| For fish species that have been extirpated from their native stream systems, reintroduction has been used to return populations to previously occupied streams. Reintroduction efforts have been used frequently, however their effectiveness can vary due to hatchery-reared fish behaviors. Beaver Brook, a stream system in Shu Swamp Nature Preserve (Mill Neck, NY, N 40.8782°, W 73.5650°) was likely originally occupied by brook trout (Salvelinus fontinalis ). The introduction of brown trout into the stream system led to competition with brook trout and eventually the extirpation of brook trout. Following the removal of the brown trout from 2000--2002, brook trout reintroduction efforts were made using hatchery-reared trout from Cold Spring Harbor Fish Hatchery (Cold Spring Harbor, NY). I predicted that newly-released hatchery-reared trout would show greater initial dispersal and would remain for less time in residences (implying that they struggle to maintain home ranges) for less time than acclimated trout. Additionally, I expected that hatchery-reared trout would be less selective in their habitat choices. Hatchery-reared trout (32 young of the year, tracked from 7/12-9/13, and 5 yearling, tracked from 4/13-7/13) were monitored via implanted radio tags and tracked approximately twice weekly. Electrofishing surveys were also performed and 10 wild (previously acclimated to the stream) trout were captured and radiotagged for monitoring. Location data, cover type and substrate type were recorded from July 2012--September 2015. Hatchery-reared and wild trout movement patterns, including time spent in a single residence, dispersal movement within the first week of release and proportion of time spent in a single residence were compared. A stream profile, measuring substrate types, flow rates, and cover availability was also performed and compared to conditions in residences. Hatchery-reared trout showed significantly more first-week dispersal movement, and although movement decreased after the first week, their dispersal was still more than wild trout. There was also evidence of predation among trout, as tag loss was very high in the first 2 weeks, which may have contributed to premature tag loss in hatchery reared trout. Hatchery-reared trout also spent significantly less time at specific locations. This implies that hatchery-reared trout were unfamiliar with the environment, or they may have experienced competition more significantly than wild trout. While there was no difference in substrate, flow or cover selections at residences of wild and hatchery-reared trout, this was likely due to small sample sizes, as well as homogeneity of the stream. |
