中西太平洋金枪鱼围网渔场变动的预报分析

Forecasting fishing grounds for tuna purse seine fisheries in the Western and Central Pacific Ocean

中西太平洋赤道海域是中国围网渔业最主要的作业海域。由于渔场存在年际间的剧烈变动,掌握渔场时空变动的预报越来越重要。本研究通过上海开创公司围网2011–2014年的渔捞日志数据,从Ni?o3.4指数和TAO数据(海洋表面温度和海表风)获得的海洋环境变量,采用时滞相关分析方法,探讨渔场变动和渔场环境变动的规律;寻找合适的预报因子和延迟数;建立回归预报模型。在2011–2014年各月海洋环境分布图和渔场中心分布图中,发现渔场中心的变动和风场、温度场变动都有明显的关系。在时滞相关分析中发现:(1)中心渔场经度和180°E与165°E平均纬向风速异常成正相关,相关系数分别达0.79和0.82,前者滞后1月,后者同步;和180°E与165°E平均经向风速异常成负相关,相关系数分别为–0.54和–0.41,前者滞后2月,后者同步;和29℃等温线经度最大相关系数0.75,同步;和Ni?o3.4指数同步,相关系数为0.47。(2)中心渔场纬度与180°E平均纬向风速异常、165°E平均经向风速异常都是正相关,相关指数分别0.55和0.63,延迟2个月和1个月;而与该两处的纬向风速变异负相关,相关性都低于0.5,延迟3个月和同步;和Ni?o3.4指数相关性不显著。(3)通过逐步最优回归拟合,获得了中心渔场的回归方程分别为:GC_Lon=137.534+2.36159UA_165_t+0.159159SST_29_t,GC_Lat=0.236156+0.51587UA_165_(t–1)–1.12848VA_165_t。在渔场经度模型中,最优模型包括了165°E平均经向风速异常和29℃等温线经度值,模型相关指数平方R^2为0.72;而经度模型中,最优模型包括了165°E平均经向风速异常和纬向风速异常,其相关指数平方R^2为0.34。在预报模型预报结果中,预报结果和实际值在经度和纬度上都存在2度以上误差,产生差异原因是船队的在东部海域购买作业许可天数不够,而西部有余所致;模型的预报结果和中国租赁船队的渔场中心经度误差在0.5°以内,纬度误差在1.5°左右,较为理想。该研究发现了风速异常和温度线分布对渔场移动有显著性影响,但风速变异较少获得关注,尤其是位于165°E和180°E的纬向风速变异对渔场的影响超过了29℃等温线。这一发现可用于以后相关研究,以及建立的预报模型的可供围网公司购买渔业许可参考使用。

The Western and Central Pacific Ocean （WCPO） purse seine fishery is an important part of Chinese oceanic fisheries. Forecasting the gravity center of a fishing ground with strong interannual change has become increasingly urgent. This study examined the relationship between a purse seine fishing ground, based on the 2011-2014 purse seine log sheet of the Shanghai Kaichuang Fishery Company, and the synchronous oceanic datasets such as Nino3.4 index, and the Tropical Atmosphere Ocean project （TAO）. The latter data set provided sea surface temperature （SST） and sea surface wind （SSW）. Data were analyzed using the time-lagged correlation method. We identified fishing ground variation induced by oceanic change, and the fields suitable for forecasting the fishing ground, along with their time-lagged number. A regression model was built and verified in this paper. A clear relationship between the fishing ground with SSW and SST was shown in the monthly maps of oceanic fields and fishing ground gravity centers for 2011-2014. In time-lagged correlation analysis results： （1） the correlation coefficient between the longitude of the gravity center with the mean zonal SSW anomaly of 180°E（UA_180）, the UA of 165°E （UA_165）, the meridian SSW anomaly of 180°E（VA_180）, the VA of 165°E （VA_165）, the 29℃ SST isothermal longitude value （SST_29） and Nino3.4 index （Nino）was 0.79, 0.82, -0.54, -0.41, 0.75 and 0.47, respectively; and the lagged time was 1, 0, 2, 0, 0 and 0 months, respectively; （2） the correlation coefficient between the latitude of the gravity center with the UA of 180°E and 165vE was 0.55 and 0.63, respectively, and the lagged time was 2 and 1 months. The correlation coefficient with the VA_180 and VA_165 was negative and less than 0.5, and the lagged time was 2 months and synchronic. There was no significant relationship between Nino and the latitude position of the fishing ground. We found a regression equation of gravity longitude center （GC_Lon） and latitude center （GC_Lat）： GC_Lon= 137.534＋2.36159UA_165t＋0.159159SST_29t, GC_Lat=0.236156＋0.51587UA_ 165（t-1）-l,12848VA_165t; and the .model R square was 0.72 and 0.34, respectively. The longitude gravity center was much more reasonable than that of the latitude. The error gap between the reality and the predictive value from the models was more than 2° in longitude and latitude, mainly because there were delays when no fishing was permitted in the fishing ground in the east WCPO in November and December 2014.The difference in the central fishing ground between the model results and the Shanghai Kaichuang Fishery Company log sheets were reasonable： the longitude was less than 0.5° and the latitude was about 1.5°. This paper presents clear evidence that the change in fishing grounds followed variations in SST and SSW, and we believe that the influence of the SSW has not been focused on in this way before. We also discovered that the zonal wind speed anomaly at 165°E and 180°E longitude had the same effective influence on the fishing ground as a 29℃ sea surface isotherm. These findings will advance related research into purse seine fishing grounds, and the forecasting models may assist purse seine companies in budgeting for their permitted fishing days.