Downstream effects of hydroelectric dam operation on thermal habitat use by Brook Trout (Salvelinus fontinalis) and Slimy Sculpin (Cottus cognatus)

Hydroelectric dams can alter downstream water temperatures, impacting thermal habitat available for fishes. Decreases in river water temperatures resulting from hydroelectric dam operations may be beneficial to coldwater species and could potentially offset warming resulting from climatic trends. We used two coldwater fish species, Slimy Sculpin (Cottus cognatus) and Brook Trout (Salvelinus fontinalis) to assess the impact of a cool water draw below a 15 MW hydroelectric dam on fish thermal habitat use relative to a nearby naturally flowing river. Cooler water temperatures below the dam corresponded with significantly cooler mean growth season temperature use for Slimy Sculpin, but not Brook Trout, relative to the natural river. As well, mean growing season temperature use by Slimy Sculpin was significantly cooler relative to Brook Trout in both rivers, and significantly different amongst studied sites in the regulated river. Fish condition was significantly correlated with temperature use for Slimy Sculpin in the naturally flowing river only. Our results indicate that manipulating river water temperatures through hydroelectric dam operations to benefit multiple fish species will be difficult given the complexity of riverine thermal habitat and species‐specific differences in thermal preferences and behaviour.     

Oocyte Diameter and Plasma Vitellogenin as Predictive Factors to Identify Potential Channel Catfish,Ictalurus punctatus,Suitable for Induced Spawning

This study monitors the progression of oocyte size and plasma hormone profiles of female channel catfish, Ictalurus punctatus, at monthly intervals to stage expectant ovulating, females for strip spawning. The “critical minimum” diameter of an oocyte to reach threshold maturity for channel catfish was 2.5 ± 0.21 mm. Monthly increases of oocyte diameters and plasma vitellogenin concentrations were linear until spawning. The reproductive performance of cannulated and noncannulated catfish did not differ, negating adverse effects of routine cannulation. This study suggests oocyte diameter in channel catfish can be used as a predictive factor to determine and stage potential broodfish suitable for hormone‐induced spawning.     

全球化分工与合作,共赢木地板大市场——专访美国木地板协会CEO Edward S.Korczak

编者按:一面是中国地板企业出口美国受阻,一面是中美两国地板巨头谈合作.冲撞与联合彰显着中国地板国际化道路上的艰辛与希冀.中国地板出口美国面临什么样的问题,中美两国地板商在全球化产业链条中有怎样的纷争与合作.本刊远赴美国木地板研讨展览会,对美国木地板协会CEO Edward S.Korczak先生进行了专访.     

Assessing the nutrition of juvenile hybrid poplar using a steady state technique and a mechanistic model

Fiber farming utilizing fast growing trees provides a means to satisfy the increasing demand for hardwood fiber. To maximize growth during the establishment phase, it is important to understand the relationship between maximal growth rate, plant nutrient requirements, and the ability of the soil to supply nutrients. The objectives of this study were: (i) to use a steady state nutrition technique to establish threshold N, P, and K ratios associated with maximal growth and (ii) to use the Barber–Cushman nutrient uptake model as a means of coupling information on the nutrient supplying capacity of the soil with the optimum N:P:K ratio. Growth chamber and greenhouse studies, using Populus nigra×maximowiczii (NM-6), were conducted to determine maximal growth rate, optimal N, P, and K content, uptake kinetics, and soil supply characteristics. Maximal growth rate was 0.12 g g⁻¹ per day at a whole plant ratio of 100N:11P:37K. The Barber–Cushman model was run using soil supply and root growth data from the greenhouse study. Nitrogen, P, and K uptake were simulated for a 105-day period in response to the addition of a slow release 17–6–12 fertilizer at rates equivalent to 0, 75, or 150 kg ha⁻¹ of N. Model predictions of uptake improved as the amount of fertilizer added increased. Uptake estimates at the 150 level were 96, 120, and 98% of observed uptake for N, P, and K, respectively. The model predicted that the supply of N was not adequate to support sustained plant uptake throughout the study period. Plant uptake and soil supply observations confirmed that N uptake occurred primarily in the first half of the growth period and that soil N supply was quickly depleted. Model simulations of P uptake support earlier observations that uptake is not solely a function of supply. A 10-fold increase in simulated supply increased uptake by a factor of 6. Much more needs to be done before a soil supply model like Barber–Cushman can be used as a nutrient management tool in forestry applications. However, establishing optimum levels, ratios, and rates of nutrient addition provides a good starting point for further evaluation.     

Size class distribution and spatial pattern of Vitellaria paradoxa in relation to farmers' practices in Mali

The impact of human activities on size class distribution and spatial distribution of Vitellaria paradoxa (karité or shea butter tree) in the parklands of sub-Saharan Africa has not been reported in the literature. Two sites (Koumantou and Mperesso) in southern Mali and three treatments (cultivated field, fallow and forest) per site were involved in the present study. Results of a statistical test for random distribution showed that the spatial pattern of Vitellaria paradoxa became progressively aggregated from cultivated field to fallow and then to forest. A permanent aggregated pattern found at Koumantou was not found at Mperesso. A test of the independence of larger and smaller tree locations shows that size classes clump together at Koumantou but not at Mperesso. Results of the third test showed that in the cultivated field, auto-correlation was only observed at large scale. In the fallow the trend was towards negative correlation for both sites. In the forest, negative correlation was observed up to 20 m at Koumantou whereas at Mperesso, positive correlation was observed around 35 m and above 50 m. Site differences may be explained by the intensity of fruit production and recruitment, bound to rainfall and land use pressure. Greater regularity of the spatial pattern in cultivated field, then fallow, may be the result of human intervention.This revised version was published online in November 2005 with corrections to the Cover Date.     

Television food advertising to children: the extent and nature of exposure

OBJECTIVE: To describe the pattern and prevalence of food and drink advertisements to children on commercial television in Sydney, Australia, and compare these with advertising regulations set out in the Children's Television Standards and results from a similar study in 2002. DESIGN: Data were collected by recording television from 06.00 hours until 23.00 hours on all three commercial channels from Sunday 14 May 2006 to Saturday 20 May 2006 (357 h). The study analysed advertisements in two children's viewing periods, one as defined in the 2002 study and the other according to current standards. Food advertisements were coded using 18 food categories and were analysed by time period and popular children's programmes. RESULTS: Food advertisements occurred in similar proportions during children's viewing hours and adult's viewing hours (25.5 vs. 26.9% of all advertisements, respectively), although there was a higher rate of high-fat/high-sugar food advertisements during children's viewing hours (49 vs. 39% of all food advertisements, P < 0.001). There were even more advertisements for high-fat/high-sugar foods during popular children's programmes, contributing to 65.9% of all food advertisements. Estimates of exposure indicate that children aged 5-12 years were exposed to 96 food advertisements, including 63 high-fat/high-sugar advertisements per week. Since 2002, there has been a reduction in overall food and high-fat/high-sugar food advertisements.CONCLUSION: Despite reductions in overall levels of food advertising, children continue to experience high levels of exposure to food advertisements, which remain skewed towards unhealthy foods. Further food advertising regulation should be required to curtail the current levels of advertising of high-fat/high-sugar foods to children, to make them commensurate with recommended levels of consumption.     

Geographical classification of honey samples by near-infrared spectroscopy: a feasibility study

The potential of near-infrared (NIR) spectroscopy to determine the geographical origin of honey samples was evaluated. In total, 167 unfiltered honey samples (88 Irish, 54 Mexican, and 25 Spanish) and 125 filtered honey samples (25 Irish, 25 Argentinean, 50 Czech, and 25 Hungarian) were collected. Spectra were recorded in transflectance mode. Following preliminary examination by principal component analysis (PCA), modeling methods applied to the spectral data set were partial least-squares (PLS) regression and soft independent modeling of class analogy (SIMCA); various pretreatments were investigated. For unfiltered honey, best SIMCA models gave correct classification rates of 95.5, 94.4, and 96% for the Irish, Mexican, and Spanish samples, respectively; PLS2 discriminant analysis produced a 100% correct classification for each of these honey classes. In the case of filtered honey, best SIMCA models produced correct classification rates of 91.7, 100, 100, and 96% for the Argentinean, Czech, Hungarian, and Irish samples, respectively, using the standard normal variate (SNV) data pretreatment. PLS2 discriminant analysis produced 96, 100, 100, and 100% correct classifications for the Argentinean, Czech, Hungarian, and Irish honey samples, respectively, using a second-derivative data pretreatment. Overall, while both SIMCA and PLS gave encouraging results, better correct classification rates were found using PLS regression.