Assessing spatiotemporal dynamics in HERring POPulation Structure under climate change

For their assessment and management, fish of a given species within a defined geographic region are lumped in a box, also called stock. Per definition, all fish within this pre-defined box will never leave their box. A border between two boxes exists for example at 62° N separating the Norwegian Sea from the North Sea. However, since fish do not have a passport and border controls are not deployed, yet, migratory pelagic fish such as Atlantic herring are crossing this border on their annual migrations. Therefore, HERPOPS will think outside the box! A new genetic method has been recently developed to identify the origin of individual herring. This method demonstrated that herring do migrate between boxes. It also indicated that several herring populations co-exist within a box. This challenges the sustainable harvesting of herring. We will use this new genetic method and thus, will be able to identify herring which have left their box. Furthermore, these “strayers” can be added back to the abundance estimation of their original box. This will improve their assessment and management and secure sustainable harvesting. This new method can also be used to analyze historical data. Herring scales have been collected since 1907 and will be utilized to extract DNA. The genetic results of historical samples will provide unique insights into the dynamics of herring during the last century. During this period several herring stocks had collapsed. Our genetic results will demonstrate if genetic biodiversity has changed after a collapse. HERPOPS will generate knowledge of how climate change and the stock collapse influenced the dynamics of different herring stocks. Furthermore, this newly gained knowledge will be directly implemented in assessment models. Today’s models only work for one box. Our plan is to develop models accounting for migration of herring between boxes. This will allow us to define future management strategies to secure long-term sustainable exploitation.

Basic knowledge of the spatiotemporal occurrence of populations in marine ecosystems of species is essential for their management. While traditional population identification methods have often failed to resolve these issues, genomic methods have revealed clarity in the identification of marine populations, and the underlying mechanisms tunings their distributions. A key player in ecosystems throughout the north-eastern Atlantic having a complex population structure is the commercially important and highly valued Atlantic herring (Clupea harengus). HERPOPS, based on the use of innovative genomic research, including wild populations with up to 100 years of data, will explore the processes influencing population structure in relation to climate change of herring. A recently established genomic method using population-diagnostic single nucleotide polymorphism (SNP) markers will be used to identify the population of origin for individual herring. By applying this genomic method over a large-scale area, both in space and time, this project will obtain completely new and in-depth information about the spatiotemporal distribution of herring populations. Furthermore, HERPOPS will apply environmental DNA (eDNA) analyses to identify small-scale dynamics of spring and autumn spawning herring on a local spawning ground. This will help to answer if spawning type switching is a prevalent trait affecting metapopulation dynamics. HERPOPS aims to take the advantage of the new knowledge to assess the abundance of different populations having a dynamic mixing. Genomic results will be directly implemented by new novel research on assessment models and future management strategies to secure long-term sustainable exploitation while maintaining intraspecific biodiversity. The project outcomes will have a direct impact on the advisory process for several populations inhabiting the different ecosystems.