The role of hydrodynamics on the sustainable mussels’ culture activity. The case of the chalastra basin (nw gulf of thessaloniki)

Abstract

In line with the framework of strategic guidelines for marine aquacultures, mussel cultures have to be operated in Areas of Organized Aquaculture Development (AOAD). Forty per cent of the national mussel culture production, which is based in Chalastra (NW Gulf of Thessaloniki, part of the Thermaikos Gulf), uses pole and longline systems. Due to legislative changes, both farm-ers and the authorities are in the process of reforming the existing units and planning processes based on the principles of sustainability, as defined in AOAD. The aim of this study is to estimate the appropriate orientation lines on which the mussel socks are to be placed in the mussel culturing units, in relation to the direction of sea currents for optimum water circulation in AOAD. The hydrodynamics of the Chalastra basin is mainly wind driven and affected by prevailing northerly and southerly winds during winter and summer periods, respectively. When placed perpendicular to sea currents, the socks in the mussel production lines form an obstacle. Thus, the appropriate orientation of pole and longline units based on natural current directions can comprise a useful tool for sustainable mussel cultures. The benefits arising from the application of the proposed scheme are twofold: (a) productivity through the appropriate circulation and regeneration of nutrients can be maximized and (b) the environmental impacts of mussel culture activity can be minimized, as byproducts can more easily be dispersed of and biodegraded. In the present study, two basic schemes are proposed: (a) the division of AOAD is being researched into three sub-areas for pole and long-line units respectively and (b) the placement of the shortest possible length of production lines parallel to sea currents.