Comparison of growth, diet and food consumption of sea‐run and lake‐dwelling Arctic charr

Abstract

Sea-run post-smolt Arctic charr Salvelinus alpinus (15-26 cm) from Storvatn, northern Norway (70 39 48N) had significantly higher average specific growth rates in two years (1·64 and 1·66) than the corresponding lake-dwelling charr (0·53 and 1·20). The post-smolts displayed fast compensatory growth in the first 2-3 weeks of their sea residency, but then almost stopped growing prior to their return to fresh water. Lake-dwelling charr grew more evenly during the same time period. Thus, the anadromous charr may return to the lake after only 5-6 weeks in the sea, because the potential to maintain a high growth rate in the sea is reduced. The marine diet consisted mainly of the two crustacean plankton species Calanus finmarchicus and Thysanoëssa sp. (88%), and less of fish (6%), insects (4%) and benthos (2%). The diet of lake-dwelling charr consisted mainly of insects (58%, mostly chironomid pupae) and zoobenthos (29%), and less of zooplankton (13%) during the same time period. Although post-smolts had the highest growth rates, they had significantly lower food consumption rates and higher frequencies of empty stomachs than the corresponding lake-dwelling fish. Possible explanations for this paradox are discussed in relation to stomach evacuation rates, water temperature, feeding behaviour and the energy content of the food in the two environments. 2000 The Fisheries Society of the British Isles

Between-watershed movements of two anadromous salmonids in the Arctic

“…In the Arctic region of Norway, anadromous Arctic char usually stay at sea for 1-2 months and brown trout for 2-3 months each summer to feed, and with a few exceptions, both immature and mature individuals return to fresh water every year to overwinter (Rikardsen et al 2000;Klemetsen et al 2003;. Given that no tagged individuals of the Halselva populations were recaptured at sea outside the normal sea sojourn period, even Table 2.…”

Salmon lice infection on wild salmonids in marine protected areas: an evaluation of the Norwegian ‘National Salmon Fjords’

“…These species are good indicators of the local sea lice infection pressure because, as opposed to Atlantic salmon smolts, which ultimately leave the fjord environment in their migration out to sea, they spend most of their seawater phase inside the fjords, within close range of their native rivers (Lyse et al 1998, Rikardsen et al 2000. No differences in lice intensity are expected between these 2 species (Bjørn & Finstad 2002).…”

Preference for nearshore and estuarine habitats in anadromous Arctic char (Salvelinus alpinus) from the Canadian high Arctic (Victoria Island, Nunavut) revealed by acoustic telemetry

“…Arctic char migrate to marine environments to exploit their increased productivity (Gross et al 1988) and generally attain faster growth than nonmigratory individuals (Rikardsen et al 2000). In fact, summer feeding is crucial for Arctic char to build the energy reserves required for the winter months, where much energy is expanded for spawning and survival with little opportunity for replenishment until the next summer (Dutil 1986).…”