Into the wild: escaped farmed rainbow trout show a dispersal-associated diet shift towards natural prey

NABAES JODAR, DIEGO NICOLÁS; CUSSAC, VÍCTOR ENRIQUE; BECKER, LEANDRO ANÍBAL

HYDROBIOLOGIA

SPRINGER

Lugar: Berlin; Año: 2019

0018-8158

The feeding ecology of farmed fishescapees has seldom been assessed, although theyare one of aquaculture?s main environmental impacts.Here we tested if the diet of Oncorhynchus mykissrainbow trout escapees was affected by their dispersalfrom farms in a reservoir in Argentine Patagonia bycombining stomach content and stable isotope data,and compared their spatial patterns with those of cagedand wild (previously naturalized) conspecifics. Ourresults reveal a shift in the stomach content and d13Cvalues of escapees, reflecting a farm (pellets) to wild(mainly Daphnia sp.) diet transition associated todispersal from farms. The d13C signal of escapeessampled within the farming area was close to that ofcaged fish, whereas the d13C of escapees captured farfrom it was indistinguishable from that of wildrainbow trout. Furthermore, escapee dispersal fromfarms was associated with a transition from indiscriminate surface feeding (on indigestible floatingitems) typical of caged fish to preying heavily onDaphnia sp. In contrast, wild fish diet was homogeneous across all sites. Farm escapees graduallyacquiring the feeding behavior of their wild conspecifics as they disperse from the farms may promotecompetition for food and space, and increase theirchances for survival in the wild.