Nova Scotia Bays case study
Liverpool Bay and Shelburne Harbour are two marine systems on the southwest shore of Nova Scotia, Canada. Both have some freshwater input but are largely marine. They are widely exposed to the ocean at their mouths with entrances of 10 and 20km width respectively. Aquaculture sites are situated at 20m depth over soft sediments. Temperature regimes in November Scotia are not influenced by the Gulf Stream and are generally colder than much of Europe. Low temperature mortality of cultured fish is always of concern. Sea lice are not a problem in Nova Scotia now, but are problematic in adjacent provinces. ISA virus has occurred in the past.
Each Atlantic salmon farm occupies an area of approximately 100 x 300 m, involving perhaps 12 cages. The production output of a single farm is 2000 t. A single farm exists in both Shelburne and Liverpool. Two more farms are planned for Liverpool.
In addition to GIS and finite element modelling, we are using acoustic habitat mapping in the field to characterize bottom type. This is ground-truthed with a tethered video ROV. In Liverpool there is an oceanographic mooring consisting of acoustic Doppler current profiling, fluorometer, transmissomter, CTD, and oxygen sensors. We will soon deploy a quadcopter drone to map the shoreline.
A single salmon farm generates 10 million euros, and two additional farms are intended for Liverpool (one presently operating) and at potentially one more for Shelburne (one presently operating). If production is successfully achieved, a processing plant will also be built in Shelburne.
The permitting process is slow in Nova Scotia especially in light of a new regulatory regime. There is more than adequate space for 3 farms in Liverpool. We are developing a 2D circulation model for this bay and will run numerical tracer experiments in the model to determine connectivity between proposed sites. Although Cooke already has plans for specific site locations, we are able to fine tune them with suggestions for ways of improving waste dispersion and decreasing disease risk.
Overlap with lobster habitat and fishing grounds are also of concern. Using our habitat mapping results, this will be the basis of decisions regarding further separation of aquaculture from other coastal resource activities.
A GIS-spatial modelling approach consistent with our previous work in aquaculture ecosystems is being employed. The basis of this framework is a physical circulation model in which a connectivity matrix is determined. The matrix is used for risk analysis of disease propagation between sites. Zones of influence for nutrient and particle waste dispersion are also predicted.
Acoustic habitat-mapping will be used to generate GIS layers for lobster habitat. This will be mapped with the above layers to look at overlap as input to siting decisions. We anticipate that out input to farm locations will be a demonstration of the value of advance planning in increasing the sustainability of salmon cage culture in terms of managing environmental impact, increasing biosecurity, and respecting social carrying capacity.
Expansion of aquaculture in Europe requires detailed planning input with specific goals of decreased disease incidence and reduced environmental impact. The simultaneous achievement of multiple management objectives is difficult but necessary in the resource competitive environment of the European coastal zone. The tools and approaches we employ will be applicable widely to European aquaculture.