Relative abundance indices of bluefin tuna (Thunnus thynnus) caught by the Moroccan and
Spanish traps in the area close to the Strait of Gibraltar were estimated for the period 1981-
2013. Standardized CPUEs were estimated through a General Linear Modeling (GLM)
approach under a negative binomial error distribution assumption.Versión del edito

Abid, N.

Faraj, A.

Macías-López, A.D. (Ángel David)

Ortiz-de-Urbina-Gutiérrez, J.M. (José María)

Saber-Rodríguez, S. (Sámar)

Serna-Ernst, J.M. (José Miguel) de-la

English

Relative abundance indices of bluefin tuna (Thunnus thynnus) caught by the Moroccan and
Spanish traps in the area close to the Strait of Gibraltar were estimated for the period 1981-
2013. Standardized CPUEs were estimated through a General Linear Modeling (GLM)
approach under a negative binomial error distribution assumption

Saber, S. (Sámar)

Repositorio Institucional Digital del IEO

SCRS/2014/060 Collect. Vol. Sci. Pap. ICCAT, 71(3): 1308-1312 (2015)    UPDATED STANDARDIZED JOINT CPUE INDEX FOR  BLUEFIN TUNA (THUNNUS THYNNUS) CAUGHT BY MOROCCAN  AND SPANISH TRAPS FOR THE PERIOD 1981- 2013   N. Abid1, A. Faraj1, J.M. de la Serna2, D. Macías2, S. Saber2, J. Ortiz de Urbina2   SUMMARY  Relative abundance indices of bluefin tuna (Thunnus thynnus) caught by the Moroccan and Spanish traps in the area close to the Strait of Gibraltar were estimated for the period 1981- 2013. Standardized CPUEs were estimated through a General Linear Modeling (GLM) approach under a negative binomial error distribution assumption.  RÉSUMÉ  Des indices d’abondance relative de thon rouge (Thunnus thynnus) capturé par des madragues espagnoles et marocaines dans la zone proche du détroit de Gibraltar ont été estimés pour la période allant de 1981 à 2013. Des CPUE standardisées ont été estimées par le biais d’une approche de modélisation linéaire généralisée (GLM) en postulant une distribution d'erreur binomiale négative.  RESUMEN  Se estiman índices de abundancia relativa para las capturas de atún rojo (Thunnus thynnus) de las almadrabas marroquíes y españolas del estrecho de Gibraltar para el período 1981-2013. Las CPUE se estandarizaron mediante técnicas de GLM asumiendo un error de tipo binomial negativo. KEYWORDS  CPUE, Catch, Effort, Abundance, Trap fishing, Bluefin tuna     1. Introduction  The Moroccan and Spanish trap abundance indices have been traditionally used for VPA- calibrating purposes at BFT Eastern Stock Assessment Sessions (ICCAT 2011). These indices are applied to spawners’ (age group 10+).  A previous document (Ortiz de Urbina et al, 2006) explored the adequacy of the traditionally used effort unit and model error assumptions for the standardization of the trap CPUE index. Based on the conclusions of the above mentioned document, the BFT Eastern Stock Assessment Working Group decided to use standardized trap catch, in number of fish, assuming a negative binomial error distribution.  This document updates previously reported information (Ortiz de Urbina et al., 2009; Ortiz de Urbina et al., 2011; Abid and Idrissi, 2010; Abid et al., 2012) on bluefin tuna standardized catch rates for both countries from 1981 to 2013.  In order to implement Rec.[06-05] and Rec.[08-05], both the Moroccan and Spanish Administrations set up a quota-by-gear system, starting in 2008. As a result, the traps are forced to release previously caught fish in case the awarded quota be reached. Data on Spanish catch for 2008 was not affected since the traps did not reach the awarded quota. For the period 2009- 2012, estimated number of released fish, reported by the traps operators                                                  1 Fisheries biologist, INRH, Regional Centre of Tangiers, Morocco 2 Head of fisheries department, INRH, Casablanca, Morocco. 3 Instituto Español de Oceanografía (IEO- CO Málaga). 1308 from both countries, was included in the data base for the analysis. For year 2013, scientific monitoring of the Moroccan traps was carried out as for previous years. On the other hand, scientific monitoring of the Spanish traps could not be carried out.   2. Material and Methods  Data were obtained from the Moroccan and Spanish trap fishery for bluefin tuna in areas close to the Strait of Gibraltar. Information on catch in number of individuals, size composition, effort, and trap characteristics was collected from 1981 to 2012 for the Spanish traps and from 1986 to 2013 for the Moroccan ones.  Table 1 shows the number of observations by factor considered in the model.  A Generalized Linear Modeling (GLM) approach (McCullagh and Nelder, 1989) with number of fish for the whole trap season as the response variable, year and trap as explanatory factors, and a negative binomial error distribution was used.    3. Results  Deviance analysis results are reported in Table 2. Based on its statistical significance as well as the percentage of the deviance explained by each factor, final model for catch in number of fish for the whole fishing season included both factors year and trap.  Diagnostic plots (residuals vs fitted values and cumulative normalized residual plots) are shown in Figure 1. In general, residual patterns are not far from expected under the negative binomial error distribution assumption, which suggests a reasonably good fit.  Annual standardized relative abundance indices (fitted values and fitted values scaled to the first year in the time series) are reported in Table 3 for catch in number of fish for the whole trap season.  Trends for the estimated standardized catch rates and corresponding 95 % confidence limits based on a normal approximation are shown in Figure 2.   References  Abid, N, A. Faraj, J.M. De La Serna, D. Macías, S. Saber, J. Ortiz de Urbina. 2013. Updated standardized joint  CPUE index for bluefin tuna (Thunnus thynnus) caught by Moroccan and Spanish traps for the period 1981-  2011. Col.Vol. Sci. Pap. ICCAT, 69(1): 235-239.  Abid, N., M. Idrissi. 2010. Updated standardized CPUE of bluefin tuna (Thunnus thynnus) caught by the  Moroccan Atlantic traps in the area of influence of the strait of Gibraltar during the period 1986- 2009.  Col.Vol. Sci. Pap. ICCAT, 65(3): 1096-1102.  ICCAT, 2011. Report of the 2010 Atlantic Bluefin Tuna Stock Assessment Session (Madrid, Spain - September  6 to 12, 2010). Col. Vol. Sci. Pap. ICCAT, 66(2): 505-714.  McCullagh, P. and J.A. Nelder. 1989. Generalized linear models. Second Edition. Chapman & Hall. University  Press. Cambridge. 511 pp.  Ortiz De Urbina, J.M., J.-M. Fromentin, V.R. Restrepo, H. Arrizabalaga, J.M. De La Serna. 2006. Standardized  CPUE of bluefin Tuna (Thunnus thynnus) caught by Spanish traps for the period 1981- 2004. Col. Vol. Sci.  Pap. ICCAT, 60(3): 913- 927.  Ortiz De Urbina, J.M., J.M. De La Serna, D. MACÍAS 2009. Standardized CPUE of bluefin tuna (Thunnus  thynnus) caught by Spanish traps for the period 1981-2007. Col. Vol. Sci. Pap. ICCAT, 64(2): 535- 540.  1309 Ortiz De Urbina, J.M., E. Rodríguez-Marín, J.M. De La Serna, D. Macías, P. Rioja 2011. Standardized CPUE of  bluefin tuna (Thunnus thynnus) caught by Spanish traps for the period 1981-2009. Col. Vol. Sci. Pap. ICCAT,  66(2): 829-834.   Table 1. Observations by factor. Moroccan and Spanish Traps 1981- 2013.   Country-trap Year mo1 mo2 mo3 mo4 sp1 sp2 sp3 sp4 1981 NA NA NA NA 1 NA NA NA 1982 NA NA NA NA 1 1 1 NA 1983 NA NA NA NA 1 1 1 NA 1984 NA NA NA NA 1 1 1 NA 1985 NA NA NA NA 1 1 1 NA 1986 1 NA NA NA 1 1 1 1 1987 1 NA NA NA 1 1 1 1 1988 1 NA NA NA 1 1 1 1 1989 1 NA 1 NA 1 1 1 1 1990 1 1 1 1 1 1 1 1 1991 1 1 1 1 1 1 1 1 1992 1 1 1 1 1 1 1 1 1993 1 1 1 1 1 1 1 1 1994 1 1 1 1 1 1 1 1 1995 1 1 1 1 1 1 1 1 1996 1 NA 1 1 1 1 1 1 1997 1 NA 1 1 1 1 1 1 1998 1 NA 1 1 1 1 1 1 1999 1 NA 1 1 1 1 1 1 2000 1 1 1 1 1 1 1 1 2001 1 1 1 1 1 1 1 1 2002 1 1 1 1 1 1 1 1 2003 1 1 1 1 1 1 1 NA 2004 1 1 1 1 1 1 1 1 2005 1 1 1 1 1 1 1 1 2006 1 1 1 1 1 1 1 1 2007 1 1 1 1 1 1 1 1 2008 1 1 1 1 1 1 1 1 2009 1 1 1 1 1 1 1 1 2010 NA 1 1 1 1 1 1 1 2011 1 1 1 1 1 1 1 1 2012 1 1 1 1 1 1 1 1 2013 NA 1 1 1 NA NA NA NA     1310 Table 2. Deviance analysis results. BFT catch in number. Moroccan and Spanish Traps. 1981- 2013. Δ deviance refers to change in deviance; % deviance: percent of deviance explained with respect to the null model; p-value: χ2 probability between consecutive models.  (whole season) residual residual       Model factors df deviance Δ deviance % deviance p-value null 213 545.58    Year 181 391.73 181.41 31.65 2.20E-16 Year+ Trap 174 225.11 166.62 29.07 2.20E-16  Table 3. GLM estimated standardized relative abundance indices, standard errors and coefficient of variation (CV %). BFT catch in number. Moroccan and Spanish Traps. 1981- 2013. Catch for the whole season.  Year Nominal Index scaled std. Error CV upp95CI low95CI 1981 768.36 1.00 439.39 57.19 1629.57 1982 1038.12 1.35 359.55 34.63 1742.84 333.41 1983 1092.05 1.42 378.22 34.63 1833.35 350.74 1984 1200.27 1.56 415.68 34.63 2015.01 385.54 1985 814.46 1.06 282.12 34.64 1367.42 261.50 1986 394.33 0.51 110.63 28.05 611.16 177.50 1987 433.53 0.56 121.61 28.05 671.88 195.18 1988 1014.56 1.32 284.34 28.03 1571.87 457.24 1989 531.45 0.69 138.67 26.09 803.24 259.66 1990 614.37 0.80 138.83 22.60 886.47 342.27 1991 727.86 0.95 164.44 22.59 1050.15 405.56 1992 313.95 0.41 71.03 22.63 453.18 174.73 1993 325.36 0.42 73.61 22.62 469.63 181.09 1994 341.90 0.44 77.34 22.62 493.49 190.31 1995 223.43 0.29 50.61 22.65 322.62 124.24 1996 375.22 0.49 92.38 24.62 556.28 194.16 1997 992.41 1.29 244.05 24.59 1470.75 514.08 1998 925.14 1.20 227.52 24.59 1371.07 479.21 1999 1137.45 1.48 279.69 24.59 1685.64 589.26 2000 739.23 0.96 167.01 22.59 1066.57 411.90 2001 1284.62 1.67 290.08 22.58 1853.18 716.06 2002 1130.42 1.47 255.28 22.58 1630.77 630.06 2003 662.66 0.86 156.91 23.68 970.20 355.11 2004 332.36 0.43 75.19 22.62 479.73 184.99 2005 677.39 0.88 153.05 22.59 977.37 377.41 2006 633.94 0.83 143.25 22.60 914.70 353.18 2007 1000.60 1.30 225.99 22.59 1443.53 557.66 2008 634.18 0.83 143.30 22.60 915.05 353.32 2009 876.71 1.14 198.03 22.59 1264.85 488.57 2010 1042.24 1.36 246.59 23.66 1525.56 558.92 2011 674.97 0.88 152.50 22.59 973.87 376.06 2012 1187.75 1.55 280.99 23.66 1738.50 637.01 2013 4285.56 5.58 1419.51 33.12 7067.79 1503.33 1311 Figure 1.   Figure 2(normal a Diagnostic p. Estimated pproximationlots: residualsstandardized ). Moroccan  vs fitted valurelative abuand Spanish tr es and cumulndance indexaps. 1981- 20ative normali  and corresp13. zed residual ponding 95% lot.  confidence limits 1312

Updated standardized joint CPUE index for bluefin tuna (Thunnus thynnus) caught by Moroccan and Spanish traps for the period 1981- 2012.

http://www.repositorio.ieo.es/e-ieo/bitstream/10508/9401/1/SCRS_2014_060.pdf

Updated standardized joint CPUE index for bluefin tuna (Thunnus thynnus) caught by Moroccan and Spanish traps for the period 1981- 2012.

Abstract

Similar works

Full text

Available Versions

Repositorio Institucional Digital del IEO