The Upper St. Lawrence estuary is an area where many physical factors such as the wind, the freshwater runoff, the tides and the bathymetry interact to generate a strong spatio-temporal variability of measurable parameters. Six Landsat-5 Thematic Mapper thermal images were analysed to study the sea surface temperature spatial variability of this complex region. Results show that the bathymetry is the principal factor controlling this structure. Sea surface temperatures are usually warmer in shallower areas. Bathymetry is also responsible for the localization of the principal density front close to le aux Coudres. Finally, the results show that the sea surface temperature is influenced by the intense tidal mixing and by wind-induced upwellings. Data analysis finally showed that the Thematic Mapper sensor was able to significantly detect spatial temperature gradients that are stronger than 1°C. L'estuaire superieur du Saint-Laurent est une region ou interagissent divers facteurs physiques tels que le vent, le debit d'eau douce, la maree et la bathymetrie qui generent une forte variabilite spatio-temporelle des parametres mesurables. Six images thermiques du capteur Thematic Mapper de Landsat-5 ont ete analysees afin d'etudier la structure spatiale du champ de temperature de surface de cette region complexe. Les resultats montrent que la bathymetrie est le facteur principal controlant cette structure. Les temperatures de surface de l'eau sont ainsi generalement plus chaudes dans les zones moins profondes. La bathymetrie est aussi responsable de la position du principal front de densite situe pres de l' le aux Coudres. Finalement, les resultats montrent que la temperature de surface de l'eau est aussi affectee par endroits par le melange intense cause par la maree ainsi que par des remontees d'eau induites par le vent. L'analyse des donnees a finalement permis de montrer que le capteur TM permettait de detecter de facon significative des changements spatiaux de temperature de surface de la mer lorsque ceux-ci sont superieurs a environ 1°C.

tability of the variables affecting the numerical productivity of the sows.The herd of origin accounted for about 5 per cent of the variance of litter size and for 30 to 5 j per cent of that of the lactation length.Estimations of the repeatability of the litter size varied from o.ig to o. y those of the other variables were less homogenous.Within-litter linear correlations between variables showed that the litter size was independent of the weaning-fertilization interval, but tended to decrease with lactation length.The curves representative of the polynomial regression equations accounting for the variations of the litter size at weaning in terms of litter size at birth show that the latter variable increases up to a maximum of 17 piglets born for Large White and French Landrace, 15 for I'ietrain and16for Belgian Landrace.However, a piglet has a maximum of chances for surviving until weaning when born in a litter whose size varies from 6 to 9 in the first two breeds and from 5 to 8 in Belgian Landrace.