The efficiency of different methods for sampling semipelagic animals was compared in the deep basins of Lake Paasivesi and Lake Puruvesi of the complex Lake Saimaa, Finland, during 1990-92. Certain semipelagic animals, such as Mysis relicta, amphipods and larvae of ChaoborusJlavicans, are important bioindicators of water and benthic quality. However, owing to their high mobility and vertical migrations they are difficult to sample quantitatively with traditional benthic methods.The equipment used for sampling was comprised of: 1. Vertical nets (0.56 and 0.13 m2) placed on the bottom for 5 minutes or 12 hours and hauled up vertically. 2. Plexiglass traps placed on the bottom for 12-14 hours. 3. Mysis-trawl hauled horizontally c. 250-300 metres on the bottom. 4. Ekman-grab.In 1992, parallel samples were taken with vertically hauled nets (12 h and plexiglass traps baited with fish or liver or provided with a chemical light. Large vertically hauled nets were the most efficient equipment for catching Gammaracanthus lacustris, M. relicta and larvae of Ch. Jlavicans whilst baited or lighted nets were less effective. Lighted plexiglass traps were most effective in catching Pallasea quadrispinosa and water mites, but baited and control traps sampled inefficiently. The trawl sampled M. relicta and P quadrispinosa relatively well, but was less efficient in sampling other groups. The Ekman-grab was effective only for sampling Monoporeia aflnis.The semipelagic community differed between the studied basins. The dominant semipelagic animals in the humic, deep L. Paasivesi were M. relicta, amphipods and larvae of Ch. fivicans whilst the number of water mites was low in the catches. In the shallower, clear-water L. Puruvesi the densities of crustaceans and Chaoborus-larvae were low whilst some water mites, such as Pionapusilla, occurred in high numbers. Nocturnal sampling was more effective, especially for M. relicta.

Temporal and spatial occurrence and upstream flight of lotic mayflies and caddisflies were studied by means of kick netting, slit traps and floating emergence traps in Lake Konnevesi and its outlet stream (Siikakoski), mainly in 1983. Twenty species of mayflies and 78 species of caddisflies were recorded. Clearly lotic mayflies in the material were Baetis subalpinus, Heptagenia sulphurea and Ephemerella mucronata, which occurred only in the stream samples. Females of lotic Baetis rhodani had a long distance upstream flight in the area and occurred frequently in the floating emergence traps especially in sandy littoral habitats of L. Konnevesi. Procloeon bifidum and Nixe joernensis, which in some regions occur mainly in streams, were frequently found in the stony littoral belt of L. Konnevesi. Most of the mayflies recorded in the area were univoltine, but Baetis rhodani and Centroptilum luteolum at least had two generations in 1983. Strictly lotic species among caddisflies were Ceratopsyche nevae, Hydropsyche saxonica, Halesus digitatus, Ceraclea perplexa, Ylodes detruncatus, Athripsodes commutatus and Hydroptila forcipata. These were mainly found in stream samples. A short distance upstream flight of females (c. 0.1-0.4 km) was observed in the populations of H. siltalai, Psychomyia pusilla and Oxyethira frici and a moderate distance flight (at least 0.6 km) by females of Hydropsyche pellucidula, Cheumatopsyche lepida and Polycentropus irroratus. The most abundant caddisflies of the stream Siikakoski (Brachycentrus subnubilus, Neureclipsis bimaculata, Rhyacophila nubila, Agapetus ochripes, Micrasema setiferum and Hydroptila cornuta) were frequently found also in floating emergence traps in the lake (3. 7 km from the rapids). Females of Brachycentrus, Neureclipsis and Rhyacophila favoured traps on sandy substrata while females of Hydroptila were usually found in the stony belt. In the trap material of Agapetus ochripes, males were more abundant than females. According to emergence data, all caddisflies recorded in the area were univoltine though the emerging period of several species such as Rhyacophila nubila and Neureclipsis bimaculata was long. Maximum emergence was observed in early June when brachycentrids were swarming and another peak in August when limnephilids and leptocerids were abundant.

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The composition of the fish stock, food and 'macroparasites' were studied in eleven basins (22-100 m) of Lake Jyvasjarvi and North Paijanne in August-September 1976 . The fishing was done by means of a series of nets (meshes 15, 21 and 35 mm) laid on the bottom overnight . No fish were found in the two northernmost basins owing to bad oxygen conditions caused by waste waters . Smelt and burbot were the most abundant fish in the catches in other basins but the vendace was rare . Relict crustaceans and some `deep water' copepods (e .g . Heterocope borealis) played an important role in the food of fish in all basins .Parasites spreading via relict crustaceans were abundant in smelt and burbot, but absent in vendace and ruffe . The most common parasite in smelt was Cystidicola farionis, in burbot Echinorhynchus borealis, in ruffe Triaenophorus nodulosus and in vendace the gill parasite Ergasilus sieboldi. Females of a relatively rare copepod Salmincola lotae were found in the oral cavity of five burbot (at depths of 50 and 100 m) .