PhD defence about fish stock recruitment and marine ecological prediction

Understanding and modelling the production of marine fish is essential for sustainable management of exploited fish populations. However, marine fish are notoriously difficult to predict, especially where recruitment is highly variable on a year-to-year basis. 

Recruitment is primarily modelled as relationship between the spawning stock biomass and number of recruits. However, early life-stages and spawners are both known to be vulnerable to environmental impacts. Even small variations in the physical environment can cause huge effects on a  cohort's survival. Christian Kiær, DTU Aqua, argues in his PhD thesis “Fish stock recruitment and marine ecological prediction” that incorporating environmental driven forecasts in stock assessment models can potentially change the management standards, and increase sustainability.

Christian Kiær presents a framework for modelling recruitment based on novel methods commonly used in other disciplines, such as atmospheric science, meteorology, and machine learning.

He has applied this method on e.g. North Sea sandeel—an ecologically and economically important species, which currently sustains a large fishery. Here, the framework outperforms conventional methods in two out of four selected stocks, by including environmentally information. Additionally, he quantifies potential economic value and shows a large potential for industrial use of recruitment models.

Christian Kiær has also examined the explanatory potential of the relationship between the spawning stock biomass and recruits in 103 stocks in the North Atlantic and North Pacific. In most stocks, environmental information and low-frequency variability explained more of the observed recruitment variability compared to spawning stock biomass. Furthermore, in stocks with habitats close to the thermal threshold of the species, temperature was observed as the primary model ensemble driver.

About the PhD defence

Christian Kiær will defend his PhD thesis "Fish stock recruitment and marine ecological prediction" on Monday 21 November 2022, 13:00 on Zoom (find link below) and at DTU, Asmussens Allé, 2800 Kgs. Lyngby, building 308, auditorium 11.

Supervisors

• Principal supervisor: Senior Researcher Stefan Neuenfeldt, DTU Aqua
• Co-supervisor: Climate Scientist Mark Payne, DMI

Examiners

• Senior Researcher Martin Lindegren, DTU Aqua (chair)
• Principal Scientist Richard D.M. Nash, Centre for Environment, Fisheries and Aquaculture Science (Cefas), UK
• Senior Scientist Niels Hintzen, Wageningen University and Research, The Netherlands

Chairperson at defence

• Professor Brian MacKenzie, DTU Aqua

Learn more

A copy of the thesis is available by e-mail on request. Please contact Karin Stubgaard, stub@aqua.dtu.dk