不同规格玉筋鱼的营养分析与评价

为了解玉筋鱼(Ammodytes personatus)的营养价值,系统分析了3种不同规格玉筋鱼的基本营养成分、氨基酸组成、脂肪酸组成和无机元素组成。结果显示,样品规格越小,其水分、灰分和粗蛋白含量越高,粗脂肪含量越低。17种被检出的水解氨基酸中含量最高的4种氨基酸分别为谷氨酸、天门冬氨酸、赖氨酸和亮氨酸,并且规格越小,水解氨基酸含量和必需氨基酸含量越高;根据氨基酸评分分析结果可知,玉筋鱼的第一限制性氨基酸为缬氨酸,第二限制性氨基酸为异亮氨酸;根据化学评分可知,其第一限制性氨基酸为含硫氨基酸(蛋氨酸+半胱氨酸),第二限制性氨基酸为缬氨酸;其必需氨基酸指数分别为90.75、85.74和86.04。不同规格样品的脂肪酸组成有明显的差异,饱和脂肪酸含量由小到大分别为41.71、60.68和69.31 mg/g,单不饱和脂肪酸分别为31.81、65.03和103.91 mg/g,多不饱和脂肪酸(PUFA)分别为83.17、110.71和109.39 mg/g,并且规格越大,C20:5 n3占PUFA的比例越高,C22:6 n3占PUFA的比例越低。玉筋鱼富含人体所需的多种无机元素,常量元素中Na和K含量最高,微量元素中Fe和Zn的含量最高。研究表明,玉筋鱼是一种营养价值较高、味道鲜美的优质鱼类。     

Interannual decrease in condition factor of the western sand lance Ammodytes japonicus in Japan in the last decade: Evidence for food‐limited decline of the catch

Annual catch of the western sand lance Ammodytes japonicus in the eastern Seto Inland Sea, Japan, has shown a decreasing trend since the 1990s. To examine whether food shortage was the main cause for the catch decrease, we investigated the condition factor of the age‐0 fish at the beginning of the estivation period (late July) in Harima‐Nada, eastern Seto Inland Sea, for 10 years from 2008 to 2017. The mean abundance of copepods as food for the age‐0 fish during the fish growth period (from February to June) around the estivation area was also determined. The condition factor showed a significant decrease, and values for 2011 and later years were mostly lower than the known minimum threshold (4.2) for maturation. In the recent 4 years from 2013 to 2016, the mean copepod abundance was much lower than values for the other years. The condition factor showed a significant positive correlation with the copepod abundance. These results indicate that decline of western sand lance catch after 1990 was caused mainly by food shortage.     

Comparison of spatial distribution models to predict subtidal burying habitat of the forage fish Ammodytes personatus in the Strait of Georgia,British Columbia,Canada

1. The Pacific sand lance (Ammodytes personatus) is a key forage species for many commercially important fish (e.g. salmon and groundfish), marine birds, and whales found in nearshore coastal waters of British Columbia, Canada.
2. Sand lance lack a swim bladder and have a requirement for low-silt, medium-coarse sandy sea-bed habitat for burying. Little information is available describing the distribution of burying habitat, partly because there are no commercial fisheries for A. personatus in British Columbia.
3. This information is required by habitat and wildlife managers to identify and protect uncommon patches of burying habitats from detrimental activities, including dredging, infilling, and oil spills.
4. In this study, habitat distribution results from five suitability modelling algorithms were evaluated: maximum entropy, generalized linear model, generalized additive model, random forest, and an ensemble model of the latter three.
5. The maximum entropy model had the highest performance score (area under the receiver operator characteristic curve was 0.78) and was selected as the model that most accurately identified the presence of suitable A. personatus burying habitat.
6. Model results indicate that suitable burying habitat is primarily influenced by derived sea-bed substrate, distance to estuary, distance to sand-gravel beaches, and bottom sea temperature.
7. Overall, the spatial modelling identified only 105 km² of highly suitable sand lance burying habitat, or 2.6% of the study area (0–150 m), primarily in Haro Strait, along the east coast of Vancouver Island, and in northern regions of the strait near Cortes, Savary, and Harwood islands.
8. Identification of this uncommon and patchy burying habitat will contribute to the ongoing conservation of an important coastal prey species.

     

Seal predation on salmon and forage fish schools as a function of tidal currents in the San Juan Islands, Washington, USA

Tidal patterns in feeding behaviour are known in several upper trophic level predators. Although harbour seal ( Phoca vitulina richardsi ) movements between resting and foraging areas are often correlated with tidal phase, little is known about tidal influences on seal foraging because it is difficult to make direct observations of predation events. This study sought to determine whether harbour seals exhibit tidal patterns in their at-sea distribution, abundance, and foraging success and to discuss how changes in capture rates or prey types might affect the ability of an individual to meet its daily energy requirement. During 1995–97, seal abundance in the water during flooding tides was significantly greater than median daily abundance. Seals aggregated near a channel constriction. Salmon accounted for 50% and 87% of observed captures of single, large fish in 1996 and 1997, respectively. Predation on schooling fishes involved juvenile sandlance or herring. Large-fish captures were episodic (16.9% and 27.5% of observations with nonzero capture rates) and occurred more often on the incoming tide near constricted water flow. Median per capita capture rates were highest in currents during slower flooding (0.31 fish·seal^–1 h^–1). Surface attacks on forage fish schools were more common than large-fish captures (54.0% and 66.7% of observations with at least one attack on forage fish). Night-time and subsurface feeding were not assessed. Given what is known about seal food requirements, tidal differences in capture rates are predicted to have a significant impact on both the hunting strategy and energy intake of individuals. Results support the idea that interactions among tidal currents, topographic features, and fish play a role in structuring marine predator–prey dynamics.     

室内模拟条件下的胃含物法测定玉筋鱼摄食与生态转换效率

研究在室内大型玻璃钢水槽中进行 ,在流水条件下 ,以卤虫幼体为饵料 ,应用Eggers模型研究了黄、东海主要小型经济鱼类玉筋鱼(Ammodytespersonatus)的摄食、生长和生态转换效率等生态能量学特征。结果表明 ,玉筋鱼体重与空消化道重量的关系可用指数函数W =0 .2 71e79.984·ESW加以定量描述 ,通过这一定量关系 ,可推导出其瞬时全消化道内含物量计算公式为St=1 0 0× [SW -(LnW +1 .30 5) / 79.984] /W ;全消化道内含物随时间变化的拟合曲线为St=1 .784e 0 .2 1 4t,公式两边取负对数可求得瞬时排空率为 0 .2 1 4g/ 1 0 0 g·h (W .W .) ;按Eggers模型可求得日摄食量为 2 2 .53g/ 1 0 0g·d (W .W .)或 60 .1 4kJ/ 1 0 0 g·d ;从玉筋鱼的平均日生长量实测值为 3.45g/ 1 0 0 g·d (W .W .)或 2 2 .94kJ/ 1 0 0 g·d,可求得其生态转换效率为 1 5.34 % (W .W .)或 38 1 4 %kJ。     

Acoustic characterization of biological backscatterings in the Kuroshio-Oyashio inter-frontal zone and subarctic waters of the western North Pacific in spring

The acoustic characteristics of biological backscattering in the western North Pacific were studied to verify expert knowledge on species composition in the echosigns. The survey was conducted in the Kuroshio-Oyashio inter-frontal zone and the subarctic waters in April 2003. The species composition of backscatterings was identified by using midwater trawl, Isaacs-Kidd midwater trawl and Bongo net. The differences of mean volume backscattering strengths between 120 and 38 kHz (ΔMVBS₁₂₀₋₃₈) were calculated for the backscatterings. Six types of backscatterings were classified based on the results of net samples and the ΔMVBS₁₂₀₋₃₈. The ΔMVBS₁₂₀₋₃₈ of each group was as follows: copepods 13.7–17.3 dB, krill 11.6–15.3 dB, Japanese anchovy −1.6 to 1.1 dB, a myctophid, Diaphus theta −0.8 dB, sand lance 6.1 dB and larvae and juveniles of pelagic and mesopelagic fish −9.6 to −4.0 dB. The results suggest that biological backscatterings in the Kuroshio-Oyashio inter-frontal zone and subarctic waters of the western North Pacific in spring can be characterized by using ΔMVBS.