UPDATED STANDARDIZED CPUE FOR ALBACORE CAUGHT BY JAPANESE LONGLINE FISHERY IN THE ATLANTIC OCEAN,

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1 SCRS/00/160 UPDATED STANDARDIZED CPUE FOR ALBACORE CAUGHT BY JAPANESE LONGLINE FISHERY IN THE ATLANTIC OCEAN, Koji Uosaki 1 SUMMARY CPUEs of Atlantic albacore (Thunnus alalunga) caught by the Japanese longline fishery from 1975 to1999 were standardized using two kinds of model with different error structures (log-normal and distribution) under the hypotheses of separate north and south stocks. The standardized CPUEs decreased for in the north Atlantic, whereas the CPUEs fluctuated for , and showed no clear trend in the south Atlantic. The standardized CPUEs between these two models were fairly similar in both the north and the south Atlantic. RÉSUMÉ La CPUE du germon atlantique (Thunnus alalunga) capturé par les palangriers japonais de 1975 à 1999 a été standardisée au moyen de deux types de modèles comportant une structure différente de l erreur (distribution log-normale et de ) selon l hypothèse de l existence de stocks distincts nord et sud. La CPUE standardisée a diminué en dans l Atlantique nord, alors qu elle a fluctué en sans montrer de tendance claire ldans l Atlantique sud. Les deux modèles donnaient une CPUE standardisée assez similaire dans l Atlantique nord et sud. RESUMEN Las CPUEs del atún blanco atlántico (Thunnus alalunga) capturado por la pesquería de palangre japonesa entre 1975 y 1999, fueron estandarizadas por medio de dos modelos con diferentes estructuras de error (lognormal y ) con la hipótesis de dos stock separados, al norte y al sur. Las CPUEs estandarizadas descendieron de 1975 a 1999 en el Atlántico norte, mientras que en el Atlántico sur las CPUEs fluctuaron entre 1975 y 1988 sin una tendencia clara. Las CPUEs estandarizadas de estos dos modelos eran bastante similares tanto en el norte como en el sur del Atlántico. KEYWORDS Atlantic, albacore, abundance index, standardization 1. INTRODUCTION For Atlantic albacore caught by Japanese longline fishery, the CPUE standardization using the General Linear Model (GLM) with the assumption that the error structure belongs to log-normal had been carried out (Uozumi 1994a). Uosaki (1996, 1997) carried out the standardization assuming error structure with to overcome a problem of zero CPUE treatment. In that study, standardized CPUEs were calculated separately for the , and periods according to Uozumi (1994b), which classified three periods of "Target", "Transition" and "By-catch" in the history of the 1 National Research Institute of Far Seas Fisheries, 7-1, Orido 5-chome, Shimizu-shi, Japan

2 Japanese longline fishery on the Atlantic Ocean based on their fishery strategy. In the present study the standardized CPUE for the north and south stocks in the Atlantic was updated using those two models up to 1999 as the By-catch period. 2. MATERIALS AND METHODS 2.1. Data The data used in this study were obtained from the Japanese longline fishery statistics based on the logbooks and compiled at the National Research Institute of Far Seas Fisheries. The data was made by breaking the Task II catch-and-effort data down with gear configuration information i.e., number of hooks per basket, for The data in 1999 was still preliminary. CPUE was defined as the number of fish caught per 1,000 hooks. Observations with less than 3,000 hooks were excluded from this analysis. In addition, observations which belong to the EEZ were also excluded to avoid inconsistency of data coverage during a long historic period Standardization In order to standardize CPUE of albacore, two different models were used, i.e., model with the assumption of log-normal error structure, and model with the assumption of error structure, using GLM and GENMOD procedures of SAS software package (Ver. 6.12), respectively. Year, season, subarea and gear configuration were incorporated as main effects. Quarter was used for fishing season. Nine subareas for each stock were defined based on the spatial distribution pattern of nominal CPUE of albacore (Fig. 1). The gear configuration was categorized to four levels (3-7, 8-11, and hooks between float). The model used was: ln(cpue+constant)=µ+y+q+a+g+interactions+e where µ : intercept Y : effect of year Q : effect of quarter A : effect of subarea G : effect of gear e : error term Interactions : any combinations of two-way interaction between main factors In order to include observations with fishing effort but no catch of albacore, a value which adds to CPUE (constant) were used. The constants 1.0 and 0.1 were selected for north and south stock, respectively, as approximate 10% of mean CPUE of albacore. The 10% of mean CPUE as the constant was recommended in Bluefin Species Group (ICCAT, 1997). The model is: E(C)=H exp(µ+y+q+a+g+interactions) where E(C): expectation of catch in number which belong to distribution. H: number of hooks used. In the analysis of GENMOD procedure, overdispersion was observed, therefore DSCALE option which estimates dispersion parameter was included. All statistics were adjusted according to the dispersion parameter appropriately. Model selection was according to the result of Uosaki (1997) based on Akaike s Information Criterion (AIC). The models were as follows: model north stock : ln(cpue+0.1)= µ+y+q+a+g+q*a+q*g south stock : ln(cpue+0.1)= µ+y+q+a+g+y*q+q*a+q*g+a*g model north stock : E(C)=H exp(µ+y+q+a+g+y*q+q*a+q*g) south stock : E(C)=H exp(µ+y+q+a+g+y*q+q*a+q*g+a*g)

3 As done at the ICCAT albacore species group meeting in 1998 (Madrid), standardized (predicted) CPUE for the model was calculated as follows; predicted CPUE=exp(LSM+1/2(MSE))-constant where LSM: least square mean of response variable for the effect of year MSE: mean square error of the model 3. RESULT AND DISCUSSION The ANOVA for the model using GLM procedure, and goodness of fit for the model using GENMOD procedure are shown in Tables 1 and 2. For the model, F value shows that the models are highly significant in the ANOVA (Table 1). The R-squares were 0.53 and 0.34 for north and south stocks, respectively. Whereas, for the model, scaled Pearson χ 2 in Table 2 show the model are highly significant as well. Although, the effect of gear in the south stock (χ 2 =0.37) were not significant, interactions which include effect of gear (Q*G and A*G) were significant. The scaled CPUEs which were adjusted to 1.0 in 1975, for are shown in Fig 1, and those for are shown in Table 3 for the north, Table 4 for the south stock. For the north stock there is no substantial difference in the CPUE trend between models for The CPUEs declined from 1.0 to around 0.2 for the period. For the south stock, there is no substantial difference in the CPUE trend between the models for , as well as the north stock. The CPUEs fluctuated and showed no clear trend for And then, the CPUEs were, however, stable after LITERATURE CITED ICCAT Report of the bluefin tuna methodology session. ICCAT Col. Vol. Sci. Pap. XLVI (1); pp UOSAKI, K Updated standardized CPUE for albacore caught by Japanese longline fishery in the Atlantic Ocean. ICCAT Col. Vol. Sci. Pap. XLIII; pp UOSAKI K Updated standardized CPUE for albacore caught by Japanese longliner in the Atlantic Ocean, ICCAT Col. Vol. Sci. Pap. XLVI (3); pp UOZUMI, Y. 1994a. The historical trend of standardized CPUE for albacore caught by Japanese longline fishery in the Atlantic Ocean. ICCAT Col. Vol. Sci. Pap. XLIII; pp UOZUMI, Y. 1994b. A historical review of Japanese longline fishery and albacore catch in the Atlantic Ocean. ICCAT Col. Vol. Sci. Pap. XLIII; pp UOZUMI, Y Recent Status of the Japanese longline fishery in the Atlantic Ocean laying stress on albacore catch. ICCAT Col. Vol. Sci. Pap. XLVI (3); pp

4 Table 1. ANOVA for the model (lognormal error structure assumption) in the north and south Atlantic. North Atlantic South Atlantic Source DF SS Mean Sq. F Value Pr > F Source DF SS Mean Sq. F Value Pr > F Model Model Error Error Corr. Tot Corr. Tot R-square= C.V.= R-square= C.V.= Source DF Type III SS Mean Sq. F Value Pr > F Source DF Type III SS Mean Sq. F Value Pr > F Y Y Q Q A A G G Q*A Y*Q Q*G Q*A A*G Q*G Table 2. Goodness of fit for the model ( error structure assumption) in the north and south Atlantic. North Atlantic South Atlantic Source NDF DDF F Pr>F ChiSquare Pr>Chi Source NDF DDF F Pr>F ChiSquare Pr>Chi Y Y Q Q A A G G Y*Q Y*Q Q*A Q*A Q*G Q*G A*G

5 Table 3. Standardized CPUEs and scaled CPUEs with the confidence intervals for the model and those for the model in the north Atlantic. The value of scaled CPUE was adjusted to 1.0 in CPUEs for is revised from Uosaki (1996), by adding 1/2 mean square error to least square mean at obtaining index. Year Target Transition Baycatch (scaled) Target Transition Baycatch (scaled) Mean Mean Mean Mean Lower Upper Mean Mean Mean Mean 59 29,086 5,976 5,002 7,133 2,274 7, ,266 4,164 3,157 5,470 2,104 6, ,537 4,836 3,135 7,395 1,755 5, ,304 6,226 4,651 8,310 2,410 7, ,983 3,695 3,007 4,528 1,236 3, ,412 4,194 3,845 4,574 1,232 3, ,036 2,678 2,507 2,861 0,791 2, ,119 2,695 2,469 2,941 0,924 2, ,364 2,951 2,677 3,252 1,067 3, ,232 3,335 2,984 3,725 0,989 3, ,024 12,386 2,881 2,545 3,259 1,000 3,185 3, ,651 2,943 2,651 3,264 2,954 2, ,251 1,687 1,535 1,851 1,806 1, ,676 1,088 0,948 1,244 1,135 1, ,316 1,237 1,059 1,439 1,176 1, ,554 1,059 0,912 1,227 1,420 1, ,299 2,835 1,000 0,840 1,190 1,000 1,501 1, ,630 0,928 0,770 1,116 1,925 1, ,613 0,569 0,458 0,705 1,011 0, ,320 0,466 0,385 0,562 0,632 0, ,550 0,547 0,453 0,658 0,434 0, ,163 0,410 0,345 0,487 1,234 0, ,590 0,561 0,482 0,652 2,051 0, ,224 0,432 0,371 0,501 2,206 0, ,185 0,418 0,348 0,500 1,273 0, ,106 0,390 0,327 0,464 1,303 0, ,189 0,419 0,359 0,489 2,021 0, ,804 0,284 0,238 0,338 2,275 0, ,659 0,232 0,193 0,278 0,931 0, ,928 0,327 0,276 0,388 0,688 0, ,933 0,329 0,284 0,381 0,986 0, ,731 0,258 0,219 0,303 0,860 0, ,762 0,269 0,228 0,316 1,007 0, ,646 0,228 0,192 0,269 1,049 0, ,712 0,251 0,212 0,296 0,889 0, ,726 0,256 0,217 0,301 0,896 0, ,616 0,217 0,185 0,255 0,652 0, ,645 0,228 0,195 0,264 0,835 0, ,607 0,214 0,183 0,249 1,101 0, ,526 0,185 0,159 0,216 0,975 0, ,609 0,215 0,182 0,254 1,000 0,217

6 Table 4. Standardized CPUEs and scaled CPUEs with the confidence intervals for the model and those for the model in the south Atlantic. The value of scaled CPUE was adjusted to 1.0 in CPUEs for is revised from Uosaki (1996), by adding 1/2 mean square error to least square mean at obtaining index. Year Target Transition Baycatch (rescaled) Target Transition Baycatch (rescaled) Mean Mean Mean Mean Lower Upper Mean Mean Mean Mean 59 45,626 15,987 13,357 19,130 7,231 51, ,419 12,761 10,739 15,158 6,192 44, ,832 9,752 8,554 11,117 4,325 30, ,544 8,250 7,290 9,334 3,267 23, ,071 7,383 6,535 8,339 2,755 19, ,339 7,827 6,977 8,780 3,008 21, ,338 5,374 4,860 5,943 2,436 17, ,143 5,656 5,069 6,310 2,390 16, ,137 6,005 5,272 6,837 2,285 16, ,767 5,174 4,543 5,890 2,274 16, ,825 10,249 2,742 2,384 3,148 1,000 7,109 7, ,554 1,753 1,520 2,017 4,808 4, ,774 2,080 1,800 2,397 6,208 6, ,252 1,672 1,422 1,960 3,377 3, ,044 1,082 0,897 1,296 1,674 1, ,902 1,312 1,013 1,679 1,749 1, ,738 0,721 1,000 0,807 1,233 1,000 1,501 1, ,767 1,065 0,815 1,380 1,925 1, ,674 0,935 0,749 1,161 1,011 0, ,803 1,114 0,902 1,371 0,632 0, ,536 0,744 0,618 0,891 0,434 0, ,669 0,929 0,812 1,059 1,234 0, ,017 1,412 1,236 1,611 2,051 1, ,889 1,233 1,090 1,393 2,206 1, ,670 0,931 0,770 1,119 1,273 0, ,673 0,934 0,817 1,066 1,303 0, ,031 1,431 1,276 1,604 2,021 1, ,884 1,226 1,077 1,395 2,275 1, ,606 0,841 0,722 0,976 0,931 0, ,453 0,629 0,558 0,706 0,688 0, ,575 0,799 0,718 0,886 0,986 0, ,559 0,776 0,700 0,858 0,860 0, ,592 0,822 0,741 0,911 1,007 0, ,509 0,706 0,629 0,791 1,049 0, ,499 0,692 0,621 0,770 0,889 0, ,573 0,795 0,720 0,877 0,896 0, ,421 0,584 0,524 0,649 0,652 0, ,450 0,625 0,561 0,695 0,835 0, ,488 0,678 0,604 0,759 1,101 0, ,516 0,716 0,632 0,809 0,975 0, ,509 0,707 0,616 0,809 1,000 0,666

7 Fig.1. Subarea used in standardization of CPUE. Scaled CPUE 1,200 1,000 0,800 0,600 0,400 North stock m odel P oisson m odel 0,200 Fig. 2. Scaled standardized CPUEs of the north and south Atlantic using two different models. The value of CPUE was adjusted to 1.0 in Scaled CPUE 0,000 1,800 1,600 1,400 1,200 1,000 0,800 0, South stock m odel model 0,400 0,200 0,