Printer Friendly

The Mako: most picturesque of all the sharks.

Mako sharks, shortfin mako (Isurus oxyrinchus) and longfin mako (Isurus paucus), belong to the family Lamnidae, which also includes the great white shark (Carcharodon carcharias), porbeagle (Lamna nasus), and salmon shark (Lamna ditropis). Lamnids are strong and powerful predators who are dubbed mackerel sharks. This is due to some morphological aspects that they have in common with bony fishes belonging to the Scombridae family. In particular they have the same tapered shape, a thin caudal peduncle that forms a dorso-ventrally depressed, laterally expanded keel, and a half-moon-shaped caudal fin.

The name mako, of unknown etymology, comes from the Maori language from New Zealand. There are many secondary names in the English language, including bonito shark, blue pointer, mackerel shark, sharp-nosed mackerel shark, snapper shark, blue porpoise shark, spriglio, and paloma.

Makos have very ancient origins, appearing in prehistoric oceans between forty and sixty million years ago. We know other mako species that lived in prehistory, thanks to the discovery of their fossil teeth, which often are of very big dimensions. Isurus hastalis, a huge mako now extinct, is common in the Miocenic and Pliocenic deposits in many parts of the world. Paleontologists estimate that this giant shark was twenty to twenty-seven feet in length, which suggests Isurus hastalis was the largest mako to have ever lived.

The body of the mako is very spindle-shaped and thin when they are young but it becomes very robust and powerful when they are adults. The snout is pointed, conical, and relatively long. The eyes are round, big, and dark. Teeth are big, long, and arched, and have smooth and cutting borders, lower teeth being prominent and even visible when the shark has its mouth closed. The shape of mako teeth is most suited to seize fast prey of small dimensions and to tear bits from bigger prey. There are up to seven rows of teeth, but only the first two are functional; the others in the back are replacements.

Sharks don't have swim bladders, the buoyancy organ that is present in bony fishes. The lack of that organ is compensated for by the light weight of the cartilaginous skeleton, the presence of a large liver, and by the continuous movement they must maintain to keep afloat. In most shark species the upper and lower lobes of the caudal fin are asymmetrical, the upper flap of the tail providing lift force to raise the tail and depress the anterior part of the body and head toward the bottom, a motion counterbalanced by the lift provided by the flat underside of the snout and the large horizontal pectoral fins. In mako sharks the caudal fin is moon-shaped and symmetrical, providing more power but less of a head-depressing effect, allowing the snout to be more hydrodynamicallly conical rather than dorso-ventrally flattened. The caudal peduncle is flattened dorso-ventrally and laterally enlarged to form the caudal keels. Mako skin, like other sharks, is covered with dermal denticles, which have a protective function and by reducing friction improve the body hydrodynamics. All these adaptations have the purpose of helping the mako attain great speed in swimming.

The two species are quite easy to recognize. The shortfin mako has smaller eyes. Its teeth are bent to the inside of the mouth, but at their apex they are slightly flexed to the outside. The pectoral fins are rather short. There is a unique pair of caudal keels. The coloration is deep blue in the upper part of the body with metallic reflections on the flanks; the whole lower part of the body is white, usually including the area around the mouth. The longfin mako has larger eyes. Its teeth are simply bent to the inside of the mouth, with their apex not flexed to the outside. The pectoral fins are longer, about the same length as the head. There are two pairs of caudal keels. The coloration is dark blue in the upper part of the body, and differs from the shortfin mako in a darker coloration, since the lower part of the head, under the snout and around the mouth, is usually as dark as the upper parts.

In makos, as it occurs in most shark species, females reach bigger dimensions than males. The maximum length is fourteen feet, seven inches for the shortfin mako, which was caught off Six-Fours les-Plages, France, in September 1973. Maximum length for the longfin mako is thirteen feet, eight inches, which was caught on May 19, 1978, between Jupiter Inlet and Sebastian Inlet, Florida.

Mako sharks are fish and they breathe through gills. Makos, due to their high metabolic activity, require more oxygen than many of the other sharks. This fact explains why mako sharks captured in the nets are found dead more often than other shark species. The shortfin mako is a highly active species. It is considered among the fastest of all sharks, since it can reach speeds of twenty-two to thirty-five miles per hour and can jump more than twenty feet out of the water. But how can shortfin makos be capable of performances like this? Most sharks are cold-blooded, with the exception of the family Alopiidae or thresher sharks (Alopias spp.), and most of the mackerel sharks. Shortfin makos are partially warm-blooded (the longfin mako does not appear to be warm-blooded). Shortfin makos have a modified circulatory system in comparison to other sharks, which allows them to keep body temperature 7-10 degrees Centigrade higher than the environment around them. This mechanism allows the mako to digest and process food more rapidly. Consequently, the shortfin mako has at its disposal more metabolic energy and more muscular power for its active lifestyle.

In Isurus oxyrinchus males reach sexual maturity at six feet, five inches, females between nine feet and nine feet, eight inches. Regarding Isurus paucus, it is not known at what size it reaches sexual maturity. The mating of two mako sharks has never been observed but the fact that scars from bites have been reported in some parts of the female bodies of shortfin mako make us deduce that the male holds the female with the mouth during courtship and mating. Makos exhibit a placental viviparity: the eggs are retained in the uterus throughout development and fetuses obtain nourishment from their yolk sacs and also by feeding on the unfertilized eggs produced by the mother (oophagy). In the shortfin mako, gestation lasts fifteen to eighteen months (in the longfin mako it may have a similar duration) and the parturition may happen in late winter to the middle of spring in both hemispheres. Litter size of the shortfin mako is four to twenty-five and at birth the pups are between twenty-seven and twenty-eight inches. Longfin makos bear litters of two and their size at birth is between thirty-three and thirty-eight inches.

The shortfin mako is a species that can be found in the open ocean and in coastal waters. Although it occasionally moves inshore it prefers relatively deep waters. It is largely distributed in temperate and tropical waters. Shortfin makos are often found close to the surface but can dive to at least five hundred feet deep. The longfin mako is an oceanic species found in tropical and warm-temperate waters. It has been recorded to reach at least 2,450 feet of depth. Eyes are larger in Isurus paucus than in Isurus oxyrinchus, a characteristic possibly related to the tendency that the longfin has to swim in deeper waters than the shortfin. The longfin mako is known to be a much less common animal, even though its range is very wide.

The shortfin mako is able to travel great distances. Some of these migrations have been recorded thanks to tagging programs led by marine biology institutes. Tagging is one of the most useful methods in the study of sharks because it allows the collection of valuable data on the geographical distribution, habitat, migratory movements, age and rate of growth, as well as population dynamics. The shark is tagged, measured, weighed and released. When the same specimen is caught for a second time the data gathered during the recapture can be compared with the previous existing data.

The most significant tagging program was started by the U.S. government in 1962 with the collaboration of professional fishermen and sport anglers. It started at the Sandy Hook Marine Laboratory in New Jersey, and since 1966 has been carried on by the National Marine Fisheries Service Laboratory (NMFS) in Narragansett, Rhode Island. The NMFS Cooperative Shark Tagging Program (CSTP) achieved great results, with a total of 106,449 sharks of 33 species tagged between 1962 and 1993 and 4,598 specimens of 29 species recaptured. Of 3,457 shortfin makos tagged, 320 have been recaptured. Results of NMFS's Cooperative Shark Tagging Program reveal that the blue shark (Prionace glauca) is the only species with recorded movements of over three thousand nautical miles. Only three species have documented movements between three thousand and two thousand nautical miles: the shortfin mako, the dusky shark (Carcharhinus obscurus) and the sandbar shark (Carcharhinus plumbeus). The maximum recorded distance traveled by a shortfin mako is 2,453 nautical miles.

Makos have the speed and agility to catch fast-swimming prey. Sometimes scars from mako bites are found on tuna and swordfish. These scars are usually located on the ventral part of the body and on the caudal peduncle. A vertical approach may be used by makos to kill fast-swimming animals, such as tuna, swordfish and dolphins. Biting the caudal peduncle of the prey can sever the swimming muscles, spinal column and blood vessels, with the effect of immobilizing the animal.

The diet of the shortfin mako is very diverse. It includes bony fish (such as mackerel, tuna, anchovies, herrings, sardines, flying fish, ocean sunfish, swordfish, marlins, sailfish, barracudas), cartilaginous fish (such as blue sharks, dusky sharks, hammerhead sharks, dogfish, cat sharks, eagle rays), sea turtles, small cetaceans, pinnipeds, squid, pelagic red crab, salps, porifera, and birds. The diet of the longfin mako shark is unknown but it most likely consists of schooling bony fish and pelagic cephalopods, and possibly swordfish. Some makos have been found with a swordfish bill driven into their body after fighting with prey.

The shortfin mako is considered a dangerous species. Attacks on divers, swimmers and boats are known. Attacks on humans are rare because this shark prefers offshore waters and rarely goes near the coast. If the mako is attracted by the presence of blood in the water, it may become very dangerous. Threat displays performed by the shortfin mako include gaping its lower jaw slightly and turning in figure eights as it swims closer to the diver. While the great white shark has attacked boats many times without being provoked, most of the time the mako attacks after being provoked, for example when it is hooked or harpooned. In these circumstances the mako can be extremely dangerous and can attack the boat or even jump inside causing great danger to those on deck.

Sharks like the makos have almost no enemies except parasites, killer whales, sharks (including the great white and the blue shark) and man. The shortfin mako is fished all over the world and is prized for the high quality of its meat. It is captured with different types of fishing gears but primarily is caught with the same pelagic long lines used to fish tuna and swordfish. In some areas, the number of sharks caught accidentally on long lines can reach ninety percent of total captures. Even if the longfin mako is fished for human consumption, its importance as a resource is limited since it is much less abundant. Unfortunately the mako shark, like many other shark species, is relentlessly fished by Asian fisheries. They pillage oceans all over the world for valuable shark fins that are used to produce the famous soup that sells at very high prices. Mako fins are considered the best along with those of hammerheads (Sphyrna spp.) and blue sharks.

The shortfin mako is a fast swimmer, an exceptional jumper, and the energy and fighting temper that it demonstrates when caught by hook, make it one of the most sought-after prey by the sport-fishermen. In Australia, the United States and many other countries, makos are caught through this type of fishing. Increasingly, sportsmen are becoming more conservation-minded and instead of killing these magnificent creatures, they tag and release them for science or simply release them. Undoubtedly, mako stocks are greatly reduced from their original stock size. Makos are considered to be species at risk because of their low productivity.

Alessandro De Maddalena is president of the Italian Ichthyological Society, curator of the Italian Great White Shark Data Bank, and a founding member of the Mediterranean Shark Research Group. The author and his colleagues, Antonella Preti and Robert Smith, have recently condensed nearly two centuries of scientific research in the book Mako Sharks (Krieger Publishing, 2005), the most complete reference for this species ever presented to the scientific community, combining genuine admiration for these predators with accurate scientific information.
COPYRIGHT 2005 News World Communications, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2005 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:NATURAL SCIENCE
Author:De Maddalena, Alessandro
Publication:World and I
Date:Dec 1, 2005
Words:2172
Previous Article:Kicking back on Tobacco Caye.
Next Article:Research opens the way to fast, accurate detection of explosives in airports.

Terms of use | Privacy policy | Copyright © 2020 Farlex, Inc. | Feedback | For webmasters