Increased and updated knowledge of reproductive strategies of fish is crucial to optimize the temporal and spatial planning for conducting seismic surveys; in order to reduce its potential negative ecosystems impacts. The overarching goal of this study is to investigate the current spawning times and locations for the North Sea fish stocks. Molecular barcode and traditional visual taxonomic analyses were performed on eggs and larvae, systematically collected with plankton nets along a south to north axis in the North Sea. This report describes the establishments of methodology employed and preliminary results based on samples collected during August 2017 to September 2018. In total, 129 samples have been analysed from which 22 different fish taxa are identified. Based on historic data and published literature, our results agree with the expected number of the most prevalent fish species breeding in the North Sea. Both the taxonomic and molecular methods used, demonstrate similar results in the identification of taxonomic groups. The results further demonstrate that the molecular taxonomic approach is more appropriate for identification to species levels for some taxonomic groups, whilst the identification of egg and larvae developmental stages can only be performed using the visual taxonomic method. The two techniques complement each other to provide a detailed description of the annual fish spawning cycle for the main North Sea species. There are already emerging patterns evident in the results on the timing for breeding in some species at certain areas. However, improvements of the sampling methodology are still required, and an increased number of samples collected systematically over an extended time-period must be accomplished in order to provide appropriate data as basis for advice in timing of seismic surveys
