Effects of Added Substrate on Production of Red Swamp Crawfish, Procambarus clarkii, in Earthen Ponds without Planted Forage

The effects of addition of substrate consisting of plastic mesh fencing to experimental earthen ponds were evaluated for the culture of the red swamp crawfish, Procambarus clarkii, without planted forage. Mean daily yield (kg/ha/d), number of crawfish harvested (number/ha/d), and mean individual harvest weight were compared for ponds with and without substrate during a 2‐yr period. The surface area of added substrate was equivalent to 50% of the bottom surface area of the pond. Mean daily yield in the ponds containing substrate, based on a comparison with that of the previous year, increased by 80.2% and was principally attributed to a 66.7% increase in the number of crawfish harvested. Comparative values for the ponds without substrate were ?13.1 and ?11.7%. For the second year, the treatment‐dependent response was consistent. Mean daily yield for the substrate ponds increased by 48.8% compared to 15.0% for the ponds lacking substrate. The primary benefit of the substrate appears to be provision of refuge and three‐dimensional distribution of crawfish in the pond, thereby reducing the incidence of cannibalism and increasing the total number of crawfish harvested per hectare per day. The benefit of the substrate in a commercial production setting must be weighed against its cost and longevity as well as the conditions of the particular management scenario into which it may be incorporated.     

黑龙江流域中俄保护区现状及展望

黑龙江地处中俄边界，在流域内中俄积极开展保护合作。本文分析了中俄在黑龙江两侧的保护区类型、保护对象，结果表明黑龙江流域的众保护区具有共同的保护对象，保护区的类型也惊人的相似。这些相同相似之处对于中俄保护合作深入发展有重要义。     

高温环境如何影响母猪的泌乳性能(续完)

高温环境对甲状腺素值的影响还不清楚。在泌乳期间 ,饲养于 30℃的母猪与饲养于 2 0℃和 2 2℃的母猪相比 ,观察到甲状腺素的分泌不受影响(Prunier等 ,1997) ,降低不显著 (Barb等 ,1991)或显著降低 (MessiasdeBraganca等 ,1998)。刚断奶时 ,饲养于 30℃和饲养于 2 0℃的母猪 ,甲状腺素的浓度相近 ,而以后 (断奶后 8～ 12天 )则以饲养于30℃条件下者的甲状腺素浓度较低 (Prunier等 ,1997;MessiasdeBraganca等 ,1998)。高温对三碘甲状腺素浓度的影响比较明显 ,而在热应激期间 ,无论是泌乳母猪还是断奶后母猪 ,三碘甲状腺素的浓度都降低 (P…     

Manipulated Mouse Embryos as Bioassay System for Water Quality Control

Mouse pronuclear stage embryos with intact slit zona pellucida (manipulated) were cultured in vitro until the hatched blastocyst stage in simplex optimized medium with higher K⁺ concentration (KSOM) prepared with three different water types: tap, deionized reverse osmosis (D‐O) water and Milli‐Q system (M‐Q) water. The culture media were supplemented with or without protein and ethylenediaminetetraacetic acid (EDTA, disodium salt). The rates of hatched blastocysts were significantly affected (p < 0.01) by micromanipulation, protein supplement and water source. The water source has no influence (p > 0.05) on development in EDTA‐supplemented protein‐free culture media, whereas in EDTA‐ and protein‐free culture media, the water quality significantly (p < 0.001) affected the rates of development, with higher rates in media prepared with M‐Q water. The micromanipulated embryos showed higher sensitivity to the water quality (p < 0.01). It worth mentioning that the rates of hatched blastocysts in protein‐free culture media were very low (0–7.5%). Furthermore, the three different water types were analysed by measuring the electrical conductivity, inorganic ions, total organic carbon and endotoxins to evaluate the purity. M‐Q water showed the lowest levels of inorganic ion, total organic carbon and endotoxin concentrations. We concluded that manipulated mouse embryos are good system to evaluate the quality of water used in biological system.     

An evaluation of the pesera soil erosion model and its application to a case study in Zakynthos, Greece

Abstract. The Pan‐European Soil Erosion Risk Assessment (pesera ) model was evaluated using existing soil erosion data collected under various types of climate, vegetation, landscape and soil conditions. The data used represent a variety of typical Mediterranean land uses such as winter wheat, vines, olives and bare, stony land prevailing in hilly areas. Using this data, the model was calibrated for sediment transport by overland flow and results compared to measured soil erosion values from runoff plots and a watershed on a monthly basis. The performance of the model was assessed statistically, showing that it can be satisfactorily used for predicting soil erosion rates under the conditions included in the study. The overall model estimate including all the available experimental data was 0.69 t ha^?1 yr^?1 with a maximum error of 1.49 t ha^?1 yr^?1. After validation, the model was applied to a small watershed (60 ha) of great ecological importance for the sea turtle Caretta caretta. For this purpose, soil and vegetation maps were compiled from all the necessary data for applying the model. The model was run for three years using daily data from an existing nearby meteorological station. The predicted and measured soil erosion rates for a 7‐month period were 0.31 t and 0.18 t, respectively. Application of the model to each mapping unit showed the over‐riding importance of land use for sediment generation under the given climatic conditions. Bare land, occupying 5.5% of the watershed area, generated up to 69% of the total sediments estimated for the watershed. It is concluded that the pesera model can be used as a regional diagnostic tool under a range of soil, topographic and climatic conditions for identifying the best land use type and vegetation cover to protect hilly areas from soil erosion. The calculated overall root mean square error for the model is 0.06 t ha^?1 yr^?1, compared to a soil erosion rate of 0.04 t ha^?1 yr^?1, which can be tolerated for protecting the area for the sea turtle.     

盆栽石榴养护技术要点

1、阳光充足石榴属阳性植物,喜阳光,整个生长季节要求有充足的光照。只要不缺水分,石榴是不怕强光的。光照不足必然影响植株生长,进而影响孕花孕蕾,开花结果。2、控花促长有时扦插新苗,当年就能开花结果,小苗首要的是先长“树身”,过早开花结果不利树身生长。头几年应抹去花芽,     

Evaluation of Corn Gluten Feed as a Dietary Ingredient for Pond-Raised Channel Catfish Ictalurus punctatus

Abstract.— This study was conducted to evaluate corn gluten feed as an alternative feedstuff in the diet of pond-raised channel catfish Ictalurus punctatus . Three 32%-protein diets containing 0%, 25%, or 50% corn gluten feed were tested. Channel catfish fingerlings (average weight: 57 g/fish) were stocked into 15 0.04-ha ponds at a rate of 18,530 fish/ha. Five ponds were used for each dietary treatment. Fish were fed to satiation once daily for a 147-d growing period. No differences were observed in feed consumption, weight gain, feed conversion ratio, survival, or fillet protein concentration among fish fed the test diets. Fish fed diets containing 25% and 50% corn gluten feed exhibited a lower level of visceral fat and a higher carcass yield than fish fed the control diet without corn gluten feed. The diet containing 50% corn gluten feed resulted in a lower level of fillet fat and a higher level of moisture than the control diet. There were no visible differences in the coloration of skin or fillet of channel catfish fed diets with and without corn gluten feed. Results from this study indicated that channel catfish can efficiently utilize corn gluten feed at levels up to 50%n without adverse effect on feed palatability, weight gain, or feed efficiency. Corn gluten feed may be beneficial in reducing fattiness of channel catfish and improving carcass yield by reducing the digestible energy to protein ratio of the diet.