Migration of hatchery‐reared Atlantic salmon and wild anadromous brown trout post‐smolts in a Norwegian fjord system

Abstract

Hatchery-reared Atlantic salmon Salmo salar (n ¼ 25) and wild anadromous brown trout (sea trout) Salmo trutta (n ¼ 15) smolts were tagged with coded acoustic transmitters and released at the mouth of the River Eira on the west coast of Norway. Data logging receivers recorded the fish during their outward migration at 9, 32, 48 and 77 km from the release site. Seventeen Atlantic salmon (68%) and eight sea trout (53%) were recorded after release. Mean migratory speeds between different receiver sites ranged from 0Á49 to 1Á82 body lengths (total length) per second (bl s À1 ) for Atlantic salmon and 0Á11-2Á60 bl s À1 for sea trout. Atlantic salmon were recorded 9, 48 and 77 km from the river mouth on average 28, 65 and 83 h after release, respectively. Sea trout were recorded 9 km from the release site 438 h after release. Only four (23%) sea trout were detected in the outer part of the fjord system, while the rest of the fish seemed to stay in the inner fjord system. The Atlantic salmon stayed for a longer time in the inner part than in the outer parts of the fjord system, but distinct from sea trout, migrated through the whole fjord system into the ocean. # 2005 The Fisheries Society of the British Isles

Reduced migratory performance of farmed Atlantic salmon post-smolts from a simulated escape during autumn

“…When compared with the rapid displacement of the released smolt in the present study and other experiments (Finstad et al 2005, Økland et al 2006, LaCroix 2008, these results may be interpreted to indicate that the fish dispersed randomly throughout the fjord system rather than having performed active migration. Fish that remain close to, and move between, fish farms offer a challenge to fish health man- -----) agement.…”

Use of acoustic telemetry for spatial management of southern calamary Sepioteuthis australis, a highly mobile inshore squid species

“…Finstad et al 2005) our confidence in the ability of the VR2 system to detect most boundary movements was high, with the exception of the curtain at the bottom of Mercury Passage (Curtain H). The probability of detecting an individual as it passes through a VR2 curtain or gate is a function of VR2 detection radius, which may vary with environmental conditions, minimum/maximum random tag off times, animal swimming speed, and number of animals within range (Heupel et al 2005).…”

“…Additionally, several isolated receivers were placed on discrete spawning beds. The detection ranges of receivers are highly dependent on the study site conditions and also, within a site, on turbulence, salinity and depth (Finstad et al 2005). Receivers were placed between 1 and 3 m from the seafloor by attaching them to a steel pole or rope connected to a concrete mooring, such that they were vertical in the water column.…”

Marine migrations in anadromous brown trout (Salmo trutta). Fjord residency as a possible alternative in the continuum of migration to the open sea

“…Two different telemetry studies looking at the migration patterns of wild sea trout post-smolts in a Norwegian fjord systems (Finstad et al, 2005, Thorstad et al, 2007, show that the all the sea trout post-smolts resided in the inner, and occasionally the middle parts of fjord, for the duration of the study (two months). Conversely, Moore and Potter (1994) describe the behaviour of wild sea trout smolts through a river estuary in UK where residence within the estuary normally last less than a tidal cycle, and the majority of fish migrate through the estuary on a single ebb tide (Moore and Potter 1994).…”