Recovery of a headwater stream population of brown trout after a fish kill in southeastern Minnesota, USA

After a complete fish kill on the 2-km-long, spring-fed headwater section of Garvin Brook, brown trout (Salmo trutta) population was studied over next 29 months to examine relative roles spawning migration adults and natural reproduction in recovery process. Spawning redd counts during two seasons post-kill, repeated surveys reference zones, were conducted assess adult total changes shifting age structures. One month after kill, observed zone. An estimated 100 200 spawned zone each 40% fewer than reach. Total populations similar between zones 12 16 due proportionally (80% versus 40 60%) larger numbers young within zone, but remained 4X more abundant reach until 25 kill. Age structures still differed few large Ultimately, headwaters Brook accomplished through combination migrations from downstream unimpacted reaches, producing fish, subsequent recruitment those classes.