Reproduction of chub, Leuciscus cephalus L., under controlled conditions

Research into artificial reproduction of chub was studied during three subsequent reproductive seasons. Chub reproduction was conducted in two different variations. In the first experiment different hormonal agents were given to fish, such as CPE, hCG, or an analogue of GnRH with dopamine antagonist (ovopel). In the second one, the optimum moment of applying of artificial reproduction was sought and the fish were only obtained an analogue of GnRH in different periods. The results obtained in two first seasons indicated that ovopel is the most effective agent for the artificial reproduction of chub. Consequently, it was decided that the fish would obtain only this agent in the final year of research. In last year (experiment II), chub spawners were taken to the hatchery under controlled conditions every few weeks from February to the beginning of June. Periodically, the maturity of oocytes was checked. As soon as the oocytes had achieved stage 2–3 of maturity, fish were obtained ovopel. It was noted that there was no problem with collecting semen. Obtaining oocytes was much more difficult. Most frequently, they were not obtained at all or obtained in very small amounts. It was also observed that the administration of hormones caused a very quick maturation of gonads and their over-maturation.     

Effects of silvering state on induced maturation and spawning in wild female Japanese eel <Emphasis Type="Italic">Anguilla japonica</Emphasis>

ABSTRACT:   The effects of silvering state of wild female Japanese eels Anguilla japonica on the success of induced maturation and the following spawning were examined. Thirty-eight females, collected in Mikawa Bay, were divided into four stages based on their silvering state: yellow (Y1), late-yellow (Y2), silver (S1) and late silver eels (S2). Despite injections of salmon pituitary extract (SPE) through the standard technique, Y1 and Y2 eels did not respond to the treatment with undeveloped gonad (gonad-somatic index [GSI]: 0.3–0.9), and all these females died by 5 weeks, probably due to an abnormal physiological condition. Most S1 (81%) and S2 eels (100%) matured completely (GSI: 17.8–51.4), and finally spawned successfully (69% for S1, 89% for S2). S2 eels fully matured with oocytes of over 750 μm in diameter by significantly smaller number of injections of SPE (5–6 times) than the case of S1 eels (6–8 times). The amount of eggs released by S2 eels (0.65 ± 0.11 g/fish per body weight [BW]) was significantly larger than those by S1 eels (0.54 ± 0.09 g/fish per BW). There was no difference in fertilization and hatching rates between eggs released by S1 eels and those of S2 eels. These results indicate that the success of induced maturation and spawning in wild female Japanese eels depends on their silvering state, and matured eggs can be obtained efficiently through the use of S2 eels rather than other stages.     

Ability of salmon growth hormone to accelerate somatic growth of juvenil abalone Haliotis discus hannai

ABSTRACT:   The ability of salmon growth hormone (sGH) to accelerate the somatic growth of juvenile abalone Haliotis discus hannai by immersion was examined. After immersion for one hour into a sGH-rich solution at a concentration of 30 mg/L, the sGH immunoreactivity in the body fluid of abalone was maximal after one day, and levels were still detectable at two days. No immunoreactivity was observed in the control group. Following immersion for one hour at one or two-week intervals for 120 weeks into the sGH-rich solution at 30 mg/L, the sGH-immersed abalone exhibited a significant increase in shell length and body weight. On the other hand, abalone immersed into a salmon prolactin (sPRL)-rich solution at 30 mg/L for one hour showed a lower increase in both shell length and body weight than the sGH-immersed abalone. No increases in shell length and body weight were observed in either the bovine serum albumin-immersed abalone or untreated controls. These results provide evidence that sGH can be transported from ambient water into the circulatory system of abalone, and can subsequently improve the somatic growth of juveniles.     

The combined effects of temperature and GnRHa treatment on the final stages of sexual maturation in Atlantic salmon (Salmo salar L.) females

Atlantic salmon (Salmo salar L.) females (2 SW), maturing for the first time, were reared under one of three temperature regimes (high: 14.3 ± 0.5°C; natural: 10.6 ± 1.0°C; and cold: 6.9 ± 1.0°C) in combination with one of two experimental treatments; an injection of GnRH analogue (GnRHa) contained in biodegradable microspheres, or a sham injection (microspheres only). The six experimental groups were then reared under simulated natural photoperiod for 4 weeks. Blood samples were drawn for analysis of plasma steroid levels and the fish were inspected for ovulation weekly. Batches of stripped eggs were incubated in triplicate incubators in raceways until the eyed stage. Treatment with GnRHa resulted in a substantial advancement and synchronization of ovulation at all temperatures, while exposure to cold water also appeared to advance ovulation slightly. While 75% (warm and cold) to 90% (natural) of GnRHa fish ovulated during the 4-week trial, only 30% of sham-treated females exposed to cold water, and none of the sham-treated fish held at higher temperatures, ovulated during this period. Survival rates of embryos to the eyed-stage were significantly higher for broodstock exposed to cold water. Plasma levels of testosterone (T), 17β-oestradiol (E₂), and 17α,20β-dihydroxy-4-pregnen-3-one (17,20βP) were all significantly affected by treatment with GnRHa and, to a lesser extent, temperature. The efficiency of GnRHa in counteracting the negative effects of high temperature on ovulation and the associated changes in circulating sex steroids suggest that temperature inhibition operates at least in part at the brain or pituitary.     

Effects of triploidy on the Caspian salmon <Emphasis Type="Italic">Salmo trutta caspius</Emphasis> haematology

The aim of this study was a comparison of key haematological features of diploid (2n) and triploid (3n) Caspian salmon (Salmo trutta caspius). Morphometric indices of erythrocytes were determined on blood smears by light microscopy. Triploidy significantly (P < 0.001) increased all morphometric indices measured in the erythrocytes including cell size, cell surface area, and cell volume. The increase in cell size was larger for the major (27%) axis than for the minor (22%) axis, thus making erythrocytes of 3n Caspian salmon more ellipsoidal. The estimated increase in erythrocyte nuclear volume (87%) was bigger than the theoretical expected 50% increase. Haematological indices were measured manually by hemocytometry. Triploids had lower numbers of red blood cells (RBC: 1,120,000 cells/mL in 2n vs. 700,000 cells/mL in 3n; P < 0.001) but they were larger in size (mean erythrocytic volume [MEV]: 363.1 nm³ in 2n vs. 483.3 nm³ in 3n; P < 0.001). The decrease in RBC number was not compensated by the increase in MEV and, thus, triploidy affected the haematocrit (Hct: 38.8% in 2n vs. 33.06% in 3n; P < 0.05). Total blood hemoglobin concentration was lower in triploid fish (Hb: 9.9 g/dL in 2n vs. 8.9 g/dL in 3n; P < 0.05). In contrast, mean erythrocytic hemoglobin (MEH: 95 μg in 2n vs. 133.2 μg in 3n; P < 0.001) was higher for 3n Caspian salmon as a result of their larger erythrocytes, although MEH concentration (MEHC: 0.26 g/dL in 2n vs. 0.27 g/dL in 3n) did not significantly differ (P > 0.05). White blood cell (WBC) counts (lymphocytes and neutrophiles) were measured and WBC/RBC ratios were calculated. There were no significant differences in WBC (15,710 cells/mL in 2n vs. 12,683 cells/mL in 3n; P > 0.05), lymphocytes, and neutrophils as %WBC as well as WBC/RBC ratios between two ploidy levels (P > 0.05). Triploid Caspian salmon showed higher erythrocyte abnormalities such as ‘twisted’, ‘tailed’, and ‘anucleated’ cells as well as high portions of immature RBC in blood smears in comparison with diploids (P < 0.001).     

Inter-river, -annual and -seasonal variability in fecundity of Atlantic salmon, Salmo salar L., in rivers in Newfoundland and Labrador, Canada

Abstract  Fecundity is an integral component of the calculation of Atlantic salmon, Salmo salar L., egg depositions in rivers. Fecundity determinations can be time consuming and prohibitively expensive in terms of application on a broad scale. Consequently, where river specific and annual data are not available, default means are used in calculations in Newfoundland and Labrador. It is important therefore to know the extent of variability among rivers, years and seasons and the potential error involved in using default values. Annual fecundity data were available for one river in Labrador and nine rivers in Newfoundland. Fecundity was determined from ovaries collected in the recreational fishery in the summer for all 10 rivers. For three of these rivers, fecundity determined from summer sampling was compared with that obtained from sampling at time of spawning in autumn. There was significant variability in fecundity with length as a covariate among rivers, years and seasons. Mean number of eggs per female decreased between 8.3% and 29.0% from summer to autumn while mean number of eggs per cm decreased from 5.0% to 28.5%. Depending on the measure of relative fecundity used (no. of eggs kg⁻¹ or no. of eggs cm⁻¹), results of simulations showed that estimates of egg deposition incorporating defaults can deviate from those obtained by applying year-specific and river-specific values by 50–75%, without adjusting for the seasonal reduction in fecundity, and by 30–50% with an adjustment. A sensitivity analysis revealed that of three parameters used in the calculation of egg deposition (size, percent female and fecundity), fecundity was the most influential.     

盐胁迫对野生稻种子萌发及幼苗生长的影响

以3个野生稻品种(系)和常规稻品种吉粳301(CK)为试验材料,研究了不同NaCl浓度对野生稻种子萌发及幼苗生长的影响。结果表明,盐胁迫对野生稻和常规粳稻种子萌发及幼苗生长的影响不同,NaCl浓度≤0.3%时,盐胁迫对3个野生稻种子发芽及幼苗生长没有影响,但促进吉粳301种子发芽及幼苗生长;NaCl浓度≥0.5%时,随着NaCl浓度的增大,3个野生稻种子发芽率逐渐降低,幼苗的根长、苗长、根冠比逐渐变小;NaCl浓度与3个野生稻种子发芽率有一定的负相关性;NaCl对野生稻幼苗根的抑制作用强于对苗的作用;不同野生稻品种对NaCl溶液的耐受能力不同,从大到小依次为MY-3、延引红、HY-1。     

天山野果林塞威士苹果和短距凤仙花叶斑病病原真菌的鉴定

为了解新疆天山野果林中塞威士苹果Malus sieversii与其林下伴生植物短距凤仙花Impatiens brachycentra两种植物叶斑病病原菌的多样性及同源性,采用组织分离法获得病原菌,基于rDNA-ITS序列构建系统发育树,并进行ITS序列BLAST同源性比对,对病原菌进行鉴定分类,并依据科赫氏法则测定致病性。结果显示,从新疆新源县天山野果林中的塞威士苹果及短距凤仙花病叶上共分离得到18株菌落形态各异的病原菌,分属于2属4种,绝大多数属于半知菌亚门。其中,链格孢属Alternaria sp.为塞威士苹果和短距凤仙花叶斑病病原真菌中的优势菌群。致病性测定结果显示,其中11株病原真菌对塞威士苹果具有致病性,7株病原真菌对短距凤仙花具有致病性;塞威士苹果所有的病原真菌对短距凤仙花均有致病性,而且短距凤仙花所有的病原真菌对塞威士苹果也有致病性。推测2种植物叶斑病可能由相同来源的病原真菌引发,短距凤仙花染病加剧了塞威士苹果叶斑病暴发,可能是野果林退化的重要原因。