Page 22 - ebsaws-2014-03

Page 21

a main cause of seabird mortality in the Mediterranean; while longline and other fisheries kill sea
turtles incidentally (Tudela, 2004).

Longline fleets are a particular threat to the loggerhead turtle population, as are trawlers and small-
scale gears in some areas, such as in the Gulf of Gabès. Driftnet fisheries and, to a much lesser
extent, small-scale fisheries using fixed nets and purse seine fisheries appear to account for the
highest impact on the region’s cetaceans and are also responsible for the highest rates of direct
human-induced mortality. The populations of monk seal in the Mediterranean continues to be at
risk from direct mortality by artisanal fishing gears and deliberate killing by fishermen, and are
affected by an increasing scarcity of food resources driven by overfishing (e.g., Notarbartolo di
Sciara et al. 2009).

Maritime traffic is negatively affecting Mediterranean biodiversity in a variety of ways, including ship
movement, noise, grounding and anchoring, ship-generated oil discharges and exhaust emissions,
the introduction in the environment of persistent organic pollutants, sewage and debris, and alien
species introduction and diffusion (for a review, see Abdulla and Linden 2008). The change in
marine biodiversity is proceeding at an unprecedented pace, as hundreds of exotic species --
mostly of tropical Indo-Pacific origin -- have settled in recent decades in the Mediterranean Sea.
The trend in invasive species appears to be accelerating with the rapid growth of maritime traffic
which brings with it alien fauna (introduced via ballast waters or attached to the hull). “Present-day
warming ultimately favours the spread of warm water species through direct and indirect effects,
and especially by changing water circulation. It is impossible at present to foresee to what extent
the exuberance of warm-water species will affect the trophic web and the functioning of marine
ecosystems in the Mediterranean Sea of tomorrow” (Bianchi 2007).

Furthermore, like throughout the world’s oceans (Hildebrand 2005), the Mediterranean is becoming
an increasingly noisy environment, caused by shipping, military sonar, and oil & gas prospecting,
which is impacting on various species, in particular cetaceans (Pavan 2006).