One of the biggest threats to the sustainability of the world's oceans is the over-exploitation of marine resources. To manage this threat, which is largely a product of over-fishing and other extractive activities, governments restrict the activities that can occur in their marine areas. These restrictions include regulation of fishing effort in certain locations, or the creation of no-take zones (areas where fishing or other extractive activities are prohibited).
Spatial optimisation models can help policy makers plan the best use of marine areas amongst these different activities.
Each activity will carry different opportunity and management costs while producing different levels of ecological or economic benefit. The data that is available on the spatial distribution of these benefits and costs can be incorporated into spatial optimisation models to determine the best allocation of area amongst the different activities. The aim is to maximise conservation or economic value; while meeting some objective such as a conservation target or economic constraint.
In Chile, marine species such as the Chilean-abalone or 'loco' are managed through a Territorial User Rights for Fisheries (TURF) program. This gives artisanal fishers property or user rights over a defined coastal area. To be part of this program organisations must comply with limits on total allowable catch, carry out annual population surveys for key species in their management area, and be responsible for all management costs. Management costs in Chile are all about enforcement – the costs of monitoring to deter poachers. Research has shown that species' abundance levels are higher in enforced areas; a trend attributed to decreased catch.
Katrina Davis and colleagues collected data on the costs of enforcing the existing TURF program and no-take areas in Chile to develop a spatial distribution of enforcement costs across an area in the central marine region. They then incorporated these costs into a spatial optimisation model to determine the best allocation of the area amongst activities like fishing, no-take areas, and open access areas with no management. Their objective was to understand how the revenue of artisanal fishers in Chile could be maximised while meeting conservation targets.
Their results suggest that there can be large net benefits from the enforcement of marine management areas: fishers' income was increased, and higher species' abundance levels were observed when marine management was enforced. Understanding what influences the decision of artisanal fishers in Chile to enforce their TURF management areas should be a high priority for the future.