The North Sea autumn spawning herring SSB in 2016 was estimated at 2.20 m tonnes while F2–6 in 2016 was estimated at 0.26, at the management plan target F2-6 and below Fmsy. Fishing mortality on juveniles, mean F0-1 is 0.05, just below the agreed ceiling. Recruitment in 2017 is estimated to be very low. The estimate of 0-wr fish in 2016 (2015 year class) is estimated to be at approximately 29 billion, being low but in line with recent recruitment. Year classes since 2002 are estimated to be consistently week with year classes 2002 to 2007 to be among the weakest. ICES considers that the stock is still in a low productivity phase. The Western Baltic spring spawning herring assessment was updated. The SSB in 2016 was relatively stable compared to recent years and is estimated to be around 97 000 tonnes. Fishing mortality has been estimated at 0.41 and seems to have increased again after a period of reductions. It is above the estimate of Fmsy (0.32). Recruitment in 2016 is very low and potentially the lowest in the time-series. Under an historical perspective the estimates of SSB are considered still low, and the stock seems not to be able to recover to these higher biomass levels. The Celtic Sea autumn and winter spawning stock is estimated to be at a low level, declining from a recent high biomass that peaked in 2011. SSB is currently estimated at 46 000 tonnes in 2016, coming down from 140 000 tonnes in 2011. Mean F (2–5 rings) was estimated at 0.4 in 2016, having increased from 0.07 in 2009. Recruitment has been good in recent years with several strong cohorts (2003, 2005, 2007, 2011, 2012) entering the fishery but has come down substantially in the most recent years with the poorest year class in 2015. The 2016 SSB estimate of 6.a/7.b, c herring (the combined stock of 6.aN and 6.aS/7.b, c) was 151 000 tonnes, well below Bpa. Low recruitment has caused a decline of the stock while fishing mortality is low at 0.05-0.1 in recent years. Advice has been drafted to setup a monitoring fishery to ensure data relevant for the assessment and genetic studies are secured. Irish Sea autumn spawning herring was benchmarked in 2017 and the assessment shows a stable SSB in 2016 compared to previous years at around 26 000 tonnes, estimated substantially higher than pre-benchmark. The stock increased owing to large incoming year classes in most recent years. Fishing mortality is estimated at the lowest level in the time series at 0.17, below Fmsy. Catches have been relatively stable since the 1980s, and close to TAC levels in recent years. North Sea sprat came down from a time-series high since the early ’80, driven by high recruitment in 2014 and shows another increase owing to the 2016 year class. The stock appears to be well above Bpa (142 000 t) in 2016 at 246 170t. Fishing mortality in the last years has fluctuated between 0.4–1.6. Expected recruitment for 2017 is estimated to be in line with long-term recruitment. Sprat in Division 3.a 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 3.a based on the ICES approach for data limited stocks (Category 3 / 4). (Category 3/4). The surveys show variability over time without a clear trend. The most recent change is negative compared to the 4 years before. Catch advice for sprat in the English Channel (7.d, e) was based on criteria for data limited stocks. Data available are landings and a short time series of acoustic biomass (2013–2016). The acoustic biomass indicates a decline in the stock. Quantitative advice was provided for Sprat in the Celtic Sea (spr-irls) based on criteria for data limited stocks where only data on landings are available.
The HAWG reviewed the assessments performed on seven sandeel stocks and the related advice of these stocks. Section 11 of this report contains the assessment of sandeel in Division 3.a and Subarea 4.
Standard issues such as the quality and availability of data, estimating the amounts of discarded fish, availability of data through industry surveys and scientific advances relevant for small pelagic fish were discussed.
All data and scripts used to perform the assessment and perform the forecast calculations are available on GitHub and accessible to anyone.
|Place of Publication||Copenhagen|
|Publisher||International Council for the Exploration of the Sea (ICES)|
|Number of pages||857|
|Publication status||Published - 2017|
|Series||ICES Scientific Report|