热带印度洋大眼金枪鱼渔场时空分布与温跃层关系

为了解印度洋大眼金枪鱼(Thunnus obesus)温跃层参数适宜分布区间及季节变化,采用Argo浮标剖面温度数据重构热带印度洋各月平均温跃层特征参数,并结合印度洋金枪鱼委员会(IOTC)大眼金枪鱼延绳钓渔业数据,本文绘制了月平均温跃层特征参数和月平均CPUE的空间叠加图,用于分析热带印度洋大眼金枪鱼渔场CPUE时空分布和温跃层特征参数的关系。结果表明,热带印度洋温跃层上界深度、温度和下界深度都具有明显的季节性变化,大眼金枪鱼中心渔场分布和温跃层季节性变化有关。夏季季风期间,高CPUE渔区温跃层上界深度在30~50 m,浅于冬季的50~70 m;温跃层上界温度范围为24~30℃。在冬季季风期间,高CPUE区域对应的温跃层上界温度范围为27~30℃;从马达加斯加岛北部沿非洲大陆至索马里附近海域,温跃层下界深度在170~200 m时的渔区CPUE普遍较高;当深度超过300 m时,CPUE值均非常低。采用频次分析和经验累积分布函数计算其最适温跃层特征参数分布,得出大眼金枪鱼最适温跃层的上界、下界温度范围分别是26~29℃和13~15℃;其上界、下界深度范围分别是30~60 m和140~170 m。文章初步得出印度洋大眼金枪鱼中心渔场温跃层各特征参数的适宜分布区间及季节变化特征,为金枪鱼实际生产作业和资源管理提供理论参考。     

印度洋大眼金枪鱼延绳钓适宜渔获环境的初步研究

数值分析得出大眼金枪鱼的渔获适宜环境参数值范围：温度14～17℃,盐度34．5～35．4．溶解氧浓度1．5～4．5mg／L,温跃层深度80～160m,营养盐氮、磷、硅浓度分别大于12-μg／L,09μg／L,14μg／L。聚类分析表明,钓获率与营养盐关系最为密切。另外,通过因子分析,深化了对钓获率和渔获环境因子两者间关系的理解。     

Separation of the Taiwanese regular and deep tuna longliners in the Indian Ocean using bigeye tuna catch ratios

ABSTRACT:   Taiwanese longline (LL) fisheries operating in the Indian Ocean usually target albacore tuna (ALB), swordfish (SWO) and yellowfin tuna (YFT) using regular LL. Bigeye tuna (BET), however, is targeted using deep LL. Thus, these two types of LL are considered to be different gears as they target different tuna species. Regular or deep LL fishing is defined by number of hooks per basket (NHB): regular LL if 6 ≤ NHB ≤ 10 and deep LL if 11 ≤ NHB ≤ 20. However, NHB information was available in only some of the recent LL data (1995–1999). This situation had caused problems of biased results in stock analysis in the past. Thus, the objective of our study was to explore an effective method to separate the two types of LL fishing by considering species composition. Some intervals of BET catch ratios were found to be effective in separating the regular and deep LL catches, i.e. 0.0 ≤ BET/(BET + ALB + SWO) ≤ 0.4 and 0.8 ≤ BET/(BET + ALB) ≤ 1.0, respectively. Using these two separators, the LL known data set (1995–1999) (learning data set) was classified. Correct classification occurred in 67.7% of the data, while 23.1% of the data were unclassified (11.9% due to zero catches and 11.2% due to classification into both LL types), and 9.2% were misclassifications. Then, using the methods developed, the LL unknown data set in the historical data (1979–1999) was classified and nominal CPUE values were calculated for four species. The CPUE trends based on this study were likely to be more reliable than those of previous studies.     

印度洋大眼金枪鱼生物学特性初步分析

根据 2003年 1~6月大洋性延绳钓作业中测定的数据,对印度洋大眼金枪鱼的生物学特性进行了初步分析。印度洋大眼金枪鱼的饵料种类较杂,鱼的优势叉长为 121~180cm,优势体重在 41~90kg, 雌雄比例为 1∶1．3。原条鱼重量与加工后重量之间的关系为 y=1．1345x+1．4879,相关系数 R= 0．9969;原条鱼重量与叉长的关系为 y=6×10^-5 x^2．7781 ,相关系数 R=0．9829。     

印度洋中南部水域金枪鱼延绳钓钓钩钩型对钓获对象的选择性

基于2008年9月至2009年4月在印度洋中南部水域金枪鱼延绳钓渔场收集的数据,研究分析和比较了3种钓钩钩型(传统金枪鱼钩、“J”形钩和圆形钩)的渔获效益及对钓捕对象的选择性。结果表明:(1) 从渔获种类上看,大眼金枪鱼和大青鲨金枪鱼钩钓获比例最高,“J”形钩和圆形钩的钓获比例相当;而长鳍金枪鱼则为金枪鱼钩钓获比例最高,其次为“J”形钩和圆形钩。(2) 大眼金枪鱼存活率以金枪鱼钩最高,“J”形钩最低;长鳍金枪鱼则为“J”形钩稍高于圆形钩,金枪鱼钩最低;大青鲨则以圆形钩最高,“J”形钩最低。(3) “J”形钩钓获的长鳍金枪鱼和鲨鱼平均叉长较金枪鱼钩和圆形钩稍大;而金枪鱼钩钓获的大眼金枪鱼平均叉长较圆形钩和“J”形钩稍大。(4) 3种钩型钓获的长鳍金枪鱼、大眼金枪鱼和大青鲨叉长分布均不存在显著性差异。     

Relationships among yellowfin and skipjack tuna, their prey-fish and plankton in the tropical western Indian Ocean

Stomach contents of yellowfin (Thunnus albacares) and skipjack (Katsuwonus pelamis) tuna caught by trolling and purse seining in the tropical western Indian Ocean, together with those of the prey-fish found in their stomachs, have been analysed. Epipelagic fish are the main prey of these tunas, whereas no vertically migrating fish, which inhabit subsurface layers at night, have been found in their stomachs. These tunas are thus considered day-feeders. Purse-seine-caught tunas, which belong to large schools, have a much higher number of prey-fish in their stomachs than tunas caught by trolling on small schools. Similarly, prey-fish from purse-seine tunas have a much higher number of plank-tonic prey in their stomachs than those from troll-caught tunas. Therefore, these tunas adopt a wandering strategy in small schools when food resources are scarce and form large schools when they are abundant. The planktonic organisms found in the stomachs of prey-fish are described by taxa and sizes; they represent the fraction of the planktonic biomass actually supporting the stock of tuna. Size ratios between the three links tuna-prey-fish-plankton are very high, suggesting that these tunas benefit from a short food chain which is probably efficient from the energetic point of view.     

西北印度洋大眼金枪鱼渔场预报模型建立与模块开发

根据1990—2003年印度洋大眼金枪鱼延绳钓渔业数据和美国国家海洋和大气管理局提供的海表温度、叶绿素-a历史环境数据,应用环境因子叠加方法,构建了西印度洋大眼金枪鱼渔场预报模型,用于金枪鱼渔场预报。分析得出各月适宜海表温度、叶绿素-a浓度范围和历史高产区空间位置;导入实时海表温度、叶绿素-a等遥感栅格数据,分别提取适宜海表温度、适宜叶绿素-a浓度和历史高产区的空间栅格数据集,最后在空间上对3种栅格数据进行空间叠加并取交集。交集所指空间区域即为大眼金枪鱼潜在渔场位置。通过精度检验,表明该模型渔场预报精度为60.5%。并以VC++6.0工具为开发平台,对此模型进行了设计开发,实现了模块预报西北印度洋大眼金枪鱼渔场。     

基于贝叶斯概率的印度洋大眼金枪鱼渔场预报

本文采用贝叶斯概率为模型基础框架,利用来自印度洋金枪鱼管理委员会(IOTC)的大眼金枪鱼延绳钓历史渔获统计数据和美国国家海洋大气管理局(NOAA)的海温最优插值再分析数据,进行适用于印度洋金枪鱼延绳钓渔场的模型参数估算与预报模型构建。模型回报精度验证结果表明,印度洋大眼金枪鱼延绳钓渔场综合预报的准确率达到了65.96%。模型预报结果用概率百分比来表示,符合渔业资源分布的客观特点。利用中分辨率成像光谱仪MODIS提供的SST产品进行业务化运行的渔场预报,利用模型结果每周生成印度洋大眼金枪鱼延绳钓渔场概率预报图,用不同大小的圆形来表示渔场概率的高低,可以为印度洋区域的远洋渔业生产提供信息支持。     

How much do fish aggregating devices (FADs) modify the floating object environment in the ocean?

Natural floating objects (e.g., logs) have always been a component of the habitat of tropical tunas. However, the introduction of fish aggregating devices (FADs) modifies this environment. To assess the changes due to the deployment of FADs, we compared the spatial distribution of natural and artificial floating objects (FADs), using data from observers onboard tuna purse seine vessels in the Indian Ocean from December 2006 to December 2008. Although natural objects occur more commonly in waters south of 7°S and FADs are more common in waters north of 7°S, all types of floating objects can be found everywhere. Using different spatial scales (quadrats of size 1° × 1°, 2° × 2°, 5° × 5°, and 10° × 10°), we computed the proportion of FADs observed in quadrats without natural objects. The scale of 2° × 2° quadrats represented a threshold: distributions of the two types of objects were different at scales smaller than this threshold. The strongest change that has occurred since the introduction of FADs (besides the increased catches) has been the dramatic increase in the total number of floating objects. Since the introduction of FADs, the number of objects has at least doubled everywhere (except in the Mozambique Channel and Chagos) and in some areas (e.g., Somalia area) the multiplication factor has reached as high as 20 or 40. Our study sets the ranges of values of key parameters of the floating object environment, which are crucial in the design of future experimental studies aimed at investigating the impacts of FADs on the ecology of tunas.     

Evidence for fine geographical scale heterogeneity in gene frequencies in yellowfin tuna (Thunnus albacares) from the north Indian Ocean around Sri Lanka

Yellowfin tuna are currently considered by the member nations of the Indian Ocean Tuna Commission to constitute a single stock in the Indian Ocean due to a lack of knowledge about yellowfin tuna population structure in this region. Previous studies of Indian Ocean yellowfin tuna based on morphology and fisheries data have hinted at the presence of multiple stocks in the region, and further, that stocks may mix in the north western Indian Ocean around Sri Lanka. To better understand the genetic stock structure of yellowfin tuna in the north western Indian Ocean, we examined genetic variation in 285 yellowfin individuals collected over a period of 4 years from six fishing grounds around Sri Lanka and a single fishing ground in the Maldive Islands. We screened variation in both the mitochondrial ATPase 6 and 8 region (498 bp) and three microsatellite loci. Significant genetic differentiation was detected among sites for mitochondrial DNA (Φ_ST = 0.1285, P < 0.001) and at two microsatellite loci (F_ST = 0.0164, P < 0.001 and F_ST = 0.0064, P < 0.001), while spatial analysis of molecular variance of mtDNA data identified three genetically heterogenous groups namely; western, south eastern and all remaining sites. These results suggest the possibility that genetically discrete yellowfin tuna populations may be present in the north western Indian Ocean.     

Population structure of bigeye tuna (Thunnus obesus) in the Indian Ocean inferred from mitochondrial DNA

Population structure of bigeye tuna (Thunnus obesus) in the Indian Ocean, Western Pacific Ocean and Eastern Atlantic Ocean were investigated using mitochondrial (mt) DNA sequence data. A total of 380 specimens were sampled from four regions in the Indian Ocean (Cocos Islands, Southeastern Indian Ocean, Southwestern Indian Ocean and Seychelles), and one region each from the Atlantic (Guinea) and the Western Pacific Oceans, respectively. The reconstructed neighbor-joining phylogeny based on the first hypervariable region (HVR-1) of the mitochondrial control region sequence data showed that haplotypes from the Indian and the Western Pacific Oceans could be grouped into two clades (Clades I and III), whereas in the Atlantic Ocean, two divergent clades (Clades I and II) coexisted. A single stock of bigeye tuna in the Indian Ocean was supported by hierarchical AMOVA tests and pairwise Φ_ST analyses. Clade I was the dominant population in the Indian and the Western Pacific Oceans which consisted of more than 96% of the specimens and Clade II was a specific group exclusively restricted to the Atlantic Ocean which made up 77% of its specimens. A new minor Clade, Clade III was discovered in the Indian and the Western Pacific Ocean. Overall, these analyses indicated that bigeye tuna of the Indian Ocean constituted a single panmictic population.     

ENSO与中西太平洋金枪鱼围网资源丰度及其渔场变动的关系

中西太平洋是世界金枪鱼围网的重要作业渔场之一,主要捕捞鲣鱼（Katsuwonus pelamis）、黄鳍金枪鱼（Thunnus albacares）和大眼金枪鱼（Thunnus obesus）等.     

大西洋金枪鱼延绳钓主要渔获种类及其分布

根据收集的有关文献和海上调查资料,分析了大西洋金枪鱼延绳钓生产的主要渔获品种的生物学特性、捕捞生产情况及管理措施等。此外,还根据FAO建立的金枪鱼生产数据库,采用GIS软件制作了大西洋金枪鱼延绳钓主要渔获种类捕捞产量的地理空间分布图。并分析了其资源的空间分布特征。