Common guidelines to help maturing staging of fish
An international team of scientists led by the National Institute of Aquatic Resources at the Technical University of Denmark (DTU Aqua) has put the spotlight on the maturing staging of fish and what we can do to ensure standardisation. The creation and implementation of common guidelines, specifically for sprat and herring, would result in standardised guidelines for maturity determination across the globe and would help make fish stock assessments significantly more accurate. Biologists the world over, working both in laboratories and on research vessels, assess the development of the ovaries and testicles of fish by determining the sex and maturity of these marine creatures. Experts call this maturity staging; it is used to describe where the fish are in their reproductive cycle. This gives them the information they need to determine whether sampled fish are sexually mature and ready to reproduce. A quick look at the sex organs in the body cavity of a fish lets biologists know both its sex and maturity. Maturity staging is also used to calculate approximately the size of the spawning fraction of a fish stock and to provide advice on fishing quotas. The DTU Aqua group points out that scientists can more or less figure out the size of the spawning stock of the species in a specific area when samples are taken of a fish stock in that area. This information helps biologists make an educated guess about the size of the next generation of fish as part of the stock assessment. According to the researchers, reliable assessments of the development of fish stocks can be made possible when research institutes, wherever the location, perform maturity staging in a standardised manner. With this in mind, DTU Aqua researchers invited 40 biologists from 15 European countries to take part in a workshop, 'Maturity Staging of Herring and Sprat', to agree on common guidelines for maturity staging of the two fish. Participants sampled and preserved ovaries and testicles from herring and sprat; the information was used to make a histological analysis on each of the sampled tissues. The researchers used the histological analysis to make an accurate determination of the maturity stage. With this information in hand, the workshop participants succeeded in generating standardised maturity scales for herring and sprat with descriptions and images of the different maturity stages. 'The International Council for the Exploration of the Sea (ICES) took the initiative to the workshop in order to improve consistency in maturity staging of herring and sprat among countries,' explains Jonna Tomkiewicz, a senior scientist at DTU Aqua. The workshop received financial support from the EU's Data Collection Framework Regulation. Maturity staging is a complex task. Dr Tomkiewicz explains: 'It can be difficult to determine the maturity stage of a fish ... in particular, if the fish are relatively undeveloped. Therefore, biologists can disagree on the maturity of the same fish. Biologists from one institute will say that the fish is sexually mature and would have spawned, while biologists from another institute will say that it is immature.' In conclusion, Dr Tomkiewicz says: 'The agreement among biologists from 15 countries, who worked together to establish reliable criteria for the maturity stages, will help to improve the consistency in future maturity data across borders. The participants were very engaged and the workshop was a good experience. I hope that common guidelines for maturity staging of sprat and herring will help increase data quality and thereby enhance stock assessments.'For more information, please visit: DTU Aqua:http://www.aqua.dtu.dk/English.aspx
Countries
Denmark