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Published byMaria Young Modified over 8 years ago
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FLR Fisheries Library in ‘R’ Graham Pilling Phil Large, Finlay Scott, Mike Smith Cefas
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Structure Why FLR for data deficient stocks? Background to FLR Case studies FLR’s strengths and weaknesses Future of FLR
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FLR & POORFISH Idea: Use FLR for those case studies where ‘some’ data or knowledge were available The third step on the methodological ladder framework: 1.Bayesian networks 2.WinBugs 3.FLR
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Background to FLR Extendable toolbox for implementing bio- economic simulation models of fishery systems Open source = freely available Uses the ‘R’ language: statistical modelling & graphics
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Background to FLR Collaborative approach (>10 organisations working on FLR components) Inter-disciplinary (biology, economics, social science) http://www.flr-project.org
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More information
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Many applications Fit stock-recruitment relationships Model fleet dynamics (incl. economics) Stock assessments Estimate biological reference points Management strategy evaluations –HCRs and management procedures
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Applying FLR to data deficient fisheries Largely been used within data rich fisheries – e.g. EU HCR testing for North Sea cod Three case studies undertaken in POORFISH project using FLR –Edible crab case study –Saronikos Gulf (Greece) fishery –Blue ling fishery
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‘Southern’ blue ling Deepwater fishery West of UK and France Strong decline in CPUE seen over time Overexploitation?
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Why data poor? CPUE data limited –One fleet (French trawlers from 1989) –One-way Don’t know stock structure No survey data Some length data (mean length declining) Biological knowledge limited
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Proposed management Spawning aggregations – interviews and surveys Closed areas to protect spawning aggregations
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The Question Are closed areas within the spawning period sufficient to ‘recover’ the blue ling stock?
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Simulation Very simplified biological model ‘Juveniles’ and ‘Adults’ Quarterly time step - spawning Juveniles Adults Q1Q2Q3Q4
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Simulation Two ‘fleets’ –Spawning aggregation fleet: greater catchability Juveniles Adults Q1Q2Q3Q4 –‘General’ fleet (all year around) Effort divided between fleets in Q1
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Parameterising Data limited Available information from French fleet Biological parameters WGDEEP CPUE-based assessments –Starting population (juveniles, adults) –Fishery parameters (e.g. overall F) Expert knowledge
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Scenarios Biological: –‘Optimistic’ stock-recruitment –‘Pessimistic’ stock-recruitment
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Fishery & Management No closure of spawning grounds Closure of spawning grounds (i.e. fleet 1 cannot fish) Constant F 15% increase per annum 15% decrease per annum –Up to 2x or 0.5x historical average F
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Results - SSB Constant F Increasing F Decreasing F Optimistic SRR
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Results - Landings Constant F Increasing F Decreasing F Optimistic SRR
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Summary – blue ling Not predictions – defined by assumptions Changes in fleet F had greatest effect Spawning ground closures will not recover the stock Biological assumptions (particularly SRR) are important – but not critical (recovery doesn’t occur)
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FLR – strengths & weaknesses Currently, FLR is particularly good for identifying: –What you need to know (biology, economics, etc.) –Whether your controls/approach are robust to uncertainty inherent in data deficient situations With simulations, there is a focus on parameterising models … data deficient?
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FLR future & data-deficient cases More ‘data deficient’ stock assessment approaches –E.g. stock-reduction models –E.g. PARFISH (participatory models; P. Medley) –E.g. Proto-moments model Need to move beyond purely stock- assessment and MSE approaches
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FLR and data-deficient cases Key future development will be RISK –Likely to be higher in data deficient situations –Ecological risk assessment approaches (e.g. Australia/MSC) –Current EU and UK projects looking at risk- based approaches
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