Restoration versus recolonisation: The origin of Atlantic salmon (Salmo salar L.) currently in the River Thames

Publication year: 2011
Source: Biological Conservation, In Press, Corrected Proof, Available online 24 August 2011</br>
Andrew M., Griffiths , Jonathan S., Ellis , Darryl, Clifton-Dey , Gonzalo, Machado-Schiaffino , Dylan, Bright , ...</br>
Since the 1970s, when major improvements to the water quality were made, the River Thames has been subject to a high-profile project aimed at restoring Atlantic salmon to the catchment. Whilst initially successful, with hundreds of salmon returning each year in the late 1980s, the number of adults returning to the river has declined steeply again in recent years, reaching a low in 2005 when no salmon were recorded. Using a baseline of genetic information gathered from 3830 salmon from throughout their southern European range, and incorporating samples from the hatchery fish used to stock the Thames, all 10 tagged...</br>
*Highlights:*? Despite an intensive hatchery stocking programme, since 2005 no hatchery reared salmon have been caught in the Thames. ? Genetic assignment analysis indicates that wild salmon ascending the Thames originate from other rivers in southern England. ? Wild salmon returning to the Thames between 2005 and 2008 do not originate from exogenous fish stocked into the Thames. ? Such straying highlights the potential for natural recolonisation of rivers where salmon have become locally extirpated. ? Our findings highlight the futility of long-term stocking without corresponding improvements in habitat and water quality.</br></br>

24th August 2011 21:30

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