西北印度洋延绳钓大眼金枪鱼渔获率的时间序列小波特征

Time series wavelet characters of the catch rate of bigeye tuna (Thunnus obesus) caught by longline fishery in northwest Indian Ocean

基于西北印度洋日本延绳钓金枪鱼1965-2006年间大眼金枪鱼(Thunnus obesus)每月渔获统计资料,本研究运用小波方法对大眼金枪鱼渔获率变化、印度洋涛动指数(IOI)及两者之间的响应关系进行了分析。研究发现,大眼金枪鱼渔获率在时间序列上存在48～60个月的小波振荡,IOI振荡周期主要为36月和60月,2种尺度振幅具有跷跷板效应。小波交叉分析结果表明,1994年前在36月和60月的时间尺度上大眼金枪鱼渔获率与IOI之间的响应关系是明显的,之后这种关系并不显著。在典型的小波振荡周期为4年的尺度上,IOI和大眼金枪鱼渔获率的振荡间隔在1～3年之间变化,平均为1.5年左右。IOI振荡周期在3～6年间变化,时快时慢,而大眼金枪鱼渔获率信号振荡较平稳。由于捕捞因素影响,近年来渔获率的振荡幅度不断减弱。研究认为可排除由于较大的捕捞努力量和渔业资源量时空变动导致的捕获率信号变异,从捕捞因素和环境因素上讨论了捕获率信号小波特征及其与环境变动的响应关系。

Based on the data from Japanese tuna longline fishery statistics from 1965 to 2006 in the northwest Indian Ocean（NWIO）,the variation of the monthly catch rate of bigeye tuna（Thunnus obesus）（BET）,Indian Oscillation Index（IOI）and the relationship between the above variables were analyzed by using wavelet technique.The result showed that the primary multi-year wavelet periodic bands of the BET＇s catch rate time series ranged from 48 to 60 month.The dominant periodic bands of IOI were month 36 and month 60,and seesaw effect occurred between the two oscillations amplitude.The wavelet-cross analysis indicated that there are strong response associations between IOI and BET＇s catch rate on the temporal scale of month 36 and month 60 before 1994.However,unclear associations can be found between the above variables after 1994.On the temporal scale of 4 years oscillation periodic band,there was a gap of 1-3 year between IOI and BET＇s catch rate,and mean gap was about 1.5 years.IOI＇s oscillation period was not stable and varied from 3 to 6 years,while signal oscillation of BET＇s catch rate was relative stable.Due to fishing factors,the oscillation signal of BET＇s catch rate weak ened gradually in recent years.Finally,after excluding effects on BET＇s catch rate caused by great spatio temporal variation of fishing effort and fishery resources,the wavelet features of BET＇s catch rate signal and its link with IOI were discussed from fisheries and environmental factors.