Feeding by hatchery-reared and wild brown trout, Salmo trutta L., in a Norwegian stream

Abstract

Abstract. Hatchery‐reared brown trout, Salmo trutta L., yearlings were captured shortly (3h to one week) after their release in a Norwegian stream. The feeding of recaptured hatchery fish was compared with that of wild brown trout. The investigations were carried out during three different periods (May, July and October). Investigations of drift fauna indicated that food availability was best in May. Most hatchery‐reared brown trout started feeding shortly after their release in all three periods. Hatchery fish went through a learning process with respect to feeding. This was most clearly demonstrated by the amounts of plant fragments in their stomachs, which were always greater in hatchery fish than in wild fish but which decreased with time after release in hatchery fish stomachs in all three periods. By about a week after release, hatchery trout appeared to be feeding on wild prey nearly as well as did wild fish, but they achieved this better in May than in October.

Development of a Natural Rearing System to Improve Supplemental Fish Quality, 1999-2003 Progress Report.

“…Other laboratory studies (Maynard et al 1996a, Paszkowski andOlla 1985), and many field studies (Ersbak and Haase 1983, Miller 1952, Hochachka 1961, Reimers 1963, Sosiak et al 1979, Myers 1980, O'Grady 1983, Johnsen and Ugedal 1986 have found that hatchery fish starve for several weeks after release. In the natural environment the fish are experiencing very different water sources, physical conditions (gravel, vegetation, overhead cover, temperature, sounds, and light levels), predators, and many other animals they never previously encountered.…”

“…After release, hatchery-reared fish are inefficient foragers and are often found with empty stomachs or stomachs filled with indigestible debris (Miller 1953, Hochachka 1961, Reimers 1963, Sosiak et al 1979, Myers 1980, O'Grady 1983, Johnsen and Ugedal 1986. Their social behavior also differs, with hatchery-reared fish congregating at higher densities, being more aggressive, and displaying less territory fidelity than wild-reared fish (Fenderson et al 1968, Bachman 1984, Swain and Riddell 1990.…”

“…Typically, during the first few weeks after release, cultured salmonids eat less and forage on more indigestible material than wild-reared fish (Sosiak et al 1979, Myers 1980, O'Grady 1983, Johnsen and Ugedal 1986, Hvidsten 1994, Fjellheim et al 1995.…”

Recapture and condition of pond-reared, and hatchery-reared 1 + European grayling stocked in addition to wild conspecifics in a small river

“…Näslund (1992) observed higher post-stocking survival in pond-reared brown trout compared to hatchery-reared. Johnsen and Ugedal (1986), however, found no longterm differences in post-stocking feeding of hatchery-reared and wild brown trout. Similarly, no differences were found between pond-and hatchery-reared brown trout in post-stocking feeding or in recapture rate (Johnsen and Hesthagen, 1990;Johnsen and Ugedal, 1990).…”

Effects of live feeds and compounded diet on growth parameters of brown trout fry (salmo trutta abanticus t. 1954) in the context of habitat restoration

“…There are also some studies on relationship between size of fish and their adjustment to new environment. Johnsen & Ugedal (1986) and L'Abee-Lund & Saegrov (1991) observed that small-size stocked brown trout could adapt to new conditions in a short time, whereas Hesthagen et al (1989) reported that takeable-sized brown trout adjusted slower to new conditions and it took a long time to learn how to use natural food. In our study, brown trout fries had the opportunity to consume live feed similar natural food resources.…”