The incidence of anadromy and season estuary use of native Atlantic salmon and brook charr, and invasive brown trout

Warner, Lucas Alexander (2013) The incidence of anadromy and season estuary use of native Atlantic salmon and brook charr, and invasive brown trout. Masters thesis, Memorial University of Newfoundland.

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Abstract

Brown trout were introduced to Newfoundland in the late 1800s and are now established in watersheds on the Avalon, Burin and Bonavista peninsulas. Little is known about estuary use by brown trout outside of their native or their impacts to native Atlantic salmon and brook charr. A relatively pristine watershed in eastern Newfoundland was chosen to investigate seasonal use of estuary habitat by these three species, and to investigated if I) the incidence of anadromy in each species, 2) the quality of offspring of anadromous and resident, and 3) if the waterfalls are barriers to migration. A fourth objective was to test if a laser ablation "drilling" technique can successfully extract growth history information from otoliths. Abundance of adult brown trout was relatively consistent throughout the year, but capture of adult Atlantic salmon was limited to August (28 : 1 brown trout to salmon caught). Abundance of parr and smolt was greater in spring and summer, a pattern consistent between species, with the exception of a large pulse of salmon smolt during one day. Atlantic salmon and brown trout young of year were largely offspring of anadromous females, while brook charr young of year were largely offspring of resident females. Brook charr were bigger than Atlantic salmon at post emergence midstream, upstream and end of growing season upstream. Brown trout were bigger than Atlantic salmon at post emergence midstream, while the opposite was found at end of growing season downstream. No size differences were found between brown trout and brook charr. Otolith core Sr concentration was not a function of rearing habitat and laser ablation can clearly distinguish between freshwater and marine environments using a "drilling" or retrospective technique.

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