| 英文摘要 |
We analyze the fluctuation of the skipjack tuna stock biomass using catch data of different schooling types. The daily catch data were classified into three groups according to the schooling types recorded in the logbook, then aggregated into 1 by 1 degree to compute grid CPUE (mt/vessel day). The grid CPUE were integrated with grid (1 by 1 degree) sea surface temperature (SST) data to explore the displacement characteristics of the fishing ground. The major results of the analysis are as follows:
1. The gravity of fishing ground changed mainly in longitudinal direction and seasonal movement were mainly along the Equator. However, the ENSO events would cause inter-annual variability in the gravity displacement showing significant correlation with SOI. Among the three school types, the migration range of free schools is the widest. The numbers of log and FAD schools seem to vary mutually with more log sets located west of 165￠XE and FAD sets mostly in east of 165￠XE.
2. According to the statistics of the compiled SST and SSTA in the grids where fishing located during 1994-2004, the mean SST value was 29.4￠X C suggesting the fishery ground moved along with worm pool center. The mean SSTA value drawing close to 0￠X C may imply average SST in the fishing ground had no elevated or drop tendency.
3. Cross-correlation analysis conducted using monthly time series of longitudes of 29￠XC isotherm and gravities shows that all correlation reach significant level (p4. The SCPUE standardized by GLM indicated that the school size of all school types increased with the exception of a slight decrease in 1997. The standardized BCPUE showed that the fluctuation in biomass of different school types differed greatly. The FAD and log schools moved in opposite directions in their tr |