The re-introduction of the burbot to the United Kingdom and Flanders

Summary

The burbot (Lota lota), the only fully freshwater member of the cod family, has been extinct in the UK since 1969 and in Flanders, Belgium, since 1957. The two re-introduction efforts described here sat at very different stages: the UK project remained a feasibility study assessing former distribution, likely causes of extinction such as overharvest, pollution, and habitat loss, spawning temperature requirements, genetic source populations, and stakeholder attitudes among anglers and conservation groups, while the Flemish project, launched in 1999, had already reached implementation. Flemish researchers used mitochondrial DNA and microsatellite analysis to identify four European phylogenetic clades and determined that French burbot from the river La Bar, genetically closest to the original Belgian stock, were the best source population; habitat suitability models built from that reference river then guided selection of Belgian release sites, while a captive breeding program improved larval survival over time. In spring 2005, over two million cultured French-origin larvae released into tributaries of the Grote Nete and Bosbeek rivers failed entirely, with no juveniles recaptured, but a subsequent autumn release of 2,000 and 1,000 larger age-0 fish in the same rivers showed 4 to 12 percent recapture rates with good growth, and by December 2007 sexually mature, spawning-condition males and females were captured in the Grote Nete. Encouraged, juvenile burbot were subsequently released into additional rivers. The project rated itself Partially Successful, noting natural recruitment still requires further evaluation before a self-sustaining population can be confirmed.