There are 47 species of shark inhabiting the Mediterranean Sea, over one third of which are classified as threatened. Although only a few species are directly targeted by fisheries in Greece, populations are declining as a result of indirect threats. Mediterranean shark stocks are considered close to being fully exploited.

In 2004 the world shark catch was 810,000 tonnes. The most commonly fished shark species in the Mediterranean Sea are Catsharks, Gulper sharks, Bluntnose Sixgill sharks, Blue sharks, Shortfin Mako sharks, and Thresher sharks.
Sharks are of ecological importance to marine ecosystems as keystone top predators, believe it or not, their presence in the food web maintains species diversity and abundance. Removal of sharks has complex and unpredictable implications, including a decline in important commercial species as sharks keep populations of other fish in check.

Threats

All shark species are slow growing, late to mature, have low reproduction rates, and long life spans. As a result of this, populations have a limited capacity to recover once reduced.

1. By – catch: By-catch is the main threat to survival of shark populations in Greece. As the efficiency and efforts of trawling in the Mediterranean increase, the number of sharks affected by by-catch are increasing. Records of species landed are often inaccurate, with over 50% of by-catch unrecorded. Many species are classified under the same name, or by-catch is being returned to the sea before being recorded, making it difficult to calculate the true extent of species decline. As a result of this, species depletion may go unnoticed for a long time, and once it is noticed, it may be too late to reverse the decline.

2. Shark finning: Shark fins are globally in demand, and have led to the practice of shark fining: removing the valuable sharks fins and then throwing the less valuable carcass overboard. Unfortunately, once sharks lose their fins they are unable to survive as they must swim continuously to prevent themselves from drowning. Demand for fins is increasing by 5% per year, leading to more sharks being caught for this purpose. A single basking shark fin once sold for nearly $10.000.
3. Pollution: Due to increasing coastal development, human waste is washed into the water at increasingly higher concentrations. The bioaccumulation of pollutants threatens the health of sharks. Heavy metals are highly toxic in animal tissues even at low concentrations as they inhibit DNA synthesis, alter heart functions, disrupts sperm production, and alters blood composition. Further to this, larger plastics dumped in the ocean can cause damage to gills and fins if entanglement occurs.
4. Climate change: Climate change has been shown to affect prey distribution and ocean currents, this, in turn, affects abundance and distribution of sharks, often limiting the habitats they are able to survive in.

Sandbar sharks, Great white sharks and Spiny dogfish have decreased up to 90% as a result of a combination of these threats. Basking shark populations have declined by up to 70%, with an estimated 8200 left in the world. This decline is attributed to high by-catch levels through trawling, and boat collisions as a result of the large amount of time they spend at the surface to feed.

Conservation

A number of shark species are protected in the Mediterranean and the Greek seas in particular, under the Bonn Convention, CITES, UNCLOS, UNFSA, Bern Convention and Barcelona Convention. There is also a total ban on drift netting and shark fining. Sharks must now be landed whole to encourage use of entire body, and the weight of the fins must not be more than 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, as well as a management plan implemented, and public education and awareness raising to dispel the negative image associated with sharks.

Fact and fiction
(modified from Shark Alert 2006 S Fordham)