193 hydrobiologia volume 273 (1994), contents no. 1 L. Lepist6, S. Antikainen & J. Kivinen: The occurrence of Gonyostomum semen (Ehr.) Diesing in Finnish lakes M. A. Bozek, L. D. DeBrey & J.A. Lockwood: Diet overlap among size classes of Colorado River cutthroat trout (Oncorhynchus clarki pleuriticus) in a high-elevation mountain stream M. Trémoliéres, U. Roeck, J. P. Klein & R. Carbiener: The exchange process between river and groundwater on the central Alsace floodplain (Eastern France): Il. The case of a river with functional floodplain 19 S. Romo & M. R. Miracle: Population dynamics and ecology of subdominant phytoplankton species in a shallow hypertrophic lake (Albufera of Valencia, Spain) 37 R. Moreno-Amich: Feeding habits of grey gurnard, Eutrigla gurnardus (L., 1758), along the Catalan coast (northwestern Mediterranean) 57 no. 2 A. J. Martin, R. M. H. Seaby & J. O. Young: Does body size difference in the leeches Glossiphonia complanata (L.) and Helobdella stagnalis (L.) contribute to co-existence? 67 B. Pejler & B. Bérzins: On the ecology of Lecane (Rotifera) 77 H. M. C. Chiu, |. J. Hodgkiss & B. S. S. Chan: Ecological studies of phytoplankton in Tai Tam Bay, Hong Kong 81 S. Nazneen & F. Begum: Distribution of molluscs in Layari River (Sindh), Pakistan 95 H. J. Dumont & Y. R. Reddy: Phyllodiaptomus praedictus n. sp. (Copepoda, Calanoida) from Thailand 101 B. C. Wainman & D. R. S. Lean: Methodological concerns in measuring the lipid fraction of carbon fixation 111 P. Tikkanen, P. Laasonen, T. Muotka, A. Huhta & K. Kuusela: Short-term recovery of benthos following disturbance from stream habitat rehabilitation 121 no. 3 L. Shamsudin & M. A. Sleigh: Seasonal changes in composition and biomass of epilithic algal floras of a chalk stream and a soft water stream with estimates of production 131 N. B. Edgar & J. D. Green: Calanoid copepod grazing on phytoplankton: seasonal experiments on natural communities 147 D. M. Kobuszewski & S. A. Perry: Secondary production of Rhyacophila minora, Ameletus sp., and /sonychia bicolor from streams of low and circumneutral pH in the Appalachian Mountains of West Virginia 163 G. Becker: Food preference by five trichopteran scrapers 171 R. Galli, C. D. Munz & R. Scholtz: Evaluation and application of aquatic toxicity tests: use of the Microtox test for the prediction of toxicity based upon concentrations of contaminants in soil 179 Author index (Vol. 273) 191