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Growth and Maturity of Hatchery and Wild Lean Lake Trout during Population Recovery in Michigan Waters of Lake Superior
Author(s) -
Sitar Shawn P.,
He Ji X.
Publication year - 2006
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/t05-019.1
Subject(s) - trout , hatchery , salvelinus , petromyzon , fishery , biology , population , sexual maturity , predation , ecology , zoology , lamprey , fish <actinopterygii> , demography , sociology
The recovery of populations of wild lake trout Salvelinus namaycush in Lake Superior was the first success among Great Lakes—wide rehabilitation efforts for this species. Knowledge of changes in major demographic factors (e.g., growth and maturity schedules) is very important for enhancing our understanding of stock status during the recovery process, particularly for a fish population with a relatively long life span, such as lake trout in Lake Superior. We separated the recovery time line into three periods—hatchery dominant (1970–1979), transitional (1980–1985), and wild dominant (1986–2003)—and compared growth and sexual maturity (1) between hatchery‐ and wild‐origin lake trout within each period and (2) among the three periods for a given origin. In all three periods, the lengths at old ages (age >6) were similar between wild and hatchery lake trout, but wild fish had smaller lengths at ages 4–6 and at maturity than did hatchery fish. Consequently, wild lake trout had a lower wounding rate by sea lamprey Petromyzon marinus and higher survival than did hatchery lake trout at a given maturity level. Across the three periods, both wild and hatchery lake trout showed significant declines in mean length at old ages and length at 50% maturity, while declines in length at young ages were not significant. Those temporal declines corresponded with the increase in wild lake trout abundance to historic high levels and the lower abundance of major prey fishes. Our estimates of age at 50% maturity also increased over time, but excessive variance in age determinations precluded statistical significance. The observed dynamics of lake trout growth and maturation in the context of population recovery and food web changes are valuable for studying the population dynamics of harvested fish populations.