4-Celtic Sea and Div. VIIj Herring

ICESHAWG Report 2006 295

4 Celtic Sea and Division VIIj Herring

4.1 The Fishery

The herring fisheries to the south of Ireland in the Celtic Sea and in Division VIIj exploit autumn and winter spawning components. For the purpose of stock assessment and management, these areas have been combined since 1982. The management unit covers all of Divisions VIIg,h,j and k and the southern part of Division VIIa (Figure 1.5.1).

4.1.1 Advice and management applicable to 2005 - 2006

The TAC in 2005 was 13 000 t, and in 2006 is 11 050. In 2005, ACFM considered the current level of SSB to be uncertain, but maybe below Bpa and possibly even below Blim. Though there was no short term forecast, ACFM advised that, given the risk to the stock indicated by the poor recruitment of the 2001 year class, exploitation should be significantly reduced in 2006. ACFM suggested that such a reduction should result in catches of 6 700 t corresponding to 60% of the average catch in 2002-2004. In addition, ACFM recommended supplementary measures such as the re-closure of the eastern section of the Celtic Sea (Spawning Box C), see Figure 4.1.1.1a.. ICES considered that this would be an effective measure to reduce exploitation as most of the herring catches have been taken in this area since the voluntary closure was removed in December 2003.

Ad hoc requests In October 2005, ICES was asked by Ireland to answer the following requests on this stock:

1 ) Comment on the benefit to the stock of an indefinite closure of Spawning Box C in Division VIIa as an alternative to reduction of the advised catches by 40% in 2006.

2 ) Since this stock is characterised by variable recruitment, to comment on whether the advised reduction of 40% in catches for 2006 was too severe, given that it is driven by recent low recruitments and bearing in mind that similarly low recruitments have been recorded in the past, most recently in 1991.

ICES’ response to point one was that the box closure was intended as a supplementary measure intended to support the main advice to reduce catch in 2006. The closure of Box C is not an alternative to the reduction in TAC. ICES’ response to point 2 was that in 1991 the SSB was larger (>Bpa) than in 2005. Although current SSB is uncertain, it seems low, below Bpa and maybe even below Blim. Hence, the more conservative advice was based on the current perception of SSB being low.

The TAC is set by calendar year, whilst the assessment of the stock is conducted on a seasonal basis (1st April to 31st March).

In the past three seasons, a fishery was permitted during the summer months. In 2003 it opened in July, and in subsequent years in August. This was to allow vessels to target fish outside the spawning seasons when the fish are of better quality, marketability and constituting less fish per tonne landed.

Spawning Box Closures

The spawning box closures implemented under EU legislation continued. In the 2005/2006 season, Spawning Box C was closed in the second two weeks of January (Fig 4.1.1.1a). In 2006/2007, Box A will be closed. However, Spawning Box C was not closed entirely in 2006.


In addition to these, Box A was voluntarily closed in the recent seasons, being finally reopened in December 2003. This initiative was put in place by the Irish Celtic Sea Herring Management Advisory Committee to afford extra protection to first time spawners. Areas mentioned in the text are shown in Figure 4.1.1.1b.

Management Plan

The Irish “Celtic Sea Herring Management Advisory Committee” was established to manage the Irish fishery for this herring stock, having been constituted in law in 2005. This committee, therefore, has responsibility for management of the entire fishery for this stock at present. The committee has the following objectives:

• To build the stock to a level whereby it can sustain annual catches of around 20,000 t.

• In the event of the stock falling below the level at which these catches can be sustained the Committee will take appropriate rebuilding measures.

• To introduce measures to prevent landings of small and juvenile herring including closed areas, and or appropriate time closures.

• To ensure that all landings of herring should contain at least 50% of individual fish above 23 cm.

• To maintain and if necessary expand, the spawning box closures in time and area. • To ensure that adequate scientific resources are available to assess the state of the

stock. • To participate in the collection of data and to play an active part in the stock

assessment procedure.

Local management of the fishery

In 2005 the Irish quota was 11 236 t and in 2006, is 9 549 t. The Irish quota is managed by allocating individual quotas to vessels on a weekly basis. Participation in the fishery is restricted to licensed vessels. The licensing requirements have been changed. Previously, vessels had to participate in the fishery each year to maintain their licence. Now this requirement has been lifted. This has been one of the contributing factors to the reduction in number of vessels participating in the fishery in recent seasons. The efficiency of these vessels has improved, however. Fishing is restricted to the period Monday to Friday each week, and vessels must apply a week in advance before they are allowed to fish in the following week.

4.1.2 The fishery in 2004/2005

The landings in this fishery since 1958 are shown in Figure 4.1.2.1. Prices for Celtic Sea herring were better in the current season.

In 2005/2006, 34 vessels participated in the fishery, as follows:

• 12 RSW trawlers of 23-40m, using pair trawls

• 6 dry hold trawlers of 20-24m, using pair trawls

• 16 dry hold trawlers < 20m.

Most vessels under 20 m reported landings of less than 100 t for the assessment period while a number of RSW vessels reported landings greater than 1 000 t. In addition small incidental landings, typically less than a tonne were reported by a number of other vessels. Gillnets are a minor component of the fishery in recent years.

The fishing season is divided into three periods. In quarter 3, 2005 about 3 000 t were landed. These fish were targeted in offshore feeding aggregations to the north of the Labadie Bank


and around the Kinsale Gas Field. This fishery opened on the 7th August and closed on 1st September. These catches consisted of about 7 000 fish per tonne. These catches were taken by pair trawl vessels using RSW or modified RSW fish storage. Vessels without RSW storage cannot participate in the summer fishery.

In quarter 4, 2005 about 3 000 t were landed. The fishery opened on the 13th November and closed on the 2nd December 2006. Most of the catch came from the traditional fishing grounds in Division VIIaS. About 200 t were taken from within Waterford Estuary, using single trawls by small inshore vessels. Small catches were taken from VIIj in quarter 4 only.

In quarter 1, 2006, about 3 500 t were landed. The fishery was opened in the beginning of January 2006 and was closed on the 20th January. From the 15th January, Spawning Box C was closed, and effort was diverted to the inshore grounds of VIIg, around Ballycotton and off the Daunt Rock (Figure 4.1.1.1b). Again, about 200 t were taken from within Waterford Estuary, using single trawls by small inshore vessels. These small vessels also fished outside Waterford Estuary.

4.1.3 The catches in 2005/2006

The estimated national catches from 1988–2004 for the combined areas by year and by season (1 April–31 March) are given in Table 4.1.3.1 and Table 4.1.3.2 respectively. The total catches for the fishery over the longer period from 1958 to 2004 are shown in Figure 4.1.2.1 The catch, taken during the 2005/2006 season was under 10 000 t having declined from almost 13 000 t during the previous season.

There are no estimates of discards for this fishery. Anecdotal reports from fishermen suggest that discarding is not a feature of this fishery at present.

4.2 Biological composition of the catch

4.2.1 Catches in numbers-at-age

Catch numbers at age are available for the period 1958/1959 to 2004/2005. These data include discards, when estimates were produced (until 1997). In 2005/2006, the 1-ringers were a higher proportion of the catch than at any season since 1982/1983 (Figure 4.2.1.1 and Table 4.2.1.1). The absolute numbers of 1-ringers were among the highest in recent years, along with those in 1999/2000 and 2001/2002. The proportion of 2-ringers (38%) was about average for recent seasons. The 3-ringers were very low (7%) confirming the weakness of the 2-ringers last season. It is important to note that the weakness of 3-ringers tends to inflate the proportions of the other important age groups in the catches.

The overall proportions at age were largely similar in the 4th and 1st quarter in VIIg and VIIaS. However, the catches in VIIaS (Waterford Harbour) in the 1st quarter were very different, being over 70% 1-ringer. This large proportion of 1-ringers contributed to their overall high contribution in the catches. In VIIj, the proportion at age did not differ from elsewhere, in contrast to last season.

4.2.2 Movements of fish

Juveniles

It is known that fish spawned in the Celtic Sea are present as juveniles in the Irish Sea along with native fish, especially the western part (Brophy and Danilowicz, 2002). Their results show that fish spawned in the eastern Celtic Sea are present as juveniles in the Irish Sea, where fish of local origin are also found. The fish of Celtic Sea origin then return as 1- and 2-ringers (Molloy et al. 1993).


Small fish (1-ringer) predominated in quarter 1, 2006 though not in quarter 4, 2005, in Waterford Estuary. As these fish were smaller, it seems likely that these fish migrated to the Celtic Sea from the Irish Sea.

Further work, redrawing historic larval survey data from the 1980s shows that autumn and winter spawning was taking place in the eastern Celtic Sea (Figure 4.2.2.1). Thus juveniles of Celtic Sea origin present in the Irish Sea cannot be distinguished on the basis of spawner type alone. Therefore further work is required to allow for splitting Irish and Celtic Sea origin fish.

Adults

The quarter 3 fishery targets offshore feeding aggregations of herring in VIIg. It is not known where these fish spawn. However a combination of positional data from the commercial fishery (August) and acoustic surveys (September to December) in this area displays a seasonally progressive movement towards the traditional spawning grounds inshore (Figure 4.2.2.2).

Spatial data from all groundfish surveys using the Portuguese high headline net and the GOV trawl were presented by WGFISHECO (ICES, 2006) show that herring display a continuous distribution throughout the Celtic Sea and Division VIIf. However abundance is very low in the middle area between VIIf and VIIg. However there appears to be a hiatus between VIIe and VIId, though there is little survey effort in that area. It seems possible that the summer feeding aggregations are a mixture of VIIg, VIIaS, and VIIe fish, though information is scarce.

4.2.3 Quality of catch and biological data

Since 1997 there has been a major increase in the monitoring of landings from this fishery and the management measures were again tightly enforced throughout the season. There is no information on misreporting in this fishery in recent years, but it is thought to have decreased.

Biological sampling of the catches throughout the region was comprehensive, except in VIIj. The spasmodic nature of the fishery in that area makes sample acquisition difficult, (Table 4.2.3.1). Under the Data Collection Programme the sampling of this stock is well above that required by the Minimum Programme (Section 1.5).

4.3 Fishery Independent Information

4.3.1 Acoustic Surveys

Acoustic surveys of this stock have been carried out since 1990, with the exception of 1997. Up until 1996, two acoustic surveys were carried out annually. In 1997 there was no research vessel available to do the survey. Since 1998, usually only one winter survey was conducted (Table 4.3.1.1). The survey conducted in 2005/2006, was conducted on the Celtic Explorer, for the second time.

Revision of acoustic time series

The problems with the acoustic survey have been documented in previous reports. In order to improve the series a review was conducted and the series has been revised (Clarke et al. in prep.). This review had two main aims with these being to check the internal consistency of the previous surveys and produce a new refined series for tuning the assessment.

The surveys were divided into two series, early and late, based on how far from the south coast they went. The early group, 1990-91 to 1994-95, extended to about 15 nautical miles offshore with two surveys, one in autumn (before Christmas) and another in winter (after Christmas). This design aimed to survey spawning fish close inshore with two surveys, the results of which could be added, the two legs covering the two main spawning seasons. The


off shore limits were extended in 1995 and some of these surveys had more fish off shore than close inshore. This changed the catchability, suggesting the later series should be separated from the earlier one. Consequently the years before 1995 were removed. This is not considered to be a problem because the earlier series would contribute little to the ICA anyway. Winter surveys were not always conducted in the later series, not being done in 1998 and not at all after 2000 so these were dropped too.

The autumn surveys did not cover the southwest Irish coast of VIIj in all years (3 years missing). In order to correct for this, the missing values were substituted with the mean of the available western bays SSB estimates, 7 800 t (11 values, range from 0 to 16 000 t). Numbers-at-age in these surveys were adjusted upwards by the ratio of the adjusted SSB in the SW to the south coast SSB. The abundance estimates produced are presented in Table 4.3.1.2.

Analysis errors were found in the surveys from 1998 onwards. The 2003 biomass (SSB, 85 500 t) was re-analysed after the discovery of errors in the spreadsheets used to estimate biomass. The errors affected the calculation of the weighted mean of the integrated backscatter when positive samples had lengths shorter than the base one (here, 15 minutes) and the partitioning of the backscatter for a mixture of species. Also, no account was taken of different sampling frequencies within a 10x20 minute cell (the analysis unit). The 2003 SSB came mainly from two cells that included an intensive survey in Waterford Harbour and these cells had a SSB of about 68 000 t, which was reduced to 7 300 t when all errors were corrected. There were some minor corrections in three other cells. The revised total biomass was 24 000 t and the revised spawning biomass was 22 700 t.

In addition, the cell means took no account of the implicit sampling area of transects so that the biomass coming from a large sample value depended on the number of transects passing through the cell. The data were re-analysed using mean herring density by transect as the sample unit and dividing the area into strata based on transect spacing. Areas with no positive samples were excluded from the analysis (since they have zero estimates). Zigzags in bays were analysed as before. For each stratum, a mean density was obtained from the transect data (weighted by transect length) and this was multiplied by the stratum area to obtain a biomass and numbers-at-age. The overall total was the sum of the strata estimates. The same haul assignments as in the original analysis were used. At the same time, a CV was obtained based on the transect mean densities, i.e. a survey sample error. For surveys before 1998 and the western part survey in 2002, a cv was estimated using;

n)3.1log( 2

where n is the number of positive sample values (15 minute of survey track) from Definite and Probably Herring categories. This was based on the data from the autumn surveys in 1998, 2000, 2001, 2002, and 2005. Results are shown in Table 4.3.1.2.

2005 Survey

The acoustic survey of the 2005/2006 season was carried in October 2005 (Doonan, presentation to HAWG). The survey track was begun at the northern boundary of VIIj, covering the SW bays in zig-zags and parallel transects. The main traditional grounds on the south Irish coast (VIIg and VIIaS) were covered using transects of 2nmi spacing, extending 67 nmi offshore (Figure 4.3.1.1a). In total the combined survey transect length was in the order of 2 789 nmi.

To check that the research vessel was adequate in shallower waters, another localised survey was done along parts of the south coast during October by a smaller commercial fishing


vessel. This main survey was aimed at pre-spawners as they moved inshore to spawn. The main survey area was based on an analysis of results from previous autumn surveys to make sure that it covered the likely extent of the stock at this time. The survey started at the northern boundary of VIIj, moving through it in a southerly direction, before moving eastwards through the Celtic Sea (Figure 4.3.1.1a). No substantial echo traces of adult herring were encountered in the bays and inlets of VIIj, but there were some from juveniles (Figure 4.3.1.1b). In VIIg, most herring shoals were encountered offshore, but one or two were seen inshore. Nearly all large schools were successfully fished on. The localised inshore survey also found very few herring schools indicating that the research vessel was adequate in shallower waters. It was concluded from this information that the survey estimated the stock size in these areas in 2005/2006. The age structured index of biomass and catch numbers from acoustic surveys in this area, is shown in Table 4.3.1.2, and the revised series in Table 4.3.1.3. In 2005/2006 the SSB estimate was 30 000 t.

The percentage age composition in the survey and the commercial fishery are compared in Figure 4.31.2. The survey displayed the same age distribution as the commercial fishery, both showing a strong predominance of 2-ringers and the very low abundance of 3-ringers. However the survey picked up somewhat lower numbers of 4-ringers and older.

4.3.2 Other surveys

The working group has sought alternative tuning series for this stock.

In 2005, an investigation of the utility of the Irish segment of the western IBTS survey was made (Johnston and Clarke, WD 2005). This survey displayed strong year effects and only those surveys from 2003 onwards are directly comparable because they use the same research vessel. Herring distribution in quarter 4 is very contagious, with fish being caught in large aggregations, or not at all. Consequently the signal from the survey is noisy, but when a longer time series is developed, it will at least provide qualitative information. This survey did highlight the absence of the 2001 year-class in 2004.

In 2006, the working group had access to data from the French EVHOE quarter 4 western IBTS survey (GOV trawl) and the CEFAS UK (E&W) quarter 1 survey (Portuguese high headline trawl) (Johnston et al. WD 2006). The French survey series is from 1997 to 2005 and displayed very variable observed numbers at age between years. Consequently, further exploration of the series was not perfomed.

The UK quarter 1 survey was explored further (Figure 4.3.2.1). There are strong year and age effects in the survey, particularly at 2- and 5-ringer. Total numbers per year vary widely. Because of strong year and age effects and because it was discontinued in 2002 this survey is considered unsuitable as a recruit index. However the survey does display a truncation of older age groups throughout the series, but particularly in the 1990’s (Figure 4.3.2.1). This trend is displayed in the catch numbers at age, the acoustic series and the UK quarter 1 survey. In all three cases, this trend seems progressive with time.

Other surveys that may have utility for tuning the assessment are the DARDNI Groundfish Survey of the Irish Sea, Northern Ireland and the UK quarter 4 western GFS. It is known that juveniles from the Celtic Sea are present in the Irish Sea. If it is possible to distinguish these fish from native Irish Sea herring, in the DARDNI survey then this survey could offer potential for a recruit index for Celtic Sea herring.

4.4 Mean weights-at-age and maturity-at-age

The mean weights in the catch over time are presented in Figure 4.4.1, with stock weights displayed in Figure 4.4.2. There has been an overall downward trend in mean weights at age since the mid-1980’s. The values for 2005/2006 for the important age groups are among the


lowest in the series. This trend in mean weights at age is similar to those seen in VI aN, the Irish Sea and to a lesser extent, the North Sea.

For the past three seasons substantial catches were taken outside the spawning season. For 2005/2006, the mean weights in the spawning stock were calculated from samples taken in VIIg, VIIj and VIIaS from October 2005 to February 2006. Samples from quarter 3 were not used in these calculations. No data for 8- or 9-ringers were available this year to calculate stock weights. Therefore values were calculated by linear extrapolation of the 1- to 7-ringer mean weights for these year classes.

While the maturity-at-age for this stock has been assumed to be constant throughout the whole time period (50% of 1 ring fish are assumed to be mature at age 1 and 100% mature at 2 ring), it may not be stable. A new project to develop maturity ogives for this stock from catch and survey data is being started in 2006. This project will also examine long term changes in biological parameters.

4.5 Recruitment

At present there are no recruitment estimates for this stock that can be used for predictive purposes. The 2003 recruitment was estimated as weak in the 2004 assessments, and appears to be the weakest in the series. There is little information in the assessment on the strength of recruitment in 2005, because these 1-ringers are poorly represented in the catches, though they were high.

In this stock a proportion of juvenile fish are present in the Irish Sea and do not recruit to the Celtic Sea and Division VIIj until they are mature. Therefore neither the numbers of 1-ringers in the stock as estimated from the acoustic surveys nor the numbers in the catches give a reliable indication of year class strength. The relationship between the numbers of 1-ringers taken per hour in the ground fish surveys in the Irish Sea and the numbers of 1- ringers estimated by ICA for the Celtic Sea and Division VIIj was examined in a working document presented to the 1999 WG (Armstrong et al., WD 1999) and the results suggest that these surveys may become a useful indicator of recruitment to the Celtic Sea and Division VIIj when a longer time-series is established.

4.6 Assessment

This stock is scheduled for benchmark assessment in 2007. The last time the assessment of this stock was accepted by ACFM as a basis for management advice was 2001. In 2005, the working group did not present a final assessment, but rather presented two exploratory assessments. These assessments were based on the inclusion or exclusion of the acoustic survey conducted in 2004. This survey produced the lowest abundance estimate in the series, and was not considered by the group to have measured the stock. The most important information considered by the 2005 working group was weakness of the 2001 year class. In 2006, the working group continued to conduct exploratory assessments and no final assessment was put forward by the group in 2006.

4.6.1 Data exploration

Considerable data exploration was conducted in 2005. In 2006, only exploration of the revised acoustic series was conducted. The revised acoustic series displays the same age structure as the old one over comparable years. Therefore the series was considered only to be used for tuning over 2- to 5-ringer. The series displays the same truncation of older age groups as seen in the catch at age data (Figure 4.6.1.1 and Figure 4.6.1.2). The revised acoustic series and the catch at age data display similar proportions at age (Figure 4.6.1.3).


Both acoustic series and the catch at age data displayed similar mortality signals (Figure 4.6.1.4).

4.6.2 Exploratory Assessments

In 2006, exploratory assessments were conducted to investigate:

• Behaviour of the revised acoustic series • Inclusion of 2000 and 2001 surveys which had very high CVs. • Change of the separable period to accommodate the new quarter 3 fishery. • Shape of the exploitation pattern

In each case, the same procedure as previous years was used to deal with the assumption that 50% of 1-ringers are mature. Therefore recruitment at 1-ring was replaced with geometric mean (1958-2004), 390 million fish, and the SSB was recalculated based on the stock weights and population numbers in the final year.

In order to compare the old and revised series, two runs of ICA were conducted using the same procedure as last year’s assessment (SPALY), which did not use the 2004 survey estimates. The separable period was 6 years and no shrinkage was used. The results of this analysis are presented in Figure 4.6.2.1. Patterns of SSB and recruitment were the same, but slight differences in F were observed, with the old series scaling F up slightly in the final two years. Residual patterns in the tuning series are presented for these runs in Figure 4.6.2.2. The revised series does not represent an appreciable better model fit. Strong age year effects are still present. However, because CVs are available for this series, it is possible to identify years were the survey is particularly noisy. Further diagnostics for comparing these runs are presented in Figures 4.6.2.3 and Figure 4.6.2.4 for the old and revised series respectively. Figure 4.6.2.5 shows q-q plots for the runs with the old and revised surveys. These plots show ranked percentiles of the residuals, and provide a quantitative means to compare residual patterns. This analysis shows that catch numbers-at-age distributions are similar, but with about 20% larger standard deviation (slope of the line fit) when using the new series. The distributions of the survey residuals are not quite the same and the new series’ standard deviation is much higher.

Surveys with particularly high CVs were those in 2000 and 2001. Exploration of their exclusion was performed in ICA using SPALY. Summary plots for these runs are shown in Figure 4.6.2.6 and residual patterns in the survey series in Figure 4.6.2.7, and q-q plots in Figure 4.6.2.8. Their exclusion did not change the perception of stock dynamics. However, the q q plot shows that both distributions are similar, but there is a reduction in the standard deviation when dropping the two surveys.

A priori assumptions that the new quarter 3 fishery in the last three years changed the exploitation pattern were tested by running exploratory assessments with 6 year (both using the new survey series with the 2000 and 2001 surveys excluded) and a 4 year separable period. Summary plots are presented in Figure 4.6.2.9, residuals in Table 4.6.2.1 and q-q plots in Figure 4.6.2.10. Stock perception did not change substantially, but the residual pattern did improve. When a 4 year separable period is used (both using the new survey series with the 2000 and 2001 surveys excluded), the qq plots show the same distribution, with no change in standard deviation for the survey.

In order to investigate the shape of the selection pattern, selection on at oldest age relative to reference age (3-ring) was set at 1.5 in comparison to the base case run using the revised acoustic series (Figure 4.6.2.1.). Comparative runs are shown in Figure 4.6.2.11 and residual patterns in Figure 4.6.2.12. Clearly the model fit is somewhat better when selection at the oldest age is set at 1.5 and the model seems to behave better with an increase in selection at


the oldest age, compared to setting oldest age selection = 1.0. It is also clear that using a higher S at oldest age applies a scaling factor to the SSB throughout the time series. Figure 4.6.2.13 shows the q-q plot of comparison of these exploitation patterns. The choice of 1.5 appears to improve the residual pattern.

4.7 Short term projections

There was no final assessment and consequently no short term projections.

4.8 Medium term projections

No medium term projections were conducted in 2006.

4.9 Precautionary and yield based reference points

Biological reference points were discussed in detail in the 2000 WG report (ICES 2000/ACFM:10) and in the report of the previous years (ICES 1999/ACFM:12, ICES 1998/ACFM:14). A summary of this discussion was presented in the 2003 HAWG report. Bpa is currently at 44,000t and Blim at 26,000 t for this stock Fpa and Flim are not defined. The SGPRP (ICES 2003 ACFM 15) has reviewed the methodology for the calculation of biological reference points, and applying a segmented regression to the stock and recruit data from the 2002 HAWG assessment gave a breakpoint at 61,306 t. This change point appears to be very high with respect to the historical exploitation of the stock. Given that there is a cluster of observations just above this value the sensitivity of the method to these data needs to be further investigated. The HAWG decided that the first priority for this stock should be to achieve a stable assessment and that once this was done the reference points would be reinvestigated. There is still considerable instability in the assessment, so there is no basis for a revision of reference points at this point.

4.10 Quality of the Assessment

No assessment was conducted.

4.11 Management Considerations

There is no new assessment in 2006 upon which to base management advice. However preparations are being made for benchmark assessment next year.

There are certain pieces of information that can be obtained from the available data. The revision of the acoustic survey, though not substantially improving the model fit does show the noise in the individual survey estimates. The revision of the series shows evidence of declining stock abundance. A period of high abundance is evident with reasonable CVs, a period of very fluctuating abundance with high CVs and then a period of low stock abundance with lower CVs.

In 2005, ICES based advice on the poor recruitment of the 2001 year class. In 2006, this year class weakness was further confirmed. The 2002 year class appears stronger in the catches. Although the 2003 year class (1-ringers) are considered to contribute to SSB there is insufficient information in the data available to state if this cohort is stronger than average.

In recent years the fishery has been tightly managed and it is now restricted in time and area. In 2005/2006 fishing was concentrated in the feeding area and also in a few of the traditional inshore areas. Little fishing took place in VIIj.

Though the data available are not informative as to stock status at present., and the exploratory assessments are uncertain The weak 2001-year class means that the stock is more dependent


on subsequent cohorts and also 4-ringers. The truncation of age groups in the catches in recent years along with the spatially small area of the fishery are causes for concern. The stock is probably at as low a level as when it previously collapsed. It would seem prudent to proceed with caution.


Table 4.1.3.1. Celtic Sea and Division VIIh, j and k herring landings by quota year (t), 1988–2005. (Data provided by Working Group members.) These figures may not in all cases correspond to the official statistics and cannot be used for management purposes.

Year France Germany Ireland Netherlands U.K. Unallocated Discards Total

1989 + - 16,000 1,900 - 1,300 3,500 22,700

1990 + - 15,800 1,000 200 700 2,500 20,200

1991 + 100 19,400 1,600 - 600 1,900 23,600

1992 500 - 18,000 100 + 2,300 2,100 23,000

1993 - - 19,000 1,300 + -1,100 1,900 21,100

1994 + 200 17,400 1,300 + -1,500 1,700 19,100

1995 200 200 18,000 100 + -200 700 19,000

1996 1,000 0 18,600 1,000 - -1,800 3,000 21,800

1997 1,300 0 18,000 1,400 - -2,600 700 18,800

1998 + - 19,300 1,200 - -200 - 20,300

1999 200 17,900 1300 + -1300 - 18,100

2000 573 228 18,038 44 1 -617 - 18,267

2001 1,359 219 17,729 - - -1578 - 17,729

2002 734 - 10,550 257 - -991 - 10,550

2003 800 - 10,875 692 14 -1,506 - 10,875

2004 801 41 11,024 - - -801 - 11,065

2005 821 150 8452 799 - -1770 - 8,452

Table 4.1.3.2. Celtic Sea & Division VIIj herring landings (t) by assessment year (1st April–31st March) 1988/1989-2004/2005. (Data provided by Working Group members.) These figures may not in all cases correspond to the official statistics and cannot be used for management purposes.

Year France Germany Ireland Netherlands U.K. Unallocated Discards Total

1989/1990 + - 15,000 1,900 - 2,600 3,600 23,100

1990/1991 + - 15,000 1,000 200 700 1,700 18,600

1991/1992 500 100 21,400 1,600 - -100 2,100 25,600

1992/1993 - - 18,000 1,300 - -100 2,000 21,200

1993/1994 - - 16,600 1,300 + -1,100 1,800 18,600

1994/1995 + 200 17,400 1,300 + -1,500 1,900 19,300

1995/1996 200 200 20,000 100 + -200 3,000 23,300

1996/1997 1,000 - 17,900 1,000 - -1,800 750 18,800

1997/1998 1,300 - 19,900 1,400 - -2100 - 20,500

1998/1999 + - 17,700 1,200 - -700 - 18,200

1999/2000 200 18,300 1300 + -1300 - 18,500

2000/2001 573 228 16,962 44 1 -617 - 17,191

2001/2002 - - 15,236 - - - - 15,236

2002/2003 734 - 7,465 257 - -991 - 7,465

2003/2004 800 - 11,536 610 14 -1,424 - 11,536

2004/2005 801 41 12,702 - - -801 - 12,743

2005/2006 821 150 9,494 799 - -1770 - 9,494


Table 4.2.1.1. Celtic Sea & Division VIIj herring. Comparison of age distributions (percentages) in the catches of Celtic Sea and VIIj herring over recent seasons.

Rings 1 2 3 4 5 6 7 8 9

1969 4 40 24 14 5 8 2 1 1

1970 1 24 33 17 12 5 4 1 2

1971 8 15 24 27 12 7 3 3 1

1972 4 67 9 8 7 2 1 1 0

1973 16 26 38 5 7 4 2 2 1

1974 5 43 17 22 4 4 3 1 1

1975 18 22 25 11 13 5 2 2 2

1976 26 22 14 14 6 9 4 2 3

1977 20 31 22 13 4 5 3 1 1

1978 7 35 31 14 4 4 1 2 1

1979 21 26 23 16 5 2 2 1 1

1980 11 47 18 10 4 3 2 2 1

1981 40 22 22 6 5 4 1 0 1

1982 20 55 11 6 2 2 2 0 1

1983 9 68 18 2 1 0 0 1 0

1984 11 53 24 9 1 1 0 0 0

1985 14 44 28 12 2 0 0 0 0

1986 3 39 29 22 6 1 0 0 0

1987 4 42 27 15 9 2 1 0 0

1988 2 61 23 7 4 2 1 0 0

1989 5 27 44 13 5 2 2 0 0

1990 2 35 21 30 7 3 1 1 0

1991 1 40 24 11 18 3 2 1 0

1992 8 19 25 20 7 13 2 5 0

1993 1 72 7 8 3 2 5 1 0

1994 10 29 50 3 2 4 1 1 0

1995 6 49 14 23 2 2 2 1 1

1996 3 46 29 6 12 2 1 1 1

1997 3 26 37 22 6 4 1 1 0

1998 5 34 22 23 11 3 2 0 0

1999 11 27 28 11 12 7 1 2 0

2000 7 58 14 9 4 5 2 0 0

2001 12 49 28 5 3 1 1 0 0

2002 6 46 32 9 2 2 1 0 0

2003 3 41 27 16 6 4 3 0 1

2004 5 10 50 24 9 2 1 0 0

2005 19 38 7 23 9 2 1 0 0

Mean (58-05) 8 37 24 14 7 4 3 2 2


Table 4.2.1.2. Celtic Sea & Division VIIj herring. Length frequency distributions of the Irish catches (raised numbers in ‘000s) in the 2004/2005 season in the Celtic Sea and VIIj fishery.

Length cm Quarter 3 Quarter 4 Quarter 4 Quarter 4 Quarter 4 Quarter 1 Quarter 1 Quarter 1 Total

2005 2005 2005 2005 2006 2006 2006 Celtic Sea and

VIIg VIIaS River VIIaS C.S. VIIg VIIj VIIg VIIaS River VIIaS C.S. VIIj

17 0

17.5 0

18 9 9

18.5 19 5 22 28 74

19 11 117 22 20 0 93 262

19.5 13 65 545 91 25 44 139 922

20 60 65 720 125 64 22 390 43 1489

20.5 128 57 1109 216 39 155 325 43 2072

21 322 65 1323 221 39 618 288 143 3020

21.5 477 72 2082 329 113 596 186 122 3976

22 779 133 1907 298 132 906 242 294 4691

22.5 1228 137 2374 471 162 1612 195 373 6553

23 1329 186 2335 497 157 2408 204 337 7454

23.5 1551 95 1751 437 103 1944 93 380 6354

24 1430 91 1051 333 123 1723 46 366 5163

24.5 1356 126 973 272 64 1237 56 208 4291

25 1584 133 1031 251 103 1767 139 237 5245

25.5 2155 179 934 277 118 2098 121 380 6261

26 2725 167 1226 389 137 3004 130 395 8174

26.5 2611 179 856 234 216 2606 37 330 7069

27 1477 46 272 134 270 1789 0 251 4239

27.5 779 11 136 65 260 508 19 79 1856

28 275 4 19 22 113 398 43 873

28.5 94 19 74 88 14 290

29 27 9 10 44 89

29.5 13 10 23

30 7 7

30.5 7 22 29

31 0

31.5 7 7

32

32.5

33

33.5 5 5

Nos./t 7030 8718 9826 9459 7138 8563 12458 8808 8515


Table 4.2.3.1 Celtic Sea & Division VIIj (2004/2005). Sampling intensity of commercial catches.

ICES area Year Quarter Landings (t) No. Samples No. aged No. Measured Aged/1000 t

VIIa south 2005 4 2326 16 712 1548 306

2006 1 678 7 370 858 546

1082

VIIg 2005 3 2907 12 749 3044 258

2005 4 496 6 457 1085 921

2006 1 2758 8 575 1069 209

1781

VIIj 2005 4 330 2 149 481 451

Overall 9494 51 5875 8085

Table 4.3.1.1. Celtic Sea & Division VIIj herring. Acoustic surveys of Celtic Sea and VIIj herring, by season. Number of surveys per season and type indicated along with biomass and SSB estimates. Shaded sections show surveys not used in tuning.

Old Revised

Season No. Type SSB Abundance 106 SSB

1990/1991 2 Autumn and winter spawners 91 - -





1995/1996 2 Autumn and winter spawners 114 469 36

1996/1997 1 Autumn spawners 146 1338 151

1997/1998 - No survey - - -

1998/1999 1 Autumn spawners 111 656 100

1999/2000 1 Feeding phase 23 - -

1999/2000 1 Winter-spawners 26 - -

2000/2001 2 Autumn and winter spawners 32 256 20

2001/2002 2 Pre-spawning 74 681 95

2002/2003 1 Pre-spawning 39 423 41

2003/2004 1 Pre-spawning 86 183 20

2004/2005 1 Pre-spawning 10 - -

2005/2006 1 Pre-spawning 30 312 33


Table 4.3.1.2. Celtic Sea & Division VIIj herring. Total stock numbers-at-age (106) estimated using combined acoustic surveys (age refers in winter rings, biomass and SSB in 000’s tonnes). Bold text denotes the years used as inputs to assessment input files.

1990 1991 1992 1993 1994 1995 1996 1998 1999 1999 2000 2001 2002 2003 2004 2005

1991 1992 1993 1994 1995 1996 1997 1999 2000 2000 2001 2002 2003 2004 2005 2006

0 205 214 142 259 41 5 3 - 13 - 23 19 0 25 26 13

1 132 63 427 217 38 280 134 21 398 23 18 30 41 73 13 54

2 249 195 117 438 127 551 757 157 208 97 143 160 176 323 29 125

3 109 95 88 59 160 138 250 150 48 85 36 176 142 253 32 26

4 153 54 50 63 11 94 51 201 8 16 19 40 27 61 16 50

5 32 85 22 26 11 8 42 109 1 21 7 44 6 16 3 20

6 15 22 24 16 7 9 1 32 1 8 3 23 8 5 1 5

7 6 5 10 25 2 8 14 30 2 2 17 3 2 1

8 3 6 2 2 3 9 1 4 1 11

9+ 2 - 1 2 1 5 2 1 1 23

Total 904 739 882 1107 399 1107 1253 705 677 252 250 542 404 758 119 292

Biomass (000’t)

103 84 89 104 52 135 151 111 58 30 33 80 49 89 13 33

SSB (000’t)

91 77 71 90 51 114 146 111 23 26 32 74 39 86 10 30

Table 4.3.1.3. Celtic Sea & Division VIIj herring. Revised acoustic index of abundance. Total stock numbers-at-age (106) estimated using combined acoustic surveys (age refers in winter rings, biomass and SSB in 000’s tonnes).

1995 1996 1998 2000 2001 2002 2003 2005

1996 1997 1999 2001 2002 2003 2004 2006

0 202 3 0 25 40 0 24 2

1 25 164 30 102 28 42 13 65

2 157 795 186 112 187 185 62 137

3 38 262 133 13 213 151 60 28

4 34 53 165 2 42 30 17 54

5 5 43 87 1 47 7 5 22

6 3 1 25 33 7 1 5

7 1 15 24 24 3 1

8 2 4 15

9 2 2 2 52

Abundance 469 1338 656 256 681 423 183 312

SSB (000 t) 36 151 100 20 95 41 20 33

CV (%) 53 26 36 100 88 49 34 48


Table 4.6.2.1. Celtic Sea and VIIj herring. Separable model residuals from exploratory ICA runs for 4 year and 6 year separable periods. High residuals indicated.

4 year 2000 2001 2002 2003 2004 2005

1 -0.01 0.37 -0.36 0.00

2 0.31 -0.32 0.00 0.06

3 0.34 -0.51 0.34 -0.05

4 0.14 -0.38 0.14 0.16

5 -0.31 -0.02 0.19 0.09

6 -0.21 0.46 -0.11 -0.09

7 -0.19 0.34 -0.12 -0.02

8 0.00 0.19 -0.13 0.02

6 year

1 0.03 0.55 -0.34 0.22 -0.47 0.00

2 0.54 0.24 -0.03 -0.62 -0.12 -0.01

3 -0.07 0.42 0.11 -0.65 0.28 0.05

4 -0.24 -0.11 0.02 -0.30 0.38 0.48

5 -0.23 -0.25 -0.14 -0.17 0.22 0.29

6 0.17 -0.16 0.01 0.53 -0.41 -0.20

7 -0.10 -0.16 0.09 0.58 -0.05 -0.31

8 0.00 0.10 -0.01 0.30 -0.10 -0.13


A B

C

Figure 4.1.1.1a. Celtic Sea and VIIj herring, areas mentioned in the text and spawning boxes A, B and C, south of Ireland. One of these boxes is closed each season, under EU legislation. 1 Courtmacsherry, 2 Cork Harbour, 3 Daunt Rock, 4 Kinsale Gas Field (Rigs), 5 Labadie Bank, 6 Kinsale, 8 Waterford Harbour, 9, Baginbun Bay, 10, Tramore Bay/ Dunmore East, 11, Ballycotton Bay, 12, Valentia Island, 13 Kerry Head to Loop Head, 14, The Smalls.

Figure 4.1.1.1b. Celtic Sea and VIIj herring, Location of non-spawning (open symbol) and spawning (closed symbol) herring in the Celtic Sea and SW of Ireland. Based on expert fishermens’ personal information.


Herring in the Celtic Sea, VIIj and VIIh, catches by season

0

10000

20000

30000

40000

50000

1958

1961

1964

1967

1970

1973

1976

1979

1982

1985

1988

1991

1994

1997

2000

2003

Figure 4.1.2.1 Celtic Sea and Division VIIj – working group estimates of herring landings per season.

Figure 4.2.1.1 Celtic Sea and Division VIIj – percentage age composition by metier (ICES Division and quarter).

% canum by division and quarter

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10Winter rings

%

VIIg q3 VIIg q4 VIIaS q4 W. HarbourVIIaS q4 open seaVIIg q1 VIIj q4VIIaS q1 W. Harbour VIIaS q1 open sea


Figure 4.1.3.2 Herring catches by statistical rectangle in the first, third and fourth quarters of 2005 and the first quarter of 2005. Catches in ICES division V11a south, VIIg and VIIj are those in the 33 series of statistical rectangles and lower. Quarter 1 catches for VIaS only are indicated.

LegendLand

ICES Division

Herring 2006Qtr1_05

0

0.1 - 49.99

50.01 - 99.99

100.01 - 199.99

200.01 - 499.99

500.01 - 999.99

1000.01 - 1500

ICES Statistical Rectangles

VIa South

VIa North

VIa

VIIa

VIIj

VIIe

VIIb

VIIh

VIIg

IVa

VIb

IVb

VIIf

VIIk

VIIIaVIIId

VIIc

VIIIe

10°0'0"W

10°0'0"W

50°0'0"N 50°0'0"N

LegendLand

ICES Division

Herring 2006Qtr3_05

0

0.1 - 49.99

50.01 - 99.99

100.01 - 199.99

200.01 - 499.99

500.01 - 999.99

1000.01 - 1500

ICES Statistical RectanglesVIIa SouthVIIa North

VIa South

VIa NorthVIa

VIIa

VIIj

VIIe

VIIb

VIIg

VIIh

IVb

VIIf

VIb

IVa

VIIk

VIIc

10°0'0"W

10°0'0"W

50°0'0"N 50°0'0"N

LegendLand

ICES Division

Herring 2006Qtr4_05

0

0.1 - 49.99

50.01 - 99.99

100.01 - 199.99

200.01 - 499.99

500.01 - 999.99

1000.01 - 1500


VIa North

VIa South

VIIa South

VIIa North

VIa

VIIaVIIb

VIIjVIIg

VIb

IVa

VIIf

IVb

VIIc

VIIk

Vb1Vb1 Vb2

VIIe10°0'0"W

10°0'0"W

60°0'0"N 60°0'0"N

VIIa North

VIIa South

LegendLand

ICES Division

Herring 2006Qtr1_06

0

0.1 - 49.99

50.01 - 99.99

100.01 - 199.99

200.01 - 499.99

500.01 - 999.99

1000.01 - 1500


VIa South

VIa NorthVIa

VIIa

VIIj

VIIe

VIIb

VIIh

VIIg

IVb

VIIf

VIb

IVa

VIIk

VIIc

VIIIaVIIIdVIIIe10°0'0"W

10°0'0"W

50°0'0"N 50°0'0"N

Quarter 1 2005

Quarter 1 2006 Quarter 4 2005

Quarter 3 2005


Figure 4.2.2.1 Celtic Sea and Division VIIj. Summary of larval distributions by month in 1980’s from Irish surveys.

10°W 9°W

9°W

8°W 7°W 6°W

51°N

52°N

53°N

1978

640

OctoberNovemberDecemberJanuaryFebruaryMarch

-

10°W 9°W

9°W

8°W 7°W 6°W

51°N

52°N

53°N

1979

640


-

10°W 9°W

9°W

8°W 7°W 6°W

51°N

52°N

53°N

1981

640


-

10°W 9°W

9°W

8°W 7°W 6°W

51°N

52°N

53°N

1982

640


-

10°W 9°W

9°W

8°W 7°W 6°W

51°N

52°N

53°N

1983

640


-

10°W 9°W

9°W

8°W 7°W 6°W

51°N

52°N

53°N

1984

640


-

10°W 9°W

9°W

8°W 7°W 6°W

51°N

52°N

53°N

1985

640


-

10°W 9°W

9°W

8°W 7°W 6°W

51°N

52°N

53°N

1989

640


-

10°W 9°W

9°W

8°W 7°W 6°W

51°N

52°N

53°N

1990

640


-

10°W 9°W

9°W

8°W 7°W 6°W

51°N

52°N

53°N

1980

640


-


Figure 4.2.2.2 Celtic Sea and Division VIIj. Progressive movement of main aggregations of herring inshore in quarter 3 and 4. Data are from acoustic surveys 1998 to 2005 and the summer fishery in 2005.


Figure 4.3.1.1a Celtic Sea and Division VIIj acoustic survey track and haul positions from acoustic survey, October 2005.

Figure 4.3.1.1b Celtic Sea and Division VIIj acoustic survey, total Sa values for herring obtained in October 2005.

-12 -11 -10 -9 -8 -7 -6

Longitude

50.5

51

51.5

52

52.5

53

Lat

itude

1

234

5

67

8

910

1112

13 1415

16

17

18

19202122

23

2425

26

27

28

29

30

3132

33

34

35

3637

38394041

42

43

4445

Trawl HaulCTD Cast

-12 -11 -10 -9 -8 -7 -6

Longitude

50.5

51

51.5

52

52.5

53

Latit

ude

D 8 D 9 E 0 E 1 E 2 E 3

34

33

32

31

30 0 to 10 10 to 100 100 to 1000 1000 to 12000


0

5

10

15

20

25

30

35

40

45

0 2 4 6 8

OverallVIIg q3 VIIaS q1 W. Harbour Acoustic survey Oct 05

UK Q1 Mean standardised numbers-10123456789

101986 1991 1996 2001

Figure 4.3.1.2 Celtic Sea & Division VIIj herring, comparison of percentage catches-at-age from the commercial fishery and from the acoustic survey.

Figure 4.3.2.1 Celtic Sea & Division VIIj herring, mean standardised abundance estimate from UK quarter 1 groundfish survey 1987 to 2002.


Mean weight in the catch

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

1958

1961

1964

1967

1970

1973

1976

1979

1982

1985

1988

1991

1994

1997

2000

2003

Kg

123456789

Mean weight in the spawning stock

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

1958 1963 1968 1973 1978 1983 1988 1993 1998 2003

Kg

123456789

Figure 4.4.1. Celtic Sea and VIIj herring, trends over time in mean weights in the catch.

Figure 4.4.2. Celtic Sea and VIIj herring, trends over time in mean weights in the stock at spawning time.


0

1

2

3

4

5

6

7

8

9

101957 1962 1967 1972 1977 1982 1987 1992 1997 2002

-10123456789

101994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Figure 4.6.1.1. Celtic Sea and VIIj herring. Catch numbers at age in the time series, standardised by year mean.

Figure 4.6.1.2. Celtic Sea and VIIj herring. Acoustic estimates of abundance at age in the revised time series, standardised by year mean.


0.0

1.0

2.0

3.0

4.0

5.0

6.0

0 1 2 3 4 5 6

Old total

Revised

old (1995-2005)

Revised Z = 0.87

Old all years Z = 0.82

Old 1995-2005 Z = 0.92

Figure 4.6.1.3. Celtic Sea and VIIj herring. Comparison of proportions at age in the commercial catch and in the revised acoustic survey abundance estimates.

Figure 4.6.1.4. Celtic Sea and VIIj herring. Catch curves based on acoustic abundance estimates from revised and old acoustic survey series.


SPALY,: recruits

0

200000

400000

600000

800000

1000000

1200000

1958

1961

1964

1967

1970

1973

1976

1979

1982

1985

1988

1991

1994

1997

2000

2003M

illion

s

revisedold series

SPALY: SSB

0

20000

40000

60000

80000

100000

120000

140000

1958

1962

1966

1970

1974

1978

1982

1986

1990

1994

1998

2002

SS

B '0

00 t

revisedoldB lim B pa

SPALY_ mean F

0

0.2

0.4

0.6

0.8

1

1.2

1958

1961

1964

1967

1970

1973

1976

1979

1982

1985

1988

1991

1994

1997

2000

2003F

per y

ear

revisedold

Figure 4.6.2.1. Celtic Sea and VIIj herring. Results of exploratory ICA assessments using SPALY and comparing the revised and the old acoustic sureys.


SPALY: Revised1

2

3

4

5

61989 1991 1993 1995 1997 1999 2001 2003 2005SPALY: Old

1

2

3

4

5

61989 1991 1993 1995 1997 1999 2001 2003 2005

Figure 4.6.2.2. Celtic Sea and VIIj herring. Survey series residuals of exploratory ICA assessments using SPALY and comparing the revised and the old acoustic surveys.


Figure 4.6.2.3 Herring in the Celtic Sea and Division VIIj. Exploratory assessment using updated catch data, excluding the 2004 survey data. Diagnostics of the fit of the old acoustic survey index at age 5 against the estimated spawning biomass. Top left, spawning biomass from the fitted populations (line), and predictions of spawning biomass in each year made from the index observations and estimated catchability (triangles +/- standard deviation), plotted by year. Top right, scatter plot and fitted relationship of spawning biomass from the fitted populations and larvae survey index observations. Bottom, residuals, as ln(observed index) – ln(expected index) plotted against expected values and time.

2 ringer 3 ringer

4 ringer 5 ringer


Figure 4.6.2.4. Herring in the Celtic Sea and Division VIIj. Exploratory assessment using updated catch data, excluding the 2004 survey data. Diagnostics of the fit of the revised acoustic survey index at age 5 against the estimated spawning biomass. Top left, spawning biomass from the fitted populations (line), and predictions of spawning biomass in each year made from the index observations and estimated catchability (triangles +/- standard deviation), plotted by year. Top right, scatter plot and fitted relationship of spawning biomass from the fitted populations and larvae survey index observations. Bottom, residuals, as ln(observed index) – ln(expected index) plotted against expected values and time.

4 ringer

2 ringer

5 ringer

3 ringer


Figure 4.6.2.5. Celtic Sea and VIIj herring. Q-q plots of exploratory ICA assessments using SPALY and comparing the revised and the old acoustic surveys.


F 2-7

0

0.2

0.4

0.6

0.8

1

1.2

1950 1960 1970 1980 1990 2000 2010

F pe

r yea

r

INOUT

Recruits

0

200000

400000

600000

800000

1000000

1200000

1958

1961

1964

1967

1970

1973

1976

1979

1982

1985

1988

1991

1994

1997

2000

2003

Milli

ons

In

Out

SSB

0

20000

40000

60000

80000

100000

120000

140000

1958

1961

1964

1967

1970

1973

1976

1979

1982

1985

1988

1991

1994

1997

2000

200300

0's

In

Out

Blim

Bpa

Figure 4.6.2.6. Celtic Sea and VIIj herring. Comparison of performance of revised acoustic series including and excluding surveys with high CVs (2000 and 2001).


2000, 2001 out1994199519961997199819992000200120022003200420052006

1 2 3 4 5 6

2000, 2001 in1994199519961997199819992000200120022003200420052006

1 2 3 4 5 6

Figure 4.6.2.7. Celtic Sea and VIIj herring. Survey series residuals of exploratory ICA assessments including or excluding the 2000 and 2001 points.


Figure 4.6.2.8. Celtic Sea and VIIj herring. Q-q plots of exploratory ICA assessments including or excluding the 2000 and 2001 points.


Recruits

0

200000

400000

600000

800000

1000000

1200000

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46

Mill

ions

6 year4 year

SSB

0

20000

40000

60000

80000

100000

120000

140000

1958

1960

1962

1964

1966

1968

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

'000

s t

6 year4 yearBlimBpa

F 2 - 7

0

0.2

0.4

0.6

0.8

1

1.2

1958

1961

1964

1967

1970

1973

1976

1979

1982

1985

1988

1991

1994

1997

2000

2003

F pe

r yea

r

6 year4 year

Figure 4.6.2.9. Celtic Sea and VIIj herring. Exploratory runs with 4 and 8 year separable period.


Figure 4.6.2.10. Celtic Sea and VIIj herring. Q-q plots of exploratory ICA assessment comparing 6 year and 4 year separable periods.


Figure 4.6.2.11. Celtic Sea and VIIj herring. Exploratory runs with terminal S = 1.0 and = 1.5.

F 2-7

0

0.2

0.4

0.6

0.8

1

1.2

1950 1960 1970 1980 1990 2000 2010

F pe

r yea

r

11.5

Recruits

0

200000

400000

600000

800000

1000000

1200000

1958

1961

1964

1967

1970

1973

1976

1979

1982

1985

1988

1991

1994

1997

2000

2003

Milli

ons

1

1.5

SSB

0

20000

40000

60000

80000

100000

120000

140000

1958

1961

1964

1967

1970

1973

1976

1979

1982

1985

1988

1991

1994

1997

2000

2003

000'

s

1

1.5

Blim

Bpa


S = 1.50

1

2

3

4

5

6

7

8

91999 2000 2001 2002 2003 2004 2005 2006

S = 1.00

1

2

3

4

5

6

7

8

91999 2000 2001 2002 2003 2004 2005 2006

Figure 4.6.2.12. Celtic Sea and VIIj herring. Survey series residuals of exploratory ICA assessments including or excluding the 2000 and 2001 points.


Figure 4.6.2.13. Celtic Sea and VIIj herring. Q-q plots of exploratory ICA assessment comparing choice of S at oldest age = 1 and 1.5.

Documents

4-Celtic Sea and Div. VIIj Herring