Working Group 2 on North Sea Cod and Plaice Egg Surveys in the North Sea



WGEGGS2WGEGGS2TrueMatthias KloppmannEOSG12/3/2012 2:05:00 PMmatthias.kloppmann@thuenen.de649Working Group 2 on North Sea Cod and Plaice Egg Surveys in the North Sea

The Working Group 2 on North Sea Cod and Plaice Egg Surveys in the North Sea (WGEGGS2) carries out surveys to  supply data on winter spawning North Sea fish, including cod and plaice.
​​​​​​​​​​​​​​​​​​​​​​​​​​​The first North Sea cod and plaice egg surveys were conducted in 2004 and 2009. Since 2012, the survey is carried out annually alongside the MIK herring larvae sampling during the first quarter International Bottom Trawl Survey.

The early surveys were conducted with Gulf III or VII plankton samplers, Bongo nets or CUFES. Since 2012, sampling is done with 20 cm ring nets, called MIKeyM nets, which are attached to the MIK net, which is used during the IBTS for catching large herring larvae. Sampling is carried out sampling the water column down to a maximum depth of 100 m or 5 m above the seafloor in shallower waters. The mesh size of the MIKeyM sampling equipment is 335 µm. Flowmeters are used to measure the amount of water filtered during sampling.

The database contains the haul information data, position, time, duration, water volume, depth, temperature and salinity. Eggs and larvae in the samples are sorted. All eggs > 1 mm are measured and identified to species level where possible. Eggs < 1 mm are counted, measured and identified as well. Due to a large overlap in the size of certain species of gadoids such as cod, identification by eye is impossible. For these, a genetic analysis has to be used to identify to the species. All eggs which are measured and identified are also staged following the stage descriptions in the manual. Larvae in the samples are identified to species, measured, and development stage assigned.​
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Related Publications:

Fox, C. J., Taylor, M., Dickey-Collas, M., Fossum, P., Kraus, G., Rohlf, N., Munk, P., et al. 2008. Mapping the spawning grounds of North Sea cod (Gadus morhua) by direct and indirect means. Proceedings of the Royal Society B: Biological Sciences, 275: 1543–1548.

Taylor, N., Fox, C. J., Bolle, L., Dickey-Collas, M., Fossum, P., Kraus, G., Munk, P., et al. 2007. Results of the spring 2004 North Sea ichthyoplankton surveys. The distribution of fish eggs and larvae from the international ichthyoplankton survey. 60 pp.

Munk, P., Fox, C. J., Bolle, L. J., Damme, C. J. G. v., Fossum, P., and Kraus, G. 2009. Spawning of North Sea fishes linked to hydrographic features. Fisheries Oceanography, 18: 458–469.

Damme, C. J. G. v., Bolle, L. J., Fox, C. J., Fossum, P., Kraus, G., Munk, P., Rohlf, N., et al. 2009. A reanalysis of North Sea plaice spawning-stock biomass using the annual egg production method. ICES J. Mar. Sci., 66: 1999–2011.

Nash, R. D. M., Wright, P. J., Matejusova, I., Dimitrov, S. P., O'Sullivan, M., Augley, J., and Höffle, H. 2012. Spawning location of Norway pout (Trisopterus esmarkii Nilsson) in the North Sea. ICES Journal of Marine Science: Journal du Conseil, 69: 1338–1346.


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