Case studies of Harvest Strategies in global fisheries

Management Objectives:

• Convention objective: “Ensure, through appropriate management, the conservation and optimum utilization of southern bluefin tuna”
• Harvest strategy objectives: See target reference points below

Reference Points:

• Limit Reference Point (current): N/A
• Limit Reference Point (once rebuilt to it): 20% SSB0
• Target Reference Point (interim): 20% SSB0 by 2035, with a 70% chance of success
• Target Reference Point (long-term): 30% SSB0 by 2035, with a 50% chance of success

Harvest Control Rule:

• Type: Empirical
• Management cycle: 3 years
• Data inputs: Longline catch per unit effort index, gene tagging, close-kin genetics
• Management output: Quota
• Harvest control rule: Hybrid rule that increases or decreases quota using model-based log-linear trend in adult biomass inferred by an age-structured model using genetic data and an empirical-based-staged response to CPUE.
• Other:
  Maximum quota change = 3000 t (~15-20%)
  Minimum quota change = 100 t

Harvest Strategy:

Fully-specified ‘Cape Town Procedure’ tested through comprehensive MSE process.

Outcome:

Quotas have increased each management cycle since the harvest strategy was adopted (an 87% increase between 2011 and 2020). The number of adult fish increased from 5% SSB0 in 2010 to 13% SSB0 in 2016, and there are indications that adult biomass may have reached 17% SSB0 in 2018.

Management Objectives:

• Maintain stock in green quadrant of Kobe plot with at least 60% probability while maximizing long-term yield
• Rebuild to or above SSBMSY with at least 60% probability within as short a time as possible, while maximizing average catch and minimizing TAC changes

Reference Points:

• B-Threshold Reference Point (interim): BMSY
• B-Limit Reference Point (interim): 40% BMSY
• F-Target Reference Point (interim): 80% FMSY
• F- Minimum Reference Point (interim): 10% FMSY

Harvest Control Rule:

• Type: Model-based
• Management cycle: 3 years
• Data inputs: Stock assessment estimates of current stock biomass (Bcurr) with respect to BMSY, stock biomass at maximum sustainable yield (BMSY), fishing mortality at MSY (FMSY)
• Management output: Quota
• Harvest control rule:
  If B>BTHRESHOLD (BMSY), fish at FTARGET (80%FMSY)
  If BLIM<B<BTHRESHOLD, reduce F linearly as specified in HCR
  If B<BLIM, suspend fishery and initiate scientific monitoring at FMIN (10% FMSY)
• Other:
  Maximum catch limit: 50,000t
  Maximum quota change: ±20% if current biomass is above BTHRESHOLD

Harvest Strategy:

Adopted in 2021, ICCAT successfully converted the HCR into a full harvest strategy through the addition of an exceptional circumstances protocol and the specification of the data collection and assessment methods needed to apply the the HCR.

Outcome:

The stock was declared recovered in 2016, a year before the HCR was adopted. The 2018-20 quota set by the HCR was limited by the 20% maximum change clause. Using the 2020 stock assessment, the HCR recommended a TAC increase for the 2021-23 management period which was agreed to by all parties without controversy.

Management Objectives:

• Restore to within a prescribed period of time or maintain at Bmsy (chance of B2037<Bmsy is ≤ 50%)
• The risk of failure to meet the Bmsy target and interim biomass targets within a prescribed period of time should be kept moderately low
• Low risk (<30% chance) of exceeding Fmsy
• Very low risk (<10%) of going below an established threshold [e.g. Blim or Blim proxy]
• Maximize yield in the short, medium and long term (5,10, 20 years, respectively)
• The risk of steep decline of stock biomass should be kept moderately low
• Keep inter annual TAC variation below “an established threshold” (i.e., 15%)

Reference Points:

• Target reference point: Bmsy
• Proxy limit reference point: 30%Bmsy

Harvest Control Rule:

• Type: Empirical
• Management cycle: 3 years
• Data inputs: Five survey-based abundance indices
• Management output: Quota
• Harvest control rule: Combination of a target-based and slope-based rule that increases or decreases quota depending on on the current TAC and recent trends in survey biomass
• Other:
  Maximum quota change: ±10%

Harvest Strategy:

The original HCR adopted in 2010 proved unsuccessful and was modified in 2017. The current HCR will be implemented until 2024. If circumstances occur outside the ranges tested by the MSE, the exceptional circumstances protocol will be triggered, possibly changing the HCR.

Outcome:

Greenland halibut are considered overfished. The intial HCR adopted in 2010 had to be revised in 2017 as the exceptional circumstance protocol was triggered 4 out of 6 years, likely due to annual catch estimates far exceeding the TAC. The TAC based on the current HCR increased in 2019 to 16521 t.

Management Objectives:

• Maintain stock at levels that can produce MSY, as qualified by relevant environmental and economic factors
• Use HCR to maintain stock at or above the target and well above the limit

Reference Points:

• Target/Threshold Reference Point: 40%B0
• Limit Reference Point: 20%B0
• Safety Reference Point: 10%B0

Harvest Control Rule:

• Type: Model-based
• Management cycle: 3 years
• Data inputs: Stock assessment estimates of current spawning stock biomass (Bcurr); unfished spawning stock biomass (B0); equilibrium exploitation rate (Etarg) associated with sustaining the stock at Btarg
• Management output: Quota
• Harvest control rule: Reduces catch linearly from the threshold level (0.4B0) to the safety level (0.1B0); zero catch below safety level, except for subsistence fisheries
• Other:
  Maximum catch limit: 900,000t
  Maximum quota change: ±30%

Harvest Strategy:

The current HCR is slated to be expanded to a fully specified harvest strategy in 2021.

Outcome:

Based on the 2020 stock assessment, the stock is currently not overfished or experiencing overfishing. Current spawning stock biomass is estimated to be at 0.45B0, above the target reference point. However, because there is no allocation key, the HCR-associated TAC of 470,029 t for 2018-20 was exceeded by 29% in 2018, and overages are expected to continue until the quota is allocated.

Management Objectives:

Biological

• To maintain stocks at (on average), or return to, a target biomass point BTARG or equivalent proxy (e.g. FTARG or CPUETARG) equal to the stock size that aims to maximise net economic returns for the fishery as a whole
• To maintain stocks above the limit biomass level, or an appropriate proxy, at least 90% of the time
• A reduced level of fishing if a stock is below BTARG but above BLIM (or an appropriate proxy)
• To implement rebuilding strategies, no-targeting and incidental bycatch TACs if a stock moves below BLIM (or an appropriate proxy)
• To ensure the sustainability of fisheries resources, including consideration of the individual fishery circumstances and individual species or stock characteristics, when developing a management approach

Socio-economic

• To maintain stocks at (on average), or return to, a target biomass point BTARG equal to the stock size that aims to maximise net economic returns for the fishery as a whole
• To maximise the profitability of the fishing industry and the net economic returns to the Australian community
• To minimise costs to the fishing industry, including consideration of the impacts on the industry of large or small changes in TACs and the appropriateness of multi-year TACs

Ecosystem

• To be consistent with the principles of ecologically sustainable development, including the conservation of biological diversity, and the adoption of a precautionary risk approach

Reference Points:

• Limit Reference Point: 20%B0
• Trigger Reference Point: 35%B0
• Target Reference Point: 120%BMSY and 48%B0

Harvest Control Rule:

• Type: Empirical
• Management cycle: 3 years
• Data inputs: CPUE, indices of abundance, size and age data
• Management output: Quota
• Harvest control rule: If B is below limit, no targeted fishing and a rebuilding strategy will be developed; if below trigger, TAC is set at levels that allow stocks to rebuild to target levels; if below target, rebuild stocks to target; if above target, fish at F that produces target biomass

Harvest Strategy:

This fully specified, MSE-tested harvest strategy framework applies to the Southern and Eastern scalefish and shark fishery, with each stock applying one of four different HCRs included in the harvest strategy.

Outcome:

According to the most recent 2017 assessment, the stock is considered sustainable at 42% of unfished spawning stock biomass, above Bmsy but slightly below the TRP. The current level of fishing pressure under the HCR is unlikely to deplete the stock or impair recruitment.

Management Objectives:

• Improve catch rates quickly in the short-to-medium term
• Increase the biomass level back to the MSY over 20 years
• After likely large initial cuts to achieve first objective, secure greater TAC stability over time

Reference Points:

Target Reference Point: BMSY

Harvest Control Rule:

• Type: Empirical
• Management cycle: 4 years
• Data inputs: Offshore trawl CPUE and survey abundance estimates
• Management output: Quota
• Harvest control rule: Rule that increases or decreases quota using a trend in biomass inferred by CPUE and survey abundance estimates
• Other:
  Maximum quota change: 10% increase or 5% decrease per year, unless stock biomass falls too low
  Maximum catch: 160,000 metric tons

Harvest Strategy:

A fully specified harvest strategy that has been tested via MSE. It has been successfully modified every four years to include recent data.

Outcome:

The 2018 assessment showed both hake stocks above the B-based target reference points. While the TAC trend has been downwards since 2014, the harvest strategy is responding properly to ensure the stocks are maintained at BMSY

Management Objectives:

• Maintain female spawning stock biomass above the LRP of 0.4BMSY in 95% of years measured over two sablefish generations (36 years)
• When in the Cautious Zone (i.e., 0.4BMSY<B<0.8BMSY), limit the probability of decline over the next 10 years to very low (5%) at the LRP, increasing linearly to moderate (50%) at the TRP
• Maintain the female spawning biomass above BMSY, or 0.8BMSY when rebuilding from the Cautious Zone, in the year 2052 with 50% probability
• Minimize probability that annual TAC levels are below 1,992 tonnes measured over two Sablefish generations
• Maximize the average annual catch over 10 years, subject to meeting the four objectives above

Reference Points:

• Upper Stock Reference Point: 0.8BMSY
• Limit Reference Point: 0.4BMSY
• Target Reference Point: BMSY or 0.8BMSY (when rebuilding from the Cautious Zone)

Harvest Control Rule:

• Type: Model-based
• Management cycle: Annual
• Data inputs: Stock assessment using a surplus production model
• Management output: Quota
• Harvest Control Rule: A harvest control rule in which the harvest rate on legal-sized sablefish is reduced linearly from UMSY (maximum sustainable yield), when the estimated stock is above 0.6BMSY, to zero when the estimated stock size is less than 0.4BMSY

Harvest Strategy:

A fully specified harvest strategy that has been tested via MSE. Operating models for the MSE continue to be updated, most recently in 2019, to account for new data.

Outcome:

A 2019 update found that sablefish have now recovered to or above 0.8BMSY with 50% probability, so are now outside of the Cautious Zone.

Management Objectives:

Per New Zealand’s Harvest Strategy Standard:

• Achieve the MSY-compatible target or better with at least 50% likelihood
• Limit the risk of breaching the soft limit to no more than 10%
• Limit the risk of breaching the hard limit to no more than 2%

Reference Points:

• Target Reference Point: BMSY or BREF, a historical stock size proxy from when the stock had ”good productivity and was demonstrably safe”; BREF is always ≥ Bmsy
• Soft Limit: 20%SSB0 or 50%BREF
• Hard Limit: 10%SSB0 or 25%BREF

Harvest Control Rule:

• Type: Empirical
• Management cycle: 5 years
• Data inputs: CPUE
• Management output: Quota
• Harvest control rule: There are 7 different rock lobster stocks that have an HCR, and each is slgihtly different. They include step and sliding rules.
• Other:
  Varies by stock, but most set a minimum quota change.

Harvest Strategy:

A fully specified harvest strategy that has been tested via MSE, with each updated intermittently.

Outcome:

All but one of the ten lobster stocks in New Zealand are above the target. The single stock considered overfished is still above both the soft and hard limits, according to a 2018 assessment.

Management Objectives:

• SSB/SSBMSY = 100%, with an acceptable level as low as 85%;
• Variation in annual yield is <10%, with an acceptable level as high as 25%;
• Probability of overfished 0%, with an acceptable level as high as 25%;
• Probability of herring fishery closure between 0-10%.

Reference Points:

Upper biomass parameter (overfished threshold): 50%SSBMSY
Lower biomass parameter (closes fishery): 10%SSBMSY
Maximum fishing mortality: 80%FMSY

Harvest Control Rule:

Type: Model-based
Management cycle: 3 years, but quota may be different each year
Data inputs: Recruitment estimates derived from 1995 VPA, mean weights at age, surplus production model
Management output: Quota
Harvest control rule: When biomass is greater than 50% of SSB/SSBMSY, the maximum
fishing mortality allowed is 80% of FMSY, so 20% of FMSY is left for herring predators. As biomass declines further, fishing mortality declines linearly, and if biomass falls below 10% of SSB/SSBMSY, the fishery closes.

Harvest Strategy:

N/A

Outcome:

The MSE-tested HCR was implemented for the first time in 2019.

Management Objectives:

WCPFC Interim Management Objective:

• Maintain the biomass, with reasonable variability, around its current level in order to allow recent exploitation levels to continue and with a low risk of breaching the limit reference point

MSE Candidate Mangagement Objectives:

• Maintain spawning biomass above the limit reference point
• Maintain depletion of total biomass around historical average depletion
• Maintain catches by fishery above average historical catch
• Change in total allowable catch between years should be relatively gradual
• Maintain fishing intensity (F) at the target value with reasonable variability

Reference Points:

WCPFC:
Limit Reference Point: 20%SSBcurrent F=0
Target Reference Point: To be determined based upon socioeconomic factors

Candidate Harvest Control Rules:

MSE evaluating numerous sliding, model-based harvest control rules that decrease F from Ftarget once the spawning stock biomass drops below SSBthreshold toward SSBlimit. The fishery is closed at SSBlimit.

• Sets total allowable catch or total allowable effort
• Ftarget range: F40-F50
• SSBthreshold range: 14%-30%B0
• SSBlimit range: 7.7%-20%B0

Candidate Harvest Strategies:

N/A

Progress Update & Workplan:

Final MSE results presented in 2021.

Management Objectives:

WCPFC Interim Management Objective:

• Support thriving Pacific bluefin tuna fisheries across the Pacific Ocean while recognizing that the management objectives of the WCPFC are to maintain or restore the stock at levels capable of producing maximum sustainable yield
• Maintain an equitable balance of fishing privileges among countries
• Seek cooperation with IATTC to find an equitable balance between the fisheries in the western and central Pacific Ocean (WCPO) and those in the eastern Pacific Ocean (EPO).

Reference Points:

• Initial Rebuilding Target: historical median biomass (equivalent to 6.4%SSB0) by 2024
• Second Rebuilding Target: 20% SSBF=0 by 2034
• Candidate Limit Reference Points: 5%SSBF=0, 7.7%SSBF=0, 15%SSBF=0, 20%SSBF=0
• Candidate Threshold Reference Points: 15%SSBF=0, 20%SSBF=0, 25%SSBF=0
• Candidate Target Reference Points: 10%FSPR, 15%FSPR, 20%FSPR, 30%FSPR, 40%FSPR
  Candidate Fmin: 5%Ftarget, 10%Ftarget

Candidate Harvest Control Rules:

Model-based, sliding HCRs are being explored in the initial MSE work

Candidate Harvest Strategies:

N/A

Progress Update & Workplan:

Terms of reference for the MSE were agreed in 2019.

Management Objectives:

Tuning Objectives (for MSE purposes):

• Pr(B(2029)>=B(MSY) ) = 0.5 (SB in 2029 exceeds SBMSY in exactly 50% of the simulations)
• Pr(B(2034)>=B(MSY) ) = 0.6 (SB in 2034 exceeds SBMSY in exactly 50% of the simulations)

Reference Points:

• Interim Limit Reference Point: 40% BMSY and 140% FMSY
• Interim Target Reference Point: BMSY and FMSY

Candidate Harvest Control Rules:

MSE evaluating model-based HCRs with these candidate constraints:

• Total Allowable Catch (TAC) to be set every 3 years (and held constant between settings)
• A maximum of 15% change to the TAC (increase or decrease) relative to the previous TAC

Candidate Harvest Strategies:

Australia has proposed terms for a comprehensive harvest strategy

Progress Update & Workplan:

Evaluation of candidate harvest strategies underway via MSE. Reference set of operating models were revised in 2021 due to concerns about uncertainty in the stock assessment on which the operating models are based, strengthening the MSE.

Management Objectives:

Tuning Objectives (for MSE purposes):

• Pr(mean(SB(2019:2038)>=SB(MSY)) = 0.5. Average SB over the period 2019-2038 exceeds SBMSY in exactly 50% of the simulations)
• Pr(Kobe green zone 2019:2038) = 0.5. The stock status is in the Kobe green quadrant over the period 2019-2038 exactly 50% of the time (averaged over all simulations)
• Pr(Kobe green zone 2019:2038) = 0.6. The stock status is in the Kobe green quadrant over the period 2019-2038 exactly 60% of the time (averaged over all simulations)
• Pr(Kobe green zone 2019:2038) = 0.7. The stock status is in the Kobe green quadrant over the period 2019-2038 exactly 70% of the time (averaged over all simulations)

Reference Points:

Interim Limit Reference Point: 40% BMSY and 140% FMSY
Interim Target Reference Point: BMSY and FMSY

Candidate Harvest Control Rules:

MSE evaluating HCRs with these candidate constraints:

• Total Allowable Catch (TAC) to be set every 3 years (and held constant between settings)
• A maximum of 15% change to the TAC (increase or decrease) relative to the previous TAC

Candidate Harvest Strategies:

Both model-based and empirical, CPUE-based harvest strategies are being tested.

Progress Update & Workplan:

Evaluation of candidate harvest strategies underway via MSE. The results of the 2019 assessment fall outside of the range considered by the MSE so the operating models are being reconditioned.

Management Objectives:

Tuning Objectives (for MSE purposes):

• Pr(Kobe green zone 2030:2034) = 0.5. The stock status is in the Kobe green quadrant over the period 2030:2034 exactly 50% of the time (averaged over all simulations)
• Pr(Kobe green zone 2030:2034) = 0.6. The stock status is in the Kobe green quadrant over the period 2030:2034 exactly 60% of the time (averaged over all simulations)
• Pr(Kobe green zone 2030:2034) = 0.7. The stock status is in the Kobe green quadrant over the period 2030:2034 exactly 70% of the time (averaged over all simulations)

Reference Points:

• Interim Limit Reference Point: 40% BMSY and 140% FMSY
• Interim Target Reference Point: BMSY and FMSY

Candidate Harvest Control Rules:

MSE evaluating HCRs with these candidate constraints:

• TAC setting every 3 years
• 15% TAC change limits
• 3 year lag between data and TAC implementation

Candidate Harvest Strategies:

Both model-based and empirical, CPUE-based harvest strategies are being tested.

Progress Update & Workplan:

Evaluation of candidate harvest strategies underway via MSE.

Management Objectives:

Tuning Objectives (for MSE purposes):

• Pr(Kobe green zone 2030:2034) = 0.6. The stock status is in the Kobe green quadrant over the period 2030-2034 exactly 60% of the time (averaged over all simulations)
• Pr(Kobe green zone 2030:2034) = 0.7. The stock status is in the Kobe green quadrant over the period 2030-2034 exactly 70% of the time (averaged over all simulations)

Reference Points:

Interim Limit Reference Point: 50% BMSY and 130% FMSY
Interim Target Reference Point: BMSY and FMSY

Candidate Harvest Control Rules:

MSE evaluating model-based HCRs with these candidate constraints:

• Total Allowable Catch (TAC) to be set every 3 years (and held constant between settings)
• A maximum of 15% change to the TAC (increase or decrease) relative to the previous TAC

Candidate Harvest Strategies:

N/A

Progress Update & Workplan:

Evaluation of candidate harvest strategies underway via MSE. An external review of the MSE will be conducted in 2022 before adoption in 2023.

Management Objectives:

Conceptual Management Objectives:

• Greater than [___]% probability of occurring in the green quadrant of the Kobe matrix
• Less than [___]% probability of the stock falling below BLIM
• Maximize overall catch levels
• Any increase or decrease in TAC between management periods should be less than [___]%.

Reference Points:

• Interim Limit Reference Point: 0.4BMSY
• Interim Target Reference Point: BMSY based on convention objective

Candidate Harvest Control Rules:

Using MSE to evaluate both constant and threshold model-based harvest control rules.

Candidate Harvest Strategies:

Using MSE to evaluate both constant and threshold model-based harvest strategies.

Progress Update & Workplan:

MSE process began in 2018, currently developing MSE framework and operating models

• 2021-2022: Adopt reference set of OMs, test candidate harvest strategies
• 2023: Finalize MSE and operational management objectives, adopt final harvest strategy

Management Objectives:

Conceptual Management Objectives:

• Greater than [___]% probability of occurring in the green quadrant of the Kobe matrix
• Less than [___]% probability of the stock falling below BLIM
• Maximize overall catch levels
• Any increase or decrease in TAC between management periods should be less than [___]%.

Reference Points:

Interim Target Reference Point: B0.1 and F0.1

Candidate Harvest Control Rules:

Using MSE to evaluate several empirical HCRs

Candidate Harvest Strategies:

Using MSE to evaluate several empirical harvest strategies

Progress Update & Workplan:

MSE process began in 2014; Currently finalizing MSE framework and evaluating candidate harvest strategies

• 2021: Adopt reference set of OMs, test candidate harvest strategies
• 2022: Finalize MSE and operational management objectives, adopt final harvest strategy

Management Objectives:

Interim Objective:

• The spawning biomass of skipjack tuna is to be maintained on average at a level consistent with the interim target reference point of 50% of the spawning biomass in the absence of fishing.

Draft performance indicators:

• Maintain SKJ, YFT, BET biomass at or above levels that provide fishery sustainability throughout their range
• Maximise economic yield from the fishery (average expected catch)
• Maintain acceptable CPUE
• Catch stability
• Stability and continuity of market supply (effort variation relative to a reference period)
• Stability and continuity of market supply (probability of and deviation from SB/SBF=0 >50%)

Reference Points:

• Interim Limit Reference Point: 20%SBrecent,F=0
• Interim Target Reference Point: 50%SBF=0

Candidate Harvest Control Rules:

Using MSE to evaluate both constant and threshold model-based harvest control rules.

Candidate Harvest Strategies:

Using MSE to evaluate several model-based harvest strategies; HS must have <20% chance of breaching the limit reference point

Progress Update & Workplan:

Evaluation of candidate harvest strategies underway via MSE

• 2020-21: Refine and further develop MSE and candidate harvest strategies
• 2022: Adopt final harvest strategy

Management Objectives:

Interim Objective:

• Achieve an 8% increase in catch per unit of effort (CPUE) for the southern longline fishery as compared to 2013 levels

Draft performance indicators:

• Maintain biomass at or above levels that provide fishery sustainability throughout their range
• Maximise economic yield from the fishery (average expected catch)
• Maintain acceptable CPUE
• Catch stability

Reference Points:

• Interim Limit Reference Point: 20%SBF=0 and FX%SPR, with X TBD
• Interim Target Reference Point: 56% SBF=0

Candidate Harvest Control Rules:

Using MSE to evaluate empirical harvest control rules using CPUE data.

Candidate Harvest Strategies:

Using MSE to evaluate several empirical harvest strategies; HS must have <20% chance of breaching the limit reference point

Progress Update & Workplan:

Evaluation of candidate harvest strategies underway via MSE

• 2020-22: Refine and further develop MSE and candidate harvest strategies
• 2023: Adopt final harvest strategy

Management Objectives:

In development and not officially adopted, but often assumed to be BMSY based on Article VII(1)c of the Antigua Convention

Reference Points:

Reference points being developed as part of current MSE process.

• Interim Limit Reference Point: F0.5R0 and SSB0.5R0, where steepness = 0.75 (this is equivalent to 8%SSB0)
• Interim Target Reference Point: FMSY, SSBMSY

Candidate Harvest Control Rules:

Candidate model-based HCRs to be developed as part of current MSE process.
Interim HCR developed without MSE testing:

• F should not exceed FMSY
• If >10% chance that F>Flimit, reduce F to ≤FMSY with a 50% probability and a <10% chance of F>Flimit
• If >10% chance that SSB<SSBlimit, take action to get SSB≥SSBMSY with a 50% probability and a <10% chance of SSB<SSBlimit within 2 generations or 5 years, whichever is greater

Candidate Harvest Strategies:

N/A

Progress Update & Workplan:

• 2020-23: MSE framework development and refinement; testing of candidate harvest strategies
• 2024: Finalize MSE; adopt HCR/HS

Management Objectives:

Candidate Objectives:

• Maintain Pacific halibut, on average, at a target (fixed or dynamic) female spawning biomass equal to the stock size required to produce maximum net economic returns on a spatial and temporal scale relevant to the fishery
• Maintain Pacific halibut, above a female spawning biomass limit where the risk to the stock is regarded as unacceptable (SBLIM), at least 90% of the time

Reference Points:

• Target Reference Point: 45% SSB0 and 120%SSBMSY
• Interim Trigger Reference Point: 30% SSB0
• Interim Limit Reference Point: 20% SSB0 and 50%SSBMSY

Harvest Control Rule:

Interim harvest control rule:

• The harvest control rules relies on the spawning potential ratio (SPR) of 46% (FSPR=46%). The SPR is adjusted to reduce the fishing intensity at low levels of spawning biomass by linearly increasing the SPR (i.e reducing the fishing intensity) if the estimated stock status is less than a trigger, to zero fishing intensity (SPR=100%) when the estimated stock status is less than the limit.

Harvest Strategy:

Using MSE to evaluate several model-based harvest strategies; HS must have >=50% chance of achieveing the target and <=10% chance of breaching the limit

Outcome:

• 2020: Review goals and preliminary results of MSE
• 2021: Final recommendations on scale and distribution

Management Objectives:

The objective is to ensure harvest of the stock within safe biological limits

Reference Points:

• Target Reference Point: FMSY (0.125F)
• Limit Reference Point: Flim and Blim (or proxies)

Candidate Harvest Control Rules:

An HCR is being explored that sets a TAC when biomass is above/below biological reference points (Btrigger, Blim, Bpa, etc.)

Noted Constraints:

• The TAC should not be more than 20% less or 25% more than the TAC of the preceding year

Candidate Harvest Strategies:

Using MSE to evaluate candidate harvest strategies

Progress Update & Workplan:

Different harvest control rules will continue to be evaluated by NEAFC in collaboration with ICES, with an HCR hopefully adopted by 2022/2023

Management Objectives:

N/A

Reference Points:

• Target Reference Point: FMSY (0.32F)
• Limit Reference Point: Flim and Blim (or proxies)

Candidate Harvest Control Rules:

An HCR is being explored that sets a TAC when biomass is above/below biological reference points (Btrigger, Blim, Bpa, etc.)

Noted Constraints:

• The TAC should not be more than ±20% of the preceding year’s TAC

Candidate Harvest Strategies:

Using MSE to evaluate candidate harvest strategies

Progress Update & Workplan:

Different harvest control rules will continue to be evaluated by NEAFC in collaboration with ICES, with an HCR hopefully adopted by 2022/2024