Sharks

Overview

Sharks play a key role as apex predators regulating our marine ecosystems. They are responsible for maintaining the abundance and diversity of many other marine species. Recognition and appreciation of the role sharks play is vital for their protection and conservation. Sharks are a collectively misunderstood inhabitant of our oceans and are often villainized in modern media whereas, in reality, they are the victims. On average, around the world, humans kill 100 million sharks a year and with a global decline in abundance, marine ecosystems are likely to be affected, leading to the decline of other commercially important species. Abundance in the Mediterranean Sea is also decreasing at an alarming rate, despite their status of protection which is weakly enforced. Efficient protection measures to halt the decline of the Mediterranean shark populations is of utmost priority in order to prevent any further losses to biodiversity.

Records of sharks in the Mediterranean date back to the Middle Ages. The majority of species now found are smaller-sized sharks, which occupy lower trophic levels of the food chain. Large predatory sharks in the Mediterranean Sea are thought to be functionally non-existent, but some species cluster in regions around the Mediterranean. The Mediterranean Sea is an important hotspot for shark conservation. A total of nine out of the 16 species most often caught by fishermen (both legally and illegally), are more threatened regionally than they are globally. There exists insignificant data on the total catch rate of sharks in the Mediterranean, as incidental bycatch often goes unreported. Some of the species most often found victim to bycatch in the Mediterranean include the catshark, gulper shark, bluntnose sixgill shark, blue shark, shortfin mako shark and thresher shark.

 

 

SHARK STRANDING RECORDING FORM

(description, geographic coordinates)

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SHARK SIGHTING RECORDING FORM

(description, geographic coordinates)

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(behavior, etc.)

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There are 47 species of sharks inhabiting the Mediterranean Sea, with over one third of them classified as threatened. Mediterranean shark stocks are considered close to being fully exploited.

Species of Sharks

Squatina squatina

Length:

Mature females can be 128-169 cm long, while males can grow to 80-132 cm.

Weight:

up to 80kg

Max Depth:

400 m

Feeding habits:

The angel shark spends its days lying buried in the mud or sand with just its eyes protruding. From this position it can ambush its prey and burst out at a startling speed to engulf flatfishes, skates, crustaceans or molluscs.

Habitat:

Angel sharks of the European and North African continental shelves can be found from the subtidal zone down to at least 150 m depth. They prefer mud or sandy bottom and may penetrate estuaries and brackish water.

Distinctive characteristics:

With a flat body and large pectoral fins, the angel shark resembles a large ray more than a shark. Its skin is grey to reddish or greenish brown, scattered with small white spots and blackish dots. Young angel sharks may also have white net-like markings and large, dark blotches, while adults are plainer. Whisker-like projections near the nostrils are used to taste and feel.

Population trend:

Reported as common in many areas during the 19th and early 20th century. Steep population declines have now been reported from several parts of this species’ range, including in the North Sea, British coastal waters, the French coast and large areas of the Mediterranean Sea. Fragmentation of the species range has also occurred, causing populations to become isolated from one another.

Main threats:

Spending much time resting on the seabed, angel sharks are particularly vulnerable to bottom trawls, which have become an increasingly widespread fishing technique. Touristic developments in the shark’s range have degraded the quality of its coastal habitat.

Status (IUCN):

Critically Endangered (CR)

Prionace glauca

Length:

The blue shark reaches a maximum lengbout 380 cm. About 50% of males in the Atlantic are sexually mature by 218 cm, although some may reach maturity being as small as 182 cm. Females are considered sub-adult from 173 to 221 cm and fully mature from 221 cm.

Weight:

From 27 to 55 kg in males and from 93 to 182 kg in females.

Max Depth:

1100 m

Feeding habits:

Feeding throughout the 24 hour period, but being most active at night, the blue sharks eat mainly small pelagic fish and cephalopods, particularly squids. However, invertebrates (mainly pelagic crustaceans), small sharks, cetaceans (possibly carrion) and seabirds are also taken.

Habitat:

Blue sharks are highly migratory, with complex movement patterns and spatial structure related to reproduction and the distribution of prey. They are found in a range of habitat types throughout migration.

Distinctive characteristics:

Blue sharks are light-bodied, with long pectoral fins. The top of the body is deep blue, lighter on the sides, and the underside is white.

Population trend:

Current population trend is unknown. Limited information comes from fishery assessments, which show no evidence of a declining trend in catch rates of blue sharks in the Atlantic or Indian Oceans. However, a 20% decrease was evident in the North Pacific between the periods of 1971-1982 and 1983-1993.

Main threats:

An estimated 20 million individuals annually are caught as bycatch from other fisheries. Blue sharks are also taken by sport fishermen, particularly in the United States, Europe and Australia.

Status (IUCN):

Near Threatened (NT)

Alopias superciliosus

Length:

3.3 – 4.0 m

Weight:

160 kg

Max Depth:

500 m

Feeding habits:

Diet consists mainly of pelagic bony fishes and cephalopods. The shark uses its tail to stun the pelagic fishes on which it feeds.

Habitat:

Ranges from the surface and the intertidal to at least 500 m deep (has been recorded 723 m deep). Found both in coastal waters and the high seas.

Distinctive characteristics:

Up to half of the body length is taken by the long upper lobe of the caudal fin. The body has a deep, metallic violet to purplish brown color above and creamy white below. The shark has huge, bulbous eyes up to 10 cm across.

Population trend:

Declining globally.

Main threats:

The species struggles to recover from moderate levels of exploitation. Occasionally targeted for its fin (2-3% of the fins auctioned in Hong Kong are from this species). Bycatch is another threat to bigeye thresher sharks, with many fishing gear types catching them accidentally.

Status (IUCN):

Vulnerable (VU)

Cetorhinus maximus

Length:

Males become sexually mature at a length of 5-7 m, females are mature at 8.1-9.8 m. There are unconfirmed measurements of individuals that reached 12.76 m.

Weight:

2,200 kg

Max Depth:

1000 m

Feeding habits:

Passive feeder, filtering zooplankton, small fish and invertebrates from the surface water. Basking sharks filter up to 2,000 tons of water per hour. They do not seek prey actively, but possess a large olfactory bulb which presumably guides them towards prey rich regions.

Habitat:

The basking shark is a coastal-pelagic animal, found worldwide in boreal to warm-temperate waters around the continental shelves and entering into brackish waters on occasions. It prefers temperatures of 8 to 14.5°C, but has been confirmed to cross much warmer waters at the equator.

Distinctive characteristics:

Basking sharks possess a cavernous jaw, up to 1 m wide and gill slits which almost encircle the head. Colouration varies from dark brown to black on the dorsal surface and white underside.

Population trend:

Decreasing.

Main threats:

Basking sharks have been exploited for several centuries to supply liver oil for lighting and industrial use, skin for leather and flesh for food or fishmeal. Modern fisheries yield liver oil, fins, meat and cartilage. Basking shark fins are very valuable in East Asian markets, meaning the species is often targeted for this reason, as well as caught as bycatch.

Status (IUCN):

Vulnerable (VU)

Isurus oxyrinchus

Length:

3.2 m, but the largest verified individual was 4.45 m long.

Weight:

Typically between 60 and 135 kg, but individuals weighing up to 600 kg have been recorded.

Max Depth:

500 m

Feeding habits:

This species feeds mainly on cephalopods and bony fish, but it may also eat other sharks, porpoises, sea turtles and seabirds. It hunts by lunging vertically up and tearing off chunks of flanks and fins of its prey.

Habitat:

The shortfin mako inhabits temperate and tropical seas worldwide. It is a pelagic species that can be found from the surface to the depths of 150 m, normally far from land. Rarely found in water cooler than 16˚C.

Distinctive characteristics:

Cylindrical body shape, with a vertically elongated tail. This species exhibits countershading, with brilliant metallic blue coloration dorsally and white ventrally. The juvenile mako has a clear blackish stain on the tip of the snout. Shortfin makos are also reported to have one of the biggest brains – body size ratios show the potential to learn remarkably quickly.

Population trend:

Strong evidence of decline.

Main threats:

Shortfin mako is an important target species, a bycatch in tuna and billfish longline and driftnet fisheries. It is also targeted by recreational fishermen.

Status (IUCN):

Vulnerable (VU)

Carcharodon carcharias

Length:

6.4 m with some records claiming lengths of 8 m.

Weight:

up to 3,324 kg

Max Depth:

1200 m

Feeding habits:

Marine mammals, seabirds and large fish. Can exert a bite force of 18,216 newtons. When the shark bites, it shakes its head side-to-side, helping the teeth saw off large chunks of flesh.

Habitat:

Great white sharks live in almost all coastal and offshore waters which have the temperature between 12 and 24°C. Bigger concentrations are found in the United States (northeast and California), South Africa, Japan, Oceania, Chile, and the Mediterranean. Although it has been considered an entirely coastal species, individuals were found at depths of 1,200 m.

Distinctive characteristics:

The great white shark has a robust, large, conical snout. Countershading with white underside and grey dorsal area. Great white sharks, like many other sharks, have rows of serrated teeth behind the main ones, ready to replace any that break off.

Population trend:

Unknown

Main threats:

Often persecuted due to its (somewhat exaggerated) image as a threat to human safety. This negative image also makes it an over targeted species by recreational trophy fishermen. The great white falls victim to fishing gear such as gillnets, longlines and trawl nets designed to catch other species. Coastal developments and pollution degrade important nursery habitat areas. Directed fishery exploitation of great white sharks is primarily undertaken with the aim of trading their teeth and jaws as trophies and their fins for the oriental fin trade.

Status (IUCN):

Vulnerable (VU)

Lamna nasus

Length:

2.5 m

Weight:

135 kg

Max Depth:

1300 m

Feeding habits:

Opportunistic hunter that preys mainly on bony fishes and cephalopods throughout the water column.

Habitat:

Distributed widely in cold and temperate marine waters of the North Atlantic and the Southern Hemisphere.

Distinctive characteristics:

Gray above and white below, the porbeagle has a very stout midsection that tapers towards the long, pointed snout and the narrow base of the tail. It has large pectoral and first dorsal fins, tiny pelvic, second dorsal, and anal fins, as well as a crescent-shaped caudal fin.

Population trend:

Decreasing

Main threats:

Targeted both as a game species by recreational fishermen and for its valuable meat on larger commercial scales. Often caught as bycatch, but meat and fins are still sold even in such cases. Slow life history traits mean recovery of stocks is unlikely.

Status (IUCN):

Vulnerable (VU)

Hexanchus nakamurai

Length:

4.8 m

Weight:

Up to 590 kg

Max Depth:

1100 m

Feeding habits:

The bluntnose sixgill shark commonly feeds upon a variety of prey including other sharks, skates and rays, many kinds of large bony fish, and invertebrates including squid, crabs, sea cucumbers, and shrimp

Habitat:

The bluntnose sixgill shark is found in temperate waters off of the continental shelf.

Distinctive characteristics:

While most shark species have five gills, the bluntnose sixgill species has six. The bluntnose sixgill shark also has six rows of teeth.

Population trend:

Data deficiency

Main threats:

Threatened by bycatch.

Status (IUCN):

Near threatened

Threats

 

PHASMA/M.KARAGIANNIS ΚΑΡΧΑΡΙΟΕΙΔΕΣ 8 ΜΕΤΡΩΝ ΚΑΙ 2 ΤΟΝΩΝ ΠΙΑΣΤΗΚΕ ΣΕ ΔΙΧΤΥΑ ΑΝΟΙΧΤΑ ΤΗΣ ΒΟΥΛΙΑΓΜΕΝΗΣ

1.Bycatch

Bycatch, the capture of species other than those being targeted, is the biggest threat to the survival of shark populations in Greece. Intense fishing efforts in the Mediterranean are causing a drastic decline in shark populations and as efforts increase with demand, the number of sharks being impacted is increasing tenfold. Different fishing methods such as longline, trawlers, and nets can have profound effects on species depletion. Trawlers account for only 10% of the total fishing fleet in the Mediterranean, but half of its total bycatch. However, data on shark landings due to bycatch are largely inaccurate, with over 50% going unrecorded. Many species are classified under the same common name (galeos) or individuals are returned to the sea before being recorded, making it difficult to calculate the true extent of species decline. As a result, species depletion can continue to go unnoticed and if these practices continue, it may be too late to reverse the damage and decline of this charismatic species.

2.Targeted Fishing Practices

Sharks in the Mediterranean Sea are also threatened by targeted fishing practices as fishermen are becoming aware of their commercial value. As fish stocks begin to decline due to overfishing, sharks are often substituted for more commercial species. In some countries within the Mediterranean, it is reported that fishermen are targeting sharks to be sold instead of other more commercially valuable species. Shortfin mako is marketed as swordfish in cases of seafood fraud due to the resemblance of the meat. One study in Italy found 20% of commercially sold swordfish to actually be shark meat.

Shark 1

3.Shark finning

Shark fins are globally in demand and have led to the practice of shark finning, where valuable fins are removed, and the less valuable carcass is thrown overboard. In 2005, the practice of shark finning was banned in the Mediterranean but the removal of fins at sea was not prohibited. This loophole led to the practice of cutting the fins off sharks too large to bring aboard. Sharks must swim continuously to prevent drowning, but when their fins are severed they unable to do so, and drown.

Pollution at Sea

4.Pollution

The bioaccumulation of pollutants through the food chain threatens the survival of sharks. As sharks occupy the highest trophic level, bioaccumulation leads to high concentrations of dangerous pollutants in their tissue. Heavy metals are highly toxic in animal tissues, even at low concentrations. Additionally, every year approximately 8 million tons of plastic ends up in our oceans, not only disrupting ecosystem health, but also increasing the possibility of species ingesting debris, suffocating, or becoming entangled. Fisheries-related pollution such as ghost nets that are left or lost at sea pose a major threat and have the potential to entangle marine life such as sharks.

Climate-Change5.Climate change

Climate change has been shown to affect prey distribution and ocean currents. This affects the abundance and distribution of sharks, often limiting the habitats they are able to survive in. With climate change causing the oceans to warm at rates unseen before, the effects on marine ecosystems and species are not entirely known, but are likely to be detrimental.

Conservation

Many shark species are protected in the Mediterranean, and in the Greek seas in particular, under the Bonn Convention, CITES, UNCLOS, UNFSA, the Bern Convention and the Barcelona Convention. There is also a total ban on drift netting and shark finning. Whole sharks must now be landed to encourage the use of their entire body, and the weight of the fins must not exceed 5% of the total weight of the catch. In many countries a permit system has been introduced for shark fishing.

In order to improve the current status of sharks in the Greek seas, better monitoring and landing guidelines are needed. There is a need for a management plan to be implemented, as well as public education and raised awareness in order to dispel the negative image associated with sharks.

Myths & Facts about Sharks

Myth: There are no sharks in the Mediterranean Sea

While once very abundant in the Mediterranean, today most shark species are facing a large decline in the region. Most are so rare that they are hardly ever observed, however over 47 species of sharks still survive in the Mediterreanean. Large sharks are less often seen than they used to be and small sharks in the Mediterranean are still often caught by fishermen. Species such as the Great White, Basking Shark, and Angel Shark are critically endangered.

Myth: Sharks are too ferocious to be vulnerable

Due to their late maturity and low number of offspring, populations of sharks are highly susceptible to decline. Sharks are often viewed as invincible due to their position as apex predators, but they are often subject to brutal fishing practices such as shark finning that leave them victimized. On average 100 million sharks are killed every year globally.

Myth: Shark is not in demand for consumption like other fish in Greece and the Mediterranean

You are not likely to see “shark” written on the menu because it is often marketed under a different label. In Greece most shark species are marketed in restaurants as “galeos.” In addition, due to the decline of other commercially important fish species, sharks are often substituted for other meat without the consumer's knowledge.

Myth: Shark finning is only a problem in Asia

While shark finning is predominantly believed to be an issue in Asian countries for use in shark fin soup, finning occurs in the Mediterranean as well. As demand for meat increases, every part of the fish is valuable, and for species of sharks that are too large to land on smaller boats, common practice is to cut off their fins and throw it back into the sea, leaving the shark to drown.

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