Oscillation mode analysis on time series of the abundance of unassociated school Katsuwonus pelamis in the Western and Central Pacific Ocean
Katsuwonus pelamis plays an important role in the world's tuna fishery,and the Western and Central Pacific Ocean is the main fishing ground for K.pelamis.There are significant seasonal,interannual,and interdecadal oscillations of resources in this area,and it is of great significance to grasp the temporal variability of K.pelamis resources in the area for reference of fisheries management and decision making departments to establish reasonable and effective management and restraint mechanisms.In this study,we decomposed the standardized CPUE time of K.pelamis of unassociated schools in the Central and Western Pacific Ocean from 1990 to 2019 by ensemble empirical mode decomposition method to obtain the characteristics of its fluctuation cycles;and obtained the intensity and phase difference of the corresponding relationship between each fluctuation cycle and environmental cycle by time lag analysis method.The results showed that:1)K.pelamis resources of unassociated schools in the Central and Western Pacific Ocean showed an increasing trend,caused by the biological characteristics of itself,the expansion of the scale of operating fishing vessels,and the continuous development of fishing technology and fishing forecast technology.2)The fluctuation of K.pelamis resources of unassociated schools could be considered as the combined effect of the oscillation of multiple cycles of0.3 a,0.6 a,1.5 a,3.5 a,and 5.5 a.3)0.3 a and 0.6 a were the seasonal oscillation characteristics of the resource with relatively small effects,considering that they contained Gaussian white noise added during the EEMD decomposition and the noise of the original series itself,or the combined effect of biological and environmental factors.4)The interannual oscillations of 1.5a and 3.5a had a greater impact on the variation of K.pelamis resources of unassociated schools in the area.It was a reflection of the combined effect of environmental oscillation and K.pelamis biological cycle,and 1.5a oscillation was related to the age of initial sexual maturity of K.pelamis,oscillation was correlated with the Nino index with a coefficient of 0.61 and a phase difference of 8 months,corresponding to the cycle of El Niño southern oscillation,suggesting that the passage of an El Niño event produced an environmental effect favorable to its growth and increased the survival rate of K.pelamis juveniles,causing an increase in K.pelamis CPUE of unassociated schools after 8 months.5)For low frequency oscillations,the 5.5 a fluctuation cycle had no corresponding cycle,and it was considered that it might be caused by a combination of oceanic environmental oscillations and biological characteristics;the interdecadal fluctuation cycles of 20 a and 30 a needed to be explored in depth with longer-term fisheries data and the introduction of more factors.
unassociated school K.pelamisoscillation modeensemble empirical mode decompositiontime-lag analysisWestern and Central Pacific Ocean
万方数据
维普
