Marine Research Findings of the VECTORS Project

This website provides access to the research results of the VECTORS project, which can be used to support marine management decisions, policies and governance as well as future research and investment. VECTORS was a large scale project that brought together more than 200 expert researchers from 16 different countries. It examined the significant changes taking place in European seas, their causes, and the impacts they will have on society.

Unravelling the Gordian knot! Key processes impacting overwintering larval survival and growth

North Sea herring is one of the best studies and surveyed fish population in the North Sea with detailed times series of larval abundance, spawning location, juvenile abundance and stock assessment. Despite this detailed knowledge there is still a gap in understanding especially the early life stages and the environmental drivers regulating it. Recently there has been a series of years with poor recruitment despite low fishing pressure on juveniles and adults and a high spawning stock population. Understanding the factors acting on especially the larval stages requires linking the relevant factors that steer larval survival which are larval transport, feeding and predation pressure.

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Mean size of herring larvae decreased since the 1980s. Prey concentration interacting with temperature led to an increase in Downs recruitment and partly explains recruitment variability in the remaining herring subcomponents. Despite a wealth of herring data key information able to explain recruitment variability are still lacking.

A herring larvae IBM that includes physiology, feeding, foraging, assumptions on mortaity and behaviour was linked to a hydrodynamic model to examine recruitment failure of autumn and winter spawned herring in the North Sea. The model was tightly linked to field observations on herring larvae and juveniles as well as zooplankton (prey) concentrations. With this setup we were able to partly explain spatial connectivity and growth and survival of the early live stages. Herring larvae and juveniles north of 56° mainly originate from Orkney Shetland, south of 51° from the Downs, in the German Bight from the Banks and in the central North Sea from the Buchan spawning ground. The increase of larvae from the Downs area might be an explanation why observed larval sizes in the field decreased recently, however as this shift in length was observed for all spawning components a change in prey quality/quantity is more likely which was supported by the model results. To finally determine the effect of prey on herring recruitment more detailed information on the winter zooplankton composition and size distribution is required. The study indicated that although for herring a wealth of data is available to understand a complex system with interacting factors of temperature, drift, behaviour, prey and predation changes even more or different data series are required.

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Lead Author:

Marc Hufnagl
(marc.hufnaglnospam@uni-hamburg.de)
University of Hamburg (UHAM)
Date of research: November 2014

Related articles:

The drivers of a common sole population 

Cod, recruitment, temperature and zooplankton

Connectivity: plaice spawning and nursery areas 

Impact of environmental changes on North Sea herring

Baltic cod recruitment and predation

Changes in the upper trophic level: impact on fish

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 266445
© Vectors 2015. Coordinated by Plymouth Marine Laboratory.