Diel microhabitat use of age-0 bull trout in Indian Creek, Washington

Abstract – We studied diel microhabitat use at the focal point of age‐0 bull trout, Salvelinus confluentus, in Indian Creek, Washington during mid‐summer and fall of 1997. Microhabitat variables included water depth and velocity, distance from the stream bottom, habitat and refuge use, substrate type, and substrate embeddedness. Age‐0 fish were located over fines and gravel substrates in shallow, low‐velocity water near stream margins, but were located in shallower water at night. Bull trout were highly associated with loose substrate, and used the substrate interstices for refuge cover. Diurnal bull trout counts decreased and no age‐0 fish were observed after 15 September at water temperatures below 6.1 °C. Nocturnal counts remained relatively constant throughout the study. Our results suggest that age‐0 bull trout surveys be conducted at night when summer water temperatures begin to decline.     

花羔红点鲑人工繁殖和仔鱼培育技术研究

对花羔红点鲑人工繁殖和仔鱼培育技术进步了研究，并探讨了亲鱼大小与绝对繁殖力、受精卵发育时间与温度、成熟卵大小与初次摄食仔鱼大小等问题以及人工养殖群体对野生种群的影响。     

野生与养殖羔花红点鲑群体DNA多态性RAPD分析

采用RAPD技术对野生与养殖花羔红点鲑群体各17个个体进行了DNA多态性检测.用13个随机引物在野生群体和养殖群体中分别扩增出119和86条DNA片段,其中多态性片段数分别为64和51条,多态性片段的比例分别为52.46%和41.80%,平均杂合度分别为0.2177和0.1802,遗传相似率分别为0.7844和0.7985,群体间遗传相似率为0.6468,由此得出野生群体的遗传多样性高于养殖群体.通过Nei指数统计的花羔红点鲑群体内遗传多样度平均为0.1989,群体间遗传多样度为0.1359,群体间遗传分化为34.53%.Shannon遗传多样性指数表明,两群体中的遗传变异有64.05%来自群体内,只有35.95%来自群体间,此分化值与Nei指数估测得到的遗传分化相近.     

Comparison of the growth performance of offspring from cultured versus wild populations of arctic charr,Salvelinus alpinus (L.), kept at three different temperatures

The effects of three different temperatures on the growth and maturation of the offspring of cultured versus wild populations of juvenile arctic charr (Salvelinus alpinus L.) were investigated. The fish (start weight 17 g) were reared for 5 months at constant temperatures of 12, 14 and 16°C under a continuous light regime (LD24:0). Growth performance was significantly influenced by both temperature and source population. The offspring from the farmed fish displayed significantly higher mean weights at all temperatures compared with the offspring from the wild fish. The results indicate that the optimal temperature for growth (T_opt) decreases with increasing fish size in the offspring of both cultivated and wild fish. Significant differences in length–weight relationship were found, with the offspring of wild fish displaying higher condition factor throughout the experiment. The results demonstrate that the offspring from multiple generation farmed population of arctic charr are better adapted to high temperatures compared with the offspring (F₁ generation) from a wild population of arctic charr, and the former are also able to maintain growth at higher temperatures. There was a significant difference in maturation between the two populations, as the offspring from cultured fish displayed significantly lower level of maturation: 0%, 4% and 2% mature compared with 24%, 40% and 42% in the offspring from wild fish at temperatures of 12, 14 and 16°C respectively. The offspring from farmed strains of arctic charr thus appear to be the most suitable population for aquaculture.     

Predation relationships between introduced salmonids and the native fish fauna in lakes and reservoirs in northern Patagonia

Abstract– A few native and exotic fish species are caught frequently in Andean lakes and reservoirs of northwestern Patagonia. Puyen ( Galaxias maculatus ) prey on zooplankton and benthos. Percichthys trucha has a wide range of prey, mainly benthos, while P. colhuapiensis become piscivorous when grown. Pejerrey ( Odonthestes hatcheri ) is omnivorous and large size individuals can be piscivorous. A siluroid, Diplomystes viedmensis , preys on benthos, insects, and fishes. Introduced salmonids are potential piscivorous. The puyen is the major prey category among fishes. Salmonids and perchichtids seem to partially overlap their diets but predation on Diplomystes appears to be restricted to salmonids. Present abundance of puyen, pejerrey and Percichthys spp. does not indicate a strong salmonid effect. However, the low abundance of D. viedmensis does. We studied present predation relationships among native and introduced fishes and postulated possible effects upon native fish fauna.     

不同年龄花羔红点鲑非特异性免疫指标的比较

比较分析了流水养殖池中不同年龄(1～4龄)健康花羔红点鲑血液氯化硝基四氮唑蓝阳性细胞数(NBT阳性细胞数)、超氧化物歧化酶活力、碱性磷酸酶活力、酸性磷酸酶活力、溶菌酶活力、抗菌活力、溶血素含量及酚氧化酶活力.结果表明:各年龄免疫指标中NBT阳性细胞数、抗菌活力、溶血素和酚氧化酶活力无显著变化,其余各指标均有显著性变化....     

白斑红点鲑精子形态和超微结构的研究

应用扫描和透射电镜观察了白斑红点鲑(Salvelinus leucomaenis)精子的形态和超微结构。白斑红点鲑精子由头部、中段和尾部组成。头部呈椭球形,主要结构是细胞核,核前端无顶体,后端有植入窝,植入窝较深,凹入细胞核的1/3,核中染色质致密,存在着不规则的网络状间隙;中段包括中心粒复合体和袖套,中心粒复合体主要由近端中心粒和远端中心粒组成,近端中心粒为典型的9组三联微管结构,与远端中心粒相互垂直,远端中心粒向下延伸形成轴丝。袖套与细胞核后端相连,含有丰富的线粒体和囊泡,部分线粒体彼此融合,形成复合线粒体,囊泡有两种;白斑红点鲑精子尾部细长,主要结构是轴丝,为典型的9+2微管结构,轴丝被许多囊泡包围,质膜向外突出形成上下对称,但大小不同的两个侧鳍。     

The effects of a prolonged photoperiod and light source on growth,sexual maturation,fin condition,and vulnerability to fungal disease in brook trout Salvelinus fontinalis

The effects of an artificially prolonged photoperiod on growth, survival rate, colouration, and sexual maturation in brook trout Salvelinus fontinalis during pre‐ and post‐spawning periods from 21 June to 06 November were investigated. Fish of mean initial weight ?150 g were reared at ambient photoperiod as well as with an artificially prolonged photoperiod produced by either a light‐emitting diode or a metal‐halide light. The fish groups subjected to a prolonged period of artificial light grew significantly larger and had a higher survival rate (p < 0.05), regardless of sex, and showed lower occurrence of fungal disease compared to controls reared in the natural photoperiod. We found a significantly higher number of sexually mature fish in the control groups compared with experimental groups. The increased photoperiod effectively delayed gonad development and increased somatic growth in both male and female brook trout, and also increased resistance to fungal disease. The increased photoperiod produced an observable difference in fish colouration, with control groups exhibiting more intensive spawning colouration.     

Substituting fishmeal with extruded soybean meal in diets did not affect the growth performance,hepatic enzyme activities,but hypoxia tolerance of Dolly Varden (Salvelinus malma) juveniles

Extruded soybean meal (ESBM) showed increased digestibility of crude protein, amino acids and fat, better oil retention capacities, attenuated anti‐nutrient factor effects and improved its nutritive value compared with raw soybean meal, indicating a promising application prospects for ESBM in fish culture. This study aimed to evaluate the effects of substituting fishmeal with ESBM on growth performance, hepatic antioxidant capacity and the resistance to hypoxia stress on juvenile Dolly Varden (Salvelinus malma). Five hundred and forty fish were randomly assigned to six groups fed with iso‐nitrogenous and iso‐energetic diets with ESBM for replacement of 0% (control), 10% (G1), 20% (G2), 30% (G3), 40% (G4) and 50% (G5) fishmeal. After an 81‐day feeding trial, groups fed ESBM substituted diets (G2 to G5) showed no significant differences in survival rates, final body weights, weight gain rates, feed conversion ratios, specific growth rates, hepatosomatic indexes and condition factors with the control group (G0), reflecting normal food intake and growth performance. The hepatic enzyme activities of total antioxidant capacity, catalase and superoxide dismutase were not affected by ESBM substituted diets, showing no harmful effects on ROS eliminating abilities. Hepatic HSP70 expression levels had increased 1.3 times for G5 group, reflecting a less tolerance to hypoxia for fish fed diets with high substituting level of ESBM. In conclusion, replacing, despite 50%, fishmeal with ESBM in diets had no detrimental effects on growth performance and hepatic enzyme activities, but lowering the hypoxia tolerance of juvenile Dolly Varden (Salvelinus malma).     

利用虹鳟微卫星标记评价白斑红点鲑养殖群体的遗传结构

本实验筛选出30个虹鳟Oncorhynchus mykiss微卫星标记在白斑红点鲑Salvelinus leucomaenis养殖群体中表现出多态性,并利用这30个标记来评价白斑红点鲑养殖群体的遗传结构。在随机采样的32个个体中共检测到143个等位基因,片段大小为106~454bp,标记的等位基因数(No)为2~11个,有效等位基因数(Ne)为1.135~7.161个,观测杂合度(Ho)为0.094~1.000,期望杂合度(He)为0.121~0.874,多态信息含量(PIC)为0.116~0.846。群体的5项遗传多样性参数平均值分别为4.767、3.006、0.423、0.568,及0.524。统计结果显示:白斑红点鲑养殖群体处于高度多态水平(PIC=0.524≥0.5)。经χ~2检验估计Hardy-Weinberg平衡,结果表明白斑红点鲑群体处于平衡状态,仅11个微卫星标记显著偏离了遗传平衡,其中OMM1112、OMM1130和OMM1231等6个标记表现为杂合子显著缺失(P0.05),而OMM3006、OMM3044和OMM3144等5个标记表现为杂合子显著过剩(P0.05)。本实验从近缘种中鉴定可用于白斑红点鲑遗传分析的共显性标记,评估白斑红点鲑种质的遗传多样性,为该引进种种质的保护和持续利用提供参考。