Body size trends along vertical and thermal gradients of chum salmon in the Bering Sea during summer

Relationships between the vertical distribution and thermal habitat, and body size of chum salmon Oncorhynchus keta were studied in the Bering Sea in summer using trawl surveys at various depths. Chum salmon abundance decreased with increasing depth, but the patterns of decrease differed between size groups. The abundance of small salmon fell rapidly with depth, whereas that of large salmon decreased gradually to 40 m depth, and abruptly below that. The average fork length of chum salmon collected from each trawl correlated positively with trawl net depth and negatively with water temperature. Since the optimal temperature for growth decreases with body size in this species, the observed body size‐related vertical habitat use by chum salmon may indicate size‐dependent thermal preferences.     

印度洋中南部大眼金枪鱼生物学特性研究

根据2008年9月~2009年4月在印度洋中南部金枪鱼延绳钓渔场调查期间收集的大眼金枪鱼生物学数据,对其基本的生物学特征进行了研究。结果表明:(1)叉长范围为57~184 cm,优势叉长组为101~110cm和121~130 cm,约占总数的41.7%,平均叉长为119.5 cm;(2)不分性别大眼金枪鱼叉长(FL)与加工后重(DW)的关系可表达为:DW=2.407 6×10-5FL2.931 6,雌雄个体差异不显著(F=0.207,P0.05);(3)调查期间,大眼金枪鱼雄性比例为56.55%,当叉长大于140 cm时,雄性占优势;调查期间,该海域大眼金枪鱼的繁殖期为10月~翌年4月,繁殖峰期为10月~翌年1月;(4)摄食种类中柔鱼、帆蜥鱼和虾类所占比重较高,分别占36.0%、20.1%和18.0%;各月份摄食等级1~4级分布呈显著性差异(χ2=191.20,P0.01),各叉长组大眼金枪鱼摄食等级变化无显著性差异(χ2=41.08,P0.05)。     

北太平洋(160°E～170°E)大型柔鱼渔场的初步研究

本文根据1997年6月～7月北太平洋（16°E～170°E）海域柔鱼探捕调查的资料，对渔场形成的海洋环境条件进行了初步分析。160°E～170°E海域的大型柔鱼渔场主要由亲潮策3和第4分支与黑潮的第4和第5分支交汇形成，特别是在深层（100米水层）的暖水域前端形成。其表层水温一般为11～13°，100米水层水温约为9～10℃。其中167°E～170°E海域的渔场较为稳定，可供北太平洋鱿钓船的前期生产。中心渔场形成时常有浮游生物层。浮游生物层越厚实，渔获量越高，但有关浮游生物层的形成原因需作进一步的研究与探讨。     

不同方法制备的三倍体长牡蛎养殖效果的比较

比较了细胞松弛素B(CB)和6-二甲基氨基嘌呤(6-DMAP)通过抑制受精卵极体释放的方法批量诱导三倍体长牡蛎的养殖效果.长牡蛎卵子在25℃的海水中受精,20～30min后,开始用浓度为0.5mg@L-1的CB处理,持续18～22min,受精卵处理密度为4.0～4.5×107个@L-1,三倍体产率为65.2%～70.1%,面盘幼虫孵化率为12.3%～14.5%,诱导效率指数为0.09.6-DMAP的使用浓度为400～420μmol@L-1,受精卵处理密度为3.0～3.5×107个@L-1,授精水温、处理起始和持续时间等与CB方法相同,三倍体产率为58.7%～65.4%,面盘幼虫孵化率为52.1%～55.4%,诱导效率指数为0.32.两种方法的采苗率基本相同,采苗器为基质较硬的栉孔扇贝贝壳.海区养殖采用浮筏夹苗吊养技术,两种方法诱导的三倍体牡蛎养殖性状没有明显差别.通过比较CB和6-DMAP两种诱导方法及三倍体的养殖效果表明,后者具有更好的应用性.     

Habitat analysis of the commercial tuna of the Eastern Tropical Pacific Ocean

We have extracted information on the habitats of bigeye (Thunnus obesus), skipjack (Katsuwonus pelamis) and yellowfin (Thunnus albacares) in the Eastern Tropical Pacific Ocean by matching the spatial‐temporal distribution of catch and effort of purse seine and longline fleets collected by the Inter‐American Tropical Tuna Commission with oceanographic conditions and subjecting the matched data to Quotient Analysis and General Additive Models (GAMs). These analyses yielded the following results. The habitats defined by the GAM analysis of young fish differ significantly between two periods, one before and one after the introduction of fish aggregation devices (FADs). This was not true for the older fish caught by longline. We speculate that these changes were caused by the extensive use of FADs. Younger bigeye and yellowfin caught by the purse seine fleet have a different preference of environmental variables compared to older fish caught by longline. This is to be expected since tuna of different age groups have different sizes, metabolic capabilities and swimming skills. Moreover, as revealed by GAMs, the habitats of young fish differ between species to a much larger degree than those of older fish. Our results indicate the fundamental differences between fishing methods, targeted species, and operating region of the two fisheries. Specifically, young bigeye occupy equatorial waters farther from the coast and where the hypoxic layer is deeper, young skipjack occupy more productive waters associated with equatorial and coastal upwelling, and young yellowfin occupy broad areas where waters are underlain by a shallow hypoxic layer.     

Long‐term changes in recruitment of age‐0 Pacific bluefin tuna (Thunnus orientalis) and environmental conditions around Japan

Recruitment of age‐0 Pacific bluefin tuna (Thunnus orientalis) from 1952 to 2014 was examined by a sequential regime shift detection method. The regime shifts in recruitment were detected in 1957, 1972, 1980, 1994 and 2009. The durations of regime shift ranged from 8–15 years and averaged 13.0 years. In both the total (1952–2014) and data rich (1980–2014) periods, negative relationships were found between recruitment and the Pacific Decadal Oscillation in autumn, and positive relationships were found between recruitment and sea surface temperature (SST) anomalies in the northern part of the East China Sea, in the southwestern part of the Sea of Japan, and in the waters off Shikoku and Tokai in summer and autumn. The 1994 and 2009 regime shifts in recruitment occurred in the same years as shifts in SST anomalies in the northern part of the East China Sea in summer. These results suggest that the ocean conditions in the northern part of the East China Sea are closely related to recruitment of Pacific bluefin tuna, and that the warmer conditions result in higher recruitment of the species.     

Comparative study on the utilization of crystalline methionine and methionine hydroxy analogue calcium by Pacific white shrimp (Litopenaeus vannamei Boone)

The objective of this study was to compare the supplemental effects of crystalline DL‐methionine (DL‐Met) and methionine hydroxy analogue calcium (MHA‐Ca) on growth performance of Pacific white shrimp. Eight isoproteinic (355.3 ± 2.0 g/kg diet) and isolipidic (70.0 ± 2.2 g/kg diet) diets were prepared as positive diet (20% fish meal), negative diet (15% fish meal) and DL‐Met, MHA‐Ca‐supplemented diets with the supplementation of 0.03%, 0.06%, 0.09% DL‐Met and 0.04%, 0.07%, 0.1% MHA‐Ca in negative diet respectively. Pacific white shrimp (0.92 ± 0.03 g) were fed one of the eight diets for 49 days. The results showed that dietary DL‐Met did not affect weight gain (WG) and feed conversion ratio (FCR) (p > 0.05), but the supplementation of 0.1% MHA‐Ca significantly increased WG, protein and lipid retention, and reduced FCR (p < 0.05) when compared to the negative group, and reached the similar levels as the positive control. The total free amino acids (TFAA) in haemolymph of MHA‐Ca groups and PC, NC group peaked at the 3rd hr after feeding, but the peaking time of DL‐Met groups was advanced to the 2nd hr. Activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in haemolymph of all MHA‐Ca groups peaked at the 2nd hr, but DL‐Met groups peaked at the 1st hr after feeding. The above results indicated that the supplementation of 0.1% MHA‐Ca in a low fish meal diet could improve the growth performance and feed utilization of Pacific white shrimp, but dietary DL‐Met did not significantly affect the growth.     

海洋暖化和酸化对黄姑鱼早期生长发育的影响

以黄姑鱼(Nibea albiflora)为研究对象,根据IPCC 2013典型浓度排放路径(RCP)对2100年海洋温度和p H的预测值,分别选择减缓温室气体排放情景(RCP 2.6)和高温室气体排放情景(RCP8.5),设置温度和p H两个因素,在实验室条件下模拟气候变化,探究海洋暖化和酸化对黄姑鱼早期生长、发育的影响。结果显示,在基础温度24.0℃条件下,黄姑鱼进入稚鱼期的时间为25 d,高温处理(26.0℃~28.0℃)生长加快,仅为22 d,同时,随着温度升高(26.0℃、26.6℃和28.0℃),生长率逐渐增加(0.73、0.74和0.78 mm/d),并且各处理组之间生长率存在显著差异(P0.05),但死亡率在26.6℃最高,26.0℃最低。黄姑鱼死亡率在p H为7.80、7.73和7.49时分别为3.9%、19.4%和21.7%,各处理组死亡率差异显著(P0.05),但p H对黄姑鱼早期生长率影响不显著(P0.05)。通过逻辑斯蒂生长方程拟合,结合IPCC对2100年温度和p H的预测,到2100年,在RCP 2.6情景下,黄姑鱼早期生长率为0.71 mm/d,死亡率为31.1%;在RCP 8.5情景下,黄姑鱼生长率最高达到0.76 mm/d,死亡率为23.9%。在海洋酸化和暖化的共同作用下,黄姑鱼的早期补充将会受到影响。     

渔获量不确定性对印度洋大眼金枪鱼资源评估的影响

大眼金枪鱼(Thunnus obesus)是最具经济价值的热带金枪鱼类,其资源状况一直是区域性金枪鱼渔业管理组织关注的重点。由于多种渔业作业、捕捞船队构成复杂,印度洋大眼金枪鱼的历史渔获量统计存在一定的偏差(Bias),但国际上近些年开展资源评估时都忽略了这一偏差。本研究根据1979~2015年的年渔获量、年龄结构渔获量及相对丰度指数数据,运用年龄结构资源评估模型(ASAP)对印度洋大眼金枪鱼资源进行评估,重点考查渔获量的不确定性(观测误差和统计偏差)对资源评估结果的影响。结果显示,印度洋大眼金枪鱼当前资源总体没有过度捕捞,但2015年初显示轻微的过度捕捞,通过对比基础模型与8个灵敏度分析模型的评估结果发现,渔获量观测误差(CV)的预设对资源开发状态的判断有一定的影响。当渔获量统计偏差调整量为15%时(即历史渔获量被低估了),评估结果与基础模型基本一致;统计偏差调整量为20%时,评估结果有过度捕捞的趋势。本研究结果表明,资源评估模型中渔获量观测误差的设定和历史渔获量统计偏差均会对评估结果产生影响,后者更为明显,因此,二者均不能忽略。     

Impact of Feeding Status on the Efficacy of Depuration for Decontaminating Vibrio parahaemolyticus in Pacific Oysters (Crassostrea gigas)

Vibrio parahaemolyticus causes acute human gastroenteritis and is often linked to consumption of raw oysters. Previous investigations indicated that refrigerated seawater depuration at 12.5°C could significantly reduce V. parahaemolyticus contamination in Pacific oysters; however, further optimization is necessary to achieve the regulatory target of >3.52 log most probable number (MPN)/g reduction. The current study investigated influences of algal feeding on efficacy of depuration to reduce V. parahaemolyticus in raw oysters. A V. parahaemolyticus cocktail (10290, 10292, 10293, BE 98–2029, 027-1c1) was mixed in artificial seawater (70 L) to inoculate oysters (n = 35) at 4–5 log MPN/g. Inoculated oysters were subjected to depuration with feed (algae = 0.036 ml/gram of oyster) and without feed at 12.5°C. Oysters (n = 5) were analyzed for V. parahaemolyticus using a three-tube MPN method after 0, 1, 3, 5, and 6 days of depuration. Depuration (6 days) achieved average V. parahaemolyticus reductions of 2.75 log MPN/g and 3.03 log MPN/g in the fed and unfed systems, respectively; however, feeding status did not significantly impact the efficacy of depuration to reduce V. parahaemolyticus in Pacific oysters. Further optimization of depuration is necessary to achieve the regulatory target for V. parahaemolyticus decontamination in raw oysters.