Workshop on an Ecosystem Based Approach to Fishery Management for the Irish Sea (WKIRISH6; outputs from 2019 meeting)

The Sixth Workshop on an Ecosystem Based Approach to Fishery Management for the Irish Sea (WKIRISH6), set out to operationalise the WKIrish regional benchmark process. WKIrish aimed to incorporate ecosystem information into the ICES single-species stock assessment process for the Irish Sea. Three independent ecosystems models have been in development for the Irish Sea. Of these, an Ecopath with Ecosim (EwE) model has been reviewed by the ICES Working Group on Multispecies Assessment Methods (WGSAM). WKIrish propose to use relevant ecosystem indicators to inform the FMSY within the established F ranges (FMSYLower to FMSYUpper). FIND uses indicators of current ecosystem suitability for individual stocks to refine the F target values within these precautionary ranges. FIND is based on finding ecosystem indicators which are positively related to the stock development over the model tuning range, and where the likely underlying mechanisms for this link are likely to continue acting in the short to medium term. This approach is based on the assumption that because the assessment model is tuned to data over a period of time, the model may not fully capture environmental variation occurring on a shorter time span, and hence provides a method of adjusting target F to account for this variation. In essence, the proposed system suggests that where the value of the indicator is above average for the model tuning period the ecosystem is in a favourable state for that stock and consequently F in the upper range may be advised. Conversely, where the indicator is below the average, indicating that that ecosystem may be in an unfavourable state for that stock, F should be in the lower range. In no case does the proposed F target lie outside the ranges defined as being precautionary as giving good yield, and thus the system proposed here remains according to the ICES principles of precautionarity and delivering good overall yield. This method also ensures that stock assessment, reference point and stock status determination and quota setting remain within the approved stock assessment model, with ecosystem information only being used to refine the target F.

The EwE model was used to provide ecosystem indicator(s) for individual stocks (cod, whiting, haddock, sole, plaice, herring, and Nephrops) in the Irish Sea. The selection of the indicator aimed to cover a range of possible ecosystem processes on each stock. Through this approach, WKIrish has identified a route by which ecosystem information can be incorporated into the current single species assessment process. However, the approach can be developed further; a potential framework for a more complete Ecosystem Based Fishery Management is described. This framework would use ecosystem descriptors to inform decision making within assessment benchmarking processes. This may involve, but is not limited to: exploring productivity change across the as-sessment time-series, examining trends in aspects of population dynamics such as natural mortality and recruitment success, and input into the definition of reference points.