致死胁迫对许氏平鲉锁鲜效果的影响

为通过产品设计改变许氏平鲉现有的初级农产品销售模式,从品质上限到锁鲜效应两方面开展探索。本研究从致死胁迫强度探索许氏平鲉的极限品质,包括最低胁迫下的品质上限,疲劳致死下的品质下限,并对比市售产品品质状况。然后,通过品质易逝期处置,探讨高端许氏平鲉冷鲜品的锁鲜效应。健康活体按致死胁迫程度分3个处理组,分别为最低胁迫-破坏脊髓(SCD)、低胁迫-断髓致死(SCC)和高胁迫-窒息致死(SA),市售产品则分别来自超市(SM)及鱼市(FM)。锁鲜措施为速杀后立即冷却鱼体至0°C左右,鲜品贮藏条件为2°C冷藏。从僵直指数、肌肉收缩率、断裂强度分析许氏平鲉死后僵直特性。从白度值、pH值、ATP及其关联物和显微结构等指标分析肌肉品质及其冷藏稳定性。结果显示:(1)最低胁迫下,许氏平鲉死后24 h才达到最大僵直且持续24 h,高胁迫组则在6 h后僵直指数就已达到90%,48 h后彻底解僵;肌肉收缩率与僵直指数相关,高胁迫下,肌肉在贮藏期间没有收缩迹象,而最低胁迫下的肌肉在最大僵直发生前快速收缩。冷藏期间肌肉断裂强度均呈下降趋势,而最低胁迫组显著延缓。(2)最低胁迫有较高的初始ATP值,为2.83μmol/g,最低pH值为6.58;低胁迫下,死后6 h ATP值为0.94μmol/g,最低pH值为6.56;高胁迫下,死后6 h ATP值为0.50μmol/g,最低pH值为6.54。(3)延迟效应的表现,冷藏过程中白度稳定无变化,肌肉纤维逐渐降解,肌肉细胞间隙扩大,但最低胁迫组可有效减缓上述趋势。(4)销售端品质现状的表现,鲜品品质分析结果表明,超市组与低胁迫组死后6 h品质相似,鱼市组与高胁迫组死后120 h的品质相似。研究表明,市售初级农产品许氏平鲉品质良莠不齐,通过锁鲜处置施加产品设计,不仅有效延长冷鲜货架期,且满足消费者对高品质的需求。     

三角帆蚌、池蝶蚌及其杂交F1代早期形态差异分析

测量了三角帆蚌(S)和池蝶蚌(C)及其杂交F1代(SS,CC,S♀×C♂,C♀×S♂)8月龄时的11个外部形态特征数据,使用壳长校正样本规格差异后,分别进行聚类分析、主成分分析和判别分析。聚类分析及主成分分析的结果均表明正交F1代(SC)的体型偏于母本三角帆蚌,而反交F1代(CS)的体型则介于两亲本之间。三角帆蚌与池蝶蚌之间的判别准确率较高,综合判别率达81.16%,引入正反杂交F1代进行判别则综合判别准确率下降至57.46%。以上结果暗示三角帆蚌与池蝶蚌之间的亲缘关系有可能高于现在普遍认为的种间关系。     

Ribosomal DNA sequences indicate isolated populations of Ichthyophonus hoferi in geographic sympatry in the north-eastern Pacific Ocean

Infections of Ichthyophonus hoferi, a cosmopolitan parasite of marine fish, have recently been reported in rockfish, Sebastes spp., from the north‐eastern Pacific. Because I. hoferi also infects Pacific herring, Clupea pallasi Valenciennes, and salmonids in this region, we wanted to determine if Ichthyophonus parasites from rockfishes, Pacific herring and chinook salmon, Oncorhynchus tshawytscha (Walbaum), were the same. Small subunit ribosomal deoxyribonucleic acid sequence data revealed two haplotypes that were fixed among host species in geographic sympatry, one from rockfish and the other from both Pacific herring and salmon. These isolated populations of Ichthyophonus could be part of the same species that are ecologically separated because of host behaviours, or they could be distinct species that are host specific. Dietary patterns of the hosts indicate that ecological separation among hosts is possible, but the presence of distinct species may better explain the observed Ichthyophonus haplotype association with host species.     

Effect of dietary cadmium on growth and haematological parameters of juvenile rockfish, Sebastes schlegeli (Hilgendorf)

Experiments were carried out to investigate the growth and haematological parameters in juvenile rockfish, Sebastes schlegeli, exposed to sub‐chronic dietary cadmium (Cd) (0, 0.5, 5, 25, and 125 mg kg^?1) for 60 days. The daily growth rates of weight and length of the rockfish were significantly different from control, and a significant inverse relationship was observed between weight gain and the exposure concentration of dietary Cd at 25 and 125 mg kg^?1 (P<0.05). Glucose in serum was also increased significantly (P<0.05). The concentration of total protein in serum was significantly lower than control at 5, 25, and 125 mg kg^?1. No differences were observed in serum calcium concentration. The magnesium concentration in serum was increased significantly with dietary Cd concentration.     

Dietary methionine requirement for juvenile rockfish, Sebastes schlegeli

A 65‐day growth trial was conducted at 19.5 °C to determine the optimal dietary methionine for juvenile rockfish, Sebastes schlegeli. Semipurified diets were formulated to be isonitrogenous and isoenergetic. Fish meal was used as intact protein source and crystal amino acid was used as a part of dietary protein. Six experimental diets were formulated to contain 5.8, 10.8, 15.8, 20.8, 25.8 and 30.8 g kg⁻¹ dietary methionine. The results showed that dietary methionine significantly affected specific growth rate, weight gain, food conversion ratio, protein productive value (PPV), energy retention efficiency, carcass index and body composition. No significant difference was found in hepatosomatic index. The dietary methionine requirement for maximum growth was 13.7 g kg⁻¹ dry matter or 28.0 g kg⁻¹ of dietary protein when cystine content was 1.2 g kg⁻¹ dry matter.     

Oceanographic features that define the habitat of Pacific ocean perch, Sebastes alutus

This study investigates the possibility that oceanographic features could have effects on the variations observed in the apparent abundance of a demersal rockfish, Pacific ocean perch, Sebastes alutus. Simultaneous monitoring of physical variables and indices of fish abundance was achieved by attaching oceanographic equipment to the fishing gear of commercial vessels and sampling the fish catch. It was found that perch prefer a temperature range from at least 4.8C to 6.7C and that their movement patterns are linked to the movement of these temperatures by coastal wind patterns. Perch prefer areas with steep bathymetry, characterized by turbulent activity due to interactions between the local bathymetry and tidal currents.     

温度对黑鳍棘鲷耗氧率与排氨率的影响

对体重为240.9±27.1 g的黑鳍棘鲷在不同水温(10℃、15℃、20℃、25℃、30℃)条件下的耗氧率和排氨率进行了测试分析。结果表明:黑鳍棘鲷在一定温度范围内的耗氧率和排氨率均随温度的升高而升高,但当水温超过一定值后,其耗氧率和排氨率均随温度的升高而下降。在实验条件下,黑鳍棘鲷的耗氧率与温度的回归方程为Y=-0.489 7X2+27.39X-147.39;排氨率与温度的回归方程为Y=-0.009 3X2+0.508 2X-1.247;耗氧率的最大值为235.61μg/g.h(温度为28.0℃),排氨率的最大值为5.70μg/g.h(温度为27.3℃)。黑鳍棘鲷快速生长期的最适温度为25~28℃。     

Effect of enriched live feeds on survival and growth rates in larval Korean rockfish, Sebastes schlegeli Hilgendorf

High mortality frequently occurs in larval mass production of Korean rockfish, Sebastes schlegeli Hilgendorf. Nutritional deficiencies in live feeds, rotifers and Artemia nauplii, fed to larvae could be a reason. A series of experiments was carried out to evaluate the effect of nutritional enrichment of live feeds by ω‐yeast, Spirulina powder and Super Selco^TM on survival and growth rates in rockfish larvae. Preference of rockfish larvae for the live feeds was determined by analysis of stomach contents. In addition, the effect of green water produced by the use of Chlorella ellipsoidea and Spirulina powder on the growth performance of larvae was evaluated. Larvae fed rotifers nutritionally enriched with Super Selco showed significantly higher survival rates than those fed rotifers enriched with ω‐yeast. Larvae fed rotifers that were nutritionally enriched with both Super Selco and Spirulina together exhibited improved growth and survival rates. Larvae fed Artemia nauplii nutritionally enriched with Spirulina powder showed significantly higher survival than larvae fed Artemia nauplii without enrichment. When larvae were fed rotifers, Artemia nauplii or the mixture of rotifers and Artemia nauplii, the second and last group showed significantly higher survival than the first group. Fatty acid composition in live feeds was improved by enrichment of ω‐yeast and larvae fed this feed showed higher survival and growth rates compared with larvae fed non‐enriched feeds. No positive effect of green water in the tank produced with C. ellipsoidea or Spirulina powder was observed on survival and growth rates for larvae fed nutritionally enriched rotifers with Super Selco and Spirulina powder. However, when the larvae were fed Artemia nauplii that were nutritionally enriched with ω‐yeast and Spirulina powder, green water obtained by adding Spirulina powder to the tanks resulted in significantly higher growth rates of larvae than was obtained by adding C. ellipsoidea.