大西洋鳕微卫星引物对太平洋鳕的适用性

利用Genbank中大西洋鳕的7对微卫星引物,对太平洋鳕基因组DNA进行PCR扩增。这7对引物均可较稳定地扩增出条带,它们分别是Gmo2、Gmo3、Gmo8、Gmo19、Gmo35、Gmo36、Gmo37,并且扩增出的7个位点均表现出多态性,共获得69个等位基因,每个位点的等位基因数目为4～17,大小为111～227bp。在7个位点上2种鱼的等位基因的大小存在着不同程度的差异。其中Gmo37在大西洋鳕和太平洋鳕中扩增出的条带的长度差异最大,基本无重合部分,分别为220～290bp和144～226bp,本研究结果以期对2种鳕科鱼类遗传结构的进一步研究提供帮助。     

太平洋鳕(Gadus macrocephalus)亲鱼驯化培育与早期发育特征

采捕山东威海外海黄海海域的太平洋鳕(Gadus macrocephalus)亲鱼进行驯化和培育,在人工条件下成功驯化存活野生亲鱼49尾,经短期促熟培育后,通过人工授精方式获得了多批次受精卵.对胚胎和早期仔鱼发育过程进行了观察,详细描述了从受精卵到早期仔鱼各发育时期的形态特征.结果显示,太平洋鳕成熟卵子为沉性卵,圆球形,卵径为0.9-1.1 mm,无油球.胚胎发育分为5个时期,分别为卵裂期、囊胚期、原肠胚期、神经胚期和器官形成期.在水温为9-10℃、盐度为27-29的海水中孵化,受精卵历时312 h 30 min孵化出膜.初孵仔鱼全长为(3.85±0.12) mm,6日龄仔鱼开口,肛门与外界相通,进入混合营养期.8日龄仔鱼卵黄囊消耗殆尽,开始进入外源性营养阶段.仔鱼开口饵料为轮虫(Rotifer),12日龄开始摄食卤虫(Artemia saline)无节幼体.6日龄仔鱼鳔原基形成,16日龄鳔充气成为亮泡状.12日龄仔鱼形成肠道第1个生理弯曲,22日龄仔鱼第2个肠道生理弯曲形成.研究结果可为太平洋鳕亲鱼驯化培育和苗种培育提供基础资料.     

Weight-based virtual population analysis of Pacific cod Gadus macrocephalus off the Pacific coast of southern Hokkaido, Japan

ABSTRACT:   Age-based population assessment is widely used, but there are cases where information on age or even body length of landed fish is difficult to collect. In the present study, the biomass and fishing mortality of the southern Hokkaido stock of Pacific cod Gadus macrocephalus was estimated directly from body weight composition, using weight-based virtual population analysis, from 1994 to 2000. The estimated biomass over 1 kg body weight was 5607 t in 1994 and increased to 7908 t in 2000. The increase was explained by an increase in recruitment.     

Effects of ontogeny, temperature, and light on vertical movements of larval Pacific cod (Gadus macrocephalus)

The role of behavior, especially vertical migration, is recognized as a critical component of realistic models of larval fish dispersion. Unfortunately, our understanding of these behaviors lags well behind our ability to construct three-dimensional flow-field models. Previous field studies of vertical behavior of larval Pacific cod ( Gadus macrocephalus ) were limited to small, preflexion stages (≤11 mm SL) in a narrow range of thermal conditions. To develop a more complete picture of larval behavior, we examined the effects of ontogeny, temperature, and light on vertical responses of larval Pacific cod in experimental columns. While eggs were strictly demersal, yolk-sac larvae displayed a strong surface orientation as early as 1 day post hatch (∼ 5 mm SL). Consistent with field observations, small preflexion larvae (<10 mm SL) showed no response to varying light levels. However, there was a direct effect of temperature on larval behavior: Pacific cod larvae exhibited a stronger surface orientation at 4°C than at 8°C. The behavior of larger, postflexion larvae (>15 mm SL) in experimental columns was consistent with a diel vertical migration and independent of water temperature: fish were more widely distributed in the column, and median positions were consistently deeper at higher light levels. These laboratory observations are combined with observations from discrete-depth (MOCNESS) sampling in the Gulf of Alaska to characterize the vertical distribution of larval Pacific cod and contrast ontogenetic patterns with walleye pollock ( Theragra chalcogramma ). The vertical movements of larval Pacific cod described here will be applied in the development of dispersal projections from Gulf of Alaska spawning grounds.     

Spatial distribution and feeding habits of Pacific cod (Gadus macrocephalus) larvae in Mutsu Bay, Japan

The spatial distributions and feeding habits of Pacific cod ( Gadus macrocephalus ) larvae, and the spatial distributions of copepod nauplii and copepodites, their main prey, were examined in Mutsu Bay from February to March during 1989–92. Yolk-sac larvae were caught at 30–45 m depth at the bay mouth. Larvae without yolk were collected at 8–45 m depth at the bay mouth and the inner part of the bay, and large larvae were chiefly found in the bay. This geographical pattern in larval size may have been because of transport to the inner part of Mutsu Bay by the Tsugaru Warm Current. The dominant taxa of copepod nauplii and copepodites in the diet and the environment changed each year. Larvae fed mainly on abundant taxa in the environment, suggesting that larvae are opportunistic feeders. Nauplii and copepodites were abundant in the bay, especially in 1992. Copepodites were slightly more abundant in the diet of cod larvae in 1992 than in 1991, but this difference was smaller than in the environment. In addition, larvae with empty digestive tracts were scarce in 1991 and 1992. Prey concentrations in the bay in 1991 and 1992 seem to have been high enough to sustain most Pacific cod larvae.     

太平洋鳕(Gadus macrocephalus Tilesius)仔鱼发育过程

采用显微观察、拍照、测量的方法,对太平洋鳕(Gadus macrocephalus Tilesius)人工培育苗种各阶段仔鱼的发育(0-80 dph day post hatching)进行了研究.结果显示,在水温为2-12℃、盐度为28-32、pH为7.8-8.2、光照为800-1200 Ix、微充气静水的培育条件下,太平洋鳕早期仔鱼发育主要特征为:0-5 dph仔鱼完全营内源性营养,1 dph仔鱼黑色素沉积较初孵仔鱼颜色加深,眼球出现彩虹色素,5 dph仔鱼消化道已打通(除肝脏外);6dph仔鱼开口摄食,消化道内有小颗粒物质,营混合性营养;9dph大部分仔鱼卵黄囊吸收完毕,消化道内充满褶皱臂尾轮虫(Brachionus plicatilis),进入外源性营养期,血细胞流动清晰可见;12dph仔鱼头部黄色色素带明显;15dph仔鱼黑色素和黄色素密集,鳔器官开始形成;17dph仔鱼开始出现彩虹色素;20 dph仔鱼眼球发育完善,腹动脉可观察到明显的血流,鱼体尾部色素点开始出现;30-50 dph仔鱼各鳍条雏形发育;30 dph仔鱼尾鳍鳍条开始发育;40dph仔鱼开始摄食卤虫(Artemia sp.),第1、2、3背鳍已出现雏形;50dph仔鱼尾椎骨开始上翘,臀鳍、背鳍雏形已清晰可见;60-80 dph仔鱼色素细胞迸一步发育,各鳍条逐步发育完善,胆囊清晰可见;60 dph仔鱼鳃部呈现红色;70dph仔鱼腹部有银白色鳞片雏形出现;80dph仔鱼鳃盖已基本发育完善,腹鳍出现.本研究对太平洋鳕仔稚鱼发育过程进行了描述,可为后续规模化人工繁育的开展提供基础数据.     

急性温度胁迫对太平洋鳕仔稚鱼成活率、生理生化指标的影响

为探究温度胁迫对太平洋鳕的影响,以太平洋鳕仔稚鱼为研究对象,研究了温度胁迫对太平洋鳕仔稚鱼的成活率、总超氧化物歧化酶、过氧化氢酶、丙二醛的活性的影响。试验结果表明,培育温度8℃组(对照组)成活率最高(99%),15℃组的成活率最低(43.3±10.3)%,差异显著(P0.05)。2、5、11、15℃胁迫组的总超氧化物歧化酶活性在24h后急剧升高,与8℃组差异显著(P0.05)。72h后各组总超氧化物歧化酶活性开始下降,与8℃组差异不显著(P0.05)。各胁迫组的过氧化氢酶活性在48h时开始显著升高(P0.05),表明过氧化氢酶活性的变化较总超氧化物歧化酶相比具有滞后性。丙二醛活性在胁迫24h时升高(P0.05),但在48h时略有回落,72h时表现出最大的活性。     

江鳕和大头鳕形态学的初步研究

通过对江鳕(Lota lata Linnaeus)和大头鳕(Gadus macrocephalus Tilexius)的形态学比较研究发现，江鳕和大头鳕都有胆囊、幽门盲囊，肝脏较大。脊柱和附肢骨骼种类相同，区别仅在于骨块的数量和嵴的发达程度上，尾都是等尾型。     

Preliminary Observations on Spoilage Potential of Flora from Desalted Cod (Gadus morhua)

Abstract

Desalted cod products are already marketed, although still presenting some problems. Fresh raw materials and good manufacturing practices during salting, drying and desalting are essential to improve their quality and shelf life. The production of off-odor, hydrogen sulfide, trimethylamine, ornithine, putrescine, cadaverine, histamine, indole, hydrolyzed gelatin and ammonia was investigated in 127 bacterial strains isolated from dried/wet salted cod, later desalted either at 4 or 24°C. Desalting could either introduce or recover off-odor, sulfide hydrogen and/or ornithine producing strains. Cod desalting at 4°C is of great importance in order to improve the shelf life and safety of cod desalted products.     

Incorporating an environmental stock–recruitment relationship in the assessment of Pacific cod (Gadus macrocephalus)

The robustness of a previously described environmentally mediated stock–recruitment relationship for Pacific cod in Hecate Strait, BC, Canada was tested with 10 yr of additional data. The original analysis tested several alternative hypotheses and concluded that water transport through Hecate Strait, as indicated by sea level height, coupled with cod spawning biomass formed the best model. The present analysis indicates the relationship held through the 1990s. The implications of variation in sea level on stock production were investigated with a delay‐difference stock production model that included an environmentally mediated stock–recruitment relationship. The model predicted that the maximum fishery yield would vary between 1750 and 3670 t yr^?1 over the observed range of sea level height, and the estimated unsustainable fishing mortality during periods of low productivity would be only 0.5 times that in periods of high productivity.     

Weight-based yield per recruitment and spawning-biomass per recruitment analyses of pacific cod <Emphasis Type="Italic">Gadus macrocephalus</Emphasis> off the Pacific coast of southern Hokkaido,Japan

ABSTRACT:   The present study assessed the stock state of Pacific cod Gadus macrocephalus caught off the coast of southern Hokkaido, Japan. Weight-based yield per recruitment (YPR) and spawning-biomass per recruitment (SPR) analyses were used for this assessment. The current fishing mortality (average from 1998 to 2000) was 0.65 and weight at first capture was 0.5 kg bodyweight. Under these fishing pressures, the YPR of Pacific cod in southern Hokkaido was 1.06 kg/recruitment and percentage of SPR (%SPR) was 6.9%. The %SPR was lower than the critical limit at 20%SPR. The main reason that values of both YPR and %SPR were not optimum, would be that the weight at first capture was too small. Raising the weight at first capture was thought to be a better strategy from the biological viewpoint, and reducing fishing mortality to 0.3 would be the next alternative strategy from the fisheries management viewpoint.     

Quality Changes During Salt-Curing of Cod (Gadus morhua) at Different Temperatures

ABSTRACT

The main aim of this study was to assess the quality changes and their causes during cod salt-curing for up to 76 days at different temperatures and a relative humidity below 80%. Salt-curing made the fish more yellow (L*a*b* scale), a color change that is more easily detected in sensory analysis against a cream color scale. Intense proteolytic breakdown took place at 12 and 18°C, leading to a greater proteolysis degree and a higher pH. A red surface discoloration of the flesh was apparent after 76 days at 18°C due to the high number of red-halophilic bacteria. These bacteria were also responsible for the highest intensity of “off”-odors and mucus obtained under these conditions. Cod salt-curing should be done below 12°C to reduce the spoilage activity of halophilic bacteria and is best done at chill temperature (close to 6°C) to obtain a good quality product.     

In-Pack Surface Pasteurization of Capture-Based,Pre-Rigor Filleted Atlantic Cod (Gadus morhua)

In this study, we targeted the surface bacteria of high quality vacuum-packed cod loins to investigate how this affected the shelf life. After heat processing, the storage temperature was kept at 4°C in order to mimic supermarket shelf conditions. Samples that had undergone minimal heating regimes were compared with control samples as well with samples that were heated into the core. Shelf life was assessed based on the findings of a sensory analysis and on microbial growth data and supported by measurements of liquid loss and pH. Surface pasteurization of these samples seems to prolong shelf life only to a limited degree, even for samples with a low initial contamination level. Transportation of some bacteria into the filet, possibly during the intense rigor mortis progress triggered by the heat process, may have created a general flux of water in the samples. Underneath the surface, these bacteria are exposed to a limited thermal load and very little microbial competition. Surface pasteurization is an efficient method to reduce microbial contamination of many foodstuffs. In the case of fresh fish, however, surface pasteurization seems to have a limited effect due to the structure of the muscle and the subsequent storage condition.     

Textural Changes During Iced Storage of Salmon (Salmo salar) and Cod (Gadus morhua)

Abstract

Textural properties, protein solubility, water holding capacity and activity of collagenolytic enzymes of salmon (Salmo salar) and cod (Gadus morhua) fillets were measured during iced storage. Breaking strength and hardness of fillets were reduced during iced storage. Elasticity of cod fillets was reduced, while cohesiveness of salmon increased during storage. Salmon was softer and less elastic than cod. During storage, total amount of extracted proteins was reduced for cod, and increased followed by a reduction for salmon. The fraction of salt soluble proteins increased during storage, and values for cod were higher than those for salmon. The activity of collagenolytic enzymes was higher in cod than salmon during the whole storage period.     

Optimization of Heat Processing of Farmed Atlantic Cod (Gadus morhua) Muscle with Respect to Cook Loss,Water Holding Capacity,Color, and Texture

Convenience products of fish that are heat processed in-pack are often subjected to a compromise between quality and durability within the framework of required safety. The purpose of this study was to provide knowledge for optimizing pasteurization of cod muscle by quantifying changes in water holding capacity (WHC), cook loss, color, and texture within a wide range of processing times and temperatures. A heat load equivalent to 2 min at 70°C may be applied to the cod while maintaining the WHC above 66%, the cook loss below 5.6%, and keeping hardness and whiteness low, provided that the processing temperature is kept in the range 68 ± 4°C.     

Quality and Shelf Life of Liver of Farmed Cod (Gadus morhua)

ABSTRACT

Livers of Atlantic cod (Gadus morhua) are traditionally used in cod liver oil production or consumed cooked or canned. The farming of cod is a relatively new industry in Norway. The aim of this study was to determine quality and shelf life of fresh liver from farmed cod during chilled storage on ice by hydrolysis and oxidation state and sensory quality and the influence on canned liver. In two experiments, livers from farmed cod were stored chilled and sampled from Days 0 to 13, respectively. Quality, measured as hydrolytic and oxidation degradation, was reduced after 7 days of storage, while sensory quality was reduced after 4 days. Free fatty acids increased from Day 7 in both experiments, while peroxide value and anisidine value showed no change when the livers were single wrapped. Rancid odor was the first sign of oxidation and was registered after three to four days of storage. Canning within 2 days of storage prevented leakage of oil from the canned livers. Sensory analyses of oxidation are recommended as a sensitive and rapid method to detect oxidation of chilled cod liver.     

Evaluation of Electrical Stunning of Atlantic Cod (Gadus morhua) and Turbot (Psetta maxima) in Seawater

The aim of this study was to assess electrical stunning of Atlantic cod and turbot in seawater to develop a protocol for the process of stunning and killing. An induced general epileptiform insult (unconscious) had a duration of 40 ± 27 s (n =14) in cod (2.6 ± 0.5 kg) and 34 ± 18 s (n = 19) in turbot (520 ± 65 g). Seven cod and 3 turbot displayed a physical reaction, and 11 turbot registered an electroencephalogram (EEG) response to pain stimuli administered 30 s post-stun. The heart rate was 32 ± 6 beats/min in cod and 25 ± 7 beats/min in turbot prior to stunning. Post-stunning, the electrocardiogram (ECG) revealed fibrillation and reduced activity post-stun. EEG, ECG recordings, and behavioral observations indicate that when a bipolar square wave current was applied with a frequency of 133 Hz and 43% duty cycle side to side (turbot) and at 170 Hz and 33% duty cycle (cod) head to tail, both species were stunned in seawater at current densities of 3.2 A/dm² and 2.5 A/dm², respectively. For turbot, a 5 s exposure to electricity followed by chilling in ice water for 15 min is sufficient to prevent recovery. For cod, a killing method needs to be established.     

Physicochemical and Reactive Oxygen Species Scavenging Properties of Collagen and Collagen Hydrolysates from Farmed Globefish (Fugu rubripes) Bone

Globefish (Fugu rubripes) bone collagen (GBC) was isolated and characterized. Electrophoresis and Fourier transform infrared (FTIR) spectra indicated that GBC was high-purity type I collagen with an intact triple-helical structure. Amino acid analysis revealed that GBC contained higher glycine content (364 residues/1,000 residues) than that of other fishery bones, and the imino acid content was 189 residues/1,000 residues. The denaturation temperature (T_d) of GBC was 27.1°C. GBC displayed a rapid fibril-forming rate and well-defined fibril morphology in vitro. Globefish bone collagen hydrolysates (GBCH) were optimized by neutral protease through response surface methodology (RSM) with the highest hydroxyl radical (?OH) scavenging capacity. The optimal hydrolysis condition was a reaction temperature of 48.4°C, time of 120 min, and enzyme/substrate ratio of 2520 U/g. Three fractions were collected by ultrafiltration, and the fraction GBCH-III (Mw<1 kDa) possessed the strongest ?OH scavenging ability. Reactive oxygen species (ROS) scavenging capacities were evaluated with two model systems: ?OH and nitric oxide (NO?). The ROS scavenging capacities increased in a dose-dependent manner. GBCH-III proved to be a more effective ?OH scavenger than reduced glutathione (GSH). These findings demonstrated that GBC and GBCH have potential as an alternative source of collagen-derived materials for use in pharmaceutical, nutraceutical, and cosmetic industries.     

The Effects of Light Salting on Physicochemical Characteristics of Frozen Cod (Gadus morhua) Fillets

Abstract

The effects of light salting by brine injection and brine immersion on physicochemical and textural properties of cod fillets were evaluated. Light salting significantly increased yield and water holding capacity. Adding brine injection to the process can be used to shorten the process time needed to obtain the desired salt content and increase yield. The effects on chemical composition were most significant in salt content, but water and protein content were also affected. Water content decreased from the tail to head direction of the fillets, both in unsalted and light salted fillets. Changes in protein content were in opposite proportion to changes in water content. This could be seen in the fresh fish and also after freezing, both in unsalted and light salted fillets. Texture of the fish was not significantly affected by salting and freezing.