Enhancing data-limited assessments with random effects: A case study on Korea chub mackerel (Scomber japonicus)

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Main Authors: Kim, Kyuhan, Sibanda, Nokuthaba, Arnold, Richard, A'mar, Teresa
Format: Preprint
Published: 2023
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_version_ 1866913397665169408
author Kim, Kyuhan
Sibanda, Nokuthaba
Arnold, Richard
A'mar, Teresa
author_facet Kim, Kyuhan
Sibanda, Nokuthaba
Arnold, Richard
A'mar, Teresa
contents In a state-space framework, temporal variations in fishery-dependent processes can be modeled as random effects. This modeling flexibility makes state-space models (SSMs) powerful tools for data-limited assessments. Though SSMs enable the model-based inference of the unobserved processes, their flexibility can lead to overfitting and non-identifiability issues. To address these challenges, we developed a suite of state-space length-based age-structured models and applied them to the Korean chub mackerel (Scomber japonicus) stock. Our research demonstrated that incorporating temporal variations in fishery-dependent processes can rectify model mis-specification but may compromise robustness, which can be diagnosed through a series of model checking processes. To tackle non-identifiability, we used a non-degenerate estimator, implementing a gamma distribution as a penalty for the standard deviation parameters of observation errors. This penalty function enabled the simultaneous estimation of both process and observation error variances with minimal bias, a notably challenging task in SSMs. These results highlight the importance of model checking and the effectiveness of the penalized approach in estimating SSMs. Additionally, we discussed novel assessment outcomes for the mackerel stock.
format Preprint
id arxiv_https___arxiv_org_abs_2312_01646
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Enhancing data-limited assessments with random effects: A case study on Korea chub mackerel (Scomber japonicus)
Kim, Kyuhan
Sibanda, Nokuthaba
Arnold, Richard
A'mar, Teresa
Populations and Evolution
Quantitative Methods
In a state-space framework, temporal variations in fishery-dependent processes can be modeled as random effects. This modeling flexibility makes state-space models (SSMs) powerful tools for data-limited assessments. Though SSMs enable the model-based inference of the unobserved processes, their flexibility can lead to overfitting and non-identifiability issues. To address these challenges, we developed a suite of state-space length-based age-structured models and applied them to the Korean chub mackerel (Scomber japonicus) stock. Our research demonstrated that incorporating temporal variations in fishery-dependent processes can rectify model mis-specification but may compromise robustness, which can be diagnosed through a series of model checking processes. To tackle non-identifiability, we used a non-degenerate estimator, implementing a gamma distribution as a penalty for the standard deviation parameters of observation errors. This penalty function enabled the simultaneous estimation of both process and observation error variances with minimal bias, a notably challenging task in SSMs. These results highlight the importance of model checking and the effectiveness of the penalized approach in estimating SSMs. Additionally, we discussed novel assessment outcomes for the mackerel stock.
title Enhancing data-limited assessments with random effects: A case study on Korea chub mackerel (Scomber japonicus)
topic Populations and Evolution
Quantitative Methods
url https://arxiv.org/abs/2312.01646