Adult movements and spatial distribution differ between hatchery- and natural-origin Lake Trout

ABSTRACT Objective Hatchery rearing can inadvertently alter fish behaviors and reduce the fitness of hatchery-origin fish, sometimes by impacting reproductive success in natural environments. We evaluated the effects of rearing environment (hatchery or natural) on lakewide movements associated with reproduction by comparing the adult distributions of hatchery-origin and natural-origin Lake Trout Salvelinus namaycush in Lake Champlain across three consecutive fall spawning seasons. Methods Sixty-nine hatchery-origin and natural-origin Lake Trout were tracked using acoustic telemetry with 48 passive receivers deployed in Lake Champlain (Vermont and New York states). Spatial overlap of the hatchery- and natural-origin populations was estimated annually as the average proportion of shared time that fish spent at each receiver location. Next, core areas were identified and compared for hatchery- and natural-origin adults, annually, based on receiver locations that accounted for 50% of total residency time. Lakewide distributions were also compared between hatchery- and natural-origin adults based on the duration spent at each location. Last, maximum residence time was compared between stocked and wild fish based on the cumulative residence time that individuals spent at their most occupied location each year. Results Annual spatial overlap of hatchery-origin and natural-origin distributions ranged from 43.8% to 67.1%. Core area receivers often differed between hatchery- and natural-origin adults, and lakewide distributions between these two groups were significantly different during the second and third years of the study. Hatchery-origin adults also spent significantly more time (60% longer duration) at their most occupied sites than natural-origin adults. Conclusions Potential spawning sites occupied by hatchery-origin adult Lake Trout frequently differed from sites occupied by natural-­origin adults, and hatchery-origin Lake Trout spent more time at individual locations during the spawning season. The biological significance of these differences requires further evaluation; however, these results suggest that hatchery rearing may affect the movement and distribution of adult Lake Trout in a manner that could impact reproductive success and possibly hinder population recovery efforts.