Report of the Planning Group for Herring Surveys

Executive Summary1. Terms of Reference According to C. Res. 2005/2G02 the Planning Group forHerring Surveys [PGHERS] (Chair: B. Couperus, Netherlands) will meet inFlødevigen, Norway, from 24–28 January 2006 to:a. combine the 2004 survey data to provide indices of abundance for the populationwithin the area;b. coordinate the timing, area and effort allocation, and methodologies for acousticand larvae surveys for herring and sprat in the North Sea, Divisions VIa and IIIaand Western Baltic in 2005;c. review and update the PGHERS manual for acoustic surveys to address standardizationof all sampling tools and survey gears;d. review the results of an exchange exercise on herring maturity staging, and commenton the implications of the conclusions of the sprat age reading exchange andWorkshop for the Acoustic Surveys;e. evaluate the results of the investigations of survey overlaps between vessels in theNorth Sea acoustic survey;f. to conduct an Echogram Scrutiny Workshop aiming at further harmonisation ofscrutiny procedures.2. Review of larvae surveys in 2004/2005. At the time of writing two of the sevensurveys in the North Sea remained to be carried out in January 2005. Results willbe ready for the Herring Assessment Working Group (HAWG) meeting in March2005.3. Co-ordination of larvae surveys for 2005/2006. In the 2005/2006 period, theNetherlands and Germany will undertake 6 larvae surveys in the North Sea from1 September 2004 to 31 January 2005. The Baltic Sea Fisheries Institute will continuewith the larvae survey in the Greifswalder Bodden area in 2005.4. North Sea acoustic surveys in 2005. Six acoustic surveys were carried out duringlate June and July 2004 covering the North Sea and west of Scotland. Theprovisional total combined estimate of North Sea spawning stock biomass (SSB)is 2.6 million t, a decrease from 3.1 million t in 2003. The survey again showstwo well-above average year classes of herring (1998 and 2000). Growth of the2000 year class seems still to be slower than average. The west of Scotland SSBestimate is 400,000 t (739,000 t in 2003). The surveys are reported individually inAnnex 2.5. Western Baltic acoustic survey in 2004. A joint German-Danish acoustic surveywas carried out with RV “Solea” from 29 September to 18 October in the WesternBaltic. The estimate of Western Baltic spring spawning herring SSB is192,100 t, an increase since 2003 (106,000 t). A full survey report is given inAnnex 3.6. Survey overlap between FRV “Scotia”, FRV “G.O. Sars”. During the 2004surveys two areas were selected for overlap, involving FRV Scotia and FV Enterprisein one area and “Johan Hjort”, “Walther Herwig III” and “Dana” in anotherarea. No significant differences have been found. However, this is not just confirmationof similar performance, but also illustrates the difficulty of obtainingsufficient precision to establish significant differences.7. Manuals for acoustic and herring larvae surveys. The manual for herringacoustic surveys in ICES Divisions III, IV, and VIA has been reviewed and updatedaccording to TOR (c) The new version 3.2 is provided in Annex 4. Therewas no need for an update of the IHLS manual.8. Exchange exercise on herring maturity staging. A selection of digital imageswas prepared from a collection of Dutch, Irish, Norwegian and Scottish pictures,and distributed digitally to all the participating laboratories. The overall CV washigh (16.4%) and it is recommended that the national laboratories put some effortinto improving the confidence in maturity classifications of herring. An exchangeexercise should be carried out every three year, beginning in 2007.