Ecological and landscape effects on genetic distance in an assemblage of headwater fishes

Environmental divergence along hierarchically structured longitudinal gradients may constitute barriers to gene flow in river networks for headwater specialised species. While known, this phenomenon has not been well studied, especially with regard to degree of headwater specialisation. We examined six headwater species that differ in habitat specialisation to assess whether patterns of differentiation vary according to geographic or environmental distance. We also identified regional environmental or anthropogenically induced fragmentation effects by comparing within‐drainage patterns of genetic distance across replicate watersheds. We used a comparative modelling framework to determine whether isolation by distance or isolation by resistance of large river habitats was a better predictor of genetic distance across species. The influence of reservoir presence and regional network characteristics that may influence the hydrology and size of large river habitats were also assessed. Resistance effects from large rivers were closely related to headwater specialisation, with increased specialisation leading to increased resistance and loss of drainagewide population connectivity. These results affirm that dendritic networks naturally fragment headwater specialised species. Further isolation from anthropogenic fragmentation was detected in two of the six drainages, indicating interactions with system‐specific conditions. Landscape variables related to the hydrology of large rivers also affected genetic distance in predicted ways, supporting the importance of large rivers in genetically structuring headwater species in drainage networks.     

An ecosystem-based assessment of the Korean blue crab trammel net fishery in the Yellow Sea and management implications

Landings in the blue crab, Portunus trituberculatus, fishery in Korean waters of the Yellow Sea have declined substantially from 11,000 t in the 1980s to 2,300 t in 2004. Blue crab habitat quality in the Yellow Sea has been degraded by anthropogenic activities including sand mining, land reclamation, and coastal pollution. Various traditional management measures have been implemented, including closed seasons during spawning and size limits, but these measures alone have been unsuccessful to conserve blue crab stocks. Consequently, a total allowable catch and a stock-rebuilding program using an ecosystem-based management approach were implemented in 2003 and 2006, respectively to rebuild blue crab stocks and restore habitats. This program involved assessment of both blue crab stock status and trammel-net fishery impacts at an ecosystem-level using an ecosystem-based fisheries assessment method ( [Zhang et al., 2009] and [Zhang et al., 2010]), which considered fishery data from catch and effort time-series, crab population biology, and ecosystem characteristics, including habitats and environmental conditions. Recent (2008) management status indices have shown significant positive change compared to conditions in 2000 with respect to sustainability of the stock and fishery and with regards to biodiversity and ecosystem habitat quality.     

Dietary nucleotide mixture effects on reproductive and performance,ovary fatty acid profile and biochemical parameters of female Pacific shrimp Litopenaeus vannamei

The effects of different dietary nucleotide mixture (NT) levels (0, 2, 4 and 6 g/kg) were investigated on the reproductive performance, fatty acid profile and biochemical parameters in Litopenaeus vannamei female that were co‐fed with fresh food (two times daily) and experimental diets (two times daily) for 30 days. Sampling was carried out at the first day of the trial, before eyestalk ablation (ESA) (day 21) and after ESA (day 30). Reproductive performance parameters including the hepatopancreatic index, absolute fecundity, egg diameter and latency period were higher in the NT‐supplemented groups than the control group (p < .05). Total n‐3 polyunsaturated fatty acids in the ovaries, especially eicosapentaenoic acid, were higher in the NT‐supplemented groups than in the control (222.6 ± 7.3 versus 204.7 ± 3.0 mg/g extracted lipid) (p < .05). Total hemocyte count, granular cells, plasma glucose (Glu), total protein (TP), calcium (Ca²⁺), total cholesterol (Chol), triglyceride (Tg) and high‐density lipoprotein (HDL) levels were significantly increased in the NT‐supplemented groups in comparison with the control group (p < .05). After ESA, the concentration of plasma Glu, TP, Chol and Tg significantly decreased, but HDL levels increased in all groups (p < .05). These results suggested that the application of dietary NT may present a novel strategy for increasing reproductive performance and health status in L. vannamei.     

Complementary use of natural and artificial wetlands by waterbirds wintering in Doñana,south‐west Spain

• 1. The Doñana wetland complex (SW Spain) holds more wintering waterfowl than any other wetland in Europe.
• 2. This study focused on the use made by 12 common waterbirds (eight ducks and four waders) of the natural seasonal marshes in Doñana National Park (DNP) and the adjacent Veta la Palma (VLP) fish ponds created in the early 1990s. Data used were from aerial and terrestrial surveys collected between October and February during six consecutive winters from 1998/99 to 2003/04. Changes in distribution of each bird taxon were related to changes in the extent of flooded marshes within DNP. Up to 295 000 ducks were counted in VLP during dry periods, and up to 770 000 in DNP when it was flooded.
• 3. The timing and extent of flooding in DNP was highly variable, but there was a consistent pattern in which ducks concentrated in VLP during dry months and winters but redistributed to DNP as more of it was flooded. This refuge effect was also strong for black‐tailed godwits Limosa limosa, but much less so for other waders. Waders feed mainly on invertebrates, and invertebrate biomass in VLP was found to be higher than in DNP. Ducks feed mainly on seeds and plant material, which are more abundant in DNP when flooded.
• 4. When water levels in DNP were stable over the course of a winter, or controlled for in multivariate models, the numbers of ducks at VLP declined over time, probably due to reduced availability of plant foods. In contrast, numbers of waders at VLP were more stable, and their invertebrate prey became more abundant over time, at least in the winter 2003/4.
• 5. In this extremely important wetland complex, the value of natural and artificial wetlands for wintering waterbirds are complementary, providing suitable habitat for different species and for different conditions in a highly variable Mediterranean environment.

Copyright © 2009 John Wiley & Sons, Ltd.     

Effects of the prebiotic mannan‐oligosaccharide on feed deprived zebrafish: Growth and reproduction

This study was designed to investigate whether the prebiotic mannan‐oligosaccharides (MOS) can reduce the deleterious impacts of feed deprivation on growth and reproduction in zebrafish. In the growth performance experiment, juvenile fish were distributed in the following four treatments: normal‐control (NC), starved‐control (SC), normal‐prebiotic (NP) and starved‐prebiotic (SP). After 8 weeks, NP and SC fish showed the highest and lowest growth patterns, respectively among treatments. Standard length, specific growth rate and feed conversion ratio did not differ significantly between NC and SP treatments. Autochthonous lactic acid bacteria (LAB) were significantly higher in NP and SP than the NC and SP treatments. Feed restriction resulted in significantly lower concentrations of thyroxine. In the reproductive performance experiment, additional juveniles were fed as in the growth experiment. Crossing in the final week of the experiment resulted in successful spawning in only NP fish, which showed mature sperm and oocytes in histological examinations. The number of spermatozoa was significantly lower in the fish that experienced feed restriction; however, the oocytes of SP females were at the same maturation level to that observed in NC females. Sex‐steroids changed after both starvation and MOS supplementation where NC and SP showed no differences in the levels of testosterone and female's 17β‐estradiol. These results indicate that MOS supplemented diet reduced some side effects of feed deprivation (final weight and length, SGR, FCR and levels of LAB and T3), and suggest that supplementation of the diet with MOS may ameliorate some of the negative effects of feed deprivation in zebrafish.     

有机铬对热应激蛋鸡血清生化指标的影响

目的,研究有机铬对热应激蛋鸡血清中某些生化指标的影响。方法,将处于热应激条件下的192只35周龄新罗曼褐壳蛋鸡随机分为6组,分别饲喂不添加铬的玉米-豆粕型基础饲粮和添加10、20、40及50mg/kg铬的试验饲粮49d结果:试验组中血糖、胆固醇、总蛋白、球蛋白平均含量均低于对照组,并且添加20mg/kg铬组的血糖、胆固醇、白蛋白含量与对照组相比差异显著(P<0.05)。对于AKP活性,添加40mg/kg铬组与对照组相比差异显著(P<0.05),其它各组间相比均为差异不显著(P>0.05)。对于尿酸含量,添加50mg/kg铬组与对照组相比为差异显著。结论:有机铬具有缓解热应激的作用。     

饲料糊精水平对暗纹东方鲀幼鱼生长、消化酶活性和血液生化指标的影响

配制等蛋白质(42%),等脂肪(9%),糊精水平分别为10%、15%、20%、25%、30%的5组饲料,饲养暗纹东方鲀幼鱼[初始体质量为(10.25±0.51)g]60 d,考察饲料中不同糊精水平对其生长、消化酶活性和血液生化指标的影响。结果发现,随着饲料糊精水平的升高,暗纹东方鲀幼鱼的特定生长率和饲料效率先增加后降低,25%组最高,并显著高于10%和15%组。30%组鱼的脏体比和肝体比显著高于10%组,同时其肝脂肪含量也显著高于其他组。10%组的肝糖原和血浆总氨基酸含量显著低于其他组。10%和15%组鱼的肝胰脏和肠道中淀粉酶活性显著低于其他实验组,而其肝胰脏中胰蛋白酶活性显著高于30%组。25%和30%组的血浆总胆固醇和甘油三酯含量显著高于10%和15%组。10%和15%组的血浆尿素氮含量显著高于其他实验组。15%和20%组的血细胞数量显著高于其他实验组。30%组的细胞凋亡率及细胞内活性氧(ROS)和钙离子(Ca2+)含量显著高于其他实验组。饲料糊精水平对暗纹东方鲀幼鱼的血糖含量、血浆谷草转氨酶和谷丙转氨酶活性及肝胰脏和肠道中脂肪酶活性无显著影响。在本实验条件下,暗纹东方鲀幼鱼饲料中糊精的适宜水平为20%～25%。     

园林计算机辅助设计实验课教学探讨

园林计算机辅助设计实验课是培养学生计算机辅助设计技能的重要课程,对实验课的重视、明确的实验课目标和任务及实验课教学中的控制方法运用是保证实验课教学效果的重要措施。     

LFA方法在晋西黄土区植被景观功能评价中的应用

 采用LFA(Landscape Function Analysis)方法,通过调查7种地类35组样本,评价植被类型、人类活动对林地景观功能和土壤性能的影响,并验证LFA方法在黄土区的适用性。结果表明:不同植被类型对林地土壤结构稳定性、渗透性能、养分循环性能的影响显著,其中,天然次生林改良土壤结构稳定性、渗透性和养分循环性能的作用最好,其次是刺槐人工林、油松人工林,荒草坡最差;人类活动对人工林地景观功能和林地土壤结构稳定性有显著影响;LFA方法能够较好地评价植被类型对林地土壤性能的影响,以及人类活动对人工林地景观功能和林地土壤结构稳定性的影响,在黄土残塬沟壑区有较好的适用性。     

我国森林土壤健康评价研究进展

保持和提高森林土壤健康是实现森林健康的基础。本文综述了森林土壤健康的概念、评价指标、评价方法及其优缺点。森林土壤健康评价是相对的而不是绝对的,主要以土壤的功能为基础,不同类型土壤的评价应采用不同的标准。因此,须进一步加强评价指标的标准化、综合化和应用化,选择适宜的方法来评价森林土壤健康,从而探索有利于某地区森林土壤健康的管理措施,以实现森林土壤的可持续发展。