Advice on configuring ontogenetic migration in SS3

[Paola Castellanos]

Dear SS3 developers,

We are developing an SS3 assessment model for Northeast Atlantic black scabbardfish (Aphanopus carbo) and would appreciate your advice on how best to represent its ontogenetic migration within the SS3 spatial framework.

We have experience developing single-area SS3 assessments, but this is our first attempt to implement a spatial model.

Current biological knowledge suggests the following life cycle: spawning occurs around Madeira, larvae and/or eggs progressively migrate northwards and recruitment occurs W of the British Isles where juveniles remain some years to grow, then move to the Portuguese mainland coast where they remain some years to grow, and finally immature adults move to Madeira to mature and spawn.

Our available data include:

• Commercial catches from three fleets (Madeira longline, Mainland Portugal longline, and French trawl).
• Length-composition data for all fleets.
• Growth and maturity information.
• No fishery age-composition data.

We are considering either a single-area model or a spatial model with multiple areas representing the main stages of the life cycle. Our main question, however, is not whether to use a spatial model, but how to configure the migration process in SS3.

Since SS3 implements movement by age, we would appreciate your advice on the following:

• What would be the most appropriate way to represent this type of ontogenetic migration in SS3?
• How should the age-specific movement chronology be configured to represent a progressive migration throughout the life cycle?
• Are there any published SS3 assessments or example models with similar ontogenetic migration patterns that could serve as useful references?

Our goal is to develop a biologically realistic model while keeping the configuration as simple as possible.

Thank you very much for your time and for the continued development of SS3.

Best regards,

 

[Richard Methot - NOAA Federal]

Hello Paola,

I'm glad you are considering use of SS3 for modeling the dynamics of this fish stock.  Here are some responses to your questions.

• What would be the most appropriate way to represent this type of ontogenetic migration in SS3?

• SS3 allows you to configure migration as the age-specific fraction of the stock in an area that moves to each of the other areas.  It can be set up to allow the progressive movement that you describe.  The age-specificity allows for a movement rate for young fish, a movement rate for old fish, and a linear interpolation of the rate for fish of intermediate age.  This is described in section 8.4.3 of the SS3-manual.  
• In general, SS3 can estimate movement rates when it has size or age composition data from the progressive areas.  But, you generally need to assume asymptotic selectivity in order for the differences in length composition to inform movement rates.  I attach a draft presentation from an ICES training that should be helpful.

• How should the age-specific movement chronology be configured to represent a progressive migration throughout the life cycle?

• I presume the French trawl fishery is catching fish as they move from the British Isles towards Portugal.
• The dynamic you should try to model is the degree to which the French trawl and Portuguese longline reduce the abundance of fish moving into the Madeira region.  I think you could do this with just 2 areas.  Area 1 being Madeira where most spawning and one fishery occurs.  Area 2 being not-Madeira where recruitment occurs and two fisheries operate.   In SS3, the spawning biomass is summed over all areas, so any mature fish in area 2 would be included.  The recruitment process is not explicitly spatial with movement.  In SS3, recruitment is simply the result of the total spawners and assigned to occur only in area 2.

• Are there any published SS3 assessments or example models with similar ontogenetic migration patterns that could serve as useful references?

• A few papers resulted from an international spatial modeling effort.  SS3 was included in the model testing.
• Aaron M. Berger, Daniel R. Goethel, Simon D. Hoyle, Patrick Lynch, Caren Barceló, Alistar Dunn, Brian J. Langseth, Carolina Minte-Vera, Jemery Day, Haikun Xu, Francisco Izquierdo, Dan Fu, Nicholas D. Ducharme-Barth, Mathew Vincent, Arnaud Grüss, Jonathan J. Deroba, Giancarlo M. Correa, Jeremy McKenzie, Will Butler, Jie Cao, Craig Marsh, Teresa A'mar, Valerio Bartolino, Massimiliano Cardinale, Claudio Castillo-Jordan, Bjarki Þór Elvarsson, John Hampton, Andrea Havron, Pamela Mace, Arni Magnusson, Mark Maunder, Richard Methot, Sophie Mormede, Maria Grazia Pennino, Alfonso Perez-Rodriguez, Marta Cousido-Rocha, Thomas Teears, Agurtzane Urtizberea.  ‘Building the (im)perfect beast’: Strategies for identifying appropriate spatial stock assessment model complexity from an international, blinded high-resolution simulation experiment.  Fish and Fisheries.  https://doi.org/10.1111/faf.70048
• Aaron M. Berger, Caren Barceló, Daniel R. Goethel, Simon D. Hoyle, Patrick D. Lynch, Jeremy McKenzie, Alistair Dunn, André E. Punt, Richard D. Methot, John Hampton, Clay E. Porch, Richard McGarvey, James T. Thorson, Z. Teresa A’mar, Jonathan J. Deroba, Bjarki Þór Elvarsson, Steven J. Holmes, Daniel Howell, Brian J. Langseth, Craig Marsh, Mark N. Maunder, Sophie Mormede, Scott Rasmussen. 2024. Synthesizing the spatial functionality of contemporary stock assessment software to identify future needs for next generation assessment platforms. Fisheries Research 275.   ttps://doi.org/10.1016/j.fishres.2024.107008.
  Daniel R. Goethel, Aaron M. Berger, Simon D. Hoyle, Patrick D. Lynch, Caren Barceló, Jonathan Deroba, Nicholas D. Ducharme-Barth, Alistair Dunn, Dan Fu, Francisco Izquierdo, Craig Marsh, Haikun Xu, Giancarlo M. Correa, Brian J. Langseth, Mark N. Maunder, Jeremy McKenzie, Richard D. Methot, Matthew T. Vincent, Teresa A'mar, Massimiliano Cardinale, Marta Cousido-Rocha, Nick Davies, John Hampton, Carolina Minte-Vera, Agurtzane Urtizberea. 2024.  ‘Drivin' with your eyes closed’: Results from an international, blinded simulation experiment to evaluate spatial stock assessments.  Fish and Fisheries.  https://doi.org/10.1111/faf.12819.
  

Richard  D. Methot Jr.

Stock Assessment Research Scientist (ST)

Northwest Fisheries Science Center

NOAA Fisheries | U.S. Department of Commerce

Office: (425) 666-9893

Mobile: (301) 830-2454

www.fisheries.noaa.gov 

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[Mark Maunder]

You might want to look at Hui-Hua's paper.

Lee, H-H., Piner, K.R., Maunder, M.N., Taylor, I.G., Methot Jr., R.D. 2017. Evaluation of alternative modelling approaches to account for spatial effects due to age-based movement. Canadian Journal of Fisheries and Aquatic Sciences, 2017, 74(11): 1832-1844. https://www.nrcresearchpress.com/doi/10.1139/cjfas-2016-0294#.Xpx448hKjD4

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From: 'Richard Methot - NOAA Federal' via SS3 - Forum <ss3-...@googlegroups.com>
Sent: Thursday, July 2, 2026 8:54 AM
To: Paola Castellanos <paola.cas...@gmail.com>
Cc: SS3 - Forum <ss3-...@googlegroups.com>
Subject: Re: [SS3] Advice on configuring ontogenetic migration in SS3

To view this discussion visit https://groups.google.com/d/msgid/ss3-forum/CABLA2QSAS5vM3BS2-mx3D9us39WVjNO2WzO_exzx79j%2B7skjgw%40mail.gmail.com.