Food of anadromous brown trout at sea

Abstract

The food of migratory Salmo trutta in coastal marine waters along the Norwegian Skagerrak coast varied significantly with age, season and habitat of the fish. The main prey categories in terms of frequency of occurrence were fishes followed by crustaceans, surface insects and polychaetes. Seasonal variation in diet and within habitats was found, supporting the view that brown trout is an opportunistic feeder. An ontogenetic niche shift was observed with post-smolts feeding on inshore and shallow water prey communities, while larger brown trout fed mainly on pelagic fishes. 2001 The Fisheries Society of the British Isles

Marine migration and habitat use of anadromous brown trout (Salmo trutta)

“…These results are consistent with findings by Jensen et al (2014), who found that sea trout in the Alta Fjord only spent 33% of their time in the pelagic habitat. The nearshore habitat utilization is also consistent with previous studies on sea trout feeding behaviour, which suggest that the main prey (crustaceans, polychaetes, insects, and fish) are found in nearshore, shallow areas (Pemberton 1976;Knutsen et al 2001). However, the data also show that the pelagic zone may be an important habitat for the long-distance migrants especially, and pelagic feeders are in other studies have been shown to feed almost exclusively on fish (Rikardsen and Amundsen 2005).…”

“…They suggested that this could be caused by a higher abundance of suitable fish prey for the larger individuals further out in the fjord at their study site. Similarly, Knutsen et al (2001) found that small postsmolt sea trout fed inshore on shallow water prey communities, while larger sea trout were feeding further offshore on pelagic fish.…”

“…It is likely that these fish found more energy-rich prey in the outer part of the fjord and therefore potentially gained mass faster and therefore also returned earlier to fresh water, as they had utilized their compensatory growth potential. Energy-rich pelagic fish species are often found to be a considerable part of the diet in larger sea trout, with herring (Clupea harengus) as a key prey species (Pemberton 1976;Knutsen et al 2001;Rikardsen and Amundsen 2005;Rikardsen et al 2006).…”

“…Previous studies of sea trout in the marine environment have revealed a large variation in migration timing, residence periods (Jensen 1968;Jonsson 1985;Jensen and Rikardsen 2008;, migration distance (Berg and Berg 1987;Jensen et al 2014), and prey choice (Knutsen et al 2001;Rikardsen and Amundsen 2005;Rikardsen et al 2007). In Europe, sea trout can enter estuaries from fresh water during all months of the year (Went 1962;Jonsson andJonsson 2002, 2009), and the marine residence time may differ considerably among individual fish.…”

Trophic niche similarity among sea trout Salmo trutta in central Norway investigated using different time-integrated trophic tracers

“…However, knowledge of the marine feeding ecology of S. trutta is limited (Rikardsen et al 2006). This is because S. trutta are difficult to catch at sea and most feeding studies are based on small sample sizes (Knutsen et al 2001). The few studies of S. trutta feeding that exist highlight the dietary use of marine prey, such as small fish and large crustaceans (Grønvik & Klemetsen 1987, Elliot 1997, Knutsen et al 2001, Rikardsen et al 2007, Knudsen et al 2011, and seasonal variability of the diet (Rikardsen et al 2006).…”