Satma indta, S. ga+dvmi, Ckfiwmer numay~ush, and CWC~OBIU cla$caformis failed t o fill their swim bladders while being reared without a c c m to an air surface lor 84, 50, 22, and 5G weeks after hatching, respxtively. When given access to an air surface they irllcd them. I t is concluded that, like other physostornes. they must swallow air lor the initial filling, but even if Clling is delayed their pneumatic ducts remain open. In control trout, fill in^ occurred at the beginning 05 feedinp;, and in whitefish controls, 2 to 3 months after hatching (at 20-22 rnm length). Lake troul fry with unhllec! swim bladders swam up vertical distallces ranging up to ilOO f t without marked fatiguc, indicating that fish hatched in deep water can swim to the surface with reiative ease to fill their swim bladders.'Manuscript received October 9, 1959. Contribution from the Laboratory for Experimental Limnology, which is operated jointly by the

, J. 2010. Farm practices survey and modelling to estimate monthly NH 3 emissions from swine production in 12 Ecoregions of Canada. Can. J. Anim. Sci. 90: 145Á158. The swine industry in Canada has undergone rapid growth in some areas, but has also been restricted by a variety of environmental issues. Ammonia (NH 3 ) emissions are seldom mentioned among these issues, but emissions do occur and atmospheric NH 3 causes a number of impacts including contributing to odour, deposition into sensitive ecosystems and formation of secondary particulate matter, which is a health concern in some regions of North America. This paper describes a new model to estimate NH 3 emissions from the swine sector, relying heavily on a recent survey of swine producers to determine the present N and manure management practices. The key hypothesis was that NH 3 emission rates vary across Ecoregions and over time in a way that affects the degree of impact. The survey showed many differences across Ecoregions, most importantly related to feed crude protein and landspreading practices. The model estimated that grower pigs (!20 kg to market size) excreted on average about 8.5 kg total ammoniacal N (TAN) per (occupied) pig-place per year, and based on the national average farm practices, 25% of this TAN was emitted from barns, 5.3% was emitted from manure storage, and 17% was emitted during landspreading for a total of 4.8 kg NH 3 pig-place(1 yr (1 . The total loss for grower pigs ranged from 40 to 53% of excreted TAN across the 12 Ecoregions. Nursing sows emitted over twice as much per pig. Regions varied in reliance on homegrown feeds, which affected crude protein feeding and TAN excretion rates. Western regions had relatively low emissions from land application of slurry because of more extensive use of injectors. Emissions from grower pigs in winter were about 0.2 kg NH 3 pig-place(1 month(1 , mostly from barns, to as high as 0.7 kg NH 3 pig-place (1 month (1 in May, mostly from landspreading. Total emission for all of Canada in 2006 was 73 )10 6 kg NH 3 or about 13% of agricultural emissions in Canada. The results indicate that emission reductions can be achieved with greater use of low-emission application methods and reduced crude protein in feed. The emissions model can be used in future to assess the impacts from changes in feeding regimes and barn designs, and changes in practices such as animal density and increased access to outdoor spaces.Key words: Swine, ammonia, nitrogen, manure, emissions Sheppard, S. C., Bittman, S., Swift, M.L. et Tait, J. 2010. É tude et mode´lisation des pratiques d'e´levage en vue d'estimer les e´missions mensuelles de NH 3 re´sultant de la production porcine dans 12 e´core´gions du Canada. Can. J. Anim. Sci. 90: 145Á158. L'e´levage porcin a connu une expansion rapide dans certaines re´gions du Canada, tout en subissant les contraintes associe´es a`divers proble`mes environnementaux. Les e´missions d'ammoniac (NH 3 ) font rarement partie de ces contraintes, meˆme si elles existent et meˆme si le NH 3 pre´...

Preferred temperatures were determined for yearling lake trout acclimated to 5, 10, 15, and 20 C. Acclimation temperature had virtually no effect on preferred temperature. The final preferendum was 11.7 C, which is about 2 degrees C warmer than the temperature at which lake trout are most commonly caught in thermally stratified lakes.

The modal preferred temperatures of rainbow trout acclimated to 5 °C, 10 °C, 15 °C., and 20 °C. were determined photographically to be 16 °C, 15 °C., 13 °C, and 11 °C., respectively. The final preferendum was 13 °C. The phenomenon of decreasing preferred temperature with increasing acclimation temperature has not been reported for any other species of fish.

, J. 2009. Monthly NH 3 emissions from poultry in 12 Ecoregions of Canada. Can. J. Anim. Sci. 89: 21Á35. Management of ammonia (NH 3 ) is a multi-faceted issue for farmers. It is simultaneously a toxicant that can affect farm-worker and animal health, a volatile plant nutrient that is expensive to replace if lost, and a potential contributor to environmental degradation. The environmental implications have important spatial and temporal dimensions, beyond the farm. This paper describes a model developed to estimate NH 3 emissions from poultry (broiler, layer and turkey) production in 2780 mapping units across Canada on a monthly time scale. It includes estimates of daily emission peaks within critical months. The results will contribute to estimates of haze and atmospheric aerosol production, as well as contributions to other potential impacts such as eutrophication of sensitive ecosystems. The model is based on a detailed survey of farm practices. Emissions vary strongly throughout the year, and in many regions there are peak emissions in early spring and late fall, associated with landspreading of manure. There are also markedly different nitrogen excretion rates among regions, and these and bird populations are the key factors controlling emissions. On average, 22% of excreted uric acid or ammoniacal N is emitted from barns, 2% from storage and 26% from landspreading, resulting in a total loss of 50%.