南海鸢乌贼产量与表温及水温垂直结构的关系

根据2012年9—10月秋季航次及2013年3—4月春季航次南海灯光罩网船各站点的水温数据及生产数据,对鸢乌贼(Symplectoteuthis oualaniensis)产量与表温(SST)及水温垂直结构的关系进行了分析。结果显示,春季是鸢乌贼的高产渔期,总产量及平均网产都明显高于秋季;鸢乌贼作业渔场的季节变化较为明显,春季南沙和西中沙海域都有渔场分布,产量主要集中在10°~15°N、111°~117°E海域内,而秋季鸢乌贼产量主要集中在13°~15°N、117°~118°E海域;鸢乌贼春季和秋季作业渔场的SST范围有所差异,春季作业渔场表温范围为25.6~29.6℃,秋季作业渔场表温范围为27.6~30.0℃,但最适表温都分布于28.5~29.5℃的海域;不同季节作业渔场水温垂直结构差异明显,从5~50 m水温垂直梯度来看,春季鸢乌贼0.00~0.05℃/m组距内平均网产较高,且随着水温垂直梯度的增加而减少;而秋季鸢乌贼平均网产随水温垂直梯度的增加而增加,并于0.15~0.20℃/m组距内达到最高。灰色关联度分析表明,5~50 m水温垂直梯度是对鸢乌贼产量影响最显著的因子,关联度为0.84,纬度、5~100 m水温垂直梯度、表温和经度影响次之。

Relationship between the catch of Symplectoteuthis oualaniensis and surface temperature and the vertical temperature structure in the South China Sea

The purpleback squid (Symplectoteuthis oualaniensis) is widely distributed in the South China Sea and northwestern Indian Ocean, with significant diurnal vertical movement. Therefore, it is very important to study the rela-tionship between the catch ofS. oualaniensis, the surface temperature and the vertical temperature structure. Based on catch data from a light-falling net fishing vessel and temperature data in the South China Sea from September to Octo-ber 2012 and March to April 2013, the relationships among the catch per net ofS. oualaniensis, surface temperature and vertical temperature structure were studied. The degree of gray incidence was used to confirm the greatest factors af-fecting the catch ofS. oualaniensis. The results indicated that spring was the best fishing period forS. oualaniensis; the total catch and the catch per net were obviously higher than that in autumn. Thus there was obvious seasonal variation in the fishing grounds ofS. oualaniensis. The catch was mainly concentrated in the waters near 10°–15°N, 111°–117°E in spring, and in the waters near 13°–15°N, 117°–118°E in autumn. The suitable sea surface temperature (SST) in the fishing grounds was 25.6–29.6℃ in spring and 27.6–30.0℃ in autumn; however, the optimum SST ofS. oualaniensis was the same at 28.5–29.5℃ in spring and autumn. The temperature gradient in the fishing grounds was different be-tween spring and autumn when choosing the S15 and S22 sites as representative sites. A thermoclineboth in spring and autumn was formed in the water layer at 50–100 m, and the thermocline intensity in spring was higher than in autumn. The catch per net ofS. oualaniensisdecreased with the increase in the temperature gradient from 5 m to 50 m in spring, and the catch per net in the class interval of 0.00–0.05℃/m was higher than the others. By contrast, the catch per net of S. oualaniensisincreased with the increase in the temperature gradient from 5 m to 50 m in autumn, and the catch per net in the class interval of 0.15–0.20℃/m was higher than the others. The degree of gray incidence (0.84) indicated that the temperature gradient from 5 m to 50 m was the greatest factor affecting the catch ofS. oualaniensis, followed by the latitude, temperature gradient from 5 m to 100 m, SST and longitude.