UPDATED JAPANESE LONGLINE BLUEFIN TUNA CPUE IN THE ATLANTIC OCEAN

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1 SCRS/2009/172 Collect. Vol. Sci. Pap. ICCAT, 65(3): (2010) UPDATED JAPANESE LONGLINE BLUEFIN TUNA CPUE IN THE ATLANTIC OCEAN Kazuhiro Oshima and Naozumi Miyabe 1 SUMMARY Abundance indices from the Japanese longline fishery in the Atlantic including the Mediterranean Sea were provided up to Indices were developed for three areas; West Atlantic, central Atlantic and East Atlantic, including the Mediterranean Sea. The indices were standardized with delta-normal model with random effect. The West Atlantic index decreased to the average level of recent years in 2008 after a remarkable increase in There was an observed flat trend of the central Atlantic index since There was no remarkable increase or decrease in the index in the East Atlantic in RÉSUMÉ Les indices d abondance de la pêcherie palangrière japonaise opérant dans l Atlantique, y compris la mer Méditerranée, ont été fournis jusqu en Les indices ont été élaborés pour trois zones : l Atlantique Ouest, l Atlantique central et l Atlantique Est, y compris la mer Méditerranée. Les indices ont été standardisés au moyen d un modèle delta-normal avec effet aléatoire. L indice de l Atlantique Ouest a été ramené au niveau moyen des récentes années en 2008, après une augmentation marquée en Une tendance plane accusée s'est dégagée dans l'indice de l Atlantique central dès L indice de l Atlantique Est n a dégagé aucune augmentation ou diminution remarquable en RESUMEN Se facilitaron los índices de abundancia de la pesquería de palangre japonesa en el Atlántico, incluido el Mediterráneo, hasta Los índices se desarrollaron para tres zonas: Atlántico oeste, Atlántico central y Atlántico oriental, incluido el mar Mediterráneo. Se estandarizaron los índices con un modelo delta-lognormal con un efecto aleatorio. En 2008, el índice del Atlántico oeste descendió al nivel medio de los años recientes, tras el notable incremento que experimentó en Se observó una tendencia estable en el índice del Atlántico central desde En 2008, no se produjeron incrementos o descensos importantes en el índice del Atlántico oriental. KEYWORDS Bluefin tuna, stock abundance, catch and effort, CPUE standardization, Generalized Linear Mixed Model, delta-lognormal model 1. Introduction This paper provides updated abundance trend of the bluefin stocks in West, Central and East Atlantic (Oshima et al. 2009) through the CPUE standardization by the application of Generalized Linear Modeling technique. 2. Materials and methods Data were extracted from the Japanese longline fishery catch and effort data compiled from logbook data by the National Research Institute of Far Seas Fisheries (NRIFSF) from 1975 to Catch and effort (no. of hooks) 1 NRIFSF , Orido, Shimizu, Shizuoka, Japan. oshimaka@affrc.go.jp 944

2 data were disaggregated, namely, set-by-set data. Besides information on catch and efforts, the data includes information on year, month, area, materials for main and branch lines and number of hooks between floats (NHBF). Area definition is shown in Fig. 1 and Table 1. Number of longline sets by various strata for West, Central and East Atlantic CPUE standardizations listed in Tables 2, 3 and 4. This paper followed CPUE standardization methods in Oshima et al. (2009). Year, month, area, materials for main and branch lines and NHBF were applied as main effects in our model and an interaction between month and area was maintained as a random effect. Description of the main effects is summarized in Table 5. Delta-lognormal model (Lo et al. 1992) was applied for standardizing CPUE in this study, because the database used included many zero-catch observations. Formula of logistic regression model of the 1st step model is as follows: p Log Intercept Year Month + Area +Main + Bran + NHBF + Month*Area+ Error 1 p (1) where Log(p/(1 p)) is logit function, p indicates ratio of positive catch; Main, Bran refers to materials of main and branch lines, respectively; and error is assumed to be distributed binomially. The formula of lognormal model of the 2nd step is as follows: LogCPUE Intercept + Year + Month +Area +Main + Bran +NHBF +Month*Area + Error (2) where LogCPUE indicates natural logarithm of catch rate, that is number of PBF per 1000 hooks; Main and Bran effects are the same as one in the 1st step; and error is also assumed to be distributed normally. The fitting was conducted by GLIMMIX macro and MIXED procedure of SAS/STAT package (Version 9.2) for the 1st and 2nd step, respectively. 3. Results Monthly distribution of bluefin catch by Japanese longliners by 1-degree square in 2007 and 2008 are shown in Figures 2 and 3. Results of type 3 test for positive catch ratio (1st step) and CPUE of positive catch (2nd step) are shown in Table 6. Residual patterns of positive CPUE in the 2nd step were slightly skewed and indicated right-tailed shape (Figure 4). Additionally, the residual distribution in the central Atlantic had two modes. There were large fluctuations in observed and predicted proportions of positive catch in West Atlantic (Figure 5). Annual proportion in West increased after 2005 and remained high until On the contrary, the proportions in Central and East Atlantic showed flat yearly trend compared to that in the west. Observed CPUE of positive catch in the East and West Atlantic fluctuated without any trend during and it increased remarkably in 2007 and decreased to the average level of recent years in 2008 in the west (Figure 6). On the other hand, CPUE in the central Atlantic exhibited flat trend. Standardized CPUE based on the Least Square Mean are shown in Figure 7. CPUE in West Atlantic decreased to the average level of recent years in 2008 after remarkable increase in There observed the flat trend of CPUE since 2000 in Central Atlantic. There was no remarkable increase or decrease of CPUE in East Atlantic in Historical abundance indices with those 95% confidence intervals in West, Central and East Atlantic listed in Table 7. References Lo, NC-H., Jacobson, L.D., Squire, J.L. 1992, Indices of relative abundance from fish spotter data based on delta-lognormal models. Can. J. Fish. Aquat. Sci. Vol. 49, no. 12, pp Oshima, K., Takeuchi, Y., Miyabe, N. 2009, Standardized bluefin CPUE from the Japanese longline fishery in the Atlantic up to Collect. Vol. Sci. Pap. ICCAT, 64(2):

3 Table 1. Dimension of CPUE and area. Dimension of CPUE/Area West Central East (including Mediterranean Sea) Years Month Nov.-Feb. Aug.- Mar. Mar.-Jul. Beginning or mid-year Beginning Beginning Mid-year Geographical extent 30-50N, 45-80W (Fig. 1, upper panel, areas 1-24) 38-65N, 30-45W 40-65N, 5E-30W (Fig. 1, upper panel, areas 31-35) 30-45N,45W-25E (Fig. 1, lower panel, areas 1-9) 946

4 Table 2. Number of longline sets by various strata for West Atlantic CPUE standardization. Observations were aggregated by month, area (prefixed by A), materials of main line (M1=others, M2=nylon) and branch line (F1=others, F2=nylon), number of hooks between floats (prefixed by B). Area definition is shown in Figure 1. Year is fishing year. Year Nov Dec Jan Feb A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 A16 A17 A18 A19 A20 A21 A Total

5 Table 2 (Cont). Year A23 A24 M1 M2 F1 F2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B12 B13 B14 B15 B16 B17 B18 B19 B20 B21 Total Total

6 Table 3. Number of longline sets by various strata for Central Atlantic CPUE standardization. Observations were aggregated by month, area (prefixed by A), materials of main line (M1=others, M2=nylon) and branch line (F1=others, F2=nylon), number of hooks between floats (prefixed by B). Area definition is shown in Figure 1. Year is fishing year. Year Aug Sep Oct Nov Dec Jan Feb Mar A31 A32 A33 A34 A35 M1 M2 F1 F2 B3 B Total Year B5 B6 B7 B8 B9 B10 B11 B12 B13 B14 B15 B16 B17 B18 B19 B20 B21 Total Total

7 Table 4. Number of longline sets by various strata for East Atlantic CPUE standardization. Observations were aggregated by month, area (prefixed by A), materials of main line (M1=others, M2=nylon) and branch line (F1=others, F2=nylon), number of hooks between floats (prefixed by B). Area definition is shown in Figure 1. Year is fishing year. Year Mar Apr May Jun Jul A1 A2 A3 A4 A5 A6 A7 A8 A9 M1 M2 F1 F2 B Total

8 Table 4 (Cont). Year B4 B5 B6 B7 B8 B9 B10 B11 B12 B13 B14 B15 B16 B17 B18 B19 B20 B21 Total Total

9 Table 5. Description of main effects. Main effect / Area West Central Atlantic East Atlantic (Area 5 + Med.) Year Season (month) Nov, Dec, Jan, Feb Aug.-Nov, Dec, Jan, Feb+Mar Mar, April, May, June Area 5 areas (Fig. 1) 5 areas (Fig. 1) 6 areas (Fig. 1) Material of main line Nylon, others (since 1994) Nylon, others(since 1994) Nylon, others (since 1994) Material of branch line Nylon, others (since 1994) Nylon, others(since 1994) Nylon, others (since 1994) Hooks between floats 5 13 (individual) 4-7, 8-12 hooks 4-7, 8-13 hooks Table 6. Statistical results from GLMM analysis for positive catch ratio (1st step) and CPUE of positive catch (2nd step). West Atlantic Type 3 test of fixed effect for proportion of positive catch Effect DF DF Chisq F Value Pr > ChiSq Pr > F year <.0001 <.0001 month area <.0001 <.0001 main bran br <.0001 <.0001 Type 3 test of fixed effect for LogCPUE with positive catch Effect DE DE F value Pr > F year <.0001 month area <.0001 main <.0001 bran br <

10 Table 6 (Cont). Central Atlantic Type 3 test of fixed effect for proportion of positive catch Effect DF DF Chisq F Value Pr > ChiSq Pr > F year <.0001 <.0001 month <.0001 <.0001 area <.0001 <.0001 main bran br <.0001 <.0001 Type 3 test of fixed effect for LogCPUE with positive catch Effect DE DE F value Pr > F year <.0001 month <.0001 area main <.0001 bran br East Atlantic Type 3 test of fixed effect for proportion of positive catch Effect DF DF Chisq F Value Pr > ChiSq Pr > F year <.0001 <.0001 month <.0001 <.0001 area <.0001 <.0001 main <.0001 <.0001 bran br <.0001 <.0001 Type 3 test of fixed effect for LogCPUE with positive catch Effect DE DE F value Pr > F year <.0001 month <.0001 area <.0001 main bran br

11 Table 7. Standardized abundance indices (absolute and scaled values), standard errors and coefficient of variation (CV %) for the western, central and eastern Atlantic. Year West Atlantic Central Atlantic East Atlantic Index Scaled index Std. error CV Index Scaled index Std. error CV Index Scaled index Std. error CV

12 Figure 1. Areas considered in the CPUE standardization. Upper panel indicates area stratification used for west CPUE area and central CPUE area. Numbers from 1 through 24 and from 31 through 35 denote for these area, respectively. Lower panel shows the same information for east CPUE area. Numbers indicate original area stratification used in Tables 2-4.

13 Figure 2. Monthly distribution of bluefin catch by Japanese longliners by 1-degree square in

14 Figure 3. Monthly distribution of bluefin catch by Japanese longliners by 1-degree square in

15 Western Atl. Density Residual Central Atl. Density Residual Eastern Atl. Density Residual Figure 4. Residual distributions in the 2nd steps of CPUE standardization with positive catch. Upper panel, western Atlantic; middle panel, central Atlantic; lower panel, eastern Atlantic. 958

16 Proportion of positive catch - Western Atl. Propotion Observed Predicted Year Figure 5. Observed and predicted proportion of positive catch observation. Upper panel, West Atlantic; middle panel, central Atlantic; lower panel, East Atlantic. 959

17 CPUE of positive catch - Western Atl. CPUE (ind./1000hooks) Observed Predicted Year CPUE of positive catch - Central Atl. CPUE (ind./1000hooks) Observed Predicted Year CPUE of positive catch - Eastern Atl. CPUE (ind./1000hooks) Observed Predicted Year Figure 6. Observed and predicted CPUE of positive catch set. Upper panel, West Atlantic; middle panel, Central Atlantic; lower panel, East Atlantic. 960

18 Standardized CPUE - Western Atl. Scaled CPUE Observed Standardized 95%CI Year Standardized CPUE - Central Atl. Scaled CPUE Observed Standardized 95%CI Year Standardized CPUE - Eastern Atl. Scaled CPUE Observed Standardized 95%CI Year Figure 7. Standardized CPUE with 95% confidence intervals and nominal CPUE. Upper panel, West Atlantic; middle panel, Central Atlantic; lower panel, East Atlantic. 961