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North Atlantic Albacore Management Strategy Evaluation

(Thunnus alalunga)

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Overview

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MSE work for northern albacore started in 2013 (Kell et al., 2013) and officially with Rec. 15-04 where management objectives were adopted and the development of a harvest control rule was requested by the Commission. The development of the interim Harvest Control Rule (HCR) at ICCAT was based on simulations conducted using a specifically designed (MSE) framework. The ICCAT Commission adopted an interim harvest control rule for North Atlantic albacore in 2017 (Rec. 17-04), representing the first harvest control rule adopted by ICCAT. The software and code used for the simulations was reviewed in 2018 (Sculley, 2018). In 2021, the Commission adopted a full long-term management procedure, including the Exceptional Circumstances (ECs) protocol for North Atlantic albacore (Rec. 21-04, Annex 2). The Commission has set the TACs since 2017 using the interim HCR and the management procedure for northern Atlantic albacore (Rec. 17-04, 21-04, and 23-05). The SCRS evaluates the existence of ECs every year and ECs have not been invoked since 2022.

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OM Developed
in 2013-2017

Recondition
in 2025

MP Adopted
in 2017/2021

MP since 2017

ECP adopted
in 2021

EC evaluation
No EC since 2021

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History

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The Management Strategy Evaluation (MSE) process for Northern albacore has evolved through a series of ICCAT Recommendations and SCRS initiatives over more than a decade. The process was initiated following concerns about the sustainability of the stock and the need for more robust, precautionary management frameworks. Rec. 09-05 initiated the rebuilding plan for Northern albacore, aiming to restore biomass to levels consistent with Maximum Sustainable Yield (MSY). Rec. 11-04 requested the SCRS to develop a Limit Reference point and Rec. 13-05 called for the SCRS to begin evaluating harvest control rules (HCRs), laying the groundwork for MSE development. In 2015, the SCRS identified Northern Albacore as a priority candidate for the application of MSE, noting the availability of data and scientific interest. Rec. 15-04 stablished the management objectives for the stock and explicitly requested the SCRS to develop HCRs and a dialogue process with the Commission to support the development of a MSE process.

The 2016 stock assessment further motivated this work by confirming the rebuilding trajectory of the stock, while also emphasizing the need for evaluating long-term strategies under uncertainty before any TAC increase. Rec. 16-06 provided the performance metrics that the SCRS used to evaluate alternative HCRs under uncertainty. In 2017, the Commission adopted an interim Harvest Control Rule (Rec. 17-04) and increased the TAC based on it. From 2017 to 2021, an iterative development and peer review of the MSE framework took place under the guidance of the SCRS Albacore Species Group and PA2, that culminated in a formal adoption of a Management Procedure (MP) through Rec. 21-04. Since then, this MP was used to set the TAC every 3 years.

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Contents

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Operating Models

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The Operating Models (OMs) represent a range of plausible dynamics for the Northern Albacore stock. The reference set of 132 OMs includes the main sources of uncertainty identified by the WG in the stock assessments. These include uncertainty in biology (steepness, natural mortality), data weighting (size, cpue, tagging), structure of the time series and fishery dynamics (selectivity and catchability). The outputs of Multifan-CL based stock assessment scenarios, updated with data up to 2020, were used to condition the 132 OMs. The OMs were conditioned using libraries from the FLR-project (www.flr-project.org).

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Management Objectives

Rec. 21-04

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Stock Status

Prob. >= 60% in green quadrant

Safety

Decrease F as soon as possible when B<Bmsy

Yield

Maximize overall catch

Stability

Minimize inter-annual fluctuations in TAC levels

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Candidate Management Procedure

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Only Model-based HCRs were considered, with varying parameters of the hockey-stick HCR as well as alternative stability closures.

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Management Procedure

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The Commission adopted an interim Harvest Control Rule (HCR) in 2017 (Rec. 17-04) and formally adopted a full Management procedure in 2021 (Rec. 21-04).

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The MP shall be applied to set a 3-year constant annual total allowable catch. A production model (with defined inputs and specifications) is applied and the hockey-stick type HCR determines the level of fishing mortality to apply in the next 3-year period, depending on the estimated stock status, with a maximum of 0.8*Fmsy, and decreasing fishing mortality as soon as B is estimated to be below Bmsy. The maximum TAC allowed is 50.000 t, and TAC variations are limited to +25%/-20% if B>Bmsy.

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Exceptional Circumstances

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The Commission adopted the Exceptional Circumstances Protocol in 2021 (Rec.21-04 Annex 2).

The SCRS evaluates, annually, the existence of exceptional circumstances that would preclude the application of the MP.
There have been no Exceptional Circumstances invoked since 2022

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Principles of ECs

a: When there is evidence that the stock is in a state not previously considered to be plausible in the context of the management strategy evaluation (MSE);
b: When there is evidence that the data required to apply the management procedure (MP) are not available or are no longer appropriate; and/or,
c: When there is evidence that total catch is above the TAC set using the MP.

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References

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Materials

Rec/Res

Meetings

SCRS Docs

Others

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Updated: July 7, 2025

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