Case 2: Ecospace — results in and outside of Representative Marine Biodiversity Areas
A spatial information exchange was developed between Marxan and Ecospace to quantitatively and jointly consider biodiversity and fishery objectives.
Caution: The results of these examples, like all similar model outputs, provide decision support for managers and other stakeholders and should never be assumed to represent final results or “the answer.”
NOAA Fisheries and TNC have worked together to better link EwE and Marxan, two of the most commonly used tools for fishery and biodiversity management. NOAA Fisheries developed an initial Ecospace component from the Northern California Current Ecopath model to examine different protected area designs. TNC then extended the utility of the Ecospace model to incorporate information from Marxan. We developed a spatial information exchange where priority areas from Marxan could be imported into Ecospace to examine effects of conservation on fishery production and vice versa.
Here we explore if:
- these tools can be linked
- their linkage helps to jointly inform management for fishery production and biodiversity conservation
Priority conservation areas were identified using Marxan and imported in to Ecospace. We varied the total amount of the region in priority conservation areas at five levels (0%, 25%, 37%, 40%, and 44%) to examine the effects of these different Marxan solutions on fish production. The input data for the Marxan runs included all of the biodiversity targets as well as marine fish targets and fishing effort. The five sets of priority conservation areas were imported into Ecospace, and we ran Ecosim over a 21-year trajectory to examine the effects on fish production (i.e. final biomass after 21 years).
The biomass results were examined for the 17 fish species inside and outside of the priority conservation areas. The graphs show the results for three species (Dover Sole, Lingcod, English Sole) that were illustrative of the overall patterns among fish species. It was assumed that higher amounts of biomass will be captured within priority conservation areas relative to outside, but we wanted to test this assumption quantitatively.
Not surprisingly, the biomass for most species was higher inside than outside of priority conservation areas. The biomass inside of priority conservation areas usually increased as the total area was increased, but not always. There were, for example, declines in English Sole biomass when priority conservation areas exceeded 25% of the total area within the Cape Blanco subregion.
More interestingly, the total biomass inside and outside of priority conservation areas was greatest when the conservation areas occupied 25% of the total area and declined or remained the same for larger conservation areas.