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species for the benefit of rocky bottom species induced by the change in the nature of the
substrate. Another negative effect of the presence of macro-litter on marine organisms is
demonstrated in addition to the many other known direct and indirect effects.
We analyze in the third part, the species which were reported and those not reported
during the Algerian demersal resource assessment campaigns of 1982 in comparison with
those of 2012 one and we try to establish a link with the increase in water temperature. The
results show that the frequencies of occurrence of hot anomalies have increased over time.
Thus, the appearance or progression of 3 species with hot affinity are reported. Because of
their vulnerability to anthropogenic pressure and / or the increase in temperature as well as the
particular circulation of the Algerian basin, the frequency of occurrence allowed us to classify
the species in two categories, the vulnerable species which include the elasmobranchs and the
species known as "boreal relics" and the rare species which remain rare or very rare in the
Algerian basin despite their establishment in the north of the western basin. These results are
consistent with the scenario of "meridionalisation" of the Mediterranean Sea as well as the
predictions made by the IPCC, i.e a return to a biodiversity already present in the Pliocene.
The results of this thesis should allow the competent authorities to make decisions
concerning the management of the stock by providing supporting evidence concerning the
negative impact that three different threats can have on the Algerian marine resource. What
these three pressures have in common is mainly poor regulation and a lack of control.