“ Forgotten signals in fisheries management ”

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“ Forgotten signals in fisheries management ”

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Presentation Transcript

1. “Forgotten signals in fisheries management” By, Deepak George Pazhayamadom Department of Zoology, Ecology and Plant Science (ZEPS) University College Cork (UCC), Cork, Ireland Emer Rogan (Department of ZEPS, University College Cork) Ciaran Kelly (Fisheries Science Services, Marine Institute) Edward Codling (Lecturer in Mathematical Biology, University of Essex)

2. Fisheries Management (Traditional approach) Fisheries Management (Alternative approach) SSB F MODELS (Assumptions) Limit 1000 1.5 Precautionary 1500 0.8 Acceptable 2000 0.5 SSB, F [Estimated Indicators] (Stock abundance and Exploitation) Monitor with Reference Limits (Acceptable, Precautionary, Limit) DATA Statistical Process Control[Signal Detection Method] Next Year Statistical Signals [Stock Indicators] Regulate with output controls HCR (Eg: TAC) Other measures (Eg: Effort)

3. Indicator Correlation INDICATORS (Examples) Catch numbers from age group 1 Catch numbers from age group 2 Catch weights from age group 5 Catch weights from age group 4 Proportion of catch numbers Proportion of catch weights CN11 [GOOD INDICATOR] r= 0.90395651 CN6 [BAD INDICATOR] r= 0.09310228 Correlation = Degree of relationship 0.7 = Good 0.8 = Better 0.9 = Very good PATTERNS DONT MATCH PATTERNS MATCH

4. COMPARISON TRADITIONAL APPROACH ALTERNATIVE APPROACH ESTIMATED INDICATOR Spawning Stock Biomass STOCK INDICATORS (Age based catch numbers and weights) 1. Cod (IS) 2. Megrim (CS & BB) FOR WHICH YEARS ? Acceptable In Control Precautionary Limit Out Control

5. Irish Sea Cod (Gadusmorhua) I – 1970 II – 1978 III – 1990 OC 1995 MATCH COLOUR CODES Traditional Approach - Spawning Stock Biomass Traditional Approach - Fishing Mortality CN4 CW4 CWABOVE CNABOVE

6. Celtic Sea and Bay of Biscay Megrim (Lepidorhombus whiffiagonis, L. boscii) I – 1990 II – 2004 Traditional Approach - Spawning Stock Biomass Traditional Approach - Fishing Mortality CN8 CNPP6 CNPP7 CNPP8

7. Pros and Cons • Performance of CUSUM was found to be consistent with traditional traffic light approach • CUSUM charts as real time monitoring technique for qualitative stock assessments • Efficient to detect persistent changes in the system • A handy monitoring tool for data limited fisheries • Stabilize the catch - Objective • Delayed signals occur for quick changes in the system • Delayed signals might happen when recruitment to the fishery occurs before maturity

8. THANK YOU