Report of the Herring Assessment Working Group for the Area South of 62 N (HAWG). 12-21 March 2013 ICES Headquarters, Copenhagen
|Ref.||ICES CM 2013/ACOM:06|
|Sponsor||CIEM / ICES|
|Note||ICES HAWG REPORT 2013 ICES ADVISORY COMMITTEE|
|Abstract||The ICES herring assessment working group (HAWG) met for eight days in March 2013 to assess the state of six herring stocks and four sprat stocks/populations. The working group conducted update assessments for five of the herring stocks. No analytical assessments were carried out for herring in VIaS although available survey and/or fishery data were examined. An assessment was performed for North Sea sprat and explorative assessments were carried out for English Channel sprat and IIIa sprat.
The North Sea autumn spawning herring SSB in 2012 was estimated at 2.35 m tonnes while mean F2-6 in 2012 was estimated at approximately 0.17, which is below the management agreement target F, while mean F0-1 is 0.03, below the agreed ceiling. Year classes since 2002 onwards are estimated to be among the weakest since the late 1970s. ICES considers that the stock is still in a low productivity phase. The Western Baltic spring spawning herring was assessed using new revised data and methods, based on the recent benchmark process. The use of a different assessment model, as well as the revision of the data sources and the addition of new observations, resulted in a new perception of the WBSS stock. In particular, SSB has been revised downward by approximately 20% in 2010-2011, with a consequent significant increase of the F estimate of about 40%. The SSB in 2012 was estimated to be around 87 900 t and has declined substantially in the last three years. Fishing mortality has been estimated at 0.33, and it is now above the revised estimate of Fmsy (0.28). Recruitment has significantly decreased since the late 1990s to values below 2 x 106, and remained at very low levels during the last 8 years. No sign of recovery is found in the estimated 2012 recruitment. The Celtic Sea autumn and winter spawning stock has increased considerably in recent years with the highest estimate in the time series recorded in 2012 (159 776 t), well above the Bpa reference of 61 000 t. Several strong year classes have recruited since 2005. The 2012 SSB of West of Scotland autumn spawning herring has been estimated at approximately 102 000 t (+24% from 2011) with a mean fishing mortality (F3-6) of 0.16 which continues to be below the Ftarget of the management plan (0.25). West of Ireland (Division VIaS and VIIb,c) autumn- and winter/spring-spawning stock cannot be assessed analytically because no tuning data are yet available. The current levels of SSB and F are unknown, however, there are indications that the stock is on a historically low level. F is estimated to have declined considerably in the past three years, concomitant with declining landings . Irish Sea autumn spawning herring assessment showed an increase in SSB, estimated at 21 500 t in 2012, and a continued high recruitment in recent years, with F4-6 =0.25 in 2012.Catches have been relatively stable since the 1980s, and close to TAC levels in recent years. Based on the most recent estimates the stock is being harvested sustainably and below FMSY. North Sea sprat was assessed using new revised data and methods, based on the recent benchmark process. To undertake the assessment and fit with the natural life cycle of sprat the assessment model is shifted by six months so that an assessment year and advice runs from July 1st to June 31st each year, and thus provide in-year advice. The sprat stock seems to be increasing. The stock appears to have been well above Bpa (142 000t) since 2005, with the exception of 2007 where SSB was approximately at Bpa. Since 2009 SSB has remained more or less stable around 300 000t and fishing mortality has been relatively low (0.5 – 0.7). Sprat in Division IIIa This stock was benchmarked in 2013 (WKSPRAT) but an analytical assessment is not presented. Short term projections are to be based on a combination of indices providing in year advice for IIIa based on the ICES approach for data lim ited stocks (Category 3 / 4). Since this methodology is based on catches and the TAC has not been reached in a number of years the resultant advice provides catch options which are much lower than 2013 TAC. Catch advice for sprat in the English Channel (VIId,e) was based on criteria for data limited stocks. Data available are landings, a time series of lpue (1988 – 2012) and two acoustic surveys that were carried out in 2011 and 2012 in the area where the fishery occurs. A surplus production model was fitted to data but the benchmark WKSPRAT advised that an analytical assessment was premature. Quantitative advice was provided for Sprat in the Celtic Sea (sprirls) . Data on landings are available from as early as the 1970s for some areas (i.e., VIa and VIIa) but biological data were not collected. Some acoustic estimates of biomass exist but do not cover the entire area where sprat are distributed; the estimates show high inter-annual variability. No analytical assessment is available for sprat in the Celtic Sea eco-region and the state of the stock is uncertain;.
The HAWG reviewed the assessments performed on seven sandeel stocks and the related advice of these stocks. The sandeel assessment report is a separate document, but a brief summary is given in the HAWG report (section 11).
There were no special requests to address in 2013. The working group also commented on the quality and availability of data, the problems with estimating the amounts of discarded fish, the use of the data system INTERCATCH, and provided an overview of some of the roles of herring in the ecosystem and of the existing knowledge about herring habitat. HAWG reiterated that activities that have a negative impact on the spawning habitat of herring, such as extraction of marine aggregates and construction on the spawning grounds, should not occur, and encouraged further research into the matter.