT Manual. Recovered from iccat.int.

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