Management, perspectives and final comments
There is no specific regulation for deep-water fisheries in the central Mediterranean. For the trawl fishery, other technical measures, such as the cod- end mesh size (40 mm stretched, Ragonese and Bianchini, 1996; Bianchinni et al., 1998; Ragonese et al., 2001), are also in force and other effort restrictions are adopted in the various countries, such as the 45-day closed period in Italy and the four-month closed season (from June to September) in Greece.
No precautionary reference points have been defined until now for the deep-water shrimps A. foli- acea and A. antennatus. An increase in the size at first capture and a closed season during spring-summer are recommended in order to reduce fishing pressure on juveniles. The introduction of a larger mesh size than the present one (40 mm stretched) would appear to be feasible as part of the regulation of an almost mono-specific fishery targeting deep-water shrimps on the slope. Systematic studies on this demersal resource are mostly carried out as part of national research programs, such as GRUND for the Italian waters (Relini, 1998), and the international trawl sur- veys MEDITS (Bertrand et al., 2002) and COCTEL or DESEAS (Sardà et al., 2001, 2003).
We agree with the comments made by Merrett and Haedrich (1997) regarding the questions of whether the system would be capable of supporting the fishery as a top predator, how the system responds to the new predator pressure and whether this already highly adapted system has the capacity to adapt further.
The main authors of this book also agree that the deep-sea megafauna follow the K ecological strate- gy in the more abundant and possible commercial species. Moreover, the main species studied concen- trate the ovigerous females in the deepest grounds of their distribution range. The low fecundity and the low metabolic rates in a more stable environment represent a high vulnerability of these populations. According with Kostlow et al. (2000), most deep- water stocks are today overfished or even depleted. Depletion of species from deep-sea environments that dominate mid- to upper trophic levels may have long-term ecological implications, but the risk of reducing stock size and age structure to population viability, the potential for species replacement, and the impacts on prey and predator populations are not generally known. However, trawl fisheries have been shown to have potentially severe impacts on
the benthic fauna of seamounts where these fish aggregate. The deep-sea fauna, with a high level of endemism, suggests limited reproductive dispersal. The ability of the benthic community to recover fol- lowing its removal by trawling is not known.
Thus, considering these ecological characteris- tics, the failure of management of shallower fish- eries and the Precautionary Principle with regard to the lack of knowledge of these deep ecosystems, we recommend no commercial exploitation of depths below 1000 m.
Abelló, P., F. Valladares, A. Castellón. – 1988. Analysis of the structure of decapod crustacean assemblages off the Catalan coast (North-West Mediterranean). Mar. Biol., 98: 39-49. Acosta, J., M. Canals, J. López-Martínez, A. Muñóz, P. Herranz, R. Urgeles, C. Palomo and J.L. Casamor. – 2002. The Balearic Promontory geomorphology (western Mediterranean): mor- phostructure and active processes. Geomorphology, 49: 177- 204. Aloïsi, J-C. – 1986. Sur un modèle de sédimentation deltaïque. Con- tribution à la connaissance des marges passives. Thèse de Doc- torat d’Etat. Université de Perpignan. Aloïsi, J-C., J-P. Chambón, J. Carbone, G. Cauwet, C. Millot, A. Monaco and H. Pauc. – 1982. Origine et rôle du nephéloïde profond dans le transfert des particules au milieu marin. Appli- cation au golfe du Lion. Oceanol. Acta, 5: 481-491. Aloïsi, J-C., C. Millot, H. Pauc and A. Monaco. – 1979. Dynamique des suspensions et mécanismes sédimentogénétiques sur le plateau continentale du Golfe du Lion. C. R. Acad. Sci. Paris, 289: 879-882. Aloïsi, J.C. and A. Monaco. – 1975. La sédimentation infralittorale. Les prodeltas nord-méditerranéens. C. R. Acad. Sci. Paris, 280: 2833-2836. Aloïsi, J.C. and A. Monaco. – 1980. Etude des structures sédimen- taires dans les milieux deltaïques (Rhône). Apport à la connais- sance des conditions de sédimentation et diagenèse. C. R. Acad. Sci. Paris, 290: 159-162. Angel, M.V. and R.L. Smith (eds.). – 2000. Pelagic-benthic cou- pling in the oligotrophic cretan sea. Progr. Oceanogr., 46(2-4): 1-480. Arté, P. – 1952. Datos biológicos sobre Aristeus antennatus Risso del “Sot de la Gamba” de blanes (Crustácea, Macrura, Natan- tia). Publ. Inst. Biol. Apl., X: 145-149. Astraldi, M. and G.P. Gasparini. – 1992. The seasonal characteris- tics of the circulation in the north Mediterranean Basin and their relationship with the atmospheric-climatic conditions. J. Geo- phys. Res., 97: 9531-9540. Astraldi, M., G.P. Gasparini, L. Gervasio and E. Salusti. – 2001. Dense water dynamics along the Strait of Sicily (Mediterranean Sea). J. Phys. Oc., 31: 3457-3475. Astraldi, M., G.P. Gasparini, A. Vetrano and S. Vignudelli. – 2002. Hydrographic characteristics and interannual variability of water masses in the central Mediterranean: A sensitivity test for long-term changes in the Mediterranean Sea. Deep-Sea Res., 49: 661-680. Azov, Y. – 1986. Seasonal patterns of phytoplankton productivity and abundance in nearshore oligotrophic waters of the Levant Basin (Mediterranean). J. Plankton Res., 8: 41-53. Bacescu, M. – 1985. The effects of the geological and physiologi- cal factors on the distribution of marine plants and animals in the Mediterranean. In: M. Moraitou-Apostolopoulou and V. Kiortsis (eds.), Mediterranean Marine Ecosystems, NATO Conference Series, 8, Plenum Press, New York. Barrier, P., Di Geronimo, Ch. Montenat, M. Roux and H. Zibrow- ius. – 1989. Presence de faunes bathyales Atlantiques dans le Pliocene et le Plistocene de Méditerranée (Detroit de Messine, Italie). Bull. Soc. Geol. France, 8(4): 787-796.
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