Abstract

Aquaculture continues to be the fastest growing food producing sector in the world and it is expected to bridge the future global supply–demand gap for aquatic food.1 However, this is a great challenge considering that a large proportion of current aquaculture for food is produced in fresh water and this resource is bound to be very scarce and even scarcer under climate change.2 Today, practically all marine production takes place by the coast or not far from it. Yet, coastal zones are becoming increasingly limiting for aquaculture. Therefore, use of open ocean sites can be a solution for future aquaculture activities. There is no single universally accepted definition of offshore aquaculture, or equivalently, open ocean aquaculture. In many cases these terms are used for any farming off the coast.3 Here, the definition proposed in a special publication by the Food and Agriculture Organization of the United Nations (FAO) for offshore mariculture will be used.4 That is, farming occurring away from the coastline (> 2 km), in waters deeper than 50 m and fully or partially exposed to stronger wave and wind action. The concept opposes that of coastal aquaculture, in as far as coastal refers to nearshore sites, mainly in sheltered places and those located off the coast but in waters not deeper than 40 m and with easy access. Under such a definition, currently the commercial or experimental production of offshore aquaculture is still minimal. Most countries cannot expect to develop much further their nearshore marine farming industry because (1) world competition for coastal sites and conflicts over use of space has increased, (2) coastal farming operations have seen their densities increased over the years, often becoming the cause of severe sanitary and environmental disruptions, economic losses, and instability, (3) water quality in those locations is generally getting worse, (4) the cost of coastal marine sites is becoming prohibitive, (5) and coastal communities are increasingly opposing nearshore aquaculture. Therefore, it is certain that in the coming decades, a large portion, if not most, marine aquaculture activities will have to move to open-ocean locations or, alternatively, be done land-based, with pumped water, with or without recirculation. However, even if offshore aquaculture might have some theoretical advantages, it is yet to be explored in terms of its technicalities, economic efficiency, and environmental and social sustainability.5 Currently, there are no well-established or standardized offshore aquaculture production methods for marine finfish or other species, which is why offshore farming has very limited coverage thus far. Not many industry players are willing to lead the way, possibly due to the large initial investments, extra costs, and more complicated logistics related to moving offshore, which will require larger production to offset increased outlays.