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|Title:||ICES SGHERWAY Report 2010 - Report of the Study Group on the evaluation of assess-ment and management strategies of the western herring stocks (SGHERWAY)|
|Authors:||BEGGS S.; CLARKE M.; EGAN A.; HATFIELD Emma M. C.; HINTZEN Niels T.; ROHLF N.; SIMMONDS EDMUND|
|Publisher:||International Council for the Exploration of the Sea (ICES)|
|Type:||Articles in periodicals and books|
|Abstract:||The final meeting of the ICES Study Group on the evaluation of assessment and man-agement strategies of the western herring stocks [SGHERWAY] took place in Dublin, Ireland, 14¿18 June, 2010. The Chair was Emma Hatfield (UK) and 8 people in total attended, from five nations. This is the final report of SGHERWAY. SGHERWAY was convened in 2008 to explore and evaluate the series of recommen-dations produced by the EU funded WESTHER project which suggested that, in the current stock assessment setup for herring to the west of the British Isles, two of the basic assumptions of stock assessment are violated. Currently the herring to the west of the British Isles are fished, managed and assessed separately as four ICES stocks 1: VIa North; 2: VIaS and VIIb,c; 3: VIIaN and 4: Celtic Sea and VIIj. Analytical assessments for VIa North are accepted by ICES in most years and have been accepted for the Celtic Sea and VIIj ICE stock for the last two. Analytical assessments have been rejected by ICES for VIaS and VIIb,c or VIIaN for many years. A combined assessment of the three stocks VIaN, VIaS/VIIb,c and VIIaN (the Malin Shelf metapopulation) was explored and its utility for advisory purposes investi-gated. It was found that the combined assessment gives important information on the Malin Shelf metapopulation, though it is unlikely to be useful for management advice purposes because it does not provide sufficient information on the sttus of the indi-vidual components. Alternative management strategies for the Malin shelf metapopulation were investi-gated to show how it could be sustainably managed, approaching MSY levels. The tools evaluated did not, under all conditions, suffice to manage the components of the metapopulation sustainably. The results showed that managing metapopulations is only possible with detailed information on fisheries independent data. However, whenever subcomponents of the metapopulation differ considerably in abundance, sustainable management is impossible for the smallest subcomponent. The VIIaN ICES stock should therefore continue to be assessed and managed separately. Where there is uncertainty of stock identification fishing mortality should be kept at low levels. Should identification rates increase, fishing mortality may also be increased. The evaluation of the utility of a synoptic acoustic survey in the summer for the Heb-rides, Malin and Irish shelf areas was based on results of a combined survey pro-gramme in 2008 and 2009, and an analysis of time-series of existing surveys in the area. The survey covers all areas in which mixing of the various western herring stocks is likely to occur at that time and could beused to establish time-series for the constituent components of the Malin Shelf stock complex. However, such time-series will not be available for a number of years. The amount of mixing between stocks cannot be estimated by the current sampling regime in the Malin Shelf survey. Con-sequently, a sampling programme has been developed to allow proper identification of fish population origins, making use of otolith and body shape techniques. Analy-ses will be compared to fish of known spawning origin collected during the EU pro-ject WESTHER. This sampling programme has been initiated in the 2010 synoptic acoustic survey.|
|JRC Directorate:||Space, Security and Migration|
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