0 20000 40000 60000 80000 100000
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Recruitment (millions)
st error= 0.17 average bias= 0.16
Figure 2.10.4. North Sea herring. Analytical retrospective analysis of final model fit (ICA) from 2004 to 1994. Showing recent consistency of estimation of SSB and F since 2000 with a period of poor estimation 1997 to 1999, following management change, with the estimates of 1994 and 1995 similar to current estimates.
1994 Cohort
Figure 2.10.5 North Sea herring cohort retrospectives for 1995 to 2003 yearclasses from assess-ments in 1999 to 2005
ICES HAWG Report 2005 184
North Sea herring, retrospective change in selction pattern
0 0.2 0.4 0.6 0.8 1 1.2
age 0 age 1 age 2 age 3 age 4 age 5 age 6 age 7 age 8 age 9+
Age group
selection
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Figure 2.10.6. North Sea herring. Analytical retrospective analysis of selection pattern of final model fit (ICA) from 2004 to 1994.
Figure 2.11.1. N orth Sea herring. TAC and catch of Downs herring and TAC for the whole north Sea stock (on another axis).
The TAC and estimated catch of IVc VIId herring (1986-2002)
0 50 100 150 200
1986 1988 1990 1992 1994 1996 1998 2000 2002 2004
Division IVc & VIId (1000 tonnes)
0 200 400 600
Total North Sea (1000 tonnes)
IVc VIId TAC estimated IVc VIId catch North Sea TAC
ICES HAWG Report 2005 186
Figure 2.11.2 Downs Herring. Index (numbers per hour) of small (<13 cm) 1-ringers in the North Sea area, and proportion of small 1-ringers versus all sizes in the North Sea area. From Ta-ble 2.3.3.3
0 200 400 600 800 1000 1200 1400 1600
1975 1980 1985 1990 1995 2000 2005 Year class
Index of small (<13 cm) 1-ringer abundance in the North Sea (no/h)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Proportion of small (<13 cm) 1-ringers in the North Sea Abundance
Proportion
Figure 2.11.3. North Sea herring. Proportion of herring by spawner origin within the sampled Dutch catch of North Sea herring in May to July 2004.
-4 -2 0 2 4 6
Note: the standard deviation between 6 samples within 1 ICES rectangle is 0.15.
-4 -2 0 2 4 6
ICES HAWG Report 2005 188
Figure 2.11.4 Downs herring. Larval Abundance Index (LAI) in the Channel area (line), calculated as mean of surveys per year class 1975-2004, and preliminary MIK survey results in the Channel (bars) (early spring 1995-2004). Stars denote no data.
0
1975 1980 1985 1990 1995 2000
Year class
0 5
10 15 20 25 30 35 40 45 50
MIK small herring
2000 4000 6000 8000 10000 12000 14000 16000 18000
LAI Downs index
MIK small herring LAI Downs
3 Herring in Division IIIa and Subdivisions 22–24
3.1 The Fishery3.1.1 ACFM advice and management applicable to 2004 and 2005 At the ACFM (May) meeting in 2004, it was stated that the status of the stock is unknown relative to safe biological limits, because reference points have not been determined. Although the assessment is uncertain SSB has been slightly increasing over the last four years. Fishing mortality is uncertain, but estimates for 2003 are 0.38 for adults and 0.12 for juveniles (0- and 1- ringers), which is slightly greater than Fmax.
ACFM recommended that since the current fishing mortality has lead to a stable or increased SSB, the fishing mortality should not be allowed to increase. This would correspond to catches in 2005 less than 92,000 t. According to the recent geographic distribution of catches, approximately half of the total catches should be taken from Subdivisions 22-24.
The EU and Norway agreement on a herring TACs set for 2005 was 96,000 t in Division IIIa for the human consumption fleet and a by-catch ceiling of 24,150 t to be taken in the small mesh fishery.
In previous years the International Baltic Sea Fishery Commission (IBSFC) set no special TAC for sub-division 22-24. In 2005, a TAC was set for the first time on the Western Baltic area the stock component. The TAC for 2005 was set at 46,000 t.
3.1.2 Catches in 2004
Herring caught in Division IIIa are a mixture of North Sea autumn spawners (NSAS) and Western Baltic spring spawning herring (WBSS). This Section gives the landings of both North Sea autumn spawners and Western Baltic spring spawners, but the stock assessment applies only to the spring spawners.
Landings from 1985 to 2004 are given in Table 3.1.1. In 2004 the total landings decreased to 94,200 t in Division IIIa and Subdivisions 22–24 compared with 2003 where the landings were 109,500 t, resulting in a landing figure for 2004 at the lowest level for the whole time-series. In 2004, 20,500 t were taken in the Kattegat, about 31,700 t from the Skagerrak and 42,000 t from Subdivisions 22–24. These landings represent a decrease of 15,200 t compared to 2003 and 34,700 t compared to 2002. The Danish national management regime for herring and sprat fishery in Subdivision 22 was changed in 2002. It should be noted that the total land-ings for fishery in Skagerrak have been updated for 1995-2001 because of Norwegian misre-porting of landings taken in the North Sea and reported to Skagerrak. This was also delt with in 2002 and 2003 but was not thought to occur in 2004.
The German landings in 2004 were at the same level as in 2003. Since 2001 the fishery behav-iour changed in the German fleet. In former years the dominant part of herring was caught in the passive gears, gillnets and trapnets. The share of herring, which was caught by trawlers in the area off the Rügen Island coast up to the Arcona Sea (Subdivision 24), increased from 26% in 2001 to 52% in 2004. This change was caused by new requirements for a new fish factory on Rügen Island. This factory expects to process 50,000 t per year and started during autumn 2003.
In 2004 the landing data are calculated by fleet according to the fleet definitions used when setting TACs.
The fleet definitions used since 1998 are:
ICES HAWG Report 2005 190
• Fleet C: directed fishery for herring in which trawlers (with 32 mm minimum mesh size) and purse seiners participate.
• Fleet D: All fisheries in which trawlers (with mesh sizes less than 32 mm) and small purse seiners, fishing for sprat along the Swedish coast and in the Swedish fjords, partici-pate. For most of the landings taken by this fleet, herring is landed as by-catch. Danish and Swedish by-catches of herring from the sprat fishery and the Norway pout and blue-whiting fisheries are listed under fleet D.
• Fleet F: Landings from Subdivisions 22–24. Most of the catches are taken in a directed fishery for herring and some as by-catch in a directed sprat fishery.
In table 3.1.2 the landings are given for 2001 to 2004 in thousands of tonnes by fleet and quar-ter.
3.2 Biological composition of the catch
The level of sampling of the landings for human consumption and the industrial landings was generally acceptable in the Skagerrak and Kattegat and Subdivisions 22-24. Where sampling was missing in areas and quarters on national landings, sampling from either other nations or adjacent areas and quarters were used to estimate catch in numbers and mean weight-at-age (see Table 3.2.17).
Table 3.2.2 and Table 3.2.3 show the total catch (autumn and spring spawners) in numbers and mean weight-at-age for herring by quarter and fleet landed from Skagerrak and Kattegat, re-spectively. The total numbers and mean weights-at-age for herring landed from the Kattegat, Skagerrak and Subdivisions 22 - 24 by fleets are shown in Table 3.2.10.
Based on the proportions of spring- and autumn spawners (see Section 3.2.1 and Section 3.2.2) in the landings, number and mean weights by age and spawning stock are calculated.
The total numbers and mean weight of the NSAS landed from Kattegat and Skagerrak by quarter and fleet is shown in Table 3.2.4 and 3.2.6. The total numbers and mean weight of the WBSS landed from Kattegat and Skagerrak by quarter and fleet are shown in Table 3.2.5 and 3.2.7.
The total numbers and mean weight of the NSAS by quarter and fleet landed from Division IIIa are shown in Table 3.2.8 and the WBSS in Table 3.2.9.
The total catch in numbers of WBSS in Division IIIa and the North Sea are shown in Tables 3.2.11 and 3.2.12 (see also Tables 2.2.1 – 2.2.5). The landings (SOP) of the WBSS taken in Division IIIa and the North Sea in 2004 were estimated to be about 35,078 t (Table 3.2.15) compared to about 37,075 t in 2003 and 53,544 t in 2002. This slight decrease in landings (SOP) was mainly due to a decrease in the estimated number of 1 group spring spawners in Skagerrak and Kattegat. The landings (SOP) of NSAS in Division IIIa amounted to 24,214 t compared to 32,498 t in 2003 and 26,205 t in 2002 (Table 3.2.13). The total catch in number and mean weight-at-age of WBSS in the North Sea, Division IIIa and in Subdivisions 22–24 for 1991–2004 are given in Tables 3.2.14 and 3.2.15.
3.2.1 Quality of Catch Data and Biological Sampling Data
Misreporting of fishing area still occurs. There is uncertainty about where the Danish landings for human consumption, reported from Division IIIa were actually taken. There is a high probability that these catches have been taken in the North Sea. Therefore, these catches have been transferred to the North Sea. The Norwegian landings reported as having been taken in Skagerrak for the period 1995 to 2003 may have been caught in the North Sea and have been transferred to the North Sea. However, due to changes in the Norwegian management the catches reported from Skagerrak in 2004 are reliable. Some landings, reported as taken in this