This paper aims to define which variables need to be taken into account in MSP for offshore aquaculture allocation, in order to allow its sustainable development, avoid conflicts with other human activities and impacts on the environment. The study is based on a wide review of multidisciplinary literature focused on interactions between offshore aquaculture and the surrounding environment across a spectrum of spatial scales. A recommended approach to incorporating scientific analysis in spatial planning of offshore aquaculture was developed and is described in the paper.
Questions this practice may help answer
- What are the key aspects that need to be considered to allocate aquaculture offshore?
- How diverse categories of aquaculture differ in term of spatial interactions with the environment and other maritime activities?
- What are the main tools and research analysis that can support proper allocation of off-shore aquaculture?
Aquaculture is a growing sector which is moving forward into new frontiers, both geographically and technologically. Several studies have addressed the challenges and opportunities deriving from this evolution. Furthermore, a number of software applications has been designed specifically to address where to allocate offshore aquaculture. In this context the present paper reviews the available studies and tools that can be used to improve offshore aquaculture planning.
Aspects / Objectives
The main objective of this paper was to determine which aspects have to be considered to allow effective planning of offshore aquaculture in the context of the ocean's complex ecological dynamics and the diversity of existing marine activities that can interact with or be impacted by aquaculture.
The paper is based on a wide view of existing studies and tools relevant to support correct allocation of offshore aquaculture. In order to analyse the specificities of different types of aquaculture, three main categories were identified: (i) fed (e.g., fish, most crustaceans), (ii) unfed (e.g., filter‐feeding bivalves, some grazers, and detritivores), and (iii) autotrophic species (kelp and other algae). Each of these aquaculture types interact with the environment in different ways, both in terms of external inputs to the farm and effects of the farm on its surrounding environment.
Moreover, four categories of spatial interactions between offshore aquaculture, the environment, and other uses were identified: (i) effects of the environment on aquaculture farms; (ii) effects of farms on the environment; (iii) cumulative impacts and regional planning issues; and (iv) synergies and conflicts with other ocean management goals.
The above-mentioned distinctions made possible to address the main aspects of the different aquaculture types and their specific spatial interactions with the environment and other human uses and provide useful information to support effective spatial planning of sustainable offshore aquaculture.
Main Outputs / Results
The literature review resulted in a number of considerations to support spatial allocation of offshore aquaculture for each of the four identified categories of spatial interactions:
- Effects of the environment on farms; environmental conditions which can influence farm siting are further categorised as: (i) those directly affecting productivity (e.g. water temperature and ocean currents), (ii) those that can affect the quality of sea food produced (e.g. land‐based pollutants) and which generally decrease when marine aquaculture moves into offshore environments, and (iii) those having significant impact on the cost of farm operations (e.g. depth, distance from port and associated infrastructure and processing facilities, wave conditions, etc.). Available software applications that can be used to determine the areas of highest production within a region also identified in the paper.
- Effects of farms on the environment; the main effect identified is the increase in the level of nutrients released in the open sea from aquaculture infrastructures, in particular finfish aquaculture. In this perspective a shift to integrated multi-trophic aquaculture (IMTA) is highlighted as possible solution. Another environmental concern associated with offshore aquaculture is potential negative interactions with marine mammals, birds, and other wildlife which can get caught in lines and nets or suffer impacts on their foraging grounds caused by the presence of aquaculture facilities.
- Cumulative impacts and regional planning issues; impacts deriving from an excessive number of farms in a single region are discussed, further possible solutions to these impacts are described. Main possible issues discussed are: excess of nutrient enrichment from finfish aquaculture, excessive consumption of food from the water column by shellfish aquaculture that can impact ecosystem function, risk of disease spread between farms.
- Synergies and conflicts with other ocean management goal; in this section it is considered in which ways the location of offshore aquaculture facilities can have significant effects, both positive and negative, on other ocean activities, including shipping, fishing, recreation and nature conservation. A flowchart has been developed to describe specifically how open-ocean fish farm can affect wild fisheries in off-shore areas.
In the final section of the paper (recommendations and conclusions) guidance for organizing and distilling the most important ecological questions and analysis, provided by the scientific research, for aquaculture spatial planning is discussed and summarised in the below conceptual diagram. Moreover, the section includes a table identifying main environmental risks of aquaculture that can be mitigated by spatial planning, along with planning strategies that are likely to minimize risk, and examples of available analytical tools that can be used to evaluate these risks (see below table).
Finally, It is highlighted that the profitability of an aquaculture farm and the potential environmental risks and impacts vary substantially across regions and are influenced by the number and density of farms. In addition, the concept that the most important planning considerations depend on the species being farmed and the specific ecology and environmental conditions of the farm location is stressed.
Based on literature review the paper provides a conceptual framework for the analysis of sustainable offshore aquaculture and related spatial implications (risk for the environment and conflicts with other sectors, including shipping, fishing, recreation and nature conservation).
Rebecca R. Gentry
Florida State University
Bren School of Environmental Science & Management, University of California Santa Barbara
Costs / Funding Source
Funding for the work underpinning the paper were provided by the California Sea Grant and the Waitt Foundation