Observations on the dietary habits of wild and stocked brown trout, Salmo trutta L., in Irish lakes

Abstract

The dietary habits and feeding rates of wild and stocked brown trout were compared for populations in a number of Irish lakes. Wild trout and stocked fish, which had been present in a fishery for 12 months or longer, tend to feed on the same dietary items at similar rates.Stocked fish in their immediate post-planting period (1-14 days) ate less than both the wild trout and established planted fish. In some instances recently stocked fish appear to have a preference for surface food items. They also consumed stones and detritic material. Data indicate that stocked fish adopted a natural diet in less than 5 months. Results are discussed in relation to angling crops of wild and stocked fish and the comparative success of autumn and spring plantings of salmonids.

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

“…However that is clearly not the case in the current study where there was only one fish per cage. This lower than expected stomach fullness may be representative of a hatchery (rather than wild) fish model since other studies also indicate that it is common for hatchery fish released into the wild to initially have less material in their digestive system than expected (Sosiak et al 1979, Myers 1980, O'Grady 1983, Johnsen and Ugedal 1986, Hvidsten 1994, Fjellheim et al 1995.…”

“…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.…”

Bilan des marquages de truites (LT > 8 cm) relâchées dans le lac d'Annecy et le Léman de 1964 à 1977

“…Selon CRESWELL (1981) et O'GRADY (1983 les mortalités hivernales liées en partie au manque de nourriture pourraient être un des facteurs explicatifs des différences observées entre les relâchers (1975( ) et O'GRADY (1984 qui ont mis en évidence la faible survie hivernale ( < 26%) des O"*" de fario et TAC dans les lacs irlandais. Par ailleurs selon O'GRADY (1983) les truites d'élevage récemment déversées mangent moins que les truites sauvages, utilisent peu la faune benthique au début et préfèrent la nourriture de surface.…”