Effect of type of aviary,manure and litter handling on the emission kinetics of ammonia from layer houses

1. An experiment with laying hens of 16 to 36 weeks of age was carried out to investigate differences in ammonia emission between 3 commercially available aviary housing systems and the additional effect of manure and litter handling. 2. Ammonia emission from Tiered Wire Floor (TWF), Natura and Boleg aviary systems increased rapidly from placement of the hens to a peak at 20 weeks of age and showed respective equilibrium level at 11.55, 11.24 (N.S. compared to TWF) and 14.55 (P 0.001 compared to TWF) mg ammonia per h per hen. 3. Emission increased by 5.6% on the first day and 11% on subsequent days after removal of the manure on the belts. The litter layer increased up to about 7 cm; removal of 6.5 cm reduced emission by 20%. 4. Ammonia concentrations varied between 1 and 16 ppm, while ventilation rates were between 1 and 4 m3/h per hen to maintain inside temperature at about 22 5. About 82% of the droppings produced by the hens was found on the belts, either directly deposited there, or put there as litter material. The composition of the manure on the belts and the litter, a sand-droppings mixture, changed significantly during the first part of the laying cycle and differences were found between the 3 aviary systems with respect to the DM, pH, ash, Nkjeldahl and Total Ammoniacal Nitrogen concentration. 6. The changes in time and differences between the 3 systems in ammonia emissions and manure and litter composition were related to design of the systems, behaviour of the hens and degradation (of nitrogenous components) and volatilisation processes (water and ammonia). C.     

The influence of ocean currents on latitude of landfall and migration speed of sockeye salmon returning to the Fraser River

We hypothesize that the interannual variability of the Northeast Pacific Ocean circulation affects the latitude of landfall and migration speed of adult sockeye salmon ( Oncorhynchus nerka ) returning to the Fraser River. The Ocean Surface Current Simulations (OSCURS) model was used to simulate the return migration paths of compass-orientated sockeye for two years: 1982, which had a weak Alaska Gyre circulation and low Northern Diversion Rate (defined as the percentage of sockeye returning around the north end of Vancouver Island instead of the south end); and 1983, with a strong circulation and high northern diversion rate. The majority of model sockeye made landfall further north in 1983 than in 1982. The difference in landfall between 1983 and 1982 depended on the migration start position, swim speed, direction of orientation, and migration start date. The currents assisted the shoreward migration of sockeye starting from south of 55^o N and impeded the migration of sockeye starting from further north. The simulation results were consistent with our hypothesis and suggest that the effects of the Northeast Pacific currents must be included in sockeye migration models. We propose a conceptual model for the prediction of the Northern Diversion Rate that includes Blackbourn's (1987) temperature-displacement model, enhanced to include the effects of currents during the ocean phase of migration, and the use of two predictive formulas for the coastal phase of migration: the formula of Xie and Hsieh (1989) for sockeye approaching Vancouver Island directly from the ocean, and a yet-to-be-developed formula for sockeye approaching from within the Coastal Downwelling Domain directly to the north of Vancouver Island.     

Decline and fall of the salmon fisheries in the Netherlands: is restocking the Rhine a reality?

Abstract. The Atlantic salmon, Salmo salar L., was once of major importance to the fishing industry along the River Rhine. This paper discusses the Dutch and German salmon catches over the years 1863–1950. Even up to the end of the last century, it was not uncommon for Dutch and German fishermen to land 100000 salmon a year. However, factors such as the increased use of locks and weirs along the Rhine, coupled with growth in pollution, soon led to a rapid decline in numbers. By 1933, the salmon fishing industry in the Netherlands had virtually ceased to exist. Analysis of the available catch statistics suggests that the decline in the salmon population could have started before official records began. Although the degree of scatter in the data and uncertainties in the assumptions preclude the possibility of drawing firm conclusions about the survival rate of salmon, these figures illustrate how difficult it will be to maintain a stable population in the Rhine. Moreover, a number of changes have taken place since the heyday of salmon in western Europe, which could compound the problem. Of particular importance in the context of the Rhine are:

• 1 the closure of two of the major migration routes to the sea (Haringvliet and Zuiderzee);
• 2 morphological changes in the river;
• 3 chemical and thermal pollution;
• 4 the loss of accessible spawning and nursery areas of the required quality;
• 5 the disappearance of salmon from other rivers that flow into the North Sea such as the Rivers Elbe, Weser and Ems. If salmon were only reintroduced into the Rhine, a certain proportion would probably stray and infiltrate these other rivers.

The fact that the impact of these changes is difficult to quantify increases the uncertainty associated with maintaining a stable stock of salmon in the Rhine.     

TRADE-OFFS IN THE DESIGN OF SUSTAINABLE CROPPING SYSTEMS AT A REGIONAL LEVEL: A CASE STUDY ON THE NORTH CHINA PLAIN

Since the Green Revolution cropping systems have been progressively homogenized and intensified with increasing rates of inputs such as fertilizers,pesticides and water. This has resulted in higher crop productivity but also a high environmental burden due to increased pollution and water depletion. To identify opportunities for increasing the productivity and reducing the environmental impact of cropping systems, it is crucial to assess the associated trade-offs. The paper presents a model-base...