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How reproduction impacts stock size


mackerel eggs (c) Thünen-Institut/Jens Ulleweit
mackerel eggs under a light microscope (© Thünen-Institut/Jens Ulleweit)

Investigation of fish eggs and larvae in terms of species composition and size

Knowledge on the strength of the recruiting year class of a fish stock is of tremendous importance for sustainable mangement. Successful reproduction and foraging of fry are of essential importance for the further development of the stock.

Background and Objective

Based on the triennial Mackerel and Horse Mackerel Egg Survey in West British waters and the annual Herring Larvae Survey in the North Sea, the institute investigates the distribution, species and size composition of eggs and larvae of commercially important pelagic fish species.

plankton fishing gear
A plankton fishing gear is used for catching fish eggs. (© Thünen-Institut/Jens Ulleweit)
an adult mackerel (© Thünen-Institut/Jens Ulleweit)


Catches of ichthyoplankton are conducted during the spawning season of the relevant species. It is of importance to monitor the whole spawning season and the whole spawning area to get full insights of the spawning dynamics. This is only possible in an international framework, where sampling areas and time windows can be shared and co-ordinated.

Preliminary Results

We use the survey results to estimate changes in stock size. We share and process these data in international working groups to assess the stock dynamics.

Links and Downloads

ICES data portal: eggs and larvae surveys


Involved Thünen-Partners


1.2009 - 12.2020

More Information

Projekt type:
Project status: ongoing


hits: 5

  1. Burns F, Damme CJG van, Ulleweit J, Fonn M, Thorsen A, Franco C (2013) 2013 International mackerel and horse mackerel egg survey : preliminary results ; Working Document / Survey Report, ICES WGWIDE 2013. Copenhagen: ICES, 36 p
  2. Tiedemann M, Kloppmann MHF, Ulleweit J, Gröger JP, Hagen W (2013) A spatial analysis of larval fish assemblages in the Celtic Sea off Great Britain (47° to 51° N): implications of bathymetry and ocean warming. Mar Biol Res 10(5):482-493, doi:10.1080/17451000.2013.819983
  3. Ulleweit J, Burns F, Damme CJG van, Fonn M, Kloppmann MHF, Milligan SA, Thorsen A (2010) Survey report: 2010 International mackerel and horse mackerel egg survey : preliminary results. 36 p Working Doc ICES WGWIDE 2010/1
  4. Kloppmann MHF, Ulleweit J, Damme CJG van (2008) Distribution of Snake Pipefish during the 2007 MEGS : working document presented at the Working Group for the Mackerel Egg Survey.
  5. Kloppmann MHF, Ulleweit J (2007) Off-shelf distribution of pelagic snake pipefish, Entelurus aequoreus (Linnaeus, 1758), west of the British Isles. Mar Biol 151(1):271-275, DOI:10.1007/s00227-006-0480-4

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