Morten Vinther

Using AMOEBAs to display multispecies, multifleet fisheries advice

In multispecies fish communities, predation levels change dynamically in response to changes in the abundance of predator and prey species, as influenced by the fisheries that exploit them. In addition to community-level metrics, it remains necessary to track the abundance of each species relative to its biological reference point. In situations with many interacting species, exploited by multiple fishing fleets, it can be complicated to illustrate how the effort of each fleet will affect the abundance of each species. We have adapted the AMOEBA approach to graph the reference levels of multiple interacting species exploited by multiple fleets. This method is illustrated with 10 species and eight fishing fleets in the North Sea. We fit a relatively simple response-surface model to the predictions of a fully age-structured multispecies model. The response-surface model links the AMOEBA for fishing effort to separate AMOEBAs for spawning stock biomass, fishing mortality, and yield. Ordination is used to give the shape of the AMOEBAs functional meaning by relating fish species to the fleets that catch them. The aim is to present the results of dynamic multispecies models in a format that can be readily understood by decision makers. Interactive versions of the AMOEBAs can be used to identify desirable combinations of effort levels and to test the compatibility of the set of single-species biological reference points.

Integrated assessment of marine biodiversity status using a prototype indicator-based assessment tool

Integrated assessment of the status of marine biodiversity is and has been problematic compared to, for example, assessments of eutrophication and contamination status, mostly as a consequence of the fact that monitoring of marine habitats, communities and species is expensive, often collected at an incorrect spatial scale and/or poorly integrated with existing marine environmental monitoring efforts. The objective of this Method Paper is to introduce and describe a simple tool for integrated assessment of biodiversity status based on the HELCOM Biodiversity Assessment Tool (BEAT), where interim biodiversity indicators are grouped by themes: broad-scale habitats, communities, and species as well as supporting non-biodiversity indicators. Further, we report the application of an initial indicator-based assessment of biodiversity status of Danish marine waters where we have tentatively classified the biodiversity status of Danish marine waters. The biodiversity status was in no areas classified as ‘unaffected by human activities’. In all the 22 assessment areas, the status was classified as either ‘moderately affected by human activities’ or ‘significantly affected by human activities. Spatial variations in the biodiversity status were in general related to the eutrophication status as well as fishing pressure.

Fishing for MSY: using “pretty good yield” ranges without impairing recruitment

28 Pretty Good Yield (PGY) is a sustainable fish yield corresponding to obtaining no less than a specified large 29 percentage of the Maximum Sustainable Yield (MSY). We investigated 19 European fish stocks to test the 30 hypothesis that 95% PGY yield range is inherently precautionary with respect to impairing recruitment. An FMSY 31 range was calculated for each stock as the range of fishing mortalities (F) that lead to an average catch of at 32 least 95% of MSY in the long term simulations. Further, a precautionary reference point for each stock (FP.05) 33 was defined as the F resulting in a 5% probability of the spawning stock biomass falling below an agreed 34 biomass limit below which recruitment is impaired (Blim) in long‐term simulations. For the majority of the stocks 35 analysed, the upper bound of the FMSY range exceeded the estimated FP.05. However, larger fish species had 36 higher precautionary limits to fishing mortality, and species with larger asymptotic length were less likely to 37