Presentation on theme: "Fishery indicators V.Raykov,IO-BAS"— Presentation transcript:
1 Fishery indicators V.Raykov,IO-BAS Descriptor 3Fishery indicators V.Raykov,IO-BASFive main steps were identified to assess Good Environmental Status GES for D3:• Selection of commercially exploited (shell)fish populations relevant to theMSFD (sub)region, or MS-specific sub-division, being assessed with respectto D3;• Identification of stocks that can be assessed in relation to the primary assessmentcriteria for D3.1 and D3.2;• Determination of criteria to apply to stocks that can not be assessed in relationto the primary assessment criteria, and identification of stocks thatcan be assessed according to these secondary criteria;• Interpretation of how to define GES for D3 with respect to combining individualstock assessments at the criteria level, and how to combine criterialevel assessments at the descriptor level;• Assessment of current status in relation to GES.
2 The Choice (1) Identification of the appropriate area ; (2) Match of existing spatial units to that area;(3) Choice of datasource;(4) Choice of time period;(5) Selection criteria.
3 Assessment (1) all indicators with reference levels, (2) not all reference levels, or (3) no reference levels.For commercial populations that do not have full assessments scientific monitoringsurveys were identified as a potential data source for calculating some secondary indicators.Three options for determining the current status from trend-based time serieswere considered: (1) comparing the recent period mean with the long-term average(2) comparing the current value of the indicator in relation to the historic meansetting a threshold based on appropriate percentile of the Normal distribution; (3) detectionof trends.
4 GESGES Interpretation 1: strict interpretation of the Commission Decisionwhere MSY reference levels are treated as a limit and thus all stocks mustmeet the MSY requirement• GES Interpretation 2: the MSY reference levels are considered as a targetand thus half the stocks must achieve the MSY requirement, and all stocksmust achieve precautionary reference levels• GES Interpretation 3: the MSY reference levels are considered as a targetand stocks need to achieve this requirement on average. This average iscalculated accounting for the ‘distance’ individual stocks are above or belowthe MSY reference level.
5 For the overall assessment of Descriptor 3, three approaches were considered in the case studies: (1) no aggregation across criteria; (2) application of the one-out-all-out aggregation rule or “assessment by worst case”; or (3) application of weights for the different criteria.A higher proportion of assessed stocks increases the quality of the GES assessment;species/taxa for which no information is available decreases the quality;length of the time-series (with/without Reference levels);
6 Stocks for which analytical stock assessments are conducted F, SSBthe populationsfor which only information from monitoring programs is available.Proportion of fish larger than the mean size of first sexual maturation‘catch/biomass ratio’;Mean maximum length across all species found in research vessel surveysBiomass indices95% percentile of the fish length distribution observed in research vessel surveysSize at first sexual maturation, whichmay reflect the extent of undesirable genetic effects of exploitation
7 Issues to be considered Appropriate areas – divisions/subdivisions?The time period over which the landings data are considered determines the relative importance of species or species groups;Threshold for inclusion of species – 1% but in Baltic Sea 0.5% as a threshold for salmon – important but with low catches;
8 Member States shall, when implementing their obligations under this Directive, take due account of the fact that marine waters covered by their sovereignty or jurisdiction form an integralpart of the following marine regions:(a) the Baltic Sea;(b) the North-east Atlantic Ocean;(c) the Mediterranean Sea;(d) the Black Sea.
26 Sprat and turbotLmean Reference level for the given period of “healthy stock” conditionHolt (1958), Lopt – which assure max Y/R if all specimen were caught at the Lopt.Froese et al. (2008) - Yield of the individuals reached Lopt, won’t affect negatively age structure of the population;Froese and Sampang (2012) – the stock will have proportion of older individuals,if the mean length in the catch is within the interval : Lopt +/- 10%, i.e Lopt < Lmean < 1.1 Lopt.For Lopt calculation the following equations is used:logLopt = * logL∞ (Froese and Binohlan, 2000).where: L∞ - asymtotic lenght, Lopt – length at max Y/R
27 Classification of the state of Sprat population according to Lmean 7.20 cm < Lmean < 8.80 cm.