Pacific Hake Management Strategy Evaluation Joint Technical Committee Northwest Fisheries Science Center, NOAA Pacific Biological Station, DFO School of Resource and Environmental Management, SFU 1

Main Results -Default harvest control rule results in median average depletions of ~28% for all cases and mean average depletions of ~36%. -Median average catches range t -Incorrect year class estimates often produce forecast errors -Annual vs Biennial survey benefits are marginal 2

3

Outline Introduction Review the MSE workplan objectives Methods Example simulations Describe the behavior of the existing management procedure Performance metrics Summary figures Discussion and Conclusion 4

Introduction Stock Assessment Data Harvest control rule Catch recommendation Catch that comes out of water Examples of some decisions Management ProcedureManagement Procedure -survey design/frequency -sampling protocols -converting backscatter to index - sensitivities -selectivity shape -obs/process error -areas/gender/seasons - mathematical form - target harvest rate - percentiles -Maximum catch -Carry-over -spatial restrictions -individual quotas -other opportunities 5

Management strategy evaluation Fishery objectives Stakeholders Managers Management procedure Historical Data Future data Assessment method Decision-rule Evaluation Operating model scenarios Performance measures Closed-loop simulation Peer-review Communication Performance Trade-offs Revision 6

MSE Workplan Objectives Introduce the MSE process to Pacific hake – Computer simulation (most work in 2012) – Consultation (limited in 2012, but more in 2013+…) Base simulations on the 2012 base model and current harvest control rule to evaluate: – Annual acoustic surveys – Bienniel acoustic surveys – *Alternative F spr% values Performance measured using specific statistics 7

Operating Model Stock dynamics Fishery dynamics True population Management Strategy *Data choices *Stock Assessment *Harvest control rule Catch Data Performance Statistics *Conservation objectives *Yield objectives *Stability objectives Feedback Loop Evaluation Phase 8

 Conditioning period  (2012 assessment) Short Med Long

Cases Considered No fishing Perfect Information Case Annual Survey Biennial Survey Alternative F SPR% (with perfect info) 10

No fishing case Set catches to zero, no assessment model Exists to provide the first reference case to describe how the stock will behave in the absence of fishing 11

Perfect Information Case We created a reference, perfect information case where the catch applied in the management strategy was the catch given by applying the F 40% - 40:10 rule to the operating model. No assessment model is fit, simulated catches come from the application of the control rule to the true stock “known” by the operating model (i.e., what if we didn’t have uncertain data and stock assessment errors?) 12

Biennial Survey Case Every year operating model simulates dynamics of the stock (i.e. recruitments, stock size etc) Every odd year operating model simulates and assessment model fits: – catch – survey age-composition data – commercial age-composition data – survey biomass In even years operating model simulates and assessment model fits – catch – commercial age composition data 13

Example Simulations These will be single iterations of the management procedure from Want to illustrate some iterations of the simulation to give you a more intuitive feeling for how the simulations work. We’ll talk about the aggregate performance later 14

Example Simulations Biennial survey 15

16

Annual Survey Case Every year operating model simulates stock dynamics (i.e. recruitments, numbers at age, etc) Every year operating model simulates the following data: – catch – survey age composition data – commercial age composition data – survey biomass The assessment model fits these data and returns the exploitable biomass The harvest control rule takes the exploitable biomass calculates a catch 17

18

 Conditioning period  (2012 assessment) Short Med Long But remember – starting points are not the same for each MSE run 19

Annual Survey 20

What we learned about the current management procedure 21

The assessment sometimes chases the latest survey observation 22

Assessment errors are frequent 23

Aggregate Performance Outcomes – catches – How variable the catch is – Proportion of years in specific zones (below 10%, between 10 and 40%, greater than 40% etc.) – The proportion of years that a management procedure closes the fishery Probability – How often does this occur? Time frame – Short term ( ) – Medium term ( ) – Long term ( ) 24

Statistics Break - Medians vs Means 25

Average Annual Variability in Catch (illustration) 26

Comparisons of Depletion, Catch and AAV for All Cases 27

No fishing Perfect info Annual survey Biennial survey 10% of B 0 28

Minimum Catch 29

Summary for long-term depletion 30

Summary for long term AAV 31

Summary for long-term catch 32

Key Performance Statistics Short Term Medium Term Long Term Percentage of years:PerAnnBiePerAnnBiePerAnnBie Depletion above 40%34.30%35.90%35.64%28.95%31.29%32.67%27.07%29.54%31.06% Depletion below 10%4.44%6.61%6.87%0.94%7.17%8.59%0.39%5.39%7.04% Depletion between 10 and 40%61.26%57.49% 70.11%61.54%58.74%72.54%65.08%61.90% MS closes fishery0.00%4.70%3.90%0.00%8.51%8.21%0.00%10.11%13.61% 33 Table A.6 pp 135

Key Performance Statistics II Short Term Medium Term Long Term Medians of:PerAnnBiePerAnnBiePerAnn Bie Average catch Average depletion31.7%31.4%31.6%27.9%26.9%27.8%27.6%27.3%28.0% AAV in catch (%)36.6%35.5%32.5%23.1%34.1%34.7%23.3%32.5%33.2% 34 Table A.7 pp 135

Analysis of alternative target harvest rates The hake treaty doesn't specify a target depletion level, only a target harvest rate (F40%) and a control rule (40-10). This makes it difficult to evaluate the efficacy of the control rule (i.e. relative to what?) One additional curiosity that we considered was what would the target harvest rate have to be in order to achieve a range of target depletion levels The MSE can be used to explore how changes to the target harvest rate might affect depletion, AAV, and average catch. This is an exploration of trade-offs, not a proposal to change the hake treaty. 35

Alternative target harvest rates 36

37

38

39

40

Discussion and Conclusion The current management strategy (assessment model formulation and F40%-40:10 rule) performs as follows: – Median average depletion on the 7-17 year time horizon ~28%, mean average depletion ~37% Benefits of annual survey marginal Assessment design results in chasing most recent data – Since the survey is itself variable, this produces a high probability of assessment error 41

Future work It’s not an MSE until objectives have been defined and the performance of alternative management strategies evaluated against them. The definition of these objectives and the JMC’s key interests will determine if we consider: – Operating models that consider more complicated hake life-history (i.e. movement, Canada and US areas) – Alternative management procedures to damp variability – Etc. 42

43

Extra Slides 44

Other available performance metrics First quartile depletion Third quartile depletion Median final depletion Median of lowest depletion Median of lowest perceived depletion First quartile of lowest depletion Third quartile of lowest depletion First quartile of AAV in catch Third quartile of AAV in catch First quartile of average catch Third quartile of average catch Median of lowest catch levels First quartile of lowest catch levels Third quartile of lowest catch levels Proportion with any depletion below SB10% Proportion perceived to have any depletion below SB10% 45

46