Title Page
Abstract
Contents
1. Introduction 13
2. Relationship between upper-ocean variability and tuna catches in the southwestern tropical Indian Ocean 26
2.1. Introduction 26
2.2. Materials and methods 30
2.3. Results 33
2.4. Discussion 45
2.5. Conclusions 61
3. Relationship between upper-ocean variability and tuna catches in the western central Pacific Ocean 63
3.1. Introduction 63
3.2. Materials and methods 68
3.3. Ocean conditions related to the tuna catches 72
3.4. Discussion 98
3.5. Conclusions 110
4. Potential predictability of the tuna catches in the Western Central Pacific 112
4.1. Introduction 112
4.2. Materials and methods 114
4.3. Results 117
4.4. Discussion 129
4.5. Conclusions 132
5. Conclusions 135
References 143
Abstract (in Korean) 156
Appendices 159
Appendix Ⅰ. Cyclostationary EOF analysis 159
Appendix Ⅱ. Regression analysis and statistical prediction 161
Table 1.1. The physiologies of skipjack tuna (Katsuwonus pelamis), yellowfin tuna (Thunnus albacares), and bigeye tuna (Thunnus obesus). 15
Table 3.1. The correlation coefficients among the catch amounts of the SKJ, YFT, and BET in the EEZs of the FSM and FOUR during 1990-... 80
Table 3.2. same as Table 3.1, but with detrended annual catch amounts of tuna during 1990-2018. 82
Table 4.1. Regression coefficients of each mode of 5 m salinity to the catch amounts of SKJ in the FSM during the learning period. 123
Table 4.2. Regression coefficients of each mode of 100 m temperature to the catch amounts of SKJ in the FSM during the learning period. 124
Figure 1.1. The total end tuna values of each species in 2018. 13
Figure 1.2. Schematic of the LL fishing method. 18
Figure 1.3. same as Figure 1.2, but for the PS fishing method. 18
Figure 1.4. Displacements of tagged skipjack tuna. (top) Tuna released May 1991, recaptured before February 1992 (El Niño years). (bottom)... 20
Figure 2.1. (a) Mean SSH (color shading and contours) and wind velocity (vectors) in the tropical Indian Ocean for 1990-2014. Red... 27
Figure 2.2. Meridional distribution of the (top) means and (bottom) standard deviations of the ocean environmental variables for 1990-... 34
Figure 2.3. (a) The annual catch amounts of yellowfin tuna and bigeye tuna during 1990-2014 in the four exclusive economic zones (EEZs)... 36
Figure 2.4. Meridional distributions of the regressed and reconstructed anomalies of the ocean environmental variables during 1990-2014.... 38
Figure 2.5. The R-squared values of the regression for 1990-2014 from the (a) temperature, (b) salinity, and (c) current velocity at each... 39
Figure 2.6. The regressed and reconstructed anomalies of the total precipitation (color) and 10-m wind velocity (vector) in the tropical... 41
Figure 2.7. Meridional distribution of the regressed and reconstructed anomalies of the ocean environmental variables with respect to the... 43
Figure 2.8. The R-squared values of the regression targeting the normalized indices of the DMI and the MEI for 1990-2014. The... 44
Figure 2.9. Meridional distribution of the mean (first column) and the regressed and reconstructed anomalies of the NPP (upper row) and... 50
Figure 2.10. The R-squared values of the regression for 1993-2014 from the (a) NPP and (b) CHL at each depth in the tropical Indian Ocean,... 51
Figure 2.11. Meridional distribution of the regressed and reconstructed anomalies of the ocean environmental variables with respect to the... 54
Figure 2.12. same as Figure 2.11, but for the normalized MEI. 55
Figure 2.13. The R-squared values of the lagged regression (lags: -2 years, -1 year, 0, +1 year and +2 years, respectively, from top to... 56
Figure 2.14. The yearly averaged third mode of temperature anomaly and the second mode of salinity anomaly at a depth of 200 m,... 58
Figure 2.15. Mean temperature and temperature anomaly in the SWTIO. (a) mean temperature during the period of 1990-2014, (b) temperature... 60
Figure 3.1. The exclusive economic zones (EEZs) of the FSM and the FOUR in the WCP. 64
Figure 3.2. (a-c) The catch amounts of the five dominant species in the EEZs of each nation during 1990-2018: (a) the sum of catch amounts... 64
Figure 3.3. The catch amounts of the SKJ (black), the YFT (blue), and the BET (red) in the EEZs of the FSM and the FOUR during 1990-2018:... 66
Figure 3.4. Comparison of normalized annual catches of tuna in the FSM and the FOUR during 1990-2018 SAU EEZ data (solid lines),... 69
Figure 3.5. The zonal distribution of the mean (top panel) and standard deviation (bottom panel) of various ocean environmental variables in... 72
Figure 3.6. The mean (a) and standard deviation (b) of total precipitation and 10 m height wind velocity in the equatorial Pacific... 75
Figure 3.7. The catch amounts of the SKJ, YFT, and BET in the EEZs of the FSM and FOUR during 1990-2018: (top) the catch amounts (solid... 78
Figure 3.8. The R-squared values of the regression at each depth with respect to the SKJ, YFT, and BET in the EEZs of the FSM (top panel)... 84
Figure 3.9. The zonal distributions of the regressed and reconstructed anomalies of the ocean environmental variables in the equatorial... 86
Figure 3.10. same as Figure 3.9, but for the FOUR. 90
Figure 3.11. The zonal distributions of the regressed and reconstructed anomalies of the ocean environmental variables in the... 93
Figure 3.12. The R-squared values of the regression at each depth with respect to the YFT (blue) and the BET (red) caught by the LL... 95
Figure 3.13. The zonal distributions of the regressed and reconstructed anomalies of the ocean environmental variables in the... 96
Figure 3.14. same as Figure 3.13, but for the FOUR. 97
Figure 3.15. Mean 5 m depth temperature during 1990-2014 and yearly averaged 5 m depth temperature in 2015, 2016, 2017, and 2018. Only... 101
Figure 3.16. Schematic representation of the shift in habitat of the SKJ, YFT, and BET and the corresponding warm pool, thermocline depth... 107
Figure 4.1. The autocorrelations of the annual mean catch amount of the FSM during 1990-2014. 116
Figure 4.2. R-squared values of the regression at each depth with respect to the SKJ catches in the FSM from 1990 to 2014 for (a)... 119
Figure 4.3. Regressed and reconstructed anomalies of ocean environmental variables in the equatorial Pacific Ocean with respect... 119
Figure 4.4. Observed (red), estimated and predicted annual catch amount of SKJ in the FSM based on the relationship with the 5 m... 122
Figure 4.5. Observed (red), estimated, and predicted annual catch amount of SKJ in the FSM based on the relationship with the 5 m... 126
Figure 4.6. Observed (red), estimated, and predicted annual catch amount of SKJ in the FSM based on the relationship with the 5 m... 128
Figure 5.1. Schematics of ocean conditions during an increase in yellowfin and bigeye tuna catches in the northern region of the... 137