Spatial modelling of blue whiting population dynamics in the north-east Atlantic

For this thesis project, a spatial model of the population dynamics of blue whiting, Micromesistius poutassou, in the North-East Atlantic has been developed. Since stock biomass fluctuations recorded in the past decades have raised concerns for the stock sustainability, improving our understanding of blue whiting population dynamics has become necessary for developing better fishery management strategies. Observations suggest that changes in recruitment and/or population distributions might be explained by environmental factors and spatial processes. However, it is unclear how these drivers directly affect the population, and how they might be used to predict future changes. Here I propose a spatial population model, which is essentially driven by bio-geophysical factors, and which describes the entire life cycle of blue whiting, allowing us to study the importance of different drivers and to produce long-term predictions of the population in a context of fishery and climate change.The model includes two components, one focusing on the population and individual growth, the other on behaviours and movements. For the first time, environmental gradients are explicitly used as drivers to movement direction of long-distance migratory fish, and individual growth depends on the spatial distribution of a food variable representative of the fish diet. I found that successful feeding migrations are driven by currents, food and temperature, while successful spawning migrations are mainly affected by local values and gradients of temperature and salinity. Simulations revealed emergent model properties which agree with the empirical story: (1) feeding migration pathways varied with both climate and the initial position of individuals on spawning grounds, (2) spawning location of an individual was influenced by both climate and the location of its feeding area, (3) migration timing was important for both spawning and feeding success, (4) juvenile and adult recruitment took place in areas formerly identified as nursery habitats, and (5) juvenile recruitment depended on spawning distribution and larval drift. In the model, the population response to varying fishing pressure was significantly affected by both recruitment and individual growth. I suggest this model as a tool to test and study different fishing behaviours or fishery management strategies over the long term and in a climate change context.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral-pg

Grantor dc:publisher.institution

University of Strathclyde

Year dc:date.issued

2022

Author dc:creator

• Dolmaire, Emma

Advisors dc:contributor.advisor

• Speirs, Douglas
• Heath, Mike

DOI

10.48730/dpx9-2d45

Identifier

T16407

Author Identifier

201791189

OAI identifier oai:identifier

oai:strathclyde:02870w33v