WGHMM (now WGBIE) identified a problem in the assessment of northern hake in relation to the scarce information on the abundance of large fish. 2004 WKSOUTH tested the inclusion in SS3 of Galician LPUEs from set-longline fleet targeting hake in ICES Subarea VII. This metier catches mainly adults. However, during WGBIE 2014, a serious inconsistency was detected when updating this LPUE time series, related to the assumption of the average fishing days by trip employed along the time series. The current working document provides the revision of this LPUE series by applying the actual number of fishing days by trip recorded in logbooks, which has varied greatly in the final part of the time series. The revised LPUE indices obtained were then tested in the assessment of northern hake stock. The difference in results between the assessments without LLPUE and the assessment which includes the new LPUE series were minor. In the initial part of the time series the LPUE matched the abundance closely but in the last period the increase in the LLPUE was much lower than the increase in the stock abundance

Castro, J. (José)

Cebrián-Domínguez, J.L. (José Luis)

Garcia, D.

Patiño-Alonso, B. (Baltasar)

English

Castro, José

Cebrián-Domínguez, José Luis

Patiño-Alonso, Baltasar

Digital.CSIC

Standardization of hake LPUE series of the Galician set-longline fleet in Subarea VII

Repositorio Institucional Digital del IEO

WD presented at WGBIE 2016 ICES, Copenhagen, Denmark, 13–19 May 2016 1   Standardization of hake LPUE series of the Galician set-longline fleet in Subarea VII J. Castro1, D. García2, J.L. Cebrian1 and B. Patiño1 1 Instituto Español de Oceanografía (IEO): jose.castro@vi.ieo.es 1 AZTI-Tecnalia    ABSTRACT WGHMM (now WGBIE) identified a problem in the assessment of northern hake in relation to the scarce information on the abundance of large fish. 2004 WKSOUTH tested the inclusion in SS3 of Galician LPUEs from set-longline fleet targeting hake in ICES Subarea VII. This metier catches mainly adults. However, during WGBIE 2014, a serious inconsistency was detected when updating this LPUE time series, related to the assumption of the average fishing days by trip employed along the time series. The current working document provides the revision of this LPUE series by applying the actual number of fishing days by trip recorded in logbooks, which has varied greatly in the final part of the time series. The revised LPUE indices obtained were then tested in the assessment of northern hake stock. The difference in results between the assessments without LLPUE and the assessment which includes the new LPUE series were minor. In the initial part of the time series the LPUE matched the abundance closely but in the last period the increase in the LLPUE was much lower than the increase in the stock abundance.  INTRODUCTION During the WKSOUTH benchmark (ICES, 2014a), some problems identified in the assessment of northern hake by WGHMM (ICES, 2013) were tried to be solved. One of them made reference to the little information on abundance of large fish in the setting of the SS3 model. Therefore, a new LPUE series was provided for the Galician longline fleets targeting northern hake in ICES Subarea VII (Castro et al., 2014).  This LPUE series was tested in the northern hake assessment; however it was considered that a deeper analysis of its suitability was necessary in order to use it as an abundance index (ICES, 2013). Therefore, this LPUE series was updated including 2014 value to be tested by WGBIE 2014 (ICES, 2014b). However, the 2014 effort altered the LPUE trend provided two months after. This was due to the 2014 value was based on real effort registered in logbooks, while the previous series have been compiled from sales notes, applying a mean factor of fishing days by trip. Therefore, the series could not be completed to be tested by WGBIE 2014. During 2015, an effort was made to analyze the longest time series of logbooks available, in order to detect any possible change in fishing strategy to explain the observed change in trend. This paper describes the work developed, presents the new standardized LPUE series and also provides the SS3 results obtained by including this index in the northern hake assessment. WD presented at WGBIE 2016 ICES, Copenhagen, Denmark, 13–19 May 2016 2  MATERIAL AND METHODS On one hand, landings and length frequency distributions (LFD) form the LPUE series presented at WKSOUTH were updated with 2014 and 2015 data. On the other hand, all the time series of effort was revised by analyzing the available series of Spanish logbooks, form 2003 to 2015. These analyses permitted to calculate the mean number of fishing days by trip and year, in order to detect any possible change in the fishing strategy of the Galician longline fleet operating in Subarea VII.  Regarding the northern hake assessment, this was done by applying the SS3 model (Methot and Wetzel, 2013), as well as the current setting accepted by WGBIE (ICES, 2015). RESULTS Standardization of the LPUE series The Galician set longline fleet is compounded by Spanish vessels landing in the three most important ports in Northern Galicia: A Coruña (CIO), Burela (BRL) and Celeiro (CIO). This fleet performs a homogeneous fishing strategy targeting hake in Subarea VII (72% of total effort in 2015) and Division VIIIabd (28%), very rarely accessing the Subarea VI (Figure 1). Individually, Celeiro has been the most important port in landed trips at the beginning of the series, until 2001 when they descend to the level of Burela (Figure 2). A Coruña, similar in effort to Burela at the beginning of the series, descends drastically in 1998, maintaining minimum levels since then. Regarding the data collection, the most important contribution of this paper with respect to the WD presented at WKSOUTH 2014 is the revision of the number of fishing days per trip and its evolution throughout the time series. The old series provided to WKSOUTH 2014 was based on trips recorded in sales notes, so they were transformed into fishing days by applying a factor that was assumed constant throughout the time series, i.e. 12 fishing days by trip. To calculate the actual number of fishing days that makes up a trip, the longest logbooks series available (from 2003 to 2015) was compiled to be analyzed. The study was enclosed to the effort exerted only in Subarea VII, to avoid the effect of the trips from Divisions VIIIabd which may be shorter. The results showed that the duration of the trips was varying through the time series. Indeed, trips lasted over 12 days at the beginning of the series, but since 2009 they began to shorten. Therefore, the average of fishing days by trip of years 2003 to 2008 (13.1 fd/trip) was applied to years without logbooks: 1995-2002. The actual fishing days recorded in logbooks were used in the rest of the time series: 2003-2015. Figure 3 shows the evolution in time of total fishing days and the average of fishing days by trip for the studied fleet. After holding steady around 13 fd/trip, in year 2009 effort begins a downward trend to reach 5.8 fd/trip in 2012. Since then, the Galician set-longline trips from Subarea VII show a slight upward trend, reaching 7.1 fd/trip in 2015. The revised series of fishing days by year provide a new LPUE series very different from that presented at WKSOUTH in 2014. LPUE values are lower than a tonne per fishing day during the years 1995-2008 (mean= 0.74 t/fd). In 2009, the LPUE values start to rise quickly to reach more than 2 t/fd in 2011 and get 2.77 t/fd in 2015. WD presented at WGBIE 2016 ICES, Copenhagen, Denmark, 13–19 May 2016 3   Testing the LPUE series in the assessment The revised LPUE series of Galician set-longline fleet operating in Subarea VII was tested in the northern hake assessment. This stock is assessed by using the SS3 method (Methot and Wetzel, 2013), a statistical length-structured population modelling framework highly scalable from data-weak situations where it operates as biomass production model, to complex situations where it can flexibly incorporate multiple data sources and account for biological and environmental processes.  Observed versus fitted values are shown in Figure 5. The fit in the initial part of the time series is fairly good but since 2007 the model overestimates the observed values for all years and quarters. The increase in the longline LPUE was not as high as the increase in the stock abundance. However, Pearson residuals of their length frequency distributions show a “fairly random” behaviour with no particular trend or lack of fit (Figure 6, where blue and red circles denote positive and negative residuals, respectively). The assessment results show two peaks of recruitment at the end of the time series, in 2008 and 2012 (Table 2; Figure 7). SSB begins to increase drastically from 2009, reaching a six-fold increase in 2015 the average for the period 1978-2008. F, meanwhile, reaches in 2015 the lowest value of the time series (0.2).  The run resulted from incorporating the revised LPUE series (update_lls) was compared with the “updated” run, consisted of including year 2015 to the same setting used in last assessment (ICES, 2015). Both retrospective plots show that for F and SSB the model results are sensitive to the exclusion of recent data, which provoke a revision upwards of SSB and downwards of F (Figures 8 and 9). DISCUSSION AND CONCLUSIONS It is known the importance of standardization of effort in a longline LPUE, which is strongly dependent of the number of hooks used by trip. As it was explained in WKSOUTH (ICES, 2014), this information has never been collected, however interviews with skippers describe the gear used by this fleet (number of hooks, type of bite and number sets) to be regular throughout the period recovered here (Castro et al., 2011). On the other hand, the practical lack of discards observed in this logline fleet (Pérez et al., 1996) makes reasonable to use landings (LPUE) as proxy of catches (CPUE). Now that the series has been corrected for the actual fishing days, the commercial CPUE obtained perfectly correlate with the CPUE observed by sampling. The new CPUE series of Galician set-longline in Subarea VII becomes an index that can help better understand the state of the northern hake stock. Its inclusion in the northern hake analytical assessment does not alters the picture provided by the current setting. On the one hand, not significantly change the estimates of SSB or F, and on the other, does not improve the uncertainty of the retrospective pattern in the last years of the time series. Therefore, although this CPUE series is not finally included in the annual northern hake assessment, their provision to WGBIE will expand the knowledge of the evolution of this fishery and the exploited stock.    WD presented at WGBIE 2016 ICES, Copenhagen, Denmark, 13–19 May 2016 4   References Castro, J., M. Marín, G.J. Pierce, and A. Punzón. 2011. Identification of métiers of the Spanish set-longline fleet operating in non-Spanish European waters. Fisheries Research, 107: 100-111. Castro, J., D. García and B. Patiño. 2014. Compilation of LPUE series of the Spanish set-longline fleet targeting hake in non-Spanish European waters. WD 01 at ICES WKSOUTH 2014. ICES. 2013. Report of the Working Group on the Assessment of Southern Shelf Stocks of Hake, Monk and Megrim (WGHMM), 10 - 16 May 2013, ICES Headquarters, Copenhagen. ICES CM 2013/ACOM:11A. 719 pp. ICES. 2014a. Report of the Benchmark Workshop on Southern megrim and hake (WKSOUTH), 3-7 February 2014, ICES HQ, Copenhagen, Denmark. ICES CM 2014/ACOM:40. 236 pp. ICES. 2014b. Report of the Working Group for the Bay of Biscay and the Iberian waters Ecoregion (WGBIE), 7–13 May 2014, Lisbon, Portugal. ICES CM 2014/ACOM:11. 714 pp. ICES. 2015. Report of the Working Group for the Bay of Biscay and the Iberian waters Ecoregion (WGBIE), 04-10 May 2015, ICES HQ, Copenhagen, Denmark. ICES CM/ACOM:11. 503 pp. Methot, R. D. and C. R. Wetzel. 2013. Stock synthesis: A biological and statistical framework for fish stock assessment and fishery management. Fisheries Research, 142: 86-99. Pérez, N., P. Pereda, A. Uriarte, V. Trujillo, I. Olaso y S. Lens. 1996. Descartes de la flota española en el área del ICES. Datos y Resúmenes. Vol 2. NIPO : 251–96–013-X.     WD presented at WGBIE 2016 ICES, Copenhagen, Denmark, 13–19 May 2016 5    Table 1. Landings of hake (t), effort (fishing days) and CPUE (t/fd) of the Galician set-longline fleet operating in ICES Subarea VII.  year landings fd CPUE 1995 9988 12393 0.8 1996 11343 13126 0.9 1997 7303 10349 0.7 1998 4748 9340 0.5 1999 5753 8716 0.7 2000 6262 8345 0.8 2001 6647 8410 0.8 2002 5453 8751 0.6 2003 6092 9591 0.6 2004 7526 9797 0.8 2005 7450 8891 0.8 2006 8268 9613 0.9 2007 9676 11834 0.8 2008 8593 11722 0.7 2009 10319 9013 1.1 2010 17092 9346 1.8 2011 21022 8388 2.5 2012 14294 6766 2.1 2013 10060 4112 2.4 2014 9516 3532 2.7 2015 9521 3441 2.8   WD presented at WGBIE 2016 ICES, Copenhagen, Denmark, 13–19 May 2016 6    Table 2. Summary of landings and assessment results: run including the Galician set-longline LPUE time series.   Year Rec B total Jan1 SSB Jan1 Landings (t) Discards (t) Catch (t) Yield/SSB F (15-80 cm) Numbers(Pop) 1978 294060 120170 80181 50551 NA 50551 0.6 0.5 644369 1979 274443 129513 101657 51096 NA 51096 0.5 0.5 605707 1980 306993 127734 104212 57265 NA 57265 0.6 0.6 607412 1981 584504 111008 89922 53918 NA 53918 0.6 0.7 882723 1982 407210 102620 73545 54994 NA 54994 0.8 0.7 900813 1983 148430 110214 71870 57507 NA 57507 0.8 0.6 583376 1984 284163 117179 85844 63286 NA 63286 0.7 0.7 544867 1985 667065 101765 81978 56099 NA 56099 0.7 0.8 946313 1986 404086 86396 62222 57092 NA 57092 0.9 0.9 888289 1987 475511 84647 48070 63369 NA 63369 1.3 1.0 889757 1988 516317 84096 50490 64823 2 64825 1.3 1.0 976292 1989 496463 83207 48604 66473 73 66546 1.4 1.1 960164 1990 525607 76016 45206 59954 NA 59954 1.3 1.0 949461 1991 308959 74815 45232 58129 NA 58129 1.3 0.9 727663 1992 318967 76729 45605 56617 NA 56617 1.2 1.0 658488 1993 594914 66618 43525 52144 NA 52144 1.2 1.1 901911 1994 319622 59679 33633 51259 356 51615 1.5 1.1 778153 1995 160716 65574 32612 57621 NA 57621 1.8 1.1 521843 1996 388992 59674 37997 47210 NA 47210 1.2 1.0 590238 1997 268908 50535 32411 42465 NA 42465 1.3 1.1 592805 1998 462014 48332 26442 35060 NA 35060 1.3 1.0 722320 1999 217667 52086 29202 39814 349 40163 1.4 1.0 586769 2000 193578 57868 32120 42026 83 42109 1.3 0.9 449541 2001 342608 57538 38633 36675 NA 36675 1.0 0.8 556943 2002 262948 59682 39260 40107 NA 40107 1.0 0.8 570353 2003 155968 63743 39142 43162 2110 45272 1.1 0.8 433726 2004 324207 65937 44372 46417 2552 48969 1.1 0.8 533181 2005 224119 62007 42901 46550 4676 51226 1.1 0.9 509768 2006 303434 58918 35627 41467 1816 43283 1.2 0.8 554405 2007 478261 66618 42265 45028 2191 47219 1.1 0.7 787801 2008 780376 85494 50953 47739 3248 50987 0.9 0.5 1245349 2009 261940 137616 78373 58818 9871 68689 0.8 0.4 1033596 2010 253802 225878 145666 72799 9415 82214 0.5 0.3 844100 2011 283166 290714 236591 87540 13775 101315 0.4 0.3 775598 2012 603071 298058 257100 85677 12225 97902 0.3 0.3 1059990 2013 433076 303890 254015 77753 11637 89390 0.3 0.3 1114998 2014 265150 339551 267773 89940 6548 96488 0.3 0.3 948527 2015 260352 379975 314292 93670 7396 101066 0.3 0.2 828820    WD presented at WGBIE 2016 ICES, Copenhagen, Denmark, 13–19 May 2016 7    Figure 1. Geographical distribution of effort (fishing days) of the Galician set-longline fleet operating in non-Spanish Atlantic European waters in 2015. Acronyms of ports: A Coruña (LGC), Burela (BRL) and Celeiro (CIO).    Figure 2. Effort (fishing days) of the Spanish set-longline fleet operating in ICES Subarea VII: by port (Burela, Celeiro and A Coruña). Acronyms of ports: A Coruña (LGC), Burela (BRL) and Celeiro (CIO).            0 1000 2000 3000 4000 5000 6000 7000 8000 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 BRL CIO LCG Galician set-longline effort (fishing days) in VII WD presented at WGBIE 2016 ICES, Copenhagen, Denmark, 13–19 May 2016 8    Figure 3. Evolution of the fishing days by trip of the Galician set-longline fleet in ICES Subarea VII.     Figure 4. CPUE (tons/fishing day) time series (1995-2015) of hake for the Galician set-longline fleet in ICES Subarea VII.               WD presented at WGBIE 2016 ICES, Copenhagen, Denmark, 13–19 May 2016 9    Figure 5. Observed log(abundance indices) and fitted values by quarter of the Galician set-longline CPUE indices in the northern hake assessment (SS3 model).        Figure 6. Pearson residuals of the fit to the length distributions of the Galician set-longline CPUE indices, by quarter (SS3 model). Blue and red denote positive and negative residuals, respectively.     WD presented at WGBIE 2016 ICES, Copenhagen, Denmark, 13–19 May 2016 10     Figure 7. Comparison of assessment results using updated data from 2014 assessment and including the Galician set-longline CPUE indices. Northern hake assessment by applying SS3 model.                         WD presented at WGBIE 2016 ICES, Copenhagen, Denmark, 13–19 May 2016 11    Figure 8. Retrospective plot from SS3: updated run. Northern hake assessment by applying SS3 model.      Figure 9. Retrospective plot from SS3: updated run including the Galician set-longline CPUE indices. Northern hake assessment by applying SS3 model.   

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Standardization of hake LPUE series of the Galician set-longline fleet in Subarea VII

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