Critical velocities of 17 species of fish from the Mackenzie River have been determined from increasing velocity tests in both field and laboratory, and the effects on critical velocity of different acclimation temperatures and of temperature shock were examined. In five species the relation between fatigue time and swimming speed was investigated.Critical velocity data from 10 species were analyzed by solving the regression equation V = KLe (where V = critical velocity in cm/s, L = fork length, K = constant, e = exponent). Neither acclimation to different temperatures nor temperature shock over a range of ±7 C from acclimation temperature had a significant effect on critical velocity. Intraspecific variation was found to be unrelated to maturity, sex, or condition factor.From a graphical presentation of body length vs. maximum flow rate allowable in a 100-m culvert, it appears that culvert flow rates should be kept below 30–40 cm/s to allow successful passage of the majority of mature individuals of migratory species.

Eggs were collected from a single inline processing facility weekly for 3 wk (replicates). The eggs were stored at 4 degrees C and 80% RH. Sampling began the day after collection and continued each week for 10 wk. During analysis, 24 eggs were examined for egg weight, albumen height, Haugh units (HU), shell strength, and vitelline membrane strength for each replicate. Egg weight decreased (P < 0.0001) from approximately 61 to 57 g after 10 wk of storage. Eggs from the second replicate were significantly (P < 0.0001) heavier than the other replicates by an average of 3 g. On average, albumen height decreased with extended storage (P < 0.0001) from 7.05 to 4.85 mm. Albumen height was approximately 0.2 mm higher for the eggs in replicate 2 compared with the other replicates (P < 0.01). Haugh unit values decreased during cold storage from 82.59 to 67.43 (P < 0.0001). There were no differences between replicates for HU values. No differences were detected for shell strength between replicates or during extended storage. A significant difference (P < 0.05) was found in detectable vitelline membrane strength between replicates, but this difference was less than 0.05 g. The elasticity of the vitelline membrane decreased during storage (P < 0.01) remaining low after 6 wk. Extended cold storage led to decreases in egg weight, albumen height, and HU. However, average HU values were still within the range for grade A. Shell strength was not affected by extended storage. Vitelline membrane elasticity also decreased, which could lead to yolks more easily rupturing as consumers crack the eggs. The results indicated that although the physical quality factors monitored in this study decreased during storage, egg quality was still acceptable beyond current recommended shelf life guidelines.

A move from conventional cages to either an enriched cage or a noncage system may affect the safety or quality, or both, of the eggs laid by hens raised in this new environment. The safety of the eggs may be altered either microbiologically through contamination of internal contents with Salmonella enterica serovar Enteritidis (Salmonella Enteritidis) or other pathogens, or both, or chemically due to contamination of internal contents with dioxins, pesticides, or heavy metals. Quality may be affected through changes in the integrity of the shell, yolk, or albumen along with changes in function, composition, or nutrition. Season, hen breed, flock age, and flock disease-vaccination status also interact to affect egg safety and quality and must be taken into account. An understanding of these different effects is prudent before any large-scale move to an alternative housing system is undertaken.

There is a desire by US consumers for eggs produced by hens in alternative production systems. As the retail shell-egg market offers these products to accommodate consumer demands, additional information is needed to ensure processing methodologies result in safe eggs from all egg sources. A study was conducted to determine if there were differences in the prevalence of coliforms, Salmonella, Listeria, and Campylobacter on and within eggs and in the environment of a sister flock of conventional cage and free-range laying hens. Microbial sampling occurred approximately every 6 wk between 20 and 79 wk of age. A random sampling of typical coliform colonies produced 371 viable isolates for biochemical identification. Twenty-nine genera or species of bacteria were identified. There was a significantly greater (P < 0.0001) prevalence of Campylobacter in the free-range nest box swabs compared with that in the free-range grass and conventional cage swab samples (number of positives: 8 nest box, 1 grass, 0 cage). Seven isolates of Listeria innocua were detected with no significant difference in prevalence between the treatments. Isolates were associated with eggshells (2 free-range floor, 1 cage) and the free-range environment (2 nest box, 2 grass). There were 21 Salmonella isolates detected between all sample locations, with no significant difference in the prevalence of Salmonella detection between the treatments. Additional studies are needed to fully understand the effect of alternative production methods on the prevalence of pathogens and coliforms associated with nest-run eggs and the production environment.