Spatial management of the Mediterranean bottom-trawl fisheries: the case of the southern Aegean Sea

Abstract

A time series of survey abundance indices for commercially important demersal fish and cephalopod species, inhabiting the narrow continental shelf of the southern Aegean Sea, is analyzed in relation to the topography of the area in order to evaluate the impact of different spatial fishery bans on the bottom-trawl fishery. With reference to the current situation, results suggested that implementation of the 1967/2006 EC Regulation, which bans bottom-trawl activities within 1.5 NM off the coast, will significantly increase (20-80%, depending on the species) the proportion of the populations that are inaccessible to the bottom-trawl fishery. It might also result in shifting of fishing activities toward deeper waters, adding fishing pressure onto slope resources inhabiting the slope. As depth determines, to a large extent, the distribution pattern of the species, it constitutes a variable of crucial importance for the spatial management of marine fisheries and should be taken into account when adopting relevant management regimes.

Mesoscale spatio-temporal dynamics of demersal assemblages of the Eastern Ionian Sea in relationship with natural and fisheries factors

“…Depth is known as one of the most influential factors on the distribution, abundance (e.g., Macpherson 2003;Politou et al 2003;Tserpes et al 2011) and other population and community metrics (e.g., Moranta et al 1998;Lorance et al 2002). However, depth-related patterns are ecosystem specific, especially for biodiversity (e.g., Moranta et al 1998;Lorance et al 2002, Magnussen 2002 and, as also seen in our case, they further depend on the sub-communities examined (e.g., Colloca et al 2003).…”

“…In general, Generalized Additive Models have proved powerful tools for examining the effect of such factors (e.g., Katsanevakis 2006;Tserpes et al 2011). In our case, they were able to explain large part of the variability for several metrics across the total community, the four taxonomic sub-communities, and the ten selected populations, despite the inherent high noise characterizing bottom trawl surveys (Gaertner et al 2005).…”

“…In this framework, the metrics used here might allow the identification of the preferred habitats of species and sub-communities and allow management measures to be taken. Finally, taking into account a possible fishing effort reallocation towards deeper waters resulting from EU regulation 1967/2006 (which prohibits trawling within 1.5 nautical mile of the coast and thus reduces available coastal fishing grounds; Tserpes et al 2011) as well as the increasing interest for deep-sea resources (Mytilineou and Machias 2007), the above results could be useful in designing management plans, particularly under the concept of an ecosystem approach.…”

Viability and Management Targets of Mediterranean Demersal Fisheries: The Case of the Aegean Sea

“…Similarly to the Aegean Sea, hake stocks are considered to be overexploited in most Mediterranean regions, as revealed by the stock assessments carried out by the STECF [15]. It is very likely that the implementation of EC regulation 1967/2006, which bans bottom-trawl activities within 1.5 nautical mile off the coast, has resulted in the shifting of fishing activities towards deeper waters; thus increasing fishing pressure onto slope resources, such as those of hake [16]. …”

“…This seems to be the main reason for the very low economic performance of the selectivity scenario in the case of trawlers. In addition, trawlers will not benefit much from the hake biomass increases expected from the selectivity scenario, as bigger hake is inhabiting deeper waters (>350m) that are hardly accessible to the trawl fishery [16]. …”