The Role of Hydrodynamics on the Sustainable Mussels’ Culture Activity. The Case of the Chalastra Basin (NW Gulf of Thessaloniki)

Chrysi A Papadimitriou,Amalia Moriki,Sofia Galinou-Mitsoudi,Yiannis G Savvidis

doi:10.3390/hydrology8030105

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 farmers 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 hydro-dynamics 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.

Highlights

Introduction1. Introduction with regard to jurisdictional claims in European shellfish aquaculture is based mainly on the production of mussels and oysters in coastal and intertidal environments
The final orientation of mussel farms is based on two important findings: (a) the formation of the water circulation in accordance with prevailing external forces that generate the sea currents, and (b) the angle of the mussel production line in relation to current direction
The numerical simulations that describe the water circulation in a mussel farm reveals that the pattern of water circulation in the farm for currents entering perpendicular to the longlines shows strong reduction in the velocity starting from about the center of the unit; flow velocity shows little reduction when the current enters parallel to the longlines

Summary

Introduction

1. Introduction with regard to jurisdictional claims in European shellfish aquaculture is based mainly on the production of mussels and oysters in coastal and intertidal environments. Mussel culture has been developed in Greece for more than half a century, with the most important mussel farming areas situated in the NW Gulf of Thessaloniki Figure 1A) and the NW Thermaikos Gulf. The Thermaikos Gulf is a long semi enclosed gulf with three sub-divisions based on the coastline from north to south. The Chalastra basin, located in the NW part of the central area of the Thermaikos Gulf, named the Thessaloniki Gulf, has a number of longline and pole mussel units at depths of >10 m and

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