Zusammenfassung: As the CoastWatch regional node for the Great Lakes, the Great Lakes Environmental Research Laboratory (GLERL) is working to obtain and/or develop and deliver environmental data and products for near real-time monitoring of the Great Lakes to support environmental science and decision making. In support of this goal, GLERL is providing access to near real-time and retrospective satellite observations and in-situ data for the Great Lakes to Federal, state, and local agencies and academic institutions. There are currently nearly 40 regional CoastWatch users. The goals and objectives of the Great Lakes CoastWatch Program directly support agency statutory responsibilities in estuarine and marine science, living marine resource protection, and ecosystem monitoring and management. GLERL is currently receiving an enhanced digital image product suite of 26 images including satellite derived surface-temperature, visible and near-infrared reflectance, brightness temperatures, satellite and solar zenith angle data, and cloud masks from the NOAA-12 satellite. These products are downloaded from the NOAA Ocean Products Center (OPC) via INTERNET on a daily basis and archived at GLERL. Over 32,000 image products have been received and archived since becoming the Great Lakes CoastWatch Node in 1990. GOES-8 data is also currently being received.

Zusammenfassung: Studies of predator-prey interactions have been limited to laboratories or relatively small scale field experiments because of logistic difficulties in large scale field experiments. Much evidence has suggested that predictions based on small scale experiments on predator-prey interactions may not be simply extended to large scales, e.g. whole system. This study was designed to examine predation effects on a prey fish assemblage at the whole lake scale. After a year of premanipulation study, northern pike (Esox lucius) were introduced into a small piscivore-free lake inhabited by 14 species of fishes. In the third and fourth years, the lake was divided by a large mesh fence and northern pike were introduced into one half of the lake. Predation effects on individual prey population were estimated for both direct effects (i.e., consumption of prey species) and indirect effects, including habitat changes associated with predator avoidance behavior, increase of emigration rates and changes of population size structure. The relative importance of direct versus indirect effects was examined using randomized intervention analysis along with a model that quantifies the indirect effects. Decreases of prey fish biomass due to increased emigration was at least as great as that due to the direct effect of consumption when prey biomass was high (>40 kg/ha) but not when prey biomass was low (<30 kg/ha). Significant indirect effects included dramatically decreased abundance of the dominant species (northern redbelly dace, Phoxinus eos), increase of some rare species (sunfish, Lepomis spp. and creek chub, Semotilus atromaculatus), and decreased mean sizes of redbelly dace. Indirect effects occurred rapidly and were most apparent immediately following the introduction of northern pike. Community responses to northern pike predation included changes of species composition, species diversity and community stabilities. The fish communities were significantly different among the pre-pike period, pike period and post-pike period. The greatest variance was related to abundances of redbelly dace and sunfish. However, predation effects on the prey fish community depended on the observational scales used to determine community structure. (DBO)