Modeling environmental influence on Atlantic bluefin tuna bycatch by Mexican longliners in the Gulf of Mexico

Atlantic bluefin tuna (ABFT) stocks have been considered overfished over the last decades, especially the western stock, whose main spawning grounds are in the Gulf of Mexico (GoM). Despite the current measures implemented, spawner bycatch by the longline fleet targeting yellowfin tuna (YFT) may explain the lack of recovery of local stocks. This situation demands the implementation of appropriate spatiotemporal management strategies to minimize bluefin bycatch in the GoM, which involves knowledge in depth of its distribution and environmental forcing. Using catch and effort data from the Mexican commercial longline fleet with 100% scientific observer coverage from 1999 to 2012 and satellite derived environmental data, this study investigated the influence of environmental conditions on catch per unit effort (CPUE) of ABFT and YFT. General additive models (GAMs) were fitted using a negative binomial distribution and applying Akaike information criterion (AIC) to select the best model. Bluefin CPUE exhibited a marked seasonality, reaching higher values in February and March while YFT catches occurred throughout the year. Two main locations were identified with higher ABFT bycatch rates, Campeche Bay and the western‐central area of the GoM. Higher ABFT CPUE was significantly associated with areas with negative sea level anomalies and low sea surface temperatures, characteristic of cyclonic eddies. Instead, YFT CPUE showed a lesser environmental influence in its distribution. To our knowledge, the patterns shown in this study provide the first in‐depth approach to understand ABFT bycatch in Mexican waters, which will help in further development of adequate management strategies.     

两种典型渔法金枪鱼围网网具的性能差异

摘要：为了量化分析自由鱼群渔法和漂流物渔法的网具性能差异,本文根据2011-2014年金枪鱼围网海上调查数据,采用Bootstrap和GAM方法进行分析。结果显示：（1）漂流物渔法时,网具的最大沉降深度（195.20~219.36m）约为自由鱼群渔法时最大沉降深度 （205.83~219.04m）的94.8%;网具的平均沉降速度（0.152~0.176m/s）约为自由鱼群渔法时平均沉降速度（0.180~0.193m/s）的84.4%~91.2%。（2）捕捞自由鱼群时,影响沉降速度主要因子为10m水层流速（V10）,60m水层流速（V60）和跑纲长度（L1）。（3）捕捞漂流物随附群时,影响沉降速度主要因子为60m水层流速（V60）,括纲长度（L）和放网速度（V0）。（4）GAM模型结果显示,漂流物渔法时,预测的沉降速度（0.155~0.175m/s）达到海上实测沉降速度的99.4%;自由鱼群渔法时,预测的沉降速度（0.182~0.190m/s）达到海上实测沉降速度的98.4%。本研究结果可为海上作业时,判别海况条件和控制渔法操作提供一定参考。     

金枪鱼延绳钓钓具的最适浸泡时间

根据2010年10月—2011年1月金枪鱼延绳钓海上调查数据,分两种起绳方式,建立每次作业每一根支绳的浸泡时间计算模型。将钓具的浸泡时间以1 h为间隔分别统计每个区间的支绳数量及大眼金枪鱼(Thunnus obesus)、黄鳍金枪鱼(Thunnus albacores)的渔获尾数,并计算其钓获率(CPUE)。结果表明:1)大眼金枪鱼和黄鳍金枪鱼的CPUE都随浸泡时间的增加呈现先增后减的趋势,这是由于饵料的诱引效果变化及渔获的丢失引起的;2)二次曲线可拟合浸泡时间与大眼金枪鱼和黄鳍金枪鱼CPUE的关系;3)大眼金枪鱼和黄鳍金枪鱼CPUE最高的浸泡时间分别为9.9 h和10.1 h。建议:1)今后在金枪鱼延绳钓作业中,保证每一根支绳在水中的浸泡时间为9.5~10.5 h,以提高捕捞效率并减少副渔获物;2)可把延绳钓钓具的浸泡时间作为有效捕捞努力量,并用于CPUE的标准化。研究结果可用于提高捕捞效率并减少副渔获物的技术方案制订,并为渔业生产和CPUE的标准化提供科学参考。     

The effect of water temperature on habitat use of young Pacific bluefin tuna Thunnus orientalis in the East China Sea

ABSTRACT:   Immature Pacific bluefin tuna Thunnus orientalis , tagged with archival tags, were released near Tsushima Island in the East China Sea (ECS) during the winters of 1995, 1996 and 1997. Geolocations were estimated using the archival tags from recovered fish. These data, together with sea surface temperature (SST) data from satellite remote sensing, are used to describe the habitat used by these bluefin in the ECS from January to June for 3 years (1996, 1997, 1998), and to asses the effect of water temperature on fish distribution and movement. The results indicate that their geolocations ranged from the area north-east of Tsushima Island to the offshore area in the south-west. However, the area of highest density differed among years, being furthest south in 1996 and furthest north in 1998. The differences were probably caused by changes in SST associated with La Niña (1996) and El Niño (1998) events. Another densely populated area was identified in offshore waters of latitude 28–30 °N in 1996 (only), on the cold side of the Kuroshio front. These fish may have been prevented from moving northwards by an intrusion of Kuroshio water of approximately 25°C into the region immediately to the north-east.     

Structural and thermodynamic characterization of tropomyosin from fast skeletal muscle of bluefin tuna

ABSTRACT:   Tuna tropomyosin is a mixture of nearly equimolar amounts of two isoforms (designated α and β). cDNA encoding the α form was cloned from bluefin tuna Thunnus thynnus fast skeletal muscle. The full-length cDNA contained 1220 bp, comprising an open reading frame of 855 bp encoding 284 amino acid residues, flanked by 5'-untranslational regions (156 bp) and 3'-untranslational regions (209 bp). The deduced amino acid sequence showed considerably high homology in a range of 93.7–98.6% to those of other vertebrate α-type tropomyosins. In phylogenetic analysis, bluefin tuna tropomyosin showed the closest relationship with the white croaker counterpart. The predicted mass was 32 919 Da, and isoelectric point was 4.50, assuming acetylation of the N-terminus. By differential scanning calorimetry, bluefin tuna tropomyosin gave two major endothermic peaks at 29.3 and 41.5°C, probably caused by the presence of two isoforms. Circular dichroism spectra supported such a unique denaturation profile.     

中西太平洋鲣鱼丰度的时空分布及其与表温的关系

中西太平洋是全球金枪鱼围网的主要海域,鲣鱼(Katsuwonus pelamis)是金枪鱼围网的主要作业对象。本研究利用1983～2007年中西太平洋金枪鱼围网渔获物数据,结合海洋表层温度(SST)数据,分析中西太平洋鲣鱼资源丰度在时间序列和空间位置上的分布规律。研究表明,1983～2002年,各年平均CPUE在时间序列上呈一定的上升趋势,1983～2002年,平均SST在一定范围内上下波动,平均CPUE和平均SST无显著相关性;2003～2007年,平均CPUE和平均SST均呈较大幅度上升,两者呈显著相关。从空间位置分析,鲣鱼资源量集中出现在SST为28～30℃之间的海域,在5°N和10°S附近海域CPUE反映的总体资源量较高,而在0°和5°S的资源量较低。鲣鱼资源量较大区域分布在冷暖水团交汇处。     

已充分开发渔业中估计最大可持续产量的一种近似方法

以印度洋黄鳍金枪鱼渔业为例,应用Grainger和Garcia提出的年渔获量相对增长率（RRCI）的概念,估算其最大可持续产量（MSY）近似值,并与利用其它方法估算的结果进行比较。研究结果表明,当RRCI=O时,印度洋黄鳍金枪鱼渔业MSY近似值为33．75t,比PeUa—Tomlinson模型的预测结果低3％。用本文方法只需计算年渔获量相对增长率,即可获得MSY的近似值,因此本方法可作为对常规评估模型方法的有益补充。     

印度洋大眼金枪鱼垂直分布与水温的关系

近年来,由于近海资源的衰退,国内有关渔业企业都把大洋性金枪鱼渔业作为发展的重点。大眼金枪鱼因其市场价值高,一直是我国金枪鱼船队的主要捕捞对象之一。国外学者已经对大眼金枪鱼的分布和生理、生态进行了许多的研究和探索。Mohri和Takeda[1]在印度洋通过常规和深水延绳钓探捕试验,研究大眼金枪鱼的垂直分布以及最适水温范围。Mohri[2]利用金枪鱼延绳钓生产数据和海洋环境数据推测大眼金枪鱼分布的最适水温范围。但目前国内对金枪鱼渔业的研究尚处于初期,大多局限于对金枪鱼渔业生产技术的分析探讨或渔获产量的描述统计,有关大眼金枪鱼…     

中西太平洋金枪鱼围网渔业渔获组成及叉长与体重关系

中西太平洋海区是世界金枪鱼围网作业的主要渔场之一[1]。目前从事生产的金枪鱼围网船约160艘[2]。据统计,2003年该海区的金枪鱼围网渔业总产量为117.28×104t,占其金枪鱼总产量的60%[3]。我国大陆地区金枪鱼围网渔业起步较晚,但发展较快,渔船已由2001年的1艘发展到2004年的8艘     

鲣鱼蒸煮液美拉德反应优化及氨基酸分析

为了制备风味良好的鲣鱼调味基料,本试验以鲣鱼蒸煮液(STCL)为原料,在酶解和脱腥基础上,采用感官评价、电子鼻技术结合主成分分析(PCA)及线性判别分析(LDA),通过正交试验优化美拉德工艺,并对鲣鱼蒸煮液酶解液美拉德产物进行氨基酸组成成分分析和必需氨基酸营养评价。结果表明,电子鼻技术结合LDA优于PCA,更能客观地区分不同条件下鲣鱼蒸煮液酶解液美拉德反应产物的风味差异;鲣鱼蒸煮液酶解液美拉德反应最优工艺条件为:添加木糖-葡萄糖1:2,在110℃下加热45 min,在此条件下,美拉德产物鱼香味浓郁,色泽呈黄棕色,氨基酸总量为7.036 g·100g^-1,必需氨基酸含量为2.888 g·100g^-1,必需氨基酸指数(EAAI)为64.034,说明鲣鱼蒸者液美拉德反应产物营养价值较高,是研发海鲜调味料的理想基料。本研究结果为鲣鱼调味基料的开发提供了一定的理论依据。