Brook Trout in New Zealand: A Failed Introduction @ 45° South

Brook trout (Salvelinus fontinalis) were introduced to New Zealand 135 years ago at the beginning of an intense effort to naturalize many salmonid species in the Southern Hemisphere.  Millions of brook trout were stocked on both the North and South Islands over a period from 1877 – 2004.  Most of the surviving populations are in headwater streams in the regions of Otago and Canterbury, upstream of brown trout (Salmo trutta) populations.  Mark-recapture monitoring of five populations in Otago confirmed that these populations have adopted the headwater life history characterized by early maturation (0+ & 1+), small size (>200 mm), and short life span (3yrs).  This study is the first of its kind for these New Zealand brook trout populations and while these populations do not represent a fishery, we conclude that they do have long term viability and pose a downstream invasion threat to native galaxiid fish (Galaxias sp.).  Given the amount of effort put into brook trout introduction in New Zealand, these results indicate that the establishment, or re-establishment, of riverine brook trout fisheries is difficult in the presence of brown trout even if prey is abundant and habitat and water quality are near pristine.