The public wants assurances that animals used for food are raised humanely. Conventional cages for egg laying hens do not meet hen's behavioural needs, but cages have potential advantages such as improved liveability and respiratory health because of less aerial ammonia and dust as compared to non-cage systems. Providing amenities to cages might be a compromise that allows hens to reap some of the advantages of conventional cages and also better meet their behavioural needs. This review focuses on the perch as a furnishing and how its design and addition to the cage can affect welfare and production efficiencies of egg laying strains of chickens. Hens should have access to perches because of their high motivation and preference for perching. At night, hens like to perch at the same time which requires a straight perch space of 12 and 15 cm for White Leghorn and brown hybrids, respectively. Besides meeting a behavioural need, perches in cages improve bone strength, but the improvement is not great enough to prevent adult keel fractures and deformities. Perch access improves feather quality for the back but not for other feather tract areas. Foot pad, toe, and nail health are often improved with perch access in cages of smaller group sizes. With the exception of dirty and cracked eggs, perches installed in cages do not deleteriously affect hen performance. Commercial perches are available in different shapes (e.g., round, circular, or mushroom) and compositions (e.g., wood, plastic, or metal). There is no perfect perch relative to its material composition or shape. Wooden perches offer a rougher texture but harbour mites in crevices. Future research should concentrate on perch redesign that avoids slippery surfaces allowing hen's feet to better grip the perch, prevents keel fractures, is easily cleaned, and does not harbour parasites or pathogens.

The impact of fish and cyclopoid copepod predation on zooplankton communities was evaluated using large-volume mesocosms (depth 9.5 m; volume 13 m3) in the Římov reservoir (Czech Republic). Two yearling roach and perch individuals introduced into mesocosms represented the fish treatment, which was compared to cyclopoid copepods (initial abundance of 2 ind.L−1) and a control with no initial addition of predators. Our results clearly support the hypothesis that planktivorous fish feeding leads to the suppression of large-bodied cladocerans. In the presence of fish, the cladoceran community changed from a dominance of large-bodied Daphnia spp. at the beginning to dominance by the smaller Bosmina longirostris at the end of the experiment. Chlorophyll-a concentration and rotifer abundances increased in the absence of daphnids. In the absence of fish, the presence of large-bodied cladocerans resulted in decreasing chlorophyll-a concentration. Although no significant differences were observed between cyclopoid abundances in treatments stocked with cyclopoids and the control, the proportion of large cladocerans clearly showed the effect of the manipulation. The similar trends in both of these treatments did not confirm the importance of cyclopoid predation in our experiment. The overall strong effect of fish over cyclopoid predation suggests the main role of fish predation in the forming of zooplankton communities and in turn impacting phytoplankton biomass in mesocosms.

Les micropolluants métalliques Cd, Cu, Pb et Zn ont été analysés dans plusieurs compartiments inertes et biologiques de l'écosystème de la retenue du Mirgenbach : l'eau, les matières en suspension, le seston décanté, une mousse, un mollusque et trois organes de deux espèces dominantes de poissons. Ce lac artificiel reçoit les eaux échauffées de la centrale nucléaire de Cattenom (Nord-est de la France). L'étang de Lindre et la Meuse amont ont été choisis comme sites de référence. L'ensemble des supports analytiques montre que la retenue est fortement contaminée par le cuivre et à un degré moindre par le plomb et le zinc. Des teneurs importantes de cadmium ont seulement été détectées dans le seston décanté. Les métaux entrant dans la retenue se partagent entre deux phases : la colonne d'eau et les sédiments. Les concentrations élevées observées dans le seston décanté indiquent qu'une fraction importante de chaque métal disparaît de la phase circulante et stagne dans la retenue. Dans le cas du cuivre, une estimation des flux révèle que les deux tiers de ce métal se retrouvent dans les matières décantées. L'homogénéité dans la détection des différents micropolluants dans la moule Dreissena polymorpha Pallas et la mousse Fontinalis antipyretica Hedw. confirme l'intérêt de ces deux organismes comme indicateurs biologiques de la pollution circulante. Les deux poissons, le gardon Rutilus rutilus L. et la perche Perca fluviatilis L., se distinguent par de faibles concentrations métalliques dans le muscle. Bien que certains métaux aient été accumulés dans les organes cibles comme le foie pour le cuivre et le rein pour le plomb, ils peuvent difficilement être considérés comme des organismes sentinelles.