Oxidative stability of salmon and herring roe lipids and their dietary effect on plasma cholesterol levels of rats

ABSTRACT:   The oxidative stability of lipids from salmon roe and herring roe was compared with those of commercial fish oils originated from sardine and tuna. Both fish roe lipids contained high amounts of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Total EPA and DHA was more than 35% of total fatty acids in both roe lipids. On the basis of oxygen consumption, fish roe lipids showed the higher oxidative stability than both fish oils. This tendency in oxidative stabilities was also confirmed by the determination of propanal formation during oxidation. Analyses of lipid compositions suggested that the higher oxidative stabilities of fish roe lipids would be mainly due to the presence of phospholipids in them. Dietary effects of salmon and herring roe lipids were also determined. Little increase in total cholesterol level was observed in plasma lipids in rats fed salmon and herring roe lipids, although cholesterol content in fish roe lipids were 6.3% and 9.7% of total lipids for salmon roe and herring roe.     

Effects of anesthesia and surgery on U crit performance and MO2 in chum salmon, Oncorhynchus keta

Telemetry is a useful technique for elucidating salmon behavior, but the recovery periods before fish can be safely released after the attachment of telemetry devices have not yet been established. Reported recovery times vary widely, from 2 h to 13 days. We examined how anesthesia and surgery to attach external electromyogram (EMG) transmitters affected chum salmon (Oncorhynchus keta) recovery based on three physiological parameters. Fish subjected to anesthesia plus EMG transmitter attachment (EMG group), anesthesia only (AO group), and no handling (control) were placed in a swim tunnel. Critical swimming speed (U _crit), oxygen consumption (MO₂), and muscle activity (EMG values) were assessed 0, 1, 6, 12, 24, and 30 h after treatment. The MO₂ in the EMG and AO groups was higher than in the control group 1 h after treatment, but did not differ significantly from the control in all subsequent trials (from 6 to 30 h after treatment). Values for U _crit and EMG were not significantly different from the control group in any of the trials conducted 1–30 h after treatment. We concluded that chum salmon had regained their normal swimming ability by 6 h after treatment and could be safely released into the natural environment.     

Successful therapy of furunculosis in Atlantic salmon, Salmo salar L., using the fluoroquinolone antimicrobial agent enrofloxacin

Abstract An outbreak of furunculosis was diagnosed in an Atlantic salmon, Salmo salar L., commercial sea-pen farm and treated with the fluoroquinolone antimicrobial enrofloxacin. The affected post-smolt, adult fish and broodstock readily consumed pelleted feed impregnated with enrofloxacin at concentrations of 1000, 1300 and 2000ppm, respectively, daily for 10 days. Mortalities of infected post-smolts were reduced from an average of 5.8% per month for the 2 months preceding therapy to 0.6% per month for the 2 months following therapy. Infected adult fish had a 2 month mean mortality rate of 2.6% prior to enrofloxacin treatment and 0.3% over the 2 months subsequent to therapy. Apparently noninfected (nonclinical) fish in the same farm exhibited an average monthly mortality of 0.4% over the 4-month study period. Sea water temperatures gradually rose from less than 2°C in March to approximately 12°C in September. Mean antimicrobial tissue concentrations over the 10 complete days of medication were 4.58, 7.32, 4.58, 8.89 and 3.40ppm for muscle, skin plus fat, liver, kidney and gill, respectively. Within 24h of consuming medicated feed, tissue concentrations of antimicrobial were nearly 66% of the average concentrations for the medication period. Half-lives of elimination for the antimicrobial residues were approximately 2 days for liver, 3 days for kidney, 6 days for gill, 11 days for muscle and 22 days for skin plus fat. The producers reported a successful harvest after a 180-day medication-free period.     

Roles of surface layer proteins in the regulation of Pediococcus pentosaceus on growth performance,intestinal microbiota,and resistance to Aeromonas hydrophila in the freshwater prawn Macrobrachium rosenbergii

Maintaining the balance of intestinal microbiota is vital for the growth and health of crustaceans. The current study explored the influences of the surface layer proteins (SLPs) of Pediococcus pentosaceus on the growth performance, disease resistance, and gut microbial community of the freshwater prawn Macrobrachium rosenbergii. After 28 days of feeding, obvious enhancements in the growth performance were found in the PF (a commercial basic diet + intact P. pentosaceus) group compared to the CF (a commercial basic diet, control) and RF (a commercial basic diet + LiCl-treated P. pentosaceus) groups. Meanwhile, the relative percent survival (RPS) of the PF group was found to be 82.1%, higher than the RF group (RPS = 63.2%) in the challenge test. There were noteworthy differences in the relative richness of Aeromonas among different treatments, and the PF group was the lowest. Whereas the relative abundance of Lactococcus between the CF and RF group did not markedly differences, which was obviously lower than the PF group. The prediction of bacterial phenotype indicated that the pathogenic potential of intestinal microbiota was decreased by increasing dietary SLPs-carrying P. pentosaceus. The results suggested that SLPs-carrying P. pentosaceus can improve growth, modulate intestinal microbiota, and increase the resistance of prawns against Aeromonas hydrophila infection.

     

Change in chum salmon (Oncorhynchus keta) stomach contents associated with fluctuation of pink salmon (O. gorbuscha) abundance in the central subarctic Pacific and Bering Sea

The abundance and stomach contents of salmonids (Oncorhynchus spp.) and the biomass of prey organisms were examined in the central subarctic Pacific and Bering Sea in the summer of 1991 and 1992. Salmonids were caught by surface longline using the same level of fishing effort. Chum (O. keta) and pink (O. gorbuscha) salmon were the predominant species, representing 44% and 36% sof the total catch (n = 1275) in 1991. In 1992, chum salmon composed 85% of the total catch (n = 603), but the catch of pink salmon decreased to 1% of the total catch due to the odd/even year fluctuation of Asian pink salmon abundance in the study area. It was found that chum salmon changed their dominant diet from gelatinous zooplankton (pteropods, appendicular-ians, jellyfishes, chaetognaths, polychaetes and unidentified materials) in 1991, when pink salmon were abundant, to a diet of crustaceans (euphausiids, cope-pods, amphipods, ostracods, mysids and decapods) in 1992, when pink salmon were less abundant. Local crustacean biomass (wet weight; mg m^-3) had significant negative correlation with the CPUE (catch number per 30 hachi) of pink salmon in 1991 (r = -0.586; P = 0.026) and that of chum salmon in 1992 (r =–0.616; P = 0.014). There may be a limitation in the available prey resource for production of salmonids.     

The incorporation and metabolism of polyunsaturated fatty acids in phospholipids of cultured cells from chum salmon (Oncorhynchus keta)

The incorporation and metabolism of (n-3) and (n-6) polyunsaturated fatty acids were studied in a cell line derived from chum salmon heart (CHH-1). Supplementing media with 25 M fatty acid considerably altered the cellular fatty acid composition but did not affect the lipid class composition or cause the appearance of cytoplasmic lipid droplets. CHH-1 cells exhibited considerable -6-desaturase activity but showed no preference between (n-3) and (n-6)PUFA substrates. CHH-1 cells also possess -5-desaturase activity which showed preference towards (n-3)PUFA, but -4-desaturase activity was totally absent. Elongation of 20-carbon PUFA was especially active in CHH-1 cells with 22-carbon PUFA being specifically incorporated into PE and PS lipid classes. The fatty acid composition of PI indicated specific incorporation of 20-carbon PUFA into this lipid class. Supplementation with 22:6(n-3) generated fatty acid compositions more closely resembling those of intact salmonid hearts. Substantial chain shortening of 22:6(n-3) to 20:5(n-3) occurred.Abbreviations BHT butylated hydroxytoluene - BSA bovine serum albumin - CL cardiolipin - FCS fetal calf serum - PA phosphatidic acid - PC phosphatidylcholine - PE phosphatidylethanolamine - PI phosphatidylinositol - PS phosphatidylserine - PUFA polyunsaturated fatty acid - SM sphingomyelin     

大麻哈鱼胚胎耳石的茜素红标记及其效果评价

以人工繁育大麻哈鱼(Oncorhynchus keta)发眼后胚胎为研究对象, 设置4个茜素红染料质量浓度梯度(10 mg/L, 20 mg/L, 40 mg/L, 80 mg/L)和4个浸染时间梯度(8 h, 16 h, 24 h, 32 h), 分析茜素红染料在耳石上的沉积情况, 以及不同暂养天数的动态变化, 以期为大麻哈鱼标志放流技术及效果评估提供基础参考。结果表明, 茜素红在矢耳石和微耳石上都能形成良好标记, 在可见光和黄绿激光下均检测到标记带。随着暂养时间的延长, 可见光下标记逐渐减弱, 至80 d基本消失, 而在黄绿激光下标记区能长久保持, 荧光强度无减弱迹象。对不同时间点的标记级数随浓度变化关系进行曲线拟合, 结合安全评估, 得出适宜胚胎期大麻哈鱼耳石群体标记的条件为: 浸染质量浓度(w/v)为25.9~40 mg/L, 浸染时间为15.6~24 h, 并且在二次函数y=0.055x²–3.861x+86.9(x表示时间值, y表示浓度值)之下的曲边三角形区域选择浓度和时间点。标记后不同采样时间点的新生轮纹数与暂养天数线性相关性显著, 矢耳石和微耳石相关方程的斜率分别为0.965和0.924, 表明大麻哈鱼胚胎-仔稚鱼后期矢耳石与微耳石上的沉积轮为日轮。     

Relationship between coastal water properties and adult return of chum salmon (Oncorhynchus keta) along the Sanriku coast,Japan

We investigated the relationship between adult (age‐4) return rates for chum salmon (Oncorhynchus keta) originating from the Iwate Prefecture, Japan, and coastal environmental conditions during their early ocean life in coastal residency. We analyzed distributions of water properties via intensive hydrographic observations using a conductivity–temperature–depth profiler. Both the return rates and water properties vary strongly over interannual time scales. We found that the time when the return rate decreased drastically corresponded well to the time when the frequency of warm waters in the coastal residency increased.     

An evaluation of the potential influence of SST and currents on the oceanic migration of juvenile and immature chum salmon (Oncorhynchus keta) by a simulation model

Using a salmon migration model based on the assumption that swimming orientation is temperature dependent, we investigated the determining factors of the migration of juvenile and immature chum salmon (Oncorhynchus keta) in the North Pacific. We compared the predictions of the model with catch data of immature and juvenile chum salmon collected by Japanese research vessels from 1972 to 1999. The salmon migration model reproduced the observed distributions of immature chum salmon and indicates that passive transport by wind‐driven and geostrophic currents plays an important role in the eastward migration of Asian salmon. These factors result in a non‐symmetric distribution of Asian and North American chum salmon in the open ocean. The directional swimming component contributes to the northward migration in summer. The model results indicate that during the first winter Asian chum salmon swim northward against the southward wind‐driven currents to stay in the western North Pacific. This suggests that Asian chum salmon require more energy to migrate than other stocks during the first winter of their ocean life.     

Changes in plasma prolactin and growth hormone concentrations during freshwater adaptation of juvenile chum salmon (Oncorhynchus keta) reared in seawater for a prolonged period

Freshwater adaptability of chum salmon was examined in juvenile fish reared in seawater for 4 months. The fish, weighing about 40g, were transferred directly to fresh water in October, when their cohorts are migrating in the North Pacific Ocean. Plasma sodium concentration decreased from 167 mM in seawater to about 130 mM during the first 24h, and increased gradually during 2–7 days after the transfer. No immunoreactive prolactin (PRL) was detected in the plasma of the seawater-adapted fish nor during the first 24h in fresh water. Significant levels of PRL were detected after 2–3 days. The maximal level (2.6 ng/ml) was observed after 5 days and became undetectable again after 7 days; no significant correlation was seen between the changes in plasma sodium and PRL levels during the transfer. Plasma growth hormone levels were relatively constant, except for a significant decrease 12h after the transfer. Although plasma thyroxine levels were highly variable during the experiment, a significant decrease and an increase were observed 12h and 5 days after the transfer, respectively. The present study indicates that juvenile chum salmon retain hyperosmoregulatory ability even after prolonged rearing in seawater. Examination of turnover rates, rather than changes in plasma levels, seems to be essential to clarify the osmoregulatory roles of the hormones.     

Assessing the diet of North American Atlantic salmon (Salmo salar L.) off the West Greenland coast using gut content and stable isotope analyses

Investigations on the marine feeding of Atlantic salmon (Salmo salar L.) in the Northwest Atlantic are limited compared with the Northeast Atlantic. Climate‐induced changes to food webs in Atlantic salmon feeding areas have been noted, alongside increased mortality despite a cessation of most marine fisheries. As forage efficiency may be hampering survival, it was important to address this knowledge gap. Atlantic salmon were sampled at three sites on the West Greenland coast (Sisimiut, Nuuk and Qaqortoq) between 2009 and 2011. Gut content and stable isotope analyses were combined to assess spatial and temporal differences in feeding. Capelin (Mallotus villosus) dominated the diet at Nuuk and Qaqortoq, whereas boreoatlantic armhook squid (Gonatus fabricii) was the dominant prey at Sisimiut. Hyperiid amphipods (Themisto spp.) and sand lance (Ammodytes spp.) were also important. Significant differences were found among sites for both gut contents and stable isotope analyses, with fewer differences evident temporally. Dietary differences were also evident across larger scales, with little overlap demonstrated with Northeast Atlantic diets and the emergence of boreoatlantic armhook squid as an important prey item over time. Atlantic salmon diets are frequently anchored on one or two prey items, on which they appear to specialize, but they will diversify to consume other available pelagic prey. Thus, Atlantic salmon are an opportunistic, generalist predator within the pelagic food web. The variability evident in diet suggests that the limited data available are insufficient to appropriately understand potential vulnerabilities that the species may have to ecosystem changes, and suggest further research is needed.     

Species identification of Alaska pollock,Gadus spp., and Micromesistius spp. in cod roe products using a PCR-based method

Fish species identification techniques for authentic food labeling were developed using species-specific PCR primers for cod roe products. A salted, seasoned fish roe product, karashimentaiko (chilli cod roe), is produced from the eggs of Alaska pollock, Theragra chalcogramma, according to the fair trade competition agreement authorized by the Fair Trade Commission of the Japanese government. To examine whether Alaska pollock ovaries or those of other fish species are being used as raw materials for the fish roe products, we developed species identification techniques using PCR amplification of a 255-bp fragment encoding the mitochondrial ATP synthase Fo subunit 6 (ATP6) gene with a species-specific primer set for Alaska pollock mitochondrial DNA. We also designed two species-specific primer sets corresponding to the mitochondrial ATP6 and cytochrome b (cytb) for Gadus spp. and Micromesistius spp. by PCR amplification of 332- and 223-bp fragments, respectively. We examined the species specificity of these PCR-based methods among nine commercially important Gadidae species.     

日本在西北太平洋的秋大麻哈鱼渔业

日本系秋大麻哈鱼为日本利用的重要鱼种之一,历来受到日本有关水产机构的重视,并对该鱼种进行了持续的深入研究。本文主要介绍了日本系秋大麻哈鱼的渔业概况、生物学特性、资源状况及该渔业管理方面等内容,以供相关水产单位和研究人员参考。     

Freshwater habitat associations between pink (Oncorhynchus gorbuscha), chum (O. keta) and Chinook salmon (O. tshawytscha) in a watershed dominated by sockeye salmon (O. nerka) abundance

To understand the interplay between habitat use and contemporary anadromous Pacific salmon, Oncorhynchus spp., distributions we explored the habitat associations of three species, pink (O. gorbuscha), chum (O. keta) and Chinook salmon (O. tshawytscha) in streams of the Wood River system of Bristol Bay, Alaska, where sockeye salmon (O. nerka) are numerically dominant. We developed models to investigate the occurrence of nondominant salmon in relation to habitat characteristics and sockeye salmon density, using four decades of salmon presence and abundance data. The frequency of occurrence and abundance of nondominant species increased with watershed drainage area and stream depth and decreased with sockeye salmon density. The range of occurrence varied from nonexistent to perennial for the other species in sockeye‐dominated streams. Increasing watershed area resulted in larger stream habitat area and deeper habitats, allowing for the sympatric occurrence and persistence of all salmon species. The relationships between habitat and the presence of these Pacific salmon help define their requirements but also remind us that the patterns of presence and absence, within the overall ranges of salmon species, have yet to be fully understood.     

Assessing zooplankton advection in the Barents Sea using underway measurements and modelling

The coastal shelf of northern Norway and the Barents Sea is highly advective and mainly affected by the North Atlantic Current and the Norwegian Coastal Current. The oceanographic conditions are an important factor for the spatial and temporal distribution of zooplankton in the region. To quantify zooplankton advection over the western border of the Barents Sea, a Scanfish/Optical Plankton Counter (OPC), Acoustic Doppler Current Profiler (ADCP), Multiple Opening and Closing Nets and Environmental Sampling System (MOCNESS), and hydrodynamic model were used. This study provides data from two time windows (June and July 1998) by continuous measurements between northern Norway and Bear Island. The zooplankton community structure was obtained by net tows and zooplankton abundance fields were mapped by an OPC counting zooplankton in the size range 0.7–14 mm equivalent spherical diameter. A simple zooplankton community structure was found with the copepod Calanus finmarchicus (CIII–CV) as the dominant species in this size fraction. Ocean currents were measured by a ship‐mounted ADCP and the residual currents were calculated by subtracting the tidal component obtained from a hydrodynamic model. Two measurements conducted in June and July 1998 shows a net eastward transport of water of 3.5 and 1.3 Sverdrup over the section. For the same two periods, zooplankton biomass transport is also positive towards east but varies by two orders of magnitude between the two measurements.     

Development of a fatty liver model using oleic acid in primary liver cells isolated from Atlantic salmon and the prevention of lipid accumulation using metformin

The following study aimed to develop a fatty liver model in primary hepatocytes isolated from Atlantic salmon. In order to induce the fatty liver, oleic acid (OA) at 0.2 or 0.4 mM was used. Metformin, known to prevent and cure fatty liver in mammalian cells, was used at 1 or 10 mM for 24 hr before addition of OA to test possible prevention effect of metformin on the OA‐induced fatty liver phenotype. Cells grown in 0.2 mM OA did not increase the mean number of lipid droplets, while cells grown in 0.4 mM OA increased the number of lipid droplets within the liver cells (p < 0.0001). Metformin pretreatment prior to OA supplementation reduced the mean number of lipid droplets. Gene expression of ApoB100, CD36 and PPARa increased in cells treated with metformin and most so at 10 mM. On the other hand, gene expression of LXR, SREBP2 and CPT‐1 decreased at both concentrations of metformin, while OA treatment did not affect these genes. Gene expression of IL‐8 increased by 0.4 mM OA (p = 0.002). Metformin reduced the gene expression of IL‐8. Thus, metformin efficiently enhanced the expression of genes related to transport and oxidation of lipids in hepatic cells of salmon, but required higher concentrations of OA and metformin than those required in rodent models to increase and prevent lipid accumulation, respectively.     

Chum salmon (Oncorhynchus keta) growth and temperature indices as indicators of the year–class strength of age‐1 walleye pollock (Gadus chalcogrammus) in the eastern Bering Sea

Ecosystem‐based fisheries management requires the development of physical and biological time series that index ocean productivity for stock assessment and recruitment forecasts for commercially important species. As recruitment in marine fish is related to ocean condition, we developed proxies for ocean conditions based on sea surface temperature (SST) and biometric measurements of chum salmon (Oncorhynchus keta) captured in the walleye pollock (Gadus chalcogrammus) fishery in the eastern Bering Sea in three periods (July 16–30, September 1–15 and September 16–30). The main purpose of this paper was to evaluate Pacific salmon (Oncorhynchus spp.) growth as a possible indicator of ocean conditions that, in turn, may affect age‐1 walleye pollock recruitment. Marine growth rates of Pacific salmon are the result of a complex interplay of physical, biological and population‐based factors that fish experience as they range through oceanic habitats. These growth rates can, therefore, be viewed as indicators of recent ocean productivity. Thus, our hypothesis was that estimated intra‐annual growth in body weight of immature and maturing age‐4 male and female chum salmon may be used as a biological indicator of variations in rearing conditions also experienced by age‐0 walleye pollock; consequently, they may be used to predict the recruitment to age‐1 in walleye pollock. Summer SSTs and chum salmon growth at the end of July and September explained the largest amount of variability in walleye pollock recruitment indicating that physical and biological indices of ocean productivity can index fish recruitment.     

The effect of low temperatures and photoperiods on growth and vertebra morphometry in Atlantic salmon

The aim of this study was to reveal possible interactive effects of temperature and photoperiod on somatic and skeletal growth, feed conversion, organ indexes and blood chemistry in Atlantic salmon postsmolts. A total of 1140 (initial mean weight 96.0 g ± 3.1 SEM) juvenile Atlantic salmon reared in seawater were in duplicates exposed to six different combinations of temperatures (4.3, 6.5 or 9.3 °C) and photoperiods (continuous light, LL or simulated natural photoperiod (69ºN), LDN) for 124 days. An interactive effect of photoperiod and temperature on somatic growth was found as the fish exposed to low temperature and continuous light regime (4LL) had a significantly higher growth (30 % gain in overall SGR) than the 4LDN group, corresponding to the effect of approx. 1.2 °C temperature increase. Fish in the 6 and 9 °C groups did not show any significant growth benefit of continuous light. Compared to the 4LDN group, the 4LL group showed higher total feed conversion efficiency, lower levels of blood Na⁺ and lower hepato-somatic and cardio-somatic indexes. In the skeleton, cervical vertebra were largest in the 4LL group, while the length of the head was largest in the 4LDN group, continuous light promotes growth at lower temperatures while supporting a normal development. It is suggested that a considerable growth benefit may be achieved by exposing juvenile Atlantic salmon to continuous light when reared at low (in this trial 4.3 °C) water temperature during winter.