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1 COMMISSION OF THE EUROPEAN COMMUNITIES Brussels, SEC(2007) **** COMMISSION STAFF WORKING PAPER REPORT OF THE SCIENTIFIC, TECHNICAL AND ECONOMIC COMMITTEE FOR FISHERIES EVALUATION OF THE REPORT OF THE AD HOC WORKING GROUP ON ANCHOVY IN THE BAY OF BISCAY ISPRA JUNE, 2007 This report has been evaluated by the Scientific, Technical and Economic Committee for Fisheries (STECF) in its plenary session of June 2007 This report does not necessarily reflect the view of the European Commission and in no way anticipates the Commission s future policy in this area.

2 Table of Contents 1. Background.3 2. Summary Findings of the Ad Hoc Working Group on anchovy in the Bay of Biscay STECF Comments and Advice Annex I Report of the Ad Hoc Working Group on anchovy in the Bay of Biscay 7 2

3 1. Background The scientific advice for anchovy fishery in the Bay of Biscay provided by ICES-ACFM in October 2006 was to remain closed and should be considered for opening if the acoustic and egg surveys to be carried out in May-June 2007 demonstrate a strong 2006 recruitment. Furthermore, the STECF plenary in 2006 recommended a zero TAC for the first half of the year and a possible re-opening of the fishery based on minimum spawning stock biomass level (Blim) set up at 21,000 tones. Should the results of the spring surveys indicate a lower level, the fishery should remain closed for the rest of the year. In case the SSB is greater, then the fishery could be re-opened with a new TAC level to be calculated based on simulations. An STECF subgroup was convened from June, at Casa Don Guanella, Ispra to work in work parallel to the STECF plenary with the following Terms of Reference: 1. Assess the spawning stock biomass on the basis of the 2007 spring acoustic and DEPM surveys in the Bay of Biscay. Calculate maximum allowable catches for the second half of 2007 and first half of 2008 as a function of the spawning stock biomass estimated in May 2007 and in case of low future recruitment (at different percentiles of the historical available estimates) and under the condition that the fishery would allow a spawning biomass at Bpa in Evaluate and comment on whether there is a relationship between the recruitment abundance index estimated through the acoustic and fishing surveys carried out in autumn 2006 and first semester 2007 and the abundance of age class Provide estimates of overall catches and catch rates by fishing gear and country on the basis of the results of the experimental fisheries undertaken during the first semester A comparison among years of catch statistics during the same fishing period would be advisable. STECF was requested to deliver its opinion on the subgroup s work and advise on fishing opportunities before 30 June. 2. Summary Findings of the ad hoc Working Group on Anchovy in the Bay of Biscay. The Report of the ad hoc Working Group meeting on Bay of Biscay anchovy is given in Annex I. STECF reviewed the report in its plenary meeting of June 2007 noting the following: The SSB in 2007 was estimated as 30,086 tonnes, and recruitment of the 2006 yearclass biomass as 23,082 tonnes. Although overall biomass and recruitment of Biscay anchovy appears to have improved since the historical low in 2005, the estimate of SSB in 2007 is still considered by STECF to be low. The estimated biomass of the recruiting 2006 year-class in 2007 is 23,082 t, which is low. 3

4 With the exception of the 2004 year-class, which is classified as medium, all recruiting year-classes since 2002 have been low. There is no information presently available to estimate the strength of the 2007 year-class of anchovy. Based on the historical time series of recruitment at age 1, there is a high probability that the biomass of the 2007 year-class in 2008 will also be low. If recruitment of the 2007 year-class in 2008 is low, any fishing in 2007 and the first half of 2008 will be associated with a high probability of SSB in 2008 being below B lim. An acoustic survey targeted on juvenile (age 0) anchovy in Biscay was carried out by AZTI from 13/09 to 15/10/2006 using two vessels. The survey followed the same pattern as that in The biomass estimate for age 0 anchovy was approximately 130,000 tonnes, although there were some technical problems with the acoustic gear that suggest this figure may be revised. The biomass is also somewhat higher than that estimated for the same year class in spring This may be due to high juvenile mortality in the winter and/or target strength differences. The index has shown a similar pattern to model estimates of recruitment over the last four years, suggesting it may have value in providing an advance estimate of recruitment. However, there has been little contrast over these years, and this index must be viewed with caution. Additionally, the survey has only covered the full distribution area in the last two years. Commercial vessels were used as consorts in both the PELGAS and BIOMAN surveys. In the case of PELGAS, the information from the six French trawlers, and two French and three Spanish purse seiners, were not used in the stock estimation for the assessment. This was to maintain continuity in the time series. However data exploration showed that the inclusion of catch data from these vessels did not substantially alter the perspective of the stock, and actually led to a small reduction in SSB estimate. Biological information from some of the vessels was used to improve the precision of the age composition in the stock. In the case of BIOMAN, four Spanish purse seiners worked with the two survey vessels. Adult samples from these vessels were used in the survey data analysis and proved very valuable, allowing a greater area coverage, and also in covering for the adult sampling RV when it experienced operational problems. The collaboration between industry and scientists was considered valuable for both parties, particularly in terms of mutual understanding. 13 Spanish purse seine vessels took part in a RAKE survey of the Cantabrian Sea and the southern part of the Bay of Biscay. The catch distribution was close to that of the two scientific surveys, as was the age structure of the anchovy caught. While the survey was successful, the group considered that it was of limited scientific value, and would not be used in any assessment. Additionally, the original STECF recommendation was to use purse seiners and trawlers, and that some of the vessels should deploy scientific echosounders. This did not occur. It was also recommended that the survey should be integrated between France and Spain, and cover the entire distribution area, and this also did not occur. Five French fishing vessels were allowed to carry out experimental fishing between 15/4/2007 and 10/6/2007. The catches were permitted under a range of constraints and limitations. The results proved impossible to interpret and of no value to assessment or management. 4

5 3. STECF Comments and Advice Based on the findings of the SGRST Working Group, STECF draws the following conclusions and recommendations. 3.1 STECF advice on maximum allowable catches for the second half of 2007 and first half of 2008 STECF notes that there are clear signs that the stock situation has improved compared to However, spawning stock biomass remains very low and maximum protection of the remaining spawning population is required. STECF recommends that management measures other than complete closure of the fishery in 2007 should not be considered. STECF further recommends that the fishery should remain closed in 2008 until reliable estimates of the 2008 SSB and 2007 year class become available based on the results from the spring 2008 acoustic and DEPM surveys. This implies a closure of the fishery until at least July STECF stresses that any recovery is entirely dependent on good incoming recruitment, which cannot be predicted at present. 3.2 STECF Advice on long-term management plans STECF notes that there is presently no agreed comprehensive long-term management plan for this stock and recommends that alternative or complementary management measures to output control (TAC) need to be further investigated to maintain the longer-term viability of the stock (closed seasons, closed areas, minimum size, etc.). These should only be considered after the stock has recovered to biologically safe levels, and would need to be scientifically evaluated prior to adoption. 3.3 STECF advice on surveys for Bay of Biscay anchovy The spring acoustic and DEPM surveys provide the main tuning indices to the current assessment and should be maintained. STECF recommends that if the PELGAS consort surveys are continued they should include vessels using scientific echosounders, and the selectivities of the different gears should be evaluated. The large number of vessels in both surveys was unnecessary, and the consort role could be filled by fewer vessels. The time allocated for planning and preparing for the surveys was not sufficient in 2007 and any repeat exercise should allow considerably more time. STECF concluded that the RAKE survey provided little or no new information for assessment or management. It also required considerable commitment from research staff, and STECF felt this was better applied to key questions such as early recruitment estimation. Consequently, STECF does not recommend a repetition of these surveys at this time. Should they be repeated, more advance planning should be allowed for, and the conduct of them should be integrated and coordinated between the interested parties. STECF recommends that in the absence of a scientific design, experimental fishing should not be undertaken. 5

6 Acoustic and fishing surveys should continue to be carried out in the period of September/October every year to provide an index of abundance of recruits. The survey(s) should cover the known distributional areas of the juvenile anchovy and should include pelagic trawling as well as purse seine fishing. JUVENA surveys have already incorporated these suggestions. STECF notes that the main objectives of the five or six surveys conducted each year are similar and recommends that all nations and/or institutes involved in the fishery should try to achieve further coordination to avoid duplication of effort. STECF also suggests that the ICES WGACEGG would be an ideal forum to discuss and arrange enhanced co-ordination. STECF also encourages development of any other research that could provide additional information on the recruitment process in this stock. Therefore, in addition to surveys for juvenile abundance estimation, any work (surveys) leading to a better understanding of the mechanisms causing fluctuations of anchovy recruitment should be encouraged. The similarity in the relationship between the JUVENA abundance index of anchovy juveniles and the population at age 1 at the beginning of the following year is encouraging and shows promise as a recruitment predictor. The time series at present, however, consists of only 4 years of observations preventing a proper evaluation of potential performance as a predictor. STECF considers that at least 1 more annual observation is required before a proper evaluation can be undertaken. 3.4 Timing of STECF advice on Bay of Biscay anchovy STECF wishes to point out that with the information currently available to STECF, it can provide advice on fishing opportunities for Bay of Biscay Anchovy on a half-yearly basis. Advice for fishing opportunities for the first half of the year (January to June) can be given in June of the previous year based on an assessment of SSB at that time. Advice on fishing opportunities for the second half of the year can only be given in June of the same year, because a reliable estimate of the strength of the recruiting year-class at age 1, is a prerequisite to issuing such advice. 6

7 ANNEX I Report of the Working Group on Anchovy in the Bay of Biscay COMMISSION OF THE EUROPEAN COMMUNITIES COMMISSION STAFF WORKING PAPER REPORT OF AD-HOC WORKING GROUP ON ANCHOVY IN THE BAY OF BISCAY OF THE SCIENTIFIC, TECHNICAL AND ECONOMIC COMMITTEE FOR FISHERIES (STECF) Ispra, June 2007 This report will be evaluated by the Scientific, Technical and Economic Committee for Fisheries (STECF) in its plenary session of June 2007 This report does not necessarily reflect the view of the European Commission and in no way anticipates the Commission s future policy in this area. 7

8 1. Executive Summary The work of the sub group was divided into three parts based on the ToR, and were as follows 1. Spawning Stock Biomass assessment based on the spring acoustic and DEPM surveys and calculate possible catch options. 2. Evaluation of the relationship between juvenile abundance surveys in Autumn 2006 and the abundance of age class 1 in spring Evaluation of the conduct and value of using commercial vessels in collaboration with scientists and research vessels to provide information for management 1.1. Spawning Stock Biomass assessment based on the spring acoustic and DEPM survey estimates and an analysis of possible catch options The Surveys Two surveys were carried out in the spring of The French acoustic survey (PELGAS) was carried out from 26 April - 26 May, and covered French waters in Biscay. The Spanish DEPM survey (BIOMAN) was carried out from 3-23 May, and covered the eastern end of the Cantabrian Sea and French waters in Biscay. Estimates from PELGAS were as follows: Biomass: 41,000 tonnes, CV ~10% Numbers: 2200 million Age structure: 66% age 1, 29% age 2, 5% age 3+ The survey was carried out as in previous years and using standard procedures Estimates from BIOMAN were as follows: Biomass: 25,000 tonnes, CV ~20% Numbers: 1500 million Age structure: 73% age 1, 24% age 2, 3% age 3+ The survey was carried out as in previous years and using standard procedures. The estimate was a preliminary one, as adult parameters have not yet been estimated. In addition, egg mortality could not be estimated as in previous years as the analysis provided no significant relationship. Hence, it was estimated from previous observations using an SST model. Although the two survey estimates were slightly different, they showed similar distribution patterns and age structures. Additionally they show similar patterns for the recent stock trajectory Stock assessment The stock assessment was conducted using a Bayesian Biomass based model, as used at recent ICES WGMHSA. No landings were included for 2007 due to the closure of the fishery. The surveys were used as tuning indices. The SSB in 2007 is 29% higher than in The population may be considered as above B lim (with a probability of being below it of 3.2%) while in 2006 that probability was 40% (ICES 2006). However the recruitment at age 1 in 2007 is of similar level to that in 2006, both being in the lowest range of the past recruitment series. Therefore this assessment does not indicate a recovery of recruitment levels. Consequently, the WG considers that the situation of repeated low levels of recruitment has not changed during the last years since

9 Projections Bayesian credible intervals were estimated for both these values (SSB and Recruitment), and these were then used to carry out projections for a range of recruitment scenarios, balance of fishing in the last 6 months of 2007 against the first half of 2008, and a range of catches from 0 to 30,000 tonnes. Three recruitment scenarios were used based on three modes in the histogram for historic recruitment levels. These were taken as; low, medium and high scenarios which represent each with a probability of 54%, 28% and 18% percentile of the probability density function (pdf) of the recruitment series respectively according to the historical series. Recent recruitments have all been low. The results from the projections were presented in terms of the risk of falling below B lim in 2008 for a range of catches, recruitment scenarios and balance of fishing. STECF considers that the best precautionary assumption would be that recruitment in 2008 would be low as in recent years. In this case, zero catch would give a risk of falling below B lim of ~11% in Any non zero catch would increase that risk. Table were provided to managers in digital (MS EXCEL) format providing all options of catch, balance and recruitment Recruitment to this stock has been low now for several years. Therefore, following the precautionary approach, any decisions on catch options should assume that this will continue for If fishing is to be allowed, the precautionary approach would indicate that this should be set at a level that minimizes the risk of SSB falling below B lim in 2008 given low recruitment. Options for catch, and associated risk of falling below B lim under a low recruitment scenario have been provided in a separate spreadsheet Evaluation of the relationship between juvenile abundance surveys in Autumn 2006 and the abundance of age class 1 in spring 2007 An acoustic survey targeted on juvenile (age 0) anchovy in Biscay was carried out by AZTI from 13/09 to 15/10/2006 using two vessels (JUVENA survey). The survey followed the same pattern as that in The biomass estimate for age 0 anchovy was approximately 130,000 tonnes, although there were some technical problems with the acoustic gear that suggest this figure may be revised. This value should be considered as an index of abundance and not as an absolute estimate. This biomass value is somewhat higher than that estimated for the same year class in spring This may be due to high juvenile mortality in the winter and/or target strength differences. The index has shown a similar pattern to model calculated recruitment over the last four years, suggesting it may have value in providing an advance estimate of recruitment. However, there has been little contrast over these years, and this index must be viewed with caution. Additionally, the survey has only covered the full distribution area in the last two years. An additional survey has been started at this time of year (PELACUS), but as 2006 was the first time this survey was carried out it was not possible to evaluate it as yet. The sub group recommended that the surveys be continued, as the index shows a reasonable relationship to outcome recruitment. STECF also recommends that the conduct and analysis of these surveys continue to be developed. In addition the IEO and AZTI surveys should be coordinated and integrated to be complementary and thus sample the whole area at the best resolution Evaluation of the conduct and value of using commercial vessels in collaboration with scientists and research vessels to provide information for management The STECF sub group in Spring 2007 on Bay of Biscay anchovy recommended the following: Use of commercial vessels as survey consorts Use of commercial vessels in a multi-vessel RAKE survey NO experimental fishing Survey Consorts Commercial vessels were used as consorts in both the PELGAS and BIOMAN surveys. In the case of PELGAS, the information from the six French trawlers, and two French and three Spanish purse seiners, were not used in the stock estimation for the assessment. This was to maintain continuity in the time series, and also because information of selectivity on the catches from the different sampling gears was not 9

10 available. However data exploration showed that the inclusion of catch data from these vessels did not substantially alter the perspective of the stock, and actually led to a small reduction in SSB estimate. It also showed different catchability levels between pelagic trawlers and purse seiners by species which may explain some of these differences. The data collected during PELGAS 2007 will be evaluated in this context in the near future. The biological information from some of the vessels was used to improve the age determination for the estimate, and also to refine the stratification of the survey area for analysis. The exercise was considered as valuable for both parties, particularly in terms of mutual understanding. In the case of BIOMAN four Spanish purse seiners worked with the two survey vessels (one for egg sampling and the other for adult sampling). Adult samples from these vessels were used in the survey data analysis and proved very valuable, allowing a greater area coverage, and also in covering for the adult sampling RV when it experienced operational problems. As in PELGAS, the exercise was considered as valuable for both parties, particularly in terms of mutual understanding. It was recommended that if the PELGAS consort surveys are continued they should include vessels using scientific echosounders, and the selectivity of the different gears should be evaluated. The large number of vessels in both surveys was not necessary, and the consort role could be filled by fewer vessels. The time allocated for planning and preparing for the surveys was not sufficient and any repeat exercise should allow considerably more time RAKE surveys 13 vessels took part in a RAKE survey of the Cantabrian Sea and the southern part of Biscay. The vessels were all Spanish purse seiners. The resultant catch distribution was close to that of the two scientific surveys as was the age structure of the anchovy caught. While the survey was successful, it was considered as being of limited scientific value, and would not be used in any assessment. Additionally, the original recommendation was to use purse seiners and trawlers, and that some of the vessels should deploy scientific echosounders. This did not occur. It was also recommended that the survey should be integrated between France and Spain, and cover the entire distribution area, and this also not occur. STECF concluded that while the survey results were interesting, and that the exercise proved a useful collaboration with industry, it provided little or no new information for assessment or management. It also required considerable commitment from research staff, and STECF felt this was better applied to key questions such as early recruitment estimation. The sub group did not recommend a repetition of these surveys at this time. Should they be repeated, more advance planning should be allowed for, and the conduct of them should be integrated and coordinated between the interested parties Experimental fishing Five French fishing vessels were allowed to carry out experimental fishing between 15/4 and 10/6. The catches were allowed under a range of constraints and limitations. The results proved impossible to interpret and of no value to assessment or management. It was again recommended that no experimental fishing be carried out as it is expected that this would have no appreciable value in the management of this stock. 2. Spawning stock assessment 2.1. Acoustic Survey (PELGAS) The PELGAS07 acoustic survey has been carried out from 26 th April to 26 th May in good conditions, at least for the anchovy distribution area for which the biomass assessment was possible. The bad weather mainly occurred during the second half of the survey, when the potential area of anchovy presence was already covered. The anchovy biomass from the Pelgas07 survey has been estimated using exclusively data collected on board Thalassa to be coherent with the method and strategy used since Among 412 hours of acoustic surveying, 10

11 1449 nautical miles were processed to get fish energies and 39 identification hauls (Figure 2.1.1) were used to split them into species. Figure 2.1.1: Acoustic transects and identification hauls (left) used from PELGAS07 survey for the anchovy biomass estimate and its geographical distribution (right). The biomass therefore calculated for anchovy was about 41,000t (Table 2.1.1). This biomass is globally higher than the biomass observed in 2006 and much higher than in 2005, but still below the period (Figure 2.1.5). As usual, small fish was mainly observed in the coastal area whereas bigger fish were present on the platform and offshore (Figure 2.1.2). NB individuals Inshore length(0.5cm) Offshore NB individuals length(0.5cm) Total NB individuals length(0.5cm) Figure : Length distribution of anchovy observed during PELGAS07 inshore (strata 3, 5 & 7) and offshore (strata 1, 2, 4, 6 & 8) The number of 1 year old anchovy was estimated at 1,437 millions fish (Table 2.1.1). The global population observed in the Bay of Biscay was composed of 66.2 % of age 1, 29.1 % of age 2 and 4.7 % of age 3+ (Table and Figure 2.1.3). 11

12 Observations show that the mean length of age 3 is lower than for age 2. It should also be noted that mean weight at age 1 is higher this year than last year (16.5g and 14.0g respectively) (Table 2.1.1). In spring 2007, the anchovy spatial distribution was broad but generally not dense (Figure 2.1.1). It was present all along the coast from Bayonne to l'ile d'yeu mixed with sardine or sprat and offshore mainly in "fer à cheval" area or in the southern platform mixed with horse mackerel. Table 2.1.1: Anchovy biomass estimate from PELGAS07 acoustic survey and age distribution. Biomass (t) Numbers (10 6 ) G1 G2 G3 G4 Inshore (3, 5 & 7) 24,941 1, , Offshore (1,2,4,6,8) 15, Total 40,876 2, , Mean weight (g) Mean length (cm) Coef. of var Pel00 Pel01 Pel02 Pel03 Pel04 Pel05 Pel06 Pel07 Figure 2.1.3: Age distribution of anchovy from acoustic surveys PELGAS since On the one hand, it must be noticed that this configuration of anchovy biomass is accompanied by a more traditional school pattern as it was used to be observed during the healthy years during the ninetieth or beginning of This can be also due to the rather absence of horse mackerel and sardine which were very rarely observed during the survey. Another element is that marine mammals were very rarely observed this year. All these parameters could be an explanation of the spread of a rather good presence of fish behaving in the same way than they were used to do when biomass was at its best levels. On another hand, it can be also noticed that the number of eggs observed by CUFES was particularly high, twice the amount observed in 2001 which was the highest year among the 7 years series (Figure 2.1.4). The hydrological conditions which where characterized by a strong positive anomaly (about 2 C) compared to the mean of the 15 previous years could be a part of this result. 12

13 Figure 2.1.4: Number of eggs observed during PELGAS surveys from 2000 to The biomass estimate given by the PELGAS survey since 1989 are given in Figure with the confidence intervals since Anchovy Biomass from French accoustic t survey in the Bay of Bi (to ns) Figure 2.1.5: Biomass estimate series from PELGAS DEPM Survey The research survey BIOMAN07 for the application of the Daily Egg Production Method (DEPM) for the Bay of Biscay anchovy has been conducted in May 2007 from the 3 rd to the 23 rd covering the whole spawning area of the species. A preliminary SSB estimate is obtained as the ratio between the total daily egg production (P tot ) and the daily fecundity (DF) estimates. P tot is calculated as the product of the spawning area and the daily egg production rate (P 0 ), which is obtained from the exponential mortality model fitted as a Generalized Linear Model (GLM) to the egg daily cohorts. As the adults samples are not fully processed yet, the DF estimate is based on its relationship with the average Sea Surface Temperature (SST) inferred from the historical series. The biomass estimate is 25,300 t with a coefficient of variation of 20% which is just 18% higher than the one estimated for

14 Choices on Z and df In the DEPM, daily egg production (P 0 ) and mortality (Z) rates are estimated by fitting an exponential mortality model to daily cohort abundance and age data. The model can be fitted either as a non-linear regression model or as a generalised linear model with negative binomial distribution and log link. For both types of models this year the hourly mortality rate resulted to be non-significantly different from zero (p-value and 0.1 for non linear regression and generalised linear models respectively). By the time being and given the short time available from the end of the survey to this meeting, it was decided to fix Z based on the past historical series and then, to estimate P 0 from the exponential mortality model based on the assumed value of Z. Two alternative models were considered for estimating Z: (a) average daily mortality rate from the historical series and (b) natural logarithm of Z depending linearly on sea surface temperature (SST) as has been previously proposed for pelagic fish eggs in Pepin (1991). Model (b) resulted to be significant (p-value=0.002) and explained around 40% of the variability. Its reliability in comparison with the average model (a) was checked by cross-validation following the approach described in Francis (2006). For each year y in the historical data set the method consisted on: Drop year y from the data set Fit model (a) Fit model (b) Predicted value for year y according to model (a) Predicted value for year y according to model (b) Then, the percent variance explained (PVE) statistic was computed as: PVE 100 (MSE MSE a b =, MSEa where MSE a and MSE b are the mean square error computed as the residual sum of squares between the observed value (omitted) and the one predicted by the models (a) and (b) respectively. The PVE statistic resulted to be positive (around 52%), indicating that the expected error from the average model (a) is larger than from the model depending on SST (b). The average sea surface temperature in the DEPM 2007 survey has been 15.38ºC. Hence, the expected daily mortality rate value according to model (b) is Based on this fixed value of Z the resulting P 0 and P tot estimates from the nonlinear regression and generalised linear model are given in Table Note that the coefficients of variation of Z, P 0 and P tot are underestimated, as they are based on the assumption that Z is known without error (cv(z)=0). Table : P 0 and P tot estimates depending on the model when Z is fixed to 0.2. (P 0 in terms of eggs /0.1m 2. 1-Bayesian + N linear ) 2-Bayesian + GLM Value CV Value CV P z Ptot 1.45.E E The sensitivity of P 0 estimates to the assumed value of Z for non linear regression and generalised linear model is shown in Figure The Z values in the historical series range from 0.11 in 1994 to 0.94 in June 1989, with an average value of Since 2000, the Z estimates have been between 0.13 and 0.45, which would imply P 0 to be between 36 and 68 eggs per day and m 2 14

15 P non-linear glm Z Figure : Sensitivity of the P 0 estimate (per m 2 ) to the different assumed Z values for the non-linear regression model (solid line) and the generalised linear model (dashed line). Until the adult samples are fully processed the daily fecundity (DF) cannot be estimated following the usual DEPM protocol. Hence, in order to provide a preliminary SSB estimate, two models based on the historical series were considered: (a) DF is just the average from the time series and (b) DF is linearly dependent on Sea Surface Temperature. Model (b) explains 35% of the variance and resulted to be significant (p-value=0.007). Similarly to what has been done with the model for Z, the reliability of model (b) in comparison to the average model (a) was assessed using the cross-validation method (Francis, 2006). The PVE was around 32%, suggesting that model (b) is slightly more reliable than model (a). According to the fitted model (b) and the average SST found in the DEPM 2007 survey (15.38ºC), the expected DF value for 2007 is 61 eggs per gram and day with a 95% prediction interval of (36.2, 86.5). The current preliminary SSB estimate from the DEPM for anchovy in 2007 has been derived as the ratio between P tot and DF estimates that were based on modelling Z and DF as a function of SST. These models depending on SST resulted to be more reliable than just the average value from the historical series. However, the percentage of variance explained by both models is low (less than 50%), leading to low predictive power. This practice of providing preliminary estimates of SSB from the DEPM samples, until the method is fully applied, has also been followed in previous years. Especially in the last 4 years, in which the population was at low levels and real-time management has been required. The preliminary SSB estimates provided sequentially each of the years are usually: 1. When the number of eggs have been sorted and counted but not staged yet, SSB is estimated from a linear model of SSB depending on the total number of eggs found in the survey. 2. When the eggs samples have been analysed, i.e. P tot is estimated, but the adult samples are still under process, DF is estimated from the historical series based on a model from the historical data series 3. When all the egg and adult samples have been processed, the final SSB estimate from the full application of the DEPM is obtained. Figure compares these three estimates from 1997 to The trends are similar and no systematic bias is found, supporting the use of the preliminary estimates to help on the real-time management for the species. 15

16 SSB (tones) SSB based on ABtot SSB based on DF modelled Final SSB Year Figure : Comparison between the different estimates provided from the DEPM until the final estimate from the complete application is obtained Survey results A total of 420 vertical tows were collected using a PairoVET net from which 235 stations were positive for anchovy eggs with an average of 16 eggs per positive station and a maximum of 308 eggs. The anchovy eggs were concentrated in two principal areas: the area of Cap Breton between 43º30 and 44º15 on the isoline of 200m, and at costal areas in the Gironde area between 45ºN and 46º10 until the isoline of 100m. Egg abundance was low across the Cantabric coast (Figure ) 200m BIOMAN May R/V Investigador anchovy eggs/0.1m² m Stations with 0 anchovy eggs Nantes La Rochelle Bordeaux Arcachon Santander Bi SS Figure : Plankton stations and egg abundances (eggs per 0.1m 2 ) from the DEPM survey BIOMAN07 obtained with PairoVET. There were gathered 44 adult samples, 10 of them provided by the R/V Emma Bardán and 34 by the purse-seines (Figure ). The distribution of adults and composition of the hauls is showed in Figure These 16

17 adults are at the moment been processed for the estimation of the DF but the otholits obtained from those have been used to estimate the numbers at age. Nantes BIOMAN Mayo Anchovy Sardine Mackerel HMac Other Lances nulos La Rochelle Bordeaux Arcachon Santander Bi SS Figure : Species composition of the fishing hauls from the R/V Emma Bardán and the four consort purse-seines in BIOMAN 07. The preliminary spawning stock biomass estimate for anchovy in 2007 resulted in 25,300 t with a coefficient of variation of 20% what is just 18% higher than the one estimate for A sensitivity analysis was performed for the egg mortality values (Z) ranging between the lowest past values of the series (about 0.1) and the mean value of 0.27 (rounded up to 0.3). The SSB estimates would range from 21,000 t to 30,500 t. respective to those two Z values. The percentages at age in the population were estimated as the average of proportions at age of the samples, weighted by the population each sample represents. These results are showed in Table Table : SSB 2007 estimates and the correspondent standard error (S.e.) and coefficient of variation (CV) of the proportion by age and population at age estimates, with the mean weight by age class. Parameter Estimate S.e. CV Biomass (Tons) 25,309 5, Total mean W (g) Population (millions) 1, Percent age Percent age Percent age Numb. at age 1(millions) 1, Numb. at age 2(millions) Numb. at age 3(millions) Weight at age 1 (g) 14.3 Weight at age 2 (g) 25.2 Weight at age 3 (g) 18.2 In order to provide a broader point of view for the interpretation of current survey results, distribution maps of the anchovy egg abundances in the last 12 DEPM surveys were compiled and compared (Figure ). The 17

18 whole series of biomass estimates from the DEPM, including the current preliminary estimate for 2007, are presented in Figure The historical series of numbers at age is shown in Figure Tons 130, , , ,000 90,000 80,000 70,000 60,000 50,000 40,000 30,000 20,000 10, Figure : Series of Biomass estimates (tonnes) obtained from the DEPM since Most of them are full DEPM estimates, except in 1996, 1999, 2000 and 2007, which were deduced indirectly. 6,500 6,000 5,500 5,000 4,500 4,000 Age 3+ Age 2 Age 1 3,500 3,000 2,500 2,000 1,500 1, Figure : Historical series of numbers at age in millions. 18

19 Nantes Nantes BIOMAN MAY R/V EXPLORADOR La Rochelle BIOMAN MAY R/V INVESTIGADOR La Rochelle Anchovy eggs/0.1m² Bordeaux Arcachon Anchovy eggs/0.1m² Bordeaux Arcachon Santander Bi SS Santander Bi SS Nantes Nantes BIOMAN BIOMAN MAY - 5 JUN MAY - 8 JUN La Rochelle R/V INVESTIGADOR La Rochelle R/V INVESTIGADOR Anchovy eggs/0.1m² Bordeaux Anchovy eggs/0.1m² Bordeaux Arcachon Arcachon Santander Bi SS Santander Bi SS Nantes Nantes BIOMAN MAY R/V INVESTIGADOR La Rochelle BIOMAN MAY - 8 JUN R/V INVESTIGADOR La Rochelle Anchovy eggs/0.1m² Bordeaux Anchovy eggs/0.1m² Bordeaux Arcachon Arcachon Santander Bi SS Santander Bi SS

20 Nantes Nantes BIOMAN MAY R/V INVESTIGADOR La Rochelle BIOMAN MAY - 9 JUN R/V INVESTIGADOR La Rochelle Anchovy eggs/0.1m² Bordeaux Anchovy eggs/0.1m² Bordeaux Arcachon Arcachon Santander Bi SS Santander Bi SS Nantes Nantes BIOMAN MAY R/V VIZCONDE DE EZA La Rochelle BIOMAN MAY R/V VIZCONDE DE EZA La Rochelle Anchovy eggs/0.1m² Bordeaux Anchovy eggs/0.1m² Bordeaux Arcachon Arcachon Santander Bi SS Santander Bi SS BIOMAN MAY R/V VIZCONDE DE EZA Nantes La Rochelle m BIOMAN May R/V Investigador 100m Nantes La Rochelle Anchovy eggs/0.1m² Bordeaux Arcachon anchovy eggs/0.1m² Bordeaux Arcachon Stations with 0 anchovy eggs Santander Bi Santander SS Bi SS Figure : Anchovy egg distribution obtained on the DEPM BIOMAN surveys from 1996 to

21 2.3. Pelacus spring additional information PELACUS0407 was carried out onboard R/V Thalassa between 28 th March 23 rd April, with the main aim to assess the pelagic fish community off the North Iberian Peninsula (Figure 2.3.1). Biomass estimates are obtained for the main pelagic fishes in the survey area, including sardine, mackerel, horse mackerel and, whenever it is present in sufficient fishing hauls, anchovy. For the 2007 survey, a high number of anchovy eggs in the CUFES sampler (the largest in the available time series ) was observed (Figure WD Iglesias et al.). Also, the eggs were covering most of the shelf in the area between 4 and 6 º W, west of the main egg distribution area (see Section 2.2). A total of 16 out of 52 fishing stations caught anchovy, and acoustic estimates of biomass of anchovy were 2,900 tn (Table 2.3.1), distributed in a number of small patches through the Cantabric sea (Figure 2.3.3). The PELACUS04 survey series does not cover the main area of anchovy distribution within the Bay of Biscay, and therefore anchovy biomass estimates from this survey are not used for its assessment. Nevertheless, the variable presence of anchovy in the area surveyed by PELACUS may be an index of changes in the spatial structure of the stock, related to either oceanographic or demographic properties. In this sense, anchovy data gathered in the PELACUS survey can be of interest to analyse changes in the Bay of Biscay anchovy distribution, and can be also used to improve the coverage of the acoustic and DEPM anchovy surveys. Table 2.3.1: Abundance (in million individuals) and biomass (in tonnes) acoustic estimates for the different pelagic species assessed in PELACUS0407: Sp = Sardina pilchardus, Ee= Engraulis encrasicolus, Ss= Scomber scombrus, Sj= Scomber japonicus, Tt = Trachurus trachurus, Tp = Trachurus picturatus, Bb = Boobs boobs, Mp = Micromessistius poutassou, Ca = Capros aper Sp Ee Ss Sj Tt Tp Bb Mp Ca Total Abundance 1, ,327 5,221 Biomass 96,390 2,861 19,8801 6,957 31,962 2,147 14,840 4, , ,469 21

22 Figure 2.3.1: PELACUS0407 sampling effort. Red and green (additional offshore sampling) lines indicate acoustic transects, blue round points indicate fishing stations, and purple square indicate hydrography stations (small ones indicate normal stations, big ones indicate intensive stations with multinet). 22

23 Figure 2.3.2: Distribution of anchovy eggs through the PELACUS time series ( ). Crosses indicate negative stations, while circles indicate positive stations with diameter proportional to egg abundance. All figures in the same scale. 23

24 Mug ia Ca bo Finisterre Malpica No ya La G u ar d ia Vi la garc ia Vi go La C o ru ña Ribadeo Lua r ca Cu di l le r o Ca nd as Vi la vic io sa Ri ba de se l a Ll an es Sa nt oñ a Bi lb ao Be r m eo Sa n S eb ast i án Ba y o nne VIIIc-EW VIIIb VIIIc-EE VIIIc-W # # # # # # # # # # # # # # # # # # IX a-n # # # IXa -C N N W E S Figure 2.3.3: Spatial distribution of energy allocated to anchovy during the PELACUS0407 cruise. Polygons are drawn to encompass the observed echoes, and polygon colour indicates integrated energy in m2 within each polygon. 24

25 2.4. Stock assessment In this section an update of the Bay of Biscay anchovy stock assessment conducted in September 2007 by the ICES Working Group on assessment of mackerel, horse mackerel, sardine and anchovy (WGMHSA) (ICES, 2006) is presented. The assessment is based on the Bayesian Biomass-based Model (BBM), in which the state equations describing the population dynamics separate the recruits (age 1 individuals) from the rest (individuals of age 2 and older) and the observation equations correspond to spawning stock biomass and age 1 proportion of biomass from the acoustics and DEPM surveys (ICES, 2006). The model is set up within the framework of Bayesian state-space models and inference is conducted using Markov chain Monte Carlo (MCMC) methods. The model was run assuming that DEPM and acoustic surveys provide absolute and relative Spawning Stock Biomass (SSB) estimate respectively (i.e. q depm is fixed to 1 and q ac is estimated) using the first set of priors as it was done in ICES (2006). The data used for the assessment is presented in Table Due to the closure of the fishery in the second half of 2006 and the first half of 2007, the only catches taken were those arising from the experimental fishery in spring However, these catches were very low (around 150 tonnes) and were assumed to be zero for the stock assessment. Table 2.4.1: Input data for the Bayesian biomass-based model. CATCH BIOMASS 1st PERIOD 2nd PERIOD DEPM ACOUSTICS Year h1 h2 age 1 total total age 1 total age 1 total NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 0 0 NA Summary statistics (median and 95% posterior intervals) of the posterior distributions of recruitment (age 1 biomass in tonnes in the 1st January), spawning stock biomass and harvest rates (Catch/SSB) for the historical series are shown in Table and Figure This assessment is fully consistent with the last assessment provided by ICES (ICES 2006). The largest credible intervals correspond to the period in which some data is missing. In general, recruitment is highly variable from year to year. However, in the last four years it has been kept at very low levels, with recruitment in 2005 being the lowest of the historical series (posterior median of around 4,800 tonnes and 95 % credible interval between 3,000 and 7,800 tonnes). Since 2006 recruitment has shown a slightly increasing trend (Figure 2.4.1), however in 2007 it is still among the lowest of the historical series together with 1989, 2002, 2005 and

26 Recruits 1st January (tones) Year SSB (tones) Year Harvest rate Year Figure 2.4.1: From top to bottom posterior median (solid line) and 95% credible intervals (dotted lines) for the recruitment series (in tones), the spawning stock biomass and the harvest rates (Catch/SSB) from BBM. The horizontal solid lines in the second panel correspond to the biological reference points B lim (21,000 tonnes) and B pa (33,000 tonnes). 26

27 Table 2.4.2: Median and 95 % credible intervals for recruitment (in tonnes), spawning stock biomass and harvest rates (Catch/SSB) for the Bay of Biscay anchovy as resulted from the Bayesian biomass-based model. R (tonnes) SSB (tonnes) Harvest rate Year 2.50% Median 97.50% 2.50% Median 97.50% 2.50% Median 97.50% Spawning stock biomass shows an increasing trend since 2005, which was the lowest of the historical series (Figure 2.4.1). In 2007 the posterior SSB median is around 30,000 tonnes, a 35% higher than past year s median (approximately 23,400 tonnes) (Table 2.4.2). In addition, the probability of the population of being below B lim is 3.2% (Table 2.4.3), whereas in last year it was around 40% (ICES, 2006). Current state of the population is reflected by the posterior distribution of SSB in Figure and is summarised in Table SSB Figure 2.4.2: Posterior distribution of spawning biomass in 2007 from BBM. Vertical dashed lines correspond to posterior median and 95% credible intervals. 27

28 Table 2.4.3: Summary table of the current state of the Bay of Biscay anchovy stock from the Bayesian biomass-based model. R 2007 SSB 2007 Median % C.I. ( , ) Median % C.I. P(SSB 2007 < ) P(SSB 2007 < ) (20 639, ) Catch options and risk The Bayesian biomass-based model used for the assessment of the stock (section 2.4) was used to project the population one year forward from the current state and to analyse the probability of the population in 2008 of being below the biological reference points B lim (21,000 tonnes) and B pa (33,000 tonnes) under different recruitment scenarios and alternative catch options for the second half of 2007 and the first half of The predictive distribution of recruitment at age 1 (in mass) in January 2008 was defined as a mixture of the past series of posterior distributions of recruitment: 2007 R 2008 = wy p(r y ), y= 1987 where p ( R y ) denotes the posterior distribution of recruitment in year y and w y are the weights of the mixture distribution such that w = 1. These weights can be based on information about incoming y y recruitment or on assumptions regarding different scenarios. Since currently no reliable information is available to set the weights for the mixture distribution, all the years were equally weighted, corresponding to an undetermined recruitment scenario. The resulting predictive distribution of recruitment in 2008 is shown in Figure The density had three well defined peaks of decreasing height. The local minima between the peaks (36,000 and 68,700 tonnes that correspond to the 54 and 82 percentiles of the distribution respectively) can be used to split the recruitment in three regimes that can be interpreted as corresponding to low medium and high regimes. So that, this partition was used to define mixture weights for three additional recruitment scenarios: Low recruitment scenario: Give positive equal weight to all years y for which the posterior median of recruitment (Table 2.4.2) falls in the leftmost interval (i.e. posterior median of recruitment is below 36,000 tonnes). Assign zero weight to all other years. Medium recruitment scenario: Give positive equal weight to all years y for which the posterior median of recruitment (Table 2.4.2) falls in the central interval (i.e. posterior median of recruitment is between 36,000 and 68,700 tonnes). Assign zero weight to all other years. High recruitment scenario: Give positive equal weight to all years for which the posterior median of recruitment (Table 2.4.2) falls in the rightmost interval (i.e. posterior median of recruitment is above 68,700 tonnes). Assign zero weight to all other years. The mixture weights for the four alternative recruitment scenarios (undetermined, low, medium and high) are summarised in Table The resulting predictive distributions for recruitment in 2008 are shown in Figure Starting from the posterior distribution of SSB in 2007 the population was projected forward under the alternative recruitment scenarios. Since the fishery has been closed for the first half of 2007, no catches were considered from the 15th May, in which SSB is estimated, to the end of June. Total allowable catch between 1st July 2007 and 30 June 2008 were explored from 0 (fishery closure) to 33,000 tonnes (historical annual fixed TAC for this stock) with a step of 1,000 tonnes. In addition, the effect of the percentage of those total allowable catches corresponding to the second half of 2007 was also studied by considering percentages from 0 to 100% with a step of 5%. The timing within the year in which the catches in the second half of 2007 and the first half of 2008 were assumed to occur were computed as the average time point from the historical series from 1987 to 28

29 2004 ( were not considered as the fishery was closed during some part of the year). Similarly, the percentage of catches in the first half of 2008 taken before the 15th May, when SSB is estimated, was assumed to be equal to the average from the historical series between 1987 and 2004 (58%). Probability of SSB in 2008 being below B lim and B pa was derived for each of the recruitment scenarios, total catch options and split of the total catch in the second half of 2007 and first half of 2008 (Figure 2.5.2). Currently, there is no additional information that would allow selecting a given scenario for recruitment in However, since 2002 the recruitment has been low, with the sole exception in 2004 in which it was medium (Table 2.5.1). The last high recruitment was in Thus, following the precautionary approach the recruitment in 2008 should be expected to be low. In addition, this is the more likely scenario based on the historical recruitment series (54%). Under that regime, the probability of SSB in 2008 being below B lim is always larger than 10%, even in case no catches are allowed (Figure 2.5.2). That probability increases rapidly as total catch for the second half of 2007 and first half of 2008 increases, getting to around 50% when total catch is around 15,000 tonnes. ICES seeks management to keep the stock above B pa, which according to its definition would correspond to reduce the probability of the stock falling below B lim below 5% (green contour line in the top row in Figure 2.5.2). Given that for the low recruitment scenario, this target cannot be achieved for any catch option, the STECF subgroup recommends that if any fishing was allowed they should be chosen to minimize the risk of falling below B lim. 29

30 Table 2.5.1: Mixture weights to construct the predictive distribution of recruitment in 2008 under undetermined, low, medium and high scenarios. Year Undetermined Low Medium High R undetermined R low R medium R high Figure 2.5.1: Alternative recruitment scenarios for projecting the population one year ahead from From top to bottom and from left to right the predictive distribution of recruitment in January 2008 for undetermined, low, medium and high scenarios. 30

31 % Catch 2nd half R undetermined R low R medium R high % Catch 2nd half Total catch Total catch Total catch Total catch Figure 2.5.2: Contour plots of the probability of SSB in 2008 being below B lim (top row) and B pa (bottom row) according to different total allowable catch between 1 st July 2007 and 30 June 2008 in the x-axis and percentages of that total catch taken in the second half of 2007 in the y-axis. From left to right each of the columns correspond to a different recruitment scenario: undetermined, low, medium and high. Green contour line in the top row represents the 0.05 isolines for the probability of SSB being below B lim,. 31

32 3. Recruitment Indices 3.1. JUVENA survey The JUVENA series (acoustic surveys for anchovy juveniles) aim at estimating the abundance and spatial distribution of anchovy juveniles during early autumn in the Bay of Biscay (Boyra et al., 2004, 2005a, 2005b and 2007STECFWD and Boyra & Uriarte, 2005). The long term objective of the project is to be able to assess the strength of the anchovy recruitment entering the fishery the next year (as 1 y.o.) so as to help on the provision of scientific advice to managers. In addition, the spatial distribution of the juvenile population, the growth condition and the hydrological characterization were studied The survey is presented and coordinated within WGACEGG. So far, four surveys have been conducted (Boyra et al 2004, 2005a&b, 2006 and 2007 STECFWD) (Table 3.1.1). They took place from mid September to the beginning of October covering the area from the coast to 5º- 6º W and up 46º-47º30 N, onboard commercial rented purse-seines (for the first 3 years) and with both a purse seine and the R/V Enma Bardan - a pelagic trawler in In the last two years spatial coverage was gradually enlarged to the north. Acoustic data were recorded with a 38 and 120 KHz Simrad EY60 split-beam, scientific echo sounder system (Kongsberg Simrad AS, Kongsberg, Norway), calibrated using standard procedures (Foote et al. 1987). The water column was sampled with acoustics up to depths of 100 m. A threshold of -70 db (-80dB in 2006) was applied for data collection. Acoustic back-scattered energy by surface unit (SA, MacLennan et al. 2002) was recorded for each geo-referenced nautical mile (1852 m). In addition, continuous sea surface temperature and salinity measurements and CTD casts every 10 nm were conducted. Table 3.1.1: Summary of the JUVENA acoustic surveys on juvenile anchovy carried out in the last years (including the one foreseen for 2006). JUVENA SURVEYS SERIES SURVEY VESSEL GEAR PERIOD Area in Bay of Biscay JUVENA 2003 Divino Jesús de Praga Purse seine 17 September - 15 October South 46ºN East 5ºW JUVENA 2004 Nuevo Erreinezubi Purse seine 19 September - 20 October South 46ºN East 5ºW JUVENA 2005 Gure Aita José Purse seine 12 September - 07 October South 47ºN East 5ºW Mater Bi Purse seine JUVENA 2006 Itxas Lagunak Purse seine 13 September - 15 October South 47º30'N East 6ºW Enma Bardan Pelagic trawling Fish identity and population size structure were obtained from fishing hauls and echo-trace characteristics. The hauls were grouped by strata of homogeneous species and size composition. Inside each of these homogeneous strata, the echo-integrated acoustic energy was separated by the contribution of each species according to the composition of the hauls. The composition by size and species of each homogeneous stratum is obtained by averaging the composition of the individual hauls contained in the stratum, being the contribution of each haul weighted to the acoustic energy found in its vicinity (2 nm). Afterwards, the energy corresponding to each specie-size was transformed into biomass using their corresponding conversion factor. The scattering cross section of anchovies according to their size was estimated using the parameters for anchovy detailed in Dinner & Marchand (1995). The last survey took place between the 13th of September and the 15th of October 2006, with two vessels (the R/V Enma Bardan and the rented purse seiner Itxas Lagunak) (Table 3.1.1). the availability of two survey vessels, both equipped with acoustic sensors, provided the larger coverage in the temporal series, reaching to 6º W in the Cantabrian area and 47º 30 N along the French Coast (Figure 3.1.1) 32

33 Edad 0 Edad 1 FRANCE - 48º 100 m - 47º - 46º - 45º - 44º SPAIN - 44º 6º 5º 4º 3º 2º 1º Figure 3.1.1: Summary of the JUVENA acoustic survey in 2006 survey tracks and fishing hauls (left panel) and anchovy catches by age group (0 & 1) (right panel). This year, the distribution of anchovy was confined practically to the continental shelf, extending from 6º W in the Cantabrian Coast to the 47º30 N in the French Coast (Figures and 3.1.2). In the Cantabrian Sea, anchovy was almost completely confined to the coastal area, in the proximities or inside the bays and beaches. In front of the Southern French Coast (Les Landes), the distribution of anchovy was again almost coastal. In this region, anchovy was found restricted to a narrow strip between the 15 m and 30 m isobaths. In the Northern area, around the plumes of the rivers Garonne and Loire, the distribution of anchovy notably broadened up, extending from the coast to waters of up to 100 m depth. Although the Northern limit of the positive anchovy distribution was not found in this area (anchovy was detected even in the most northern latitudes), the decrease of relative abundance of anchovy in the hauls of the last transect may indicate the proximity of such limit. Given the positive performance of the fishing gears of both vessels, we consider that the combination of them provided a very reliable estimation of the species composition in the different regions. The purse seine provides a proven efficiency in capturing anchovy juveniles, plus assures the methodological continuity of the temporal series. On the other hand, the pelagic trawl provides the capacity of fishing beyond the purse seine range (30-40 m depth) and a less selective sampling (at least a priori). In addition, the preliminary inspection of the intercalibration hauls found no differences in the size ranges obtained with each method. The capacity of both vessels to fish in shallow waters, the large amount of positive anchovy hauls (53 of 80 hauls) and the capacity of sampling close to the bottom leads to a successful fishing capability for this survey and makes this year certainly the best in the whole series in terms of fish species identification. 33

34 Figure 3.1.2: Survey tracks of JUVENA 2006 showing the spatial distribution of acoustic energy shading in green corresponding to areas with juvenile anchovy, included for the final estimates. Estimates based on the positive area (Figure 3.1.2) followed standard procedures. The survey results were first reported to the WGACEGG in November 2006 (Boyra et al. 2006). However, those estimates have been recently revised due to a configuration problem of the 38 khz echosounder on board the R/V Enma Bardan, as mentioned in the acoustic workshop report (Nantes, April 2007). This vessel covered alone about 60% of the area. The current revision bases the acoustic biomass estimate on the 120 khz echosounder. The result of this revision increases by 80% the provisional estimate provided in November This revision is reported in a WD to this STECF Working Group (Boyra and Uriarte WD2007) and have to be taken as a preliminary estimate which will be revised in the next coming ICES WGACEGG in Nov-Dec The estimates for this year 2006, along with a summary of the juvenile abundance indices from the previous JUVENA acoustic surveys, is presented in Table The whole perspective of the survey series is presented in Figure Table 3.1.2: Summary of the anchovy abundance indices from the JUVENA acoustic surveys carried out in the last years splitted by regions. (Area refers to the area where positive detection of anchovy was made. Size refers to the total length, and the Abundance index is split for adult and juvenile anchovy) (Boyra et al. STECF_WD2007). Year Region Sur Norte TOTAL <s A > Area <length>_juv <lenght>_adul 14.1 Biom_juv 97, , , Biom_adul 0 1, , Biom_TOTAL 97, , , Sur Norte , , , TOTAL 2, , , Sur , , Norte , , , TOTAL 134, , , Sur corrected , , Norte corrected , , , TOTAL corrected 130, , ,

35 The acoustic estimates produced in 2003 and 2005 and 2006 cruises reported anchovy juvenile abundances two orders of magnitude greater than the estimates for year This poor result for 2004 is congruent with the subsequent crisis of the stock and collapse of the fishery during The occupied area in those years was also larger, in clear agreement with the larger juvenile abundance estimations. The anchovy juvenile acoustic estimate for 2006 is similar to that obtained in A graph of the historical series compared to the assessment of age 1 in year Y+1 is made in section The acoustic biomass estimates provided by JUVENA series have to be taken as relative values not as absolute. The high total anchovy acoustic biomasses reported for the years 2005 and 2006 of the order of 150 and 210 thousands tonnes, if taken as absolute, give a huge contrast compared with the SSB estimate at the following springs around 20 to 30 thousand tonnes. Reasons behind these discrepancies (in absolute levels of) biomass can be to several reason starting for incorrect Ts values for juveniles and/or due also to large natural mortality in this juvenile phase of anchovy. For instance a natural mortality M of 2 throughout the 8 months elapsed time between these surveys can explain such a reduction. Figure 3.1.3: Survey tracks of JUVENA surveys showing the spatial distribution of acoustic energy and shading in green the areas corresponding to presence of juvenile anchovy. JUVENA surveys are still in a phase of consolidation and testing: Only four surveys have been conducted in the series. Although too soon for a proper testing a preliminary analysis of its performance is presented in section 3.3 of this report. The strength of this survey is that it is implemented during September and early October when juveniles are usually found in the upper layers of water as pure schools in offshore grounds, being therefore well detectable 35

36 with acoustics and well fishable with purse seine, with little risk of species misidentification. Although certainly the coastal distribution found in 2006 supposes the first exception to that a priori expected distribution. The experimental surveys carried out by AZTI and IFREMER within JUVESU project (FAIR CT , Uriarte editor 2002) in 1998 and 1999, provide additional contrasting background on the abundances and spatial distribution of juveniles, which served to establish the current JUVENA survey design. The survey has always covered the area where the bulk of juveniles is considered to be found (approximately east of 5º W, south of 46º N), although for the last years the coverage expanded until thanks to the planned adaptive sampling design. The adaptive enlargement of the surveyed area in the last two years (Figure 3.1.3) cause warnings about the comparability of the results concerning the comparability of the percentage of the potential distribution area covered throughout the time series. However that is not considered by the authors to be a major problem according to: a) during the first two years 2003 and 2004 the most northern radial (at 46ºN) was empty of anchovy detections and in the northern coastal areas around the Garonne (where relevant anchovy concentrations were found in 2006) little quantities of juveniles were found in those two years as in 2005 (see Table 3.1.2). b) Concomitant information provided by the commercial fleet in these years indicates that juveniles concentration were not being seen out from the covered areas. In addition, JUVAGA survey in 2003 (Petitgas et al. 2004) and in 2005 pointed out very little detections of anchovy juveniles to the North of the surveyed areas. All these suggest that the bulk of the juvenile concentrations were well covered during these surveys PELACUS (NEW autumn survey) The PELACUS1006 cruise (IEO; with participation of Ifremer in the 2nd leg) was carried out on board the RV Thalassa from 22/09/06 to 17/10/06. This survey is the first of a proposed project to a) provide and index of juvenile abundance, and b) study the recruitment process. The survey is split in two legs: the 1st leg for systematic sampling (estimation of biomass), while the 2nd was adaptive in order to conduct more intensive sampling in zones of occurrence of anchovy juveniles. Survey coverage is shown in Figure 3.2.1, and acoustic energy allocated to anchovy during the first leg, and used for the evaluation of anchovy juveniles in autumn is shown in Figure Total anchovy juveniles biomass estimate is 6,140 t, with main distribution areas located in front of the Garonne area and very close to the coast in the south and west areas of the Gulf of Biscay. Results of the PELACUS 1006 anchovy assessment were compared with those obtained by the 2006 JUVENA survey (see Section 3.1), both during WGACEGG (ICES 2006) and within a dedicated workshop recommended by the same ICES WG. The comparison was made both on global terms (estimates of biomass from both surveys) and in a dedicated area in front of the Garonne river mouth, which was chosen prior to both surveys in order to intercallibrate their results. Original estimates from both surveys differ by nearly two orders of magnitude (6,140 t vs 130,000 t), but survey coverage also largely differs, and the JUVENA survey covered more inshore areas and areas to the north of the PELACUS coverage. Comparisons within the dedicated area show more similar biomass levels, although the JUVENA estimates were revised after the workshop (see Section 3.1). Further comparison and intercallibration of both surveys (both are planned to be repeated in 2007) will be performed during ICES WGACEGG. 36

37 Figure 3.2.1: PELACUS1006 acoustic tracks. On red the acoustic tracks performed during the first leg and dedicated to the estimation of a juvenile biomass index, on blue the tracks performed on the second leg, dedicated to investigate the recruitment process. Figure 3.2.2: PELACUS1006 acoustic energy (in square meters by square nautical miles) allocated to anchovy. 37

38 3.3. Evaluation of prediction capabilities of recruitment from juvenile surveys For the time being, the only available series of acoustic estimates of abundance of anchovy juveniles in the Bay of Biscay is the one provided by the JUVENA surveys (section 3.1, Boyra and Uriarte 2007). These surveys began in 2003 with the long term objective of assessing the strength of the anchovy recruitment entering the fishery the next year, so as to help on the provision of scientific advice to managers. For this reason the evaluation of prediction capabilities of recruitment from acoustic surveys can by now only be based on this JUVENA series, however the short series of indices available (just four years) severely limit the testing here presented. The JUVENA surveys and their results have been presented in section 3.1. The survey has been surveying gradually increasing areas, larger than the standard one a priori defined at the beginning of the series. As discussed at the end of section 3.1, beyond the doubts this fact may induce about the comparability of the surveys, there are reasons to believe that this was not a serious problem for the series. Therefore for comparisons with the series of recruitment at age 1 the estimates over the total surveyed area will be used instead of using the estimates confined to the original standard area. Figure compares the times series of the JUVENA anchovy juveniles abundance index with the assessment at age 1 produced by Bayesian assessment presented in section 2.4 above. By the time being, the results were encouraging since the huge drop in juveniles abundance estimates recorded by JUVENA surveys in 2004 matched well with the drop in the recruitment of age 1 to the adult population occurring in On the other hand, a recovery of the recruitment at age 1 in 2006 and 2007 to similar levels are also in conformity with the JUVENA survey s abundance indices. So generally speaking, the time series of age 1 recruitment estimates from the last four years in the assessment have a globally parallel shape to that shown by the juvenile abundance index from JUVENA surveys: One very low recruitment and 3 low levels of recruitment. However that recovery was not as intense as the relative index would suggest JUVENA SERIES VS ASSESSMENT Ac.Juveniles Indices Age 1 Assessment in Y+1 Figure 3.3.1: Times series of the JUVENA anchovy juveniles abundance index vs. the assessment at age 1 produced by the Assessment presented in this report in section 2.4. The coefficient of correlation (0.64) is not significant, probably given the low amount of observations (4 years). Clearly, a lack of great contrast is seen in this series; the occurrence of a large recruitment should serve to further test the capabilities of this series to predict recruitment. In summary the results from the four points of the JUVENA abundance indices of anchovy juveniles are encouraging, but the sort nature of this series prevents yet a proper evaluation of its performance as a predictor of the age 1 entering the population and the fishery the next year. The WG recommends the series to be continued and developed so as to achieve a proper evaluation of its predictive performance. 38

39 4. Commercial vessel surveys 4.1. Consort surveys In December 2006 the European Commission established a zero TAC for the Bay of Biscay anchovy. In addition to the spring scientific surveys regularly utilised to estimate both the strength of the incoming new year-class and the Spawning Stock Biomass (SSB), namely the acoustic and DEPM surveys, the Council of Ministers decided to authorize also the use of commercial vessels to gather information on the state of the anchovy stock. In March 2007 the STECF recommended that the spring surveys (acoustic and DEPM) were supported by the Spanish and French commercial vessels involved in the experimental fishing. In this section, these consort surveys are described, their use in the assessment and their pros and cons are analysed and their added value is briefly summarised Acoustic survey (PELGAS) The consort survey accompanying the PELGAS survey was organised at a very short notice. In addition to the French vessels, 3 Spanish purse seiners were included in the process the day before the beginning of the survey. Finally, 6 commercial vessels (2 French pair trawlers, 1 coastal French purse seiner and 3 Spanish purse seiners) were part of this consort survey Inputs to stock estimate For coherent assessment comparison, the acoustic biomass estimate (see section 2.1) was only calculated on the basis of Thalassa data collected with the same strategy than during previous years. As an exercise (see the reason below) estimates were computed using consort fishing operations as extra identification hauls (32 number of hauls from the Pair trawlers, 23 from the Spanish purse seiners and 13 from the French purse seiners) (Figure ). Results (Table ) were very similar because the main quantitative aspect was driven by acoustic data and fishing operations were only used to split energies into species and most of commercial vessels catches confirmed Thalassa catches. a) Pair trawlers (nb : 32) b) Spanish purse seiners (nb : 23) c) French purse seiners (nb : 13) Figure : Fishing operations carried out by commercial vessels during consort survey PELGAS07. 39

40 Table : Different attempts to use consort commercial catches in addition to Thalassa samples. These results should be considered as preliminary, using all available data without checking validity or any correction for catchability. Therefore they must be taken with caution. STRATA Thalassa hauls Thalassa + pair trawlers Thalassa + pair trawlers + FR purse seiners Thalassa + FR+SP purse seiners Thalassa + all consort Total Pros and cons of future use of consorts The commercial vessels were not equipped of scientific echo-sounder and so only their fishing operations could be considered. Further investigations of the differences in catchability between gears and vessels should be carried out before a fully use of the results of these fishing operations can be done. During the first half of the survey, purse seiners were mainly fishing on rare mid-water schools whereas pelagic trawlers were fishing on small echo-traces more close by the bottom. The fishermen comments were that anchovy was not schooling at the surface when moon was in the ascendant phase. During the last week of the survey, the whole fleet came back in potential anchovy areas in order to have particular observations on vertical eggs distribution and anchovy day and night behaviour. It has been a great opportunity to compare pelagic trawl and purse seine catches in the same small area in traditional conditions. These data are not yet analysed, but 38 hauls were carried out during these last 6 days, including 9 by Thalassa, 14 by pair trawlers hauls and 15 by Spanish purse seiner shoots (Figure ) a) surveyed daily areas prospected by each type of vessels b) pair trawlers catches (n = 14) c) purse seiners catches (n = 15) Figure : Fishing operations carried out by commercial vessels during the last week of the PELGAS07 survey in order to compare specific catchability. 40