Both in foraging groups and in a sequential prey encounter context, learning had a visible effect on the pattern of selection for three live prey types (Ecdyonurus larvae, Hydropsyche larvae, and Gammarus) by juvenile Atlantic salmon Salmo salar. Compared to wild-caught fish, naive, hatchery-reared fish that had not been exposed to natural prey ate Hydropsyche larvae in a remarkably low proportion, and consumed a higher proportion of Gammarus. Ecdyonurus experienced a high and rather steady predation rate across the experience gradient, but after a short period of experience with live prey the consumption rate for Hydropsyche increased drastically, and that of Gammarus decreased, matching the selection pattern exhibited by wild fish. Individual fish offered prey in a sequential encounter context increased consumption rates of all the prey types as they gained experience, but the improvement was higher for the prey that were less consumed initially. Fish became more selective as they approached satiation, conforming to the prediction of optimal foraging theory that higher predator's energy requirements, as well as low food availability, result in reduced selectivity. The results also suggest that fish from distinct populations can differ in the degree of diet selectivity according to their energetic requirements for growth. The fast learning response of Atlantic salmon parr towards novel prey probably allows fish to maintain a high foraging efficiency when faced with frequent changes in the availability of different prey types. 1998 The Fisheries Society of the British Isles

The maximum swimming stamina of hatchery reared juvenile brown trout Salmo trutta, swimming against a fixed-velocity water flow of 36·6 cm s 1 (6·97 L s 1 ), was achieved at 16·1 C, and a 90% performance level occurred over a breadth of 7·7 C (12·2-19·9 C). The wide range of temperatures at which swimming performance is close to the maximal capacity could be a consequence of the implications for survival of this function. 2000 The Fisheries Society of the British Isles