Abstract
Although frequently suggested as a goal for ecosystem-based fisheries management, incorporating ecosystem information into fisheries stock assessments has proven challenging. The uncertainty of input data, coupled with the structural uncertainty of complex multi-species models, currently makes the use of absolute values from such models contentious for short-term single-species fisheries management advice. Here, we propose a different approach where the standard assessment methodologies can be enhanced using ecosystem model derived information. Using a case study of the Irish Sea, we illustrate how stock-specific ecosystem indicators can be used to set an ecosystem-based fishing mortality reference point (FECO) within the “Pretty Good Yield” ranges for fishing mortality which form the present precautionary approach adopted in Europe by the International Council for the Exploration of the Sea (ICES). We propose that this new target, FECO, can be used to scale fishing mortality down when the ecosystem conditions for the stock are poor and up when conditions are good. This approach provides a streamlined quantitative way of incorporating ecosystem information into catch advice and provides an opportunity to operationalize ecosystem models and empirical indicators, while retaining the integrity of current assessment models and the FMSY-based advice process.
Highlights
Fish stock productivity is affected by random environmental variability, environmental cycles and trends (Britten et al, 2017; Free et al, 2019)
We present an approach for the incorporation of ecosystem information into catch advice and demonstrate, by testing the approach on Irish Sea herring (Clupea harengus), cod (Gadus morhua), whiting (Merlangius merlangus), and Nephrops (N. norvegicus), how the approach has the potential to encourage more precautionary stock harvest during poor productivity phases and prevent overly cautious yields during high productivity phases
This study introduces the fishing mortality reference point (FECO) approach, which provides a quantitative mechanism for incorporating ecosystem information from empirical and model-derived indicators into the ICES single-species stock assessment process
Summary
Fish stock productivity is affected by random environmental variability, environmental cycles and trends (Britten et al, 2017; Free et al, 2019). We propose that relevant ecosystem indicators, derived from or identified by ecosystem models, could be used to provide an ecosystem informed target F within these established FMSY ranges This concept arose from a series of workshops centered on building capacity for an ecosystem-based approach to fishery management for the Irish Sea (ICES, 2020). Cod Fishing at FECO for cod, which was dynamic in response to SST changes (inverted trend with a 3-year lag), and stationary FMSY led to generally higher catches across the entire time series (Figure 7) This is because the lower initial F and catches allowed for a more productive cod stock in the long-term.
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